Underwater Technology 38.1 by SUT

Vol. 38 32 No. No. 1 3 2 2021 2014 Vol.

UNDERWATER TECHNOLOGY

A Personal View... Sustainable ocean use: An oxymoron? Not necessarily. Environmental considerations for ocean development

Philomène Verlaan

Attenuation of airborne noise by wet and dry neoprene diving hoods

Monitoring rocky reef biodiversity by underwater geo-referenced photoquadrats

Gonzalo Bravo, Juan Pablo Livore and Gregorio Bigatti

Book Review Routledge Handbook of National and Regional Ocean Policies

ISSN 1756 0543

Gurmail S Paddan and Michael C Lower

Non-linear finite element analysis of a Ti6Al4V/Inconel 625 joint obtained by explosion welding for sub-sea applications

Pasqualino Corigliano

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UNDERWATER TECHNOLOGY Editor Dr MDJ Sayer Scottish Association for Marine Science Assistant Editor E Azzopardi SUT Editorial Board Chairman Dr MDJ Sayer Scottish Association for Marine Science Gavin Anthony, GAVINS Ltd Dr MA Atamanand, National Institute of Ocean Technology, India LJ Ayling, Maris International Ltd Commander Nicholas Rodgers FRMetS RN (Rtd) Prof Ying Chen, Zhejiang University Jonathan Colby, Verdant Power Neil Douglas, Viper Innovations Ltd, Prof Fathi H. Ghorbel, Rice University G Griffi ths MBE, Autonomous Analytics Prof C Kuo FRSE, Emeritus Strathclyde University Dr WD Loth, WD Loth & Co Ltd Craig McLean, National Ocean and Atmospheric Administration Dr S Merry, Focus Offshore Ltd Prof Zenon Medina-Cetina, Texas A&M University Prof António M. Pascoal, Institute for Systems and Robotics, Lisbon Dr Alexander Phillips, National Oceanography Centre, Southampton Prof WG Price FRS FEng, Emeritus Southampton University Dr R Rayner, Sonardyne International Ltd Roland Rogers CSCi, CMarS, FIMarEST, FSUT Dr Ron Lewis, Memorial University of Newfoundland Prof R Sutton, Emeritus Plymouth University Dr R Venkatesan, National Institute of Ocean Technology, India Prof Zoran Vukić, University of Zagreb Prof P Wadhams, University of Cambridge Cover Image (top): zoonar.com/syrist Cover Image (bottom): Steve Crowther Cover design: Quarto Design/ kate@quartodesign.com

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Sustainable ocean use: An oxymoron? Not necessarily. Environmental considerations for ocean development Integrating burgeoning ocean uses with the requirements for marine environmental protection imposed by the Law of the Sea Convention is a daunting challenge. Environment and development are still presented as at the very least competing, if not diametrically antagonistic, interests. In a competition, there must be a winner. By and large, that winner is development. However, the framing of this challenge as a competition is incorrect and counter-productive. It sets up a demonstrably false dichotomy, whose clearly deleterious consequences for the marine environment (and for the earth as a whole) lead to outcomes that are profoundly unhelpful to that very development. The concept of winning merits a fresh examination. The Oceanology International conferences and exhibitions are part of many initiatives that present us with exciting and often visionary ideas for using the oceans in the 21st century. However, usually underpinning these ideas is an approach that – consciously or not – is fundamentally oriented towards winning. Yet, there is little or no attempt to define victory, or to avoid the victory becoming Pyrrhic, i.e., making sure that the costs associated with the victory do not so outweigh the benefits that there is, in fact, no real victory at all. The British physicist and author, Dr CP Snow CBE (later Baron Snow), explained the three laws of thermodynamics to his students as follows:

1. You can’t win. 2. You can’t break even. 3. You can’t get out of the game. This version of the three laws (Sherrill, 2009) facilitates reflection on the concept of winning and sustainable ocean uses. Other than in the title of this Personal View, I have so far intentionally avoided that much-used and much-abused word ‘sustainable’. I suggest that avoiding Pyrrhic victories in developing ocean uses offers a practical rule of thumb, grounded in the boundary conditions of the three laws, to assess whether an ocean use is sustainable. Quantification is needed, and a method may be found in the definition of Pyrrhic victory I have given above. The three laws mandate a redefinition of the bottom line. The need for a level playing field in this redefinition requires the active cooperation of the national government. The cost-benefit accounting associated with the development and use of ocean resources is conducted at governmental level and requires rethinking. For every ocean use, this accounting must be accurate and comprehensive, i.e., include all the environmental costs. If (more usually, when) the accounting is then adjusted for political purposes, that adjustment must also be clearly and accurately specified, and its consequent costs and benefits, including to the consumer, the taxpayer and the environment, must also be comprehensively set out. The Law of the Sea Convention also addresses social costs in the

A Personal View...

doi:10.3723/ut.38.001 Underwater Technology, Vol. 38, No. 1, pp. 1–2, 2021

context of the marine environment, such as the effect of pollution on human health. The topic of social costs is profoundly relevant to this discussion, but space constraints prevent further discussion here. Specifying the cost to the environment is important because the truism that nature takes no notice of politics continues to be so universally ignored that it remains worth repeating. For example, consider the adverse environmental consequences of the relentless and usually subsidised increase, for political reasons, in the destructive methods and catch limits for fish beyond scientific recommendations. It is not fully realised how much development, including in so-called ‘free market’ or ‘capitalist’ countries, depends on direct and indirect subsidies and other generally perverse incentives from, or borne by, the public purse. The expense of remedying adverse environmental and social consequences – even on the rare occasions when remediation is possible and actually carried out – also comes from the public purse. Remedial expenses are far greater, and the adverse environmental and social consequences far longer lasting, than the original benefits ostensibly obtained from the original development. Such benefits also are not nearly as widely distributed in society, if at all, as the costs. To the best of my knowledge, no country has yet put in place a truly national accounting of environmental and social costs and benefits associated 1

P Verlaan. Sustainable ocean use: An oxymoron? Not necessarily. Environmental considerations for ocean development

Dr Philomène Verlaan is an oceanographer specialised in the biogeochemistry and ecology of deep-sea ferro-manganese nodules and crusts (Ph.D., Imperial College London). She has extensive sea-going experience and has participated in 24 oceanographic research cruises and nine submersible dives to date. She is also an attorney-at-law specialised in international law of the sea (J.D., Florida State University; Member of the Florida Bar). She has authored over 50 refereed publications and is a Visiting Colleague at the Department of Oceanography, University of Hawai’i and Trustee of the Advisory Committee on Protection of the Sea.

with any form of development, land-based or marine. Furthermore, ocean management by countries is notoriously fragmented among many national, regional and local administrations. Yet all countries generally have one national finance and budget ministry. The oceans community in a given country is therefore represented everywhere in that country, by virtue of this national institutional fragmentation of ocean responsibilities. This could, paradoxically, be turned into a possible advantage. The oceans community, in no small part because of the sheer physical demands of the marine medium, is much more cognisant

of the true cost-benefit relationship of ocean development than their terrestrial counterparts. The ocean is not a forgiving setting. Making mistakes at sea is usually unpleasantly rewarded. As Cornelius Tacitus wrote in ~109 CE, ‘Nothing creates accidents like the sea’1. This fact tends to focus the marine mind. A similarly sharp focus could be brought to bear, from all the diverse sectors represented by the ocean community, on the national budget and finance ministry. The oceans community could mount a united effort to make its shared national common denominator, i.e., the budget and finance ministry, aware of the direct and indirect environmental and social costs associated with the disregard of ocean realities in development plans – including marine environmental and social realities – and in particular of the consequent demands on the public purse. Economically responsible uses of the public purse also require those uses to be environmentally and socially responsible. Sustainable use thus becomes responsible use, which carries a respectable pedigree of definition in all the relevant disciplines for both the sea and the land. Engineering and technology play a crucial role in this context. Thermodynamics teaches the need to be far more creative in our interactions with the natural systems of which we are an inextricable part. Therefore, to work responsibly in the ocean, which for these purposes can be equated to the marine environment as envisaged by the Law of the Sea Convention, it is necessary to design for and with the ocean and its environment. This means, to give only one example, to not

“nihil tam capax fortuitorum quam mare” Tacitus. The Annals 14.3 as translated in Haynes, 2016.

simply take land-based technology and try to submerge it. This is especially necessary when that land-based technology is already rather blatantly environmentally destructive on land. Deep-sea mining, the ocean use with which I am most involved, is, alas, at present doing exactly that. I suggest that it is a major reason why deepsea mining is encountering such growing opposition on environmental grounds. Truly responsible ocean use requires out-of-the-box practical thinking which I associate particularly with engineers and technologists: a major part of my audience here. Recall the wise words of Dr John Craven, a highly creative ocean engineer: ‘If you bring something new to the sea, the sea will bring something new to you’ (2002). This is both a promise and a threat. Creative ocean-based technology and engineering in developing ocean uses can help increase the promise and reduce the threat. Thus, sustainable ocean use becomes responsible ocean use, and the oxymoron disappears. This Personal View is based on the author’s presentation at the Ocean Futures Forum, Oceanology International Conference, held on 7 October 2020.

References Craven JP. (2002). The silent war: The Cold War battle beneath the sea. New York: Simon & Schuster, pp. 304 Natalie Haynes Stands up for the Classics Series 2, episode 4 Agrippina. 2016. BBC Radio 4. Available at: https://www. bbc.co.uk/programmes/b078xpfb, <Last accessed 4 March 2021> Sherrill, B. (2009). ISP209s Lecture 11. Slide 17. Available at: https:// people.nscl.msu.edu/~sherrill/ isp209s8/lectures/l11p.pdf, last accessed <15 January 2021>.

doi:10.3723/ut.38.003 Underwater Technology, Vol. 38, No. 1, pp. 3–12, 2021

Attenuation of airborne noise by wet and dry neoprene diving hoods Gurmail S Paddan1* and Michael C Lower2 1 Institute of Naval Medicine, Crescent Road, Alverstoke, Hampshire, PO12 2DL, UK

Technical Paper

www.sut.org

ISVR Consulting, University of Southampton, University Road, Southampton, SO17 1BJ, UK

Received 14 July 2020; Accepted 27 November 2020

Abstract The insertion losses of five neoprene diving hoods of varying thicknesses (2 mm–9 mm) were measured in one-third octave bands using a Kemar manikin in a diffuse broadband noise field. The insertion losses were measured in air for both dry and wet hoods. The insertion loss was calculated as the sound level in each frequency band measured with the hood, minus the corresponding sound level measured without the hood. The insertion losses were similar for both ears of the manikin. Both wet and dry hoods neither attenuated nor amplified sound below 250 Hz. Between 315 Hz–1250 Hz, the insertion loss of each hood was negative, displaying a broad resonance with a gain of 6–8 dB. In this frequency range the hood acts as a mass-spring system, resonating like a drum skin when stretched over the ears. Above 1000 Hz, the insertion loss increased with frequency (10 dB per octave), reaching a maximum of 5000 Hz–6000 Hz. Wetting each hood did not significantly affect the insertion loss; the ‘drum-skin’ resonance frequency was marginally lower with a wet hood, and insertion losses may be marginally greater between 1000 Hz– 10 000 Hz. The resonance frequency decreased with increasing thicknesses of hood, and the insertion loss at frequencies above the resonance increased with hood thickness. Keywords: noise, neoprene diving hood, thickness, noise attenuation, insertion loss

1. Introduction When undertaking activities in or under open water, individuals often wear some form of body covering to keep them warm, such as a drysuit or wetsuit. These activities may be work related (for example, repair and maintenance, sea rescue), or for recreation or sport, such as surfing, swimming and diving. The drysuit or wetsuit usually covers the whole body with openings for feet, hands and head; separate items (gloves and boots) might be worn on the hands and feet. To keep feet warm, socks may also be worn with the boots. A head covering * Contact author. Email address: Gurmail.Paddan472@mod.gov.uk

in the form of a hood may be used to keep the head warm. All these items are usually made from neoprene, a stretchy synthetic material composed of closed-cell foam set between layers of either nylon or Lycra®. Wetsuits and supplementary gear are available in varying thicknesses depending on the type of activity and environment in which the activity is intended. Different types of headgear can be used by divers, ranging from complete full-face helmets with selfcontained underwater breathing apparatus (SCUBA) to neoprene hoods. The type of headgear used depends on the activity being carried out. Although the primary purpose of a hood is to provide thermal protection, it is thought by some divers who operate noisy machinery under water that hoods provide some protection from noise while under water, and may also provide some reduction of the noise under dry conditions when their heads are out of the water. However, diving hoods are not designed, and should not be relied upon, to provide hearing protection against noise in air, although they can provide protection against noise when under water. The use of a neoprene hood as hearing protection arose as some wearers were increasing ‘protection’ around the ears of the hoods by ‘doubling’ the material thickness of the hood. The exposure of divers to high levels of noise is a recognised risk included in the Health and Safety Executive (HSE) Approved Code of Practice and Guidance, Commercial diving projects offshore: Diving at work regulations 1997 (Health and Safety Executive, 2014). The effect of diving hoods on hearing thresholds under water has been reported elsewhere, mostly based on experiments with one thickness of hood. A diving hood of 5 mm thickness was used in experiments conducted by Montague and Strickland (1961), and by Hollien and Feinstein (1975). Smith (1969) conducted a series of experiments on hearing thresholds using a neoprene hood of 10 mm 3

Paddan and Lower. Attenuation of airborne noise by wet and dry neoprene diving hoods

thickness. However, these experiments were not designed to determine the effect of diving hood thickness on sound attenuation when used under water, since only one thickness of diving hood was used in each of these studies. A particular problem of noise exposure was observed within the military sector. Divers wearing neoprene hoods were sometimes required to be under water for short periods before surfacing to operate noisy tools or equipment. In other cases, divers would wade or swim through water without immersing their heads before operating these tools. Thus, depending on the circumstances, divers operated the tools while wearing either ‘wet’ or ‘dry’ neoprene hoods. However, wearing hearing protection such as earplugs is not practical within this military environment. Some divers ‘double-up’ the thickness of the hood at the area near the ears with the aim that this would increase their protection from exposure to noise. Therefore, a study was undertaken to investigate the reduction of airborne noise provided by wet or dry neoprene diving hoods when worn out of water. The aims of the present study were: (i) to determine the reduction in airborne noise (i.e. the insertion loss) provided by neoprene diving hoods of varying thickness; and (ii) to determine the difference in the insertion loss between dry and wet diving hoods. The insertion loss of a hood is the noise reduction of the hood, i.e. the sound level measured at the ear (in decibels) without the hood, minus the sound level (in decibels) at the ear with the hood. The related term ‘sound attenuation’ is usually reserved for the noise reduction measured on a panel of human listeners using the ‘real-ear at threshold’ method. For the purposes of the present study, the wet diving hood condition is taken as a wet hood out of water and without water in the external ear canal to reflect what happens in practice. The insertion loss can be measured in each onethird octave band separately. These one-third octave band insertion losses can be used to calculate a noise spectrum and level at the ear by subtracting the insertion loss in each one-third octave band from the ambient external noise in that band.

The effective overall A-weighted noise level at the ear can then be calculated by A-weighting the levels in each band and summing the values.

2. Equipment and procedure 2.1. The neoprene hoods tested Five commercial neoprene diving hoods of varying thicknesses were used in the present study. These were as follows: • 2 mm thickness (Sport Series Model H30 by Waterproof) • 3 mm thickness (Typhoon Raptor) • 5 mm thickness (Typhoon Raptor) • 7 mm thickness (Typhoon Raptor) • 9 mm thickness (Santi basic diving hood), with 7 mm thickness in face area All hoods were size ‘L’, or ‘Large’, which was selected as a good fit for the Kemar manikin used in the present study. These hoods are shown in Fig 1.

2.2. Noise source and measurement The tests were carried out in the small reverberation chamber of the Institute of Sound and Vibration Research at the University of Southampton. Fig 2 is a schematic diagram of the equipment used in the present study. A ten-second long sound file with two non-coherent channels of white noise was generated on a laptop computer. The sound file was replayed on a continuous ‘loop’ from the computer to two Yamaha TX4n two-channel power amplifiers. One of the amplifiers was used to drive two Community R2-52Z full range loudspeakers, while the other was used to drive two Turbosound B18 sub-woofers. The full-range loudspeakers were placed on top of the sub-woofers and directed into two corners of the reverberant chamber to optimise the diffuse field in the room. Previous tests in this room with the same amplifier and loudspeaker set-up have shown that the sound field meets the requirements of ANSI/ASA S12.42-2010 clause 8.2.1 for uniformity in all

Fig 1: Diving hoods of different thickness used in the present study. From left to right: 2 mm, 3 mm, 5 mm, 7 mm, 9 mm thickness

Underwater Technology Vol. 38, No. 1, 2021

Fig 2: Block diagram of the equipment used

frequency bands up to 10 kHz, and clause 8.2.2 for directionality in frequency bands up to and including 8 kHz (ANSI/ASA, 2010). Fig 3 shows the sound field in the room. The spectra were measured during the tests using a Brüel & Kjær (B&K) type 2250 sound level meter. The sound level meter microphone and preamplifier were positioned 30 cm from the side of the manikin’s head. Each spectrum was averaged over a period of 30 seconds. Fig 3 shows the mean band levels and the mean ± one standard deviation of the 100 spectra. Fig 3 also shows the A- and C-weighted levels averaged over the 30 second periods; these are LAeq and LCeq, respectively. The overall level, LAeq, selected for the tests was nominally 75 dB(A).

Fig 3: One-third octave band spectra measured in the room averaged for one hundred individual measurements. Mean band levels ± one standard deviation

Paddan and Lower. Attenuation of airborne noise by wet and dry neoprene diving hoods

The spectrum in the room was stable and repeatable in the 50 Hz band and above. The band level at 20 000 Hz, though stable, was relatively low, as the outputs from the full-range loudspeakers rolled off above 16 000 Hz. Below 50 Hz the test spectrum was less repeatable, and was influenced by the room dimensions, averaging time, background noise from outside, and reduced output of the sub-woofers below 50 Hz. The optimal range for measuring the insertion loss for the neoprene hoods was therefore 50 Hz–16 000 Hz. A Kemar manikin was used to measure the insertion losses of the neoprene hoods. The manikin is a head and torso simulator incorporating two G.R.A.S. type RA0045 ear simulators, with one in each ear. Each ear simulator contains a G.R.A.S. type 40AG ‘half-inch’ pressure microphone at the eardrum position. The ‘eardrum’ microphones were each connected to a sound level meter (Brüel & Kjær type 2250) via a microphone preamplifier (G.R.A.S. type 26AC) and a microphone power module (G.R.A.S. type 12AA). Therefore, three sound level meters were used during the tests: one to measure the noise field in the room with a microphone at 30 cm from the manikin’s head, and one each to measure the sound levels at the manikin’s left and right eardrum microphones. Each of the sound level meters was programmed to measure the one-third octave band spectrum, and the overall average A- and C-weighted level (the LAeq and LCeq) over the 30 second duration of each test. The human ear does not respond equally at all frequencies; therefore, the A-weighting is applied to the audible frequency range to represent the reduction in sensitivity to the low frequencies. Long-term damage to hearing from moderate to loud noise is well correlated to noise exposure in dB(A); consequently, damage risk criteria for long-term hearing damage are usually expressed in dB(A). The difference between the LAeq and LCeq values provides an indication of the effect of the two frequency weightings and the frequency content of the noise. The mechanism of instant damage to the ear for extremely loud noise is different, and is related to peak C-weighted levels (Health and Safety Executive, 2005). The calibration of each ‘eardrum’ microphone, ear simulator and the associated sound level meter was checked using a B&K type 4220 pistonphone. The calibration of the external microphone, positioned 30 cm from the head, and its associated sound level meter was checked using a B&K type 4231 sound level calibrator. All calibrations were stable and checked before and after the tests.

2.3. Procedure The equipment used in the present study is appropriate for measurements with ‘dry ears’, but is not 6

designed for measurements with water in the ear canal, as this would destroy the microphones used. All measurements in the present study with wet or dry hoods can be classified as ‘dry ear’. The insertion loss of each neoprene hood was measured first with the hood dry, then with the hood wet. The noise field was switched on approximately 30 seconds before the first test to allow the loudspeakers to stabilise. The procedure was then as follows: 2.3.1. Tests with dry hoods With the manikin bare-headed, the spectrum and overall levels at the manikin’s two eardrum microphones were averaged over a 30 second period. The spectrum and level at the external microphone were averaged simultaneously. A dry diving hood was then fitted on the manikin and the measurements repeated. This procedure was repeated, alternating the measurements with and without the diving hood, until five tests with and five tests without the hood had been completed. Once all the measurements were completed for one hood, each of the other hoods was tested in turn. The 2 mm thick hood was tested first, then the 3 mm, 5 mm, 7 mm and 9 mm thick hoods, in that order. When fitting the hoods on the manikin, care was taken to ensure that the flexible ears were not folded over during the sound measurements. 2.3.2. Tests with wet hoods The tests with the wet hoods followed the same procedure and were in the same order as the tests with the dry hoods, starting with the 2 mm thick hood and ending with the 9 mm thick hood. Immediately before the first ‘wet’ test of each hood, the hood was immersed in a bowl of water at approximately room temperature (17 °C), and shaken and agitated for approximately 30 seconds to absorb water. The hood was then lifted from the water, and surface water was allowed to run off into the bowl. Then the hood was placed on the manikin as before. The hood was only immersed before the first ‘wet’ test, and not re-immersed before the second, third, fourth and fifth tests; each hood was therefore at its wettest during the first test and slightly drier during subsequent tests. The Kemar manikin’s head and pinnae became slightly damp during the tests, though no water entered the ear canals.

2.4. Analysis of recordings During the tests, the sound levels and spectra at the manikin’s ‘eardrum’ microphones, and the sound levels and spectra in the test chamber, were stored in the sound level meters. After the tests, the data were downloaded to a computer using B&K utility software (part number BZ‑5503). The means and

Underwater Technology Vol. 38, No. 1, 2021

Fig 4: One-third octave band spectra measured at the left ear for each of the five measurements with the 2 mm wet hood

95 % confidence intervals were calculated for the insertion losses of each hood in each frequency band, as described in Section 3.2.

3. Results 3.1. Variation in repeat measures Fig 4 shows the sound pressure levels averaged over each of the five repeat runs at the left ear of the Kemar manikin with a wet neoprene hood of 2 mm thickness. This shows that the variation between the repeat measures was low, indicating high confidence in the measured data. The hood was wetted prior to the first run; the hood would have slightly dried with successive runs. There is no consistent trend in the sound pressure levels between the five runs, indicating that the slight drying effect over the 20–25 minute duration of the tests had no measurable effect on the sound pressure levels. Because the measurements with the hood were alternated with the measurements without the hood, the hood was put on the manikin anew before each measurement. Fig 4 shows the ‘fit-refit’ variation. 3.2. Individual insertion losses The insertion loss of a hood is the sound level at the ear in decibels without the hood, minus the sound level in decibels at the ear with the hood. The insertion loss of each hood was calculated in one-third octave bands. The insertion losses of a hood depend on whether it is wet or dry, and therefore separate calculations were carried out for the hoods when wet and when dry. Insertion losses were also calculated for the Aand C-weighted levels, but these only apply for the broadband noise spectrum used in these tests. For other ambient noise spectra, the effective overall

A- and C-weighted levels at the ear will need to be calculated from the one-third octave band levels of the ambient noise spectrum outside the hood and the one-third octave band insertion losses, as described previously. The insertion losses for each dry and wet hood were calculated as follows. The mean value and standard deviation in each one-third octave band were calculated from the five measurements of the sound levels at the left eardrum microphone of the manikin without a hood, and the mean value and standard deviation were similarly calculated from the five measurements of the sound levels at the left eardrum of the manikin with a hood. The insertion loss in each band was then obtained by subtracting the mean band level with the hood from the mean band level without the hood. This procedure was then repeated using the measured levels at the manikin’s right eardrum. To estimate the variability of the insertion losses in each band in each ear, the 95 % confidence intervals of the band insertion losses were calculated. The variance in the insertion loss in each frequency band was the pooled variance of the five measurements without hoods and the five measurements with hoods. As the same number of measurements were made with and without hoods, the pooled variance was the average of the variance with and without the hood. The 95 % confidence limit was then the square root of the pooled variance (the standard error of the difference) multiplied by the value of Student’s t, where t = 2.306 (α = 0.05, two-tailed distribution, 8 degrees of freedom). The 95 % confidence intervals are shown in Fig 5.

3.3. Insertion losses for 2 mm neoprene hood Before presenting the results for all the wet and dry hoods, it is useful to review the results for one of the hoods in detail, as the same or similar features can be seen for all the hoods. The mean insertion loss values for the 2 mm thick hood are shown in Fig 5 for the four possible combinations of left and right ears with wet and dry conditions. The mean values are based on the five repeat measurements. Also illustrated in Fig 5 are the mean ± 95 % confidence limits for each onethird octave frequency band. Fig 5 shows that the hood had little if any effect on noise levels at frequencies below around 250 Hz, but amplified the noise (giving a negative insertion loss) at and around 1000 Hz, at approximately 600 Hz–1800 Hz. There was an increase in insertion loss from around 1000 Hz– 6300 Hz at a rate of approximately 10 dB–13 dB/octave. Furthermore, there was a slight reduction in insertion loss at around 10 000 Hz compared to the higher and lower bands. Superimposed on this 7

Paddan and Lower. Attenuation of airborne noise by wet and dry neoprene diving hoods

(a)

(b)

(c)

(d)

Fig 5: Insertion losses for the 2 mm thickness neoprene hood with left and right ears and with wet and dry conditions (mean ± 95 % confidence limits). (Note that the insertion losses are plotted with values increasing down the graphs)

general trend of insertion losses at different frequencies, there were small differences between left and right ears and between dry and wet conditions. Measurements at the right ear show a slight reduction in insertion loss at around 1000 Hz compared with the left ear. The main difference between wet (Figs 5b and 5d) and dry (Figs 5a and 5c) conditions of the hood is a slight decrease in the frequency at which the minimum insertion loss occurred from 1250 Hz–1000 Hz for the wet hood compared with the dry hood, possibly related to an increase in the mass of the hood when wet.

3.4. Comparison of measurements on the left and right ears Fig 6 shows the mean difference in insertion loss between left and right ears as measured on the manikin for each dry and wet hood separately. Fig 6 also shows that the values of difference in insertion loss measured on the left and right ears of the manikin were similar, and almost identical at most frequencies (from approximately 63 Hz–1600 Hz). There was a tendency, however, for the insertion loss at the right ear to be marginally less than the insertion loss at the left ear in the frequency range 8

from approximately 2000 Hz–4000 Hz (p < 0.05, Student’s t test). Although statistically significant at the 5 % level, this difference is small and not noticeable in practice. The reason for the difference was not explored but may be related to the Kemar manikin being not perfectly symmetrical. Differences in insertion loss were similar for both dry (Fig 6a) and wet (Fig 6b) conditions. Since the differences in insertion losses between the left and the right ears were minimal, the insertion losses were averaged over the two ears.

3.5. Comparison of insertion losses of the hoods when wet and dry Fig 7 shows the insertion losses of each hood when dry, compared to the insertion losses of the same hood when wet. Also shown in Fig 7 are the 95 % confidence intervals for the insertion losses. Wetting the hood had little effect on the measured insertion loss. The resonance frequency (at around 1000 Hz) may be marginally lower when the hood is wet, and the insertion losses may be marginally greater between 1000 Hz–10 000 Hz. Although the effects are visually apparent in Figs 7 and 8, these are not particularly noticeable in practice. A reduction

Underwater Technology Vol. 38, No. 1, 2021

(a)

(b)

Fig 6: Difference in insertion loss between left and right ears with a) dry conditions, and b) wet conditions of the different thickness of neoprene hoods

(a)

(b)

(c)

(d)

(e)

Fig 7: Insertion losses for dry and wet conditions for different thickness of neoprene hoods (mean and 95 % confidence intervals)

Paddan and Lower. Attenuation of airborne noise by wet and dry neoprene diving hoods

(a)

(b)

Fig 8: Effect of thickness of neoprene hood on the insertion losses under a) dry conditions, and b) wet conditions

in resonance frequency and an increase in insertion loss would, however, be consistent with the mass of the hood being slightly greater when wet than when dry. It is noted that the increase in mass would have been minimal since the neoprene hoods were composed of closed-cell foam. The data in Fig 7 show that the differences in insertion loss between wet and dry hoods were slightly greater than the differences in insertion loss between left and right ears (see Fig 5).

3.6. Effect of the thickness of a hood Fig 8 shows the mean insertion loss of each hood when dry and wet. The trend is for the peak frequency (resonance) at around 1000 Hz to decrease with increasing thickness of hood. Furthermore, the insertion loss at frequencies above the resonance appears to increase with hood thickness. The effect is more noticeable with thinner hoods of 2 mm–7 mm in thickness, compared with that between hoods of 7 mm–9 mm thickness.

4. Discussion The noise reduction can be measured using a Real Ear at Threshold (REAT) method (International Organization for Standardization, 2018) in which the hearing thresholds of several human listeners are measured with and without a hood, and the noise reduction is known as the ‘sound attenuation’. Alternatively, the noise reduction can be determined from objective measurements of sound levels with and without a hood as the ‘insertion loss’. The insertion loss of a diving hood can be measured in different ways: (i) on several real (human) heads using miniature microphones placed at the ear, or (ii) on a manikin (a head and torso simulator). Measurements on manikins make no allowance for different fits on real heads, so they are likely to produce lower variation than measurements on 10

groups of real people. The Kemar manikin used for these measurements has the dimensions and acoustic properties of a median human adult, so the measured insertion losses should be representative of a median adult (see e.g., Berger, 1992). Figs 5 to 8 show that the neoprene hoods all have similar effects on the insertion loss. Below approximately 250 Hz they neither reduce nor amplify sound. Between 315 Hz–1600 Hz, the insertion loss is negative, showing a maximum amplification of around 6 dB–8 dB. In this frequency range, the hood acts as a mass-spring system, with the neoprene providing the mass and the spring effect from the tension in the stretched hood. In effect, a hood stretched over the ears acts like a drum skin resonating in this frequency band. Above 1000 Hz, the insertion loss of each hood increases with frequency at around 12 dB per octave, reaching a maximum at around 5000 Hz–6000 Hz. When assessing the effect of thickness of hood on the insertion loss, the trend is for the ‘drum-skin’ resonance to decrease in frequency with increasing thickness of hood, and for the insertion loss at frequencies above the resonance to increase with the hood thickness. Both effects would have been expected, as the thicker hoods will have greater mass, thus resulting in a decrease in resonance frequency. Some tasks require an operator to wear a neoprene diving hood while under water and then, with their head out of the water, to operate tools that would expose them to noise. These operators would be wearing a wet hood and would be expected to have a ‘wet’ ear, that is, there would be ‘water in the auditory canal and in contact with the tympanic membrane’ (Anthony et al., 2010). In contrast, a ‘dry’ ear would have air or another gas, but not water, within the ear canal. Anthony et al. (2010) report that ‘as hearing is more sensitive in air than in water …, it is assumed that a given noise level is more damaging to the “dry” ear than the “wet” ear’.

Underwater Technology Vol. 38, No. 1, 2021

The present study arose from tasks carried out by military divers. In some cases the divers would be under water for a brief period before leaving the water to operate noise-producing tools. These divers would not be under water for long enough to get a ‘wet’ ear. In other cases, they would wade through water before operating the tools, and their heads would not be immersed in water at all. Therefore, the divers would be operating their tools with a ‘dry’ ear while wearing a neoprene hood. The study reported in the present investigation would be categorised as a ‘dry ear’ study, and a Kemar manikin is therefore ideal as the ears are not immersed in water. A comprehensive review on the human effects of noise under water, covering research up to 1989, was presented by Kirkland et al. (1989). The review, comprising three studies, indicated that thicker flexible hoods might provide greater sound reduction under water than thinner hoods, although the data were inconclusive. Another literature review, by Cudahy and Parvin (2001), reported that the thickness of a flexible diving hood only had a small effect on the reduction of noise. The sound attenuation properties of a 3 mm neoprene wetsuit hood when worn under water have been reported elsewhere (Fothergill et al., 2004): the reduction offered by the neoprene hood depends on the frequencies present in the noise. Anthony et al. (2010) state that a foam neoprene hood is likely to offer a reduction of 5 dB–15 dB, depending on the thickness of the neoprene and the frequency of the noise when assessed under water. Anthony et al. (2010) reported that the sound attenuation provided by the hood decreases as the thickness of the hood decreases with depth of the dive, caused by the compressible nature of the hood. They showed that the diving hoods reduced noise by 5 dB–15 dB, depending on the thickness of the diving hood. These previous studies were conducted under water, whereas the present study was conducted out of water. Although a direct comparison between the previous data and the present study cannot be presented because of experimental differences, a broadly similar reduction in noise is noted. The reduction offered by a diving hood when assessed under water would depend on many factors, including depth of water and whether the auditory canal was ‘dry’ or ‘wet’. Depth of water would have an effect since the mechanical impedance on either side of the diving hood would be different, depending on whether there was gas or water in the auditory canal. The measurements of the insertion loss described in the present study can be used to calculate noise

levels at the ears of personnel wearing these hoods in air, but not under water, provided the spectrum and level of the ambient noise is known or can be estimated. In the pink noise field (equal energy in all octaves of frequency) used in these tests, the reduction in the A-weighted sound levels by the hoods was between 4 dB–9 dB. In most cases, a neoprene hood will provide little reduction in airborne noise and should not be relied upon to protect hearing. The data presented in the present study are consistent with the finding that noise insertion losses increase as the thickness of neoprene increases. Although the hood will be compressed more at depth (resulting in a smaller hood thickness), the principle remains.

References ANSI/ASA. (2010). ANSI/ASA S12.42-2010. American national standard: Methods for the measurement of insertion loss of hearing protection devices in continuous or impulsive noise using microphone-in-real-ear or acoustic test fixture procedures. Acoustical Society of America, pp. 66. Available at: https://webstore.ansi.org/ Standards/ASA/ANSIASAS12422010, last accessed <2 February 2021>. Anthony TG, Wright NA and Evans MA. (2010). Review of diver noise exposure. Underwater Technology 29: 21–39. Berger EH. (1992). Using KEMAR to measure hearing protector attenuation: When it works, and when it doesn’t. In: GA Daigle and MR Stinson (eds.). The 1992 International Congress on Noise Control Engineering: Internoise 92. New York: Noise Control Foundation, 273–278. Cudahy E and Parvin S. (2001). The effects of underwater blast on divers. NSMRL Report 1218. Naval Submarine Medical Research Laboratory. Available at: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.822.49 53&rep=rep1&type=pdf, last accessed <2 February 2021>. Fothergill DM, Sims JR and Curley MD. (2004). Neoprene wet-suit hood affects low-frequency underwater hearing thresholds. Aviation, Space and Environmental Medicine 75: 397–404. Health and Safety Executive. (2014). Commercial diving projects offshore: Diving at work regulations 1997. 2nd edition. Available at: http://www.hse.gov.uk/pubns/priced/l103. pdf, last accessed <2 February 2021>. Health and Safety Executive. (2005). The Control of Noise at Work Regulations 2005. 2nd edition. Available at: http:// www.hse.gov.uk/pubns/priced/l108.pdf, last accessed <2 February 2021>. Hollien H and Feinstein S. (1975). Contribution of the external auditory meatus to auditory sensitivity underwater. The Journal of the Acoustical Society of America 57: 1488–1492. International Organization for Standardization. (2018). ISO 4869-1:2018. Acoustics – Hearing protectors – Part 1: Subjective method for the measurement of sound attenuation. 2nd edition. Available at: https://www.iso.org/ standard/65581.html, last accessed <2 February 2021>. Kirkland PC, Pence, Jr EA, Dobie RA and Yantis PA. (1989). Underwater noise and the conservation of divers’ hearing:

Paddan and Lower. Attenuation of airborne noise by wet and dry neoprene diving hoods

a review. Volume 1. Technical Report APL-UW TR 8930. Available at: https://apps.dtic.mil/sti/pdfs/ADA220935. pdf, last accessed <2 February 2021>. Montague WE and Strickland JF. (1961). Sensitivity of the water-immersed ear to high- and low-level tones. The Journal of the Acoustical Society of America 33: 1376–1381.

Smith PF. (1969). Underwater hearing in man: I. Sensitivity. Submarine Medical Research Laboratory Naval Submarine Medical Center Report No. 569. The Naval Submarine Medical Center. Available at: https://apps.dtic.mil/dtic/ tr/fulltext/u2/691403.pdf, last accessed <2 February 2021>.

doi:10.3723/ut.38.013 Underwater Technology, Vol. 38, No. 1, pp. 13–16, 2021

Non-linear finite element analysis of a Ti6Al4V/Inconel 625 joint obtained by explosion welding for sub-sea applications

Technical Paper

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Pasqualino Corigliano* Department of Engineering, University of Messina, Contrada di Dio - 98166, Messina, Italy Received 13 August 2020; Accepted 11 January 2021

Abstract Industries have shown interest in the use of dissimilar metals to make corrosion-resistant materials combined with good mechanical properties in marine environments. Explosive welding can be considered a good method for joining dissimilar materials to prevent galvanic corrosion. The aim of the present study was to simulate the non-linear behaviour of a Ti6Al4V/Inconel 625 welded joint obtained by explosion welding from the values of the tensile ultimate strength and yielding strength of the parent materials. The present study compared the stress-strain curve from tensile loading obtained by the non-linear finite element analysis with the experimental stress-strain curve of a bimetallic joint. The applied method provides useful information for the development of models and the prediction of the structural behaviour of Ti6Al4V/Inconel 625 explosive welded joints. Keywords: explosive welded joints, non-linear finite element analysis, marine structures

1. Introduction The task of joining different materials represents an important challenge, and in recent decades the explosion welding technique has become popular. Developments in explosive welding have been reviewed by Findik (2011), and bimetallic welded joints for marine application have been investigated by Young and Banker (2004). The predominant explosive welded joint used in the marine industry is the Al/Steel type joint for shipbuilding applications, and several experimental investigations have been reported (Corigliano et al., 2018a; 2018b; Kaya, 2018; Han et al., 2003; Li et al., 2015; Findik, 2011; McKenney and Banker, 1971; Acarer and Demir, 2008; Chao et al., 1997). In addition to the Al-steel joint, other dissimilar materials can be used in marine environments, such as stainless steel and Inconel 625 joints (Milititsky et al., 2010). * Contact author. Email address: pcorigliano@unime.it

Industries have shown interest in deeper-depth drilling, creating the need for new materials that can fulfil more requirements such as protection from corrosion, reduction of self-weight and higher strength (Alemán et al., 1995). Within this context, stainless steel alloys could be replaced by titanium alloys, which have a good combination of strength, creep resistance and resistance to corrosion. Since titanium has a higher potential than most other metals commonly used in seawater piping systems, it is the other metal, and not titanium, that becomes corroded. If another metal with equal galvanic potential is used (i.e. Alloy 625) throughout the system, galvanic corrosion will not occur (Francis et al., 2020). It has been shown that Ti – Inconel (Nickel alloy 625) coupling can be used for marine applications, as they belong to the same group (Francis et al., 2020). However, if traditional welding techniques are used, these materials would be difficult to join, and corrosion would not be avoided. Explosion welding for bimetallic materials has been developed to overcome such difficulties, using material of high strength metallurgically bonded to a thin corrosionresistant clad alloy. The aim of the present study was to simulate the non-linear behaviour of a Ti6Al4V/Inconel 625 joint produced by explosion welding starting from the values of the tensile ultimate strength and yielding strength of the parent metals, and to observe differences in experimental tests. In recent work, Topolski et al. (2016) investigated the microstructure and properties of a bimetallic Ti6Al4V/Inconel 625; this investigation served as reference for the comparison of the non-linear finite element analysis of the present study. The present author has previously applied procedures, based on finite element analysis (FEA) and validated by means of experimental data, for the analysis of Al-Steel explosive welded joints under static and fatigue loadings (Corigliano et al., 2018a; 2018b), 13

P Corigliano. Non-linear finite element analysis of a Ti6Al4V/Inconel 625 joint obtained by explosion welding for sub-sea applications

and structural steel under static and fatigue loading (Corigliano et al., 2015).

2. True stress–strain curves determination from static tensile strengths For a bimaterial specimen subjected to tension, in the elastic phase the stress (σ) will vary for each material, but the strain (ε) will remain uniform. Therefore, multiplying the strain by each Young’s modulus (E), the following is assumed:

σ1 = E1ε ; σ2 = E 2 ε , (1)

where subscripts 1 and 2 refer to Ti6Al4V alloy layer and Inconel 625 layer, respectively. Multiplying the stress by each area (width w and height h), the total force P is expressed as:

σ1h1w + σ2h2w = P

(2)

E1εh1w + E 2 εh2w = P ,

(3)

and the axial strain is: ε=

α=

E εpy σy

(8)

The relationship between m and the ultimate and yielding stresses was found equal to:   σ   m = 3.93 ln  u     σ y 

−0.754

(9)

The used values of the ultimate and yielding strength were determined on the parent metals (Topolski et al., 2016); these are shown in Table 1. The obtained true stress–strain curves for the two different metals are shown in Fig 1. Table 1: Ultimate and yielding strengths determined on the parent metals in (Topolski et al., 2016)

Therefore:

Assuming the plastic strain at yielding εpy = 0.002, a is calculated as:

Ti6Al4V

sy [MPa] su [MPa]

Inconel 625 1054 1079

sy [MPa] su [MPa]

570 1025

P , (4) w ( E1h1 + E 2h2 )

which allows the evaluation of the axial stresses as: σ1 = E1

P (5) w ( E1h1 + E 2h2 )

σ2 = E 2

P w ( E1h1 + E 2h2 )

(6)

Equations 5 and 6 show that in layer two, as E2 is nearly two times as large as E1, layer 2 is subjected to a stress (σ) that is almost double that of layer 1. The non-linear FEA requires the true stress and true strain curve of the two considered materials as input. Various methods to obtain the true strain curve have been described elsewhere that generally require multiple parameters. A method using just the values of the ultimate and yielding stresses was recently developed by Kamaya (2016). The method is based on the Ramberg-Osgood equation as follows: m

 σ  Eε σ = + α   (7)  σ y  σy σy

Fig 1: True stress-true strain curves of TI6Al4V and Inconel 625

3. Non-linear finite element analysis A non-linear analysis using the Ansys software was performed with a Ti6Al4V and Inconel 625 joint. The parameters of the analysed specimen were 15 mm for the width, and 2 mm height for the Ti6Al4V layer and 3.7 mm height for the Inconel 625 layer, as shown in Fig 2. These parameters were chosen to enable a comparison with the experimental results reported in Topolski et al. (2016), in which the same type of joint obtained by explosion welding was analysed. The used Young moduli for the FEA are equal to 200 GPa for Inconel 625 and 110 GPa for the

Underwater Technology Vol. 38, No. 1, 2021

Fig 2: Specimen geometry, Ti6Al4V-Inconel 625

Fig 4: Longitudinal strain at 550 MPa

Fig 3: FE model of the bimetallic joint in Ansys

Ti6Al4V layer. The SOLID186 was chosen for the used element – this consists of 20 nodes, each with three degrees of freedom: translation along the x, y and z directions. It is able to support plasticity, hyperplasticity, creep and large deflections, as well as simulate deformations of nearly incompressible elastoplastic materials and completely incompressible hyperelastic materials. The multilinear kinematic hardening (TB, KINH) model was chosen for the procedure, and the true stress–strain curves of Fig 1 were used as input. The FE model is shown in Fig 3. The results of the longitudinal strain for two values of the applied tensile stress s = F/A) equalled 550 MPa and 1000 MPa are reported in Figs. 4 and 5 respectively. Fig 6 compares the engineering stress–strain curve obtained by the non-linear finite element analysis with the experimental ones: the ‘as received’ bimetal junction (without having undergone heat treatments after the explosion welding process) and the bimetal junction with heat treatment obtained in Topolski et al. (2016). Fig 6 also shows the stress–strain curves of the two ‘as received’ base materials. The stress–strain curve obtained from the nonlinear FEA for applied stresses lower than 500 MPa is similar to the experimental curve obtained for the Inconel 625. For higher stresses there is a change in slope owing to the yielding of the Inconel 625, and the slope becomes similar to that of the Ti6Al4V alloy. As E2 is nearly two times as large as

Fig 5: Longitudinal strain at 1000 MPa

E1, layer 2 is subjected to a stress that is almost double that of layer 1. Therefore, for a nominal stress of 550 MPa, layer 1 (titanium) is subjected to a stress of 360 MPa, and layer 2 (Inconel alloy) is subjected to a stress of 653 MPa, which is higher than its yield strength. The FEA results show differences in bimetallic ‘as received’ specimens at low stress values, and higher differences for stress values above 500 MPa. These differences may be caused by the presence of residual stresses and hardening (which cannot be considered in the FEA model), resulting from

Fig 6: Results of the non-linear finite element analysis and comparison with the experimental results of Topolski et al. (2016)

P Corigliano. Non-linear finite element analysis of a Ti6Al4V/Inconel 625 joint obtained by explosion welding for sub-sea applications

the explosion welding process, as experimentally detected by means of hardness measurements in Topolski et al. (2016). Moreover, the experimental results in Topolski et al. (2016) showed that the bimetal joint is stiffer than the Inconel 625 parent metal, revealing that the Inconel layer had hardened as a result of the explosion welding process. For very high stress values higher than 900 MPa, the curve obtained by FEA is similar to the experimental curve reported in Topolski et al. (2016).

4. Conclusion A non-linear finite element analysis of a Ti6Al4V/ Inconel 625 explosive welded joint was performed. A method to construct the non-linear stress–strain curves of the parent metals was applied for the static ultimate tensile stress and tensile strength. The results of the finite element analysis showed that, for applied stresses lower than 500 MPa, the slope is similar to the experimental slope of the Inconel 625 alloy. For higher stresses there is a change in slope caused by the yielding of the Inconel 625, and the slope becomes similar to that of the Ti6Al4V alloy. Some differences in bimetallic ‘as received’ specimens were observed for low stress values, with higher differences for stress values above 500 MPa. These differences may be owing to the presence of residual stresses and hardening (which cannot be considered in the FEA model) resulting from the explosion welding process. For high stress values higher than 900 MPa, the curve obtained by FEA is similar to the experimental curve reported in Topolski et al. (2016). The applied method provides useful information for the development of models and the prediction of behavior of Ti6Al4V/Inconel 625 explosive welded joints.

Acknowledgement The present study is part of the research activities of the Research Project PRIN (Announcement 2015) ‘CLEBJOINT’, project funded by the Italian Ministry of Scientific and Technological Research.

References Acarer M and Demir B. (2008). An investigation of mechanical and metallurgical properties of explosive welded aluminium–dual phase steel. Materials Letters 62: 4158–4160.

Alemán B, Gutiérrez I and Urcola JJ. (1995). Interface microstructures in the diffusion bonding of a titanium alloy Ti 6242 to an INCONEL 625. Metallurgical and Materials Transactions A 26: 437–446. Chao RM, Yang JM and Lay SR. (1997). Interfacial toughness for the shipboard aluminum/steel structural transition joint. Marine Structures 10: 353–362. Corigliano P, Crupi V, Fricke W, Friedrich N and Guglielmino E. (2015). Experimental and numerical analysis of fillet-welded joints under low-cycle fatigue loading by means of full-field techniques. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229: 1327–1338. Corigliano P, Crupi V, Guglielmino E and Sili AM. (2018a). Full-field analysis of AL/FE explosive welded joints for shipbuilding applications. Marine Structures 57: 207– 218. Corigliano P, Crupi V and Guglielmino E. (2018b). Non linear finite element simulation of explosive welded joints of dissimilar metals for shipbuilding applications. Ocean Engineering 160: 346–353. Findik F. (2011). Recent developments in explosive welding. Materials & Design 32: 1081–1093. Francis R, Turnbull A and Hinds G. (2020). Bimetallic corrosion (Guides for good practice in corrosion control No. 5). National Physical Laboratory Report. Available at http://eprintspublications.npl.co.uk/id/eprint/8617, last accessed <1 February 2021>. Han JH, Ahn JP and Shin MC. (2003). Effect of interlayer thickness on shear deformation behaviour of AA5083 aluminium alloy/SS41 steel plates manufactured by explosive welding. Journal of Materials Science 38: 13–18. Kaya Y. (2018). Microstructural, mechanical and corrosion investigations of ship steel-aluminum bimetal composites produced by explosive welding. Metals 8: 544. Li X, Ma H and Shen Z. (2015). Research on explosive welding of aluminum alloy to steel with dovetail grooves. Materials & Design 87: 815–824. McKenney CR and Banker J. (1971). Explosion-bonded metals for marine structural applications. Marine Technology Society Journal 8: 285–292. Milititsky M, Gittos MF, Smith SE and Marques V. (2010). Assessment of dissimilar metal interfaces for sub-sea application under cathodic protection. In: Proceedings of Materials Science & Technology 2010, 17–21 October, Houston, USA. Topolski K, Szulc Z and Garbacz H. (2016). Microstructure and properties of the Ti6Al4V/Inconel 625 bimetal obtained by explosive joining. Journal of Materials Engineering and Performance 25: 3231–3237. Kamaya M. (2016) Ramberg–Osgood type stress–strain curve estimation using yield and ultimate strengths for failure assessments. Int. J. Press. Vessel. Pip. 137: 1–12. Young GA and Banker JG. (2004). Explosion welded, bimetallic solutions to dissimilar metal joining. In Proceedings of the Society of Naval Architects and Marine Engineers 13th Offshore Symposium, 24 February, Houston, USA.

doi:10.3723/ut.38.017 Underwater Technology, Vol. 38, No. 1, pp. 17–24, 2021

Monitoring rocky reef biodiversity by underwater geo-referenced photoquadrats Gonzalo Bravo1,2,3,* Juan Pablo Livore1 and Gregorio Bigatti1,2,3,4 1 LARBIM, Instituto de Biología de Organismos Marinos (IBIOMAR), CCT CONICET- CENPAT, Puerto Madryn, Argentina

Technical Briefing

www.sut.org

Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), Puerto Madryn, Argentina

Fundación ProyectoSub, Puerto Madryn, Argentina

Universidad Espíritu Santo (UEES), Ecuador

Received 13 December 2020; Accepted 26 January 2021

Abstract Digital images are an excellent tool for divers to sample hard-bottom subtidal habitats as bottom time is limited and high-definition images can be collected quickly and accurately. The present paper describes a sampling protocol for benthic rocky reef communities using geo-referenced photoquadrats and tests the method over several rocky reefs of Atlantic Patagonia. This method was tested in two localities, separated by 100 km in a semi-enclosed gulf, covering a total of 5800 m of 11 rocky reefs using track roaming transects. The protocol is non-destructive, relatively low-cost and can adequately assess changes in marine habitats as rocky reefs. The implementation of artificial intelligence analysis using human expert training may reduce analysis time and increase the amount of data collected. The present study recommends this sampling methodology for programs aimed at monitoring changes in biodiversity. Keywords: scientific diving, benthic survey, global positioning system (GPS), underwater imaging

1. Introduction Underwater sampling by SCUBA diving is challenging, and cost-effective methods are necessary to efficiently use available bottom time. Videos and still images have been shown to be an excellent tool for divers to sample hard-bottom subtidal habitats. They allow fast sampling which divers can complement with casual or qualitative in situ observations that may help to understand ecological patterns (Underwood et al., 2000). The benefits and limitations of photoquadrats for subtidal surveys are well described (Preskitt et al., 2004; Sayer and Poonian, 2007; van Rein et al., 2011; * Contact author. Email address: gonzalobravoargentina@gmail.com

Beijbom et al., 2012; Eleftheriou, 2013; Berov et al., 2016; Beisiegel et al., 2017). Among the benefits, less bottom time and non-destructive sampling are the main reasons why photoquadrats are chosen. Despite their limitation for taxonomic resolution, they are an efficient tool for detecting changes in benthic communities (e.g. Parravicini et al., 2009). This type of sampling has been used in several monitoring programmes, such as Census of Marine Life-NAGISA (Rigby et al., 2007), Victorian Subtidal Reef Monitoring Program (Hart et al., 2005), AIMS Long Term Monitoring Program (Thompson et al., 2014); some have included citizen participation (e.g. Reef Life Survey, Edgar and Stuart-Smith, 2014), with taxonomic expertise not a requisite for divers. With the continuous development of technology, the use of image-based tools for underwater surveys has increased. Digital photography has significantly improved image resolution, sensor sensitivity, image compression, battery life, apparatus size and cost. Therefore, photoquadrats should display improved quality, and combined with extra instruments (e.g. GPS, depth loggers) and basic computer skills, post-analysis should become easier and faster. Recent advances in machine learning for automated or semi-automated analysis of photoquadrats have shown promising results (Beijbom et al., 2015; González-Rivero et al., 2016; Gormley et al., 2018; Williams et al., 2019). The adequate use of this method of image analysis can aid in closing the gap between the rapid acquisition of numerous images and their required processing time. Underwater sampling protocols are often adapted or modified after field-testing under variable conditions as visibility, currents, depth, type of 17

Bravo et al. Monitoring rocky reef biodiversity by underwater geo-referenced photoquadrats

Fig 2: Diagram of diver with the sampling equipment: GPS buoy on the surface; PARALENZ (www.paralenz.com) video camera on the diver mask; underwater camera with flashes and stainless-steel structure frame. H = horizontal surfaces; V = vertical surfaces; O = overhang surfaces; and C = cavefloor surfaces. Original reef drawing by Gaston Trobbiani Fig 1: (a) Study site with black dots representing rocky reefs sampled; (b) southwest regions; (c) northeast regions; and (d) close-up of Pardelas Bay. Black lines represent the tracked transects on three reefs

habitat, etc. Small upgrades are not often shared in scientific articles, although some online platforms (e.g. protocols.io, ocean best practices) include this information and keep it up to date. In Nuevo Gulf, Atlantic Patagonia (Fig 1), several rocky reefs provide an excellent scenario to test sampling methodologies. The rocky reef extensions range from 100 m to more than 1500 m, and shapes are normally lineal with an edge that gives place to small caves (see Fig 2). The present paper describes a sampling protocol for benthic rocky reef communities using geo-referenced photoquadrats and testing the method over several rocky reefs of Atlantic Patagonia.

2. Materials and methods 2.1 Equipment set-up For the photoquadrats, a Canon 100D (SL1) camera placed in an Ikelite housing up to 60 m depth rating was used. This camera is one of the smaller and cheaper options for DSLT underwater photography, and a full-change battery can take more than 400 photos in water temperature between 12 °C– 18 °C. The camera used had an 18 mm–55 mm Canon lens, and all images were taken with a focal length of 18 mm, auto focus, ISO 400 and exposure 1/200 s at f/11. As most underwater professional photographers recommend strobes for still photography, two Ikelite DS-161 strobes were used. These 18

flashes provide more than 300 shoots (in the temperature range 12 °C–18 °C), which is a much greater amount than that provided by continuous dive lights. The through-the-lens (TTL) function was used in order to have optimal lighting in each photo, and the directions of strobes were crucial to avoid backscatter in low visibility conditions (Fig 3). The system was mounted on a rigid stainless steel structure with a 50 cm distance between the lens and the sea floor, giving a 0.0625 m2 quadrat (0.25 m × 0.25 m) in the middle of the photo. A stainless steel structure (not PVC as in Bravo et al., 2015) of 6 mm diameter was used in order to increase the stability and resistance of the tetrapod. The latter is important when taking photos in rough conditions such as strong currents or shore breaks which can cause the camera frame to suffer substantial collisions. The stainless steel structure was painted in order to avoid flash reflection. The camera and strobes were attached to the stainless steel tetrapod by a Velcro system that allowed removal of the camera from the structure whilst diving if a close-up photo is needed. The frame, camera and flashes weighed a total of 8.8 kg, which needed to be taken into consideration for the diving weight calculations. A dive computer (Oceanic Geo2) was mounted on one side of the quadrat to record depth (± 0.3 m) and temperature (±1 °C) of each photo. This information was used for descriptive and comparative purposes; for precise use of this type of data, computers should be accurately calibrated (see Azzopardi and Sayer, 2012). Divers carried a PARALENZ video camera (https://www.paralenz.com) on the

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Fig 3: Flash direction and its effect on backscattering under low visibility conditions. The diving computer can be seen in the top left of the photos

mask filming the transect, and recording depth and temperature. The information from these videos was used to characterise the rocky reefs (results not presented in this paper). A zodiac boat followed the divers’ path with the buoy on the surface as reference. When dives were performed without zodiac assistance, the reef was not further than 300 m from the coast line; a diver supervisor followed the buoy and assisted with the entrance and exit at sites that were explored before each dive.

3. Sampling Photoquadrats separated by at least 1.5 m were taken randomly along tracked roaming transects on the rocky reef. The presence of cavities with heights of 1.5 m–3 m below the rocky reef ledges provided enough space to sample four different surface orientations (horizontal, vertical, overhang and cave floor; Fig 2); when the cavities were smaller, only horizontal and vertical surfaces were sampled. Horizontal and vertical surface orientations were sampled in all reefs. In order to compare rocky reefs from two regions of Nuevo Gulf, six rocky reefs in the southwest and five reefs in the northeast were sampled during the same year. Reefs were separated by more than 100 m within each region.

3.1. Georeferencing photoquadrats The geolocation procedure used for transects was: 1) GPS and camera time were synchronised. This was done by aligning the camera clock with the GPS clock before each dive. 2) The GPS was set on track mode recording one waypoint every 3 seconds.

3) The portable GPS (e.g. Garmin etrex 10) was placed in a dry bag on top of a rescue can buoy connected to the diver by a monofilament line using a diving reel (Fig 2). The use of two GPS devices on the buoy was ideal to reduce the risk of losing data caused by low battery or other drawbacks of the GPS. 4) Divers maintained the monofilament line as tightly as possible in order to avoid angles between the buoy and the diver. This could produce a vertical force over the diver, and the reel with the line needed a safety fast release. 5) At the end of the survey, divers saved the track file on the GPS. 6) Photos were georeferenced using the function ‘Auto-tag photos’ in Adobe Lightroom Classic version: 9.1. This software allows uploading of .gpx files and synchronises photos using time. Other options for performing this task are: GPS-Photo Link software, the open-source code ‘benthic photo survey’ (Kibele, 2016) or a customised R code (e.g. https://github.com/gonzalobravoargentina/photoquadrats). 7) GPS position was stored on the metadata of each photo, and this information could be processed in a GIS software.

3.2. Image analysis Images were prepared for analysis using photo processing software (Adobe Lightroom Classic version: 9.1). Lightroom presents many functionalities which improve the organisation and processing of photos, such as the ‘Auto Sync’ tool which allows changes to be applied to a set of photos (e.g. cropped area of interest, lens corrections, addition of metadata). All images passed through the same workflow in the Lightroom program: 19

Bravo et al. Monitoring rocky reef biodiversity by underwater geo-referenced photoquadrats

(1) geo-referencing with the gpx file using ‘Autotag photos’; (2) including depth, site and surface orientation data on photo´s metadata; (3) white balance selecting a white tape on the frame; (4) cropping the area of interest (0.25 m × 0.25 m); and (5) automatic lens distortion correcting using the lens profile. Blurry or out-of-focus images were discarded and those that were too dark or bright were corrected. In order to follow the same guidelines in the metadata information, depth was included on the elevation field, surface orientation was included in the caption field, and site was included on the sublocation field in the Lightroom program. The process of including depth on the metadata information can be time demanding as it must be done individually for each photo in Lightroom. An alternative would be to use an R code to merge GPS, depth and temperature data to each photo and obtain a .csv file (e.g. https://github.com/gonzalobravoargentina/photoquadrats). The photoquadrat analyses were performed in CoralNet (https://coralnet.ucsd.edu). This open

source and free software can be used from any computer via an internet server and allows several users to work on the same source. The metadata for all photos was uploaded using a .csv file that was created by reading photo metadata by R code. While some studies suggested changing the photo name in order to have all metadata information included in the file name, it was noted that leaving the original name of the photo or an ID number allows faster filtering when using CoralNet and Lightroom. Percentage cover of algae and sessile invertebrates was calculated using a 100-point grid overlaid on each photo. Grid points lacking substrate were removed and percentage cover of each taxa was recalculated without these. All slow mobile fauna per image were counted to calculate density of each species. At the end of the process three matrices were obtained: 1) percentage cover; 2) density; and 3) presence-absence combining species from cover and density data. Some species that are difficult to identify by photo were grouped in a category or taxonomic group using the classification proposed

Fig 4: Cropped photoquadrats (0.25 m × 0.25 m) examples. Close-ups to show image definition of: (a) anemone; (b) ribs on laminated algae; (c) nudibranch; and (d) small benthic fish

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Fig 5: Boxplot of taxa richness among southwest (n = 424 photoquadrats) and northeast (n = 470 photoquadrats) region of Nuevo Gulf. The * indicates p < 0.001, obtained by randomisation test using the R package ‘rich’ (Rossi, 2011) with the presence-absence matrix of horizontal and vertical surfaces as input

by the Collaborative and Automated Tools for Analysis of Marine Imagery (CATAMI, Althaus et al., 2015) to standardise the analysis. As CoralNet provides machine learning, all photos analysed manually served to train the robot of the source.

4. Results and discussion The underwater survey protocol using georeferenced photoquadrats to estimate percentage cover and density of epibenthic communities was tested, with good results obtained under various conditions of visibility, water currents and low water temperature at two zones (northeast and southwest) of Nuevo Gulf, Patagonia. Of note is that all bottom time was used for displacement and taking photos, which allowed the exploration of larger areas; this is important when studying habitats with high spatial heterogeneity (Beisiegel et al., 2020). A total of 20 transects were performed, covering 5800 m of rocky reefs during seven diving days. On average, transect length was 305.65 m (SD:149 range: 101– 629), which took 25 minutes (SD:11.11, range:1147) at a depth range of 2 m -15 m and an average speed of 0.77 km/hr with more than 123 photos per transect. The extension of the survey could be increased using underwater scooters (see Bryant et al., 2017). However, this involves a higher cost, more logistics and greater difficulty upon water entry on shore dives. The use of flashes for photoquadrats resulted in high-quality images that enabled the detection of

small species with good definition (Fig 4a, c, d; for more examples, see https://coralnet.ucsd.edu/ source/1933/), and assisted in taxonomic identification. In some cases, the observation of morphological features such as ribs on laminated algae was useful for genus or family distinction (Fig 4b). Species that were difficult to identify by photo (e.g. Porifera and colonial tunicates) were pooled into functional groups in accordance with the CATAMI classification scheme which has well described and updated documentation. As the images are stored on the CoralNet server and the annotations are searchable, it is possible to review previous annotations. The latter feature also helps to train new users with the taxa identification. Photoquadrats (n = 894) detected 76 taxa in total in the Nuevo Gulf region. The northeast region presented a higher richness (65 versus 53) and a greater number of species per quadrats than the southwest sites (Fig 5). Small (<5 cm) cryptic fish species such as Helcogrammoides cunninghami (Fig 4c) were distinguished on images, and density estimations using photoquadrats should be compared with visual quadrats under the same conditions in order to test if the method presented in the present study is adequate for cryptic fish estimations. This protocol was designed for estimation of cover and abundance of benthic sessile or slow moving species. However, incorporating visual census for estimation of fish abundance and diversity, similar to Reef Life Survey (2017), will improve the present study’s data. The videos recorded by the Paralenz camera carried by divers were unstable and unsuitable for fish counts, and were only used for describing the habitat. The most common method for fine-scale sampling on rocky bottoms is quadrats along transects with a variation in quadrat size (1 m2, 0.25 m2 and 0.0625 m2). The choice of the sampling unit should consider the size of the sampled organism and the aggregation among them (Underwood and Chapman, 2013). However, in subtidal habitats water visibility must also be considered when using photoquadrats. In most parts of the Atlantic Patagonian coasts, visibility ranges from 0.5 m to 10 m (with an average of 4 m), and in order to obtain a 0.50 m × 0.50 m photoquadrat the camera must be positioned at least 0.60 m from the bottom. Under low visibility this distance results in poor-quality photos which are unsuitable for analysis. The present study used 0.25 m × 0.25 m quadrats, as the resulting photoquadrats were suitable under various visibility conditions. Concurrently, a large number of small-sized quadrats rather than fewer larger-sized quadrats represent the spatial variability with better accuracy (Bohnsack, 1979; Andrew and Mapstone, 1987; Sayer and Poonian, 2007). 21

Bravo et al. Monitoring rocky reef biodiversity by underwater geo-referenced photoquadrats

Fig 6: Taxa accumulation curve and expected number of taxa (Chao2 = dashed lines) for rocky reefs assemblages on northeast and southwest sites in Nuevo Gulf. Calculated with the ‘poolaccum’ function of the ‘Vegan’ R package (Oksanen et al., 2019)

The use of track roaming transects provided numerous benefits, such as: 1) time is not spent having to deploy tape measures; 2) each photoquadrat is geo-referenced for better accuracy, which provides coordinates to return to a specific area of interest; 3) the path is not required to be straight; 4) parts of the reef that are not suitable for sampling can be avoided; and 5) GPS position assists in labelling photos by transect, site and location. Although portable GPS devices have been available since the early 1990s, existing literature that used geo-referencing techniques on subtidal photoquadrats is scarce. There are some examples that used similar techniques for fish census (Lynch et al., 2015; Irigoyen et al., 2018) and benthic surveys (Roelfsema and Phinn, 2009; Niedzwiedz and Schories, 2011; Sanamyan et al., 2015). However, most likely owing to the added complexities on diving logistics, the use of GPS devices on surface buoys is not a common practice. Other options with the same principle and floating antennas include the GPS diving computer (Kuch et al., 2012) or a GPS inside a housing (Niedzwiedz and Schories, 2014). However, the use of cables presents additional problems (Niedzwiedz and Schories, 2014) and cables often do not resist the same strain as ropes. In the present study, the use of a robust floating device (rescue can buoy) presented good hydrodynamics and enabled tensing of the cord to provide less difference between the position of the diver and the GPS. Recently developed technologies for underwater geolocation offer high precision without the use of cables or ropes, giving greater freedom to divers (https://uwis.fi/en). However, the 22

costs of these technologies are high which limits the ubiquity of their use globally. Species accumulation curves are often used for determining the sampling effort (i.e. minimum number of photoquadrats) to obtain reliable estimations of richness (Ugland et al., 2003). Species accumulation curves performed for southwest and northeast sites in the Nuevo Gulf showed that with 200 photos the horizontal asymptote is nearly reached, capturing 87 % and 85 % of the total species richness in each gulf area, respectively (Fig 6). This shows that the actual number of photoquadrats per transect (~124) should be increased in order to achieve a better estimation of richness. However, increasing this number is challenging owing to the time required for analysis. Artificial intelligence could help to reduce this processing time, enabling a greater number of photos and better estimations of richness. CoralNet software provides semi- and fully-automated annotations after a large set of photos are analysed by experts. The Alleviate operational mode (semi-automated) decides when to make an automated annotation using a classification score. Beijbom et al. (2015) showed that 50 % of the annotations performed by the robot had no effect on the quality of percentage cover of estimates of 20 categories. Using this mode for processing photoquadrats can increase the total number of photoquadrats analysed. The non-destructive and relatively low-cost protocol of our study can adequately assess changes in marine habitats as rocky reefs (as was shown in the same area of the present paper; see Bravo et al., 2020) which provide important ecosystem services. Essential Ocean Variables (EOVs; Miloslavich et al., 2018) such as macroalgal cover, benthic invertebrate abundance and benthic invertebrate diversity can be estimated with this methodology. This is useful for broad scale monitoring programmes such as MBON (Duffy et al., 2013). The present method relies on high-quality, underwater images taken under a standardised method, which reduces the variation in photo resolution, angle of view, distance to the sea floor, and compensation of light attenuation, and will assist with the implementation of artificial intelligence analysis that may be affected by these variations.

Acknowledgement The present authors are grateful to the divers and technicians who participated in the field work: Ricardo Vera, Néstor Ortiz, Facundo Irigoyen, Fabián Quiroga, Julio Rua, Nicolás Battini, Claudio Nicolini, Yann Herrera Fuchs, Axel Schmid, Gastón Trobbiani and Alejo Irigoyen. Special thanks are

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given to Punta Ballena (https://www.puntaballena. com.ar) for logistical assistance in Puerto Pirámides. Field studies in Natural Protected Areas were done under permit (Nº 014- MTyAP-19). The present work was funded by Patagonia Inc. (grant award TF2002-089196), Rapid Ocean Conservation grant (Waitt Foundation-https://www.waittfoundation. org) and PICT-2018-0969 (ANPCyT- ARGENTINA). This is publication number 147 of LARBIM.

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Rigby PR, Iken K and Shirayama Y (eds.). (2007). Sampling biodiversity in coastal communities: NaGISA protocols for seagrass and macroalgal habitats. Kyoto: Kyoto University Press, pp. 160 Roelfsema CM and Phinn SR. (2009). A manual for conducting georeferenced photo transects surveys to assess the benthos of coral reef and seagrass habitats. Version 3.0. Brisbane: University of Queensland. Available at: https://epic.awi.de/id/eprint/31165/1/GPS_Photo_ Transects_for_Benthic_Cover_Manual.pdf, last accessed <7 February 2021>. Rossi JP. (2011). rich: An R package to analyse species richness. Diversity 3: 112–120. Sanamyan NP, Sanamyan KE and Schories D. (2015). Shallow water Actiniaria and Corallimorpharia (Cnidaria: Anthozoa) from King George Island, Antarctica. Invertebrate Zoology 12: 1–51. Sayer MDJ and Poonian C. (2007). The influences of census technique on estimating indices of macrofaunal population density in the temperate rocky subtidal zone. Underwater Technology 27: 119–139. Thompson AA, Lønborg C, Costello P, Davidson J, Logan M, Furnas M, Gunn K, Liddy M, Skuza M, Uthicke S, Wright M, Zagorskis I and Schaffelke B. (2014). Marine

Monitoring Program. Annual Report of AIMS Activities 2013–2014. Inshore water quality and coral reef monitoring. Report for the Great Barrier Reef Marine Park Authority. Townsville: Australian Institute of Marine Science. Available at: https://elibrary.gbrmpa.gov.au/ jspui/handle/11017/2975, last accessed <7 February 2021>. Ugland KI, Gray JS and Ellingsen KE. (2003). The species– accumulation curve and estimation of species richness. Journal of Animal Ecology 72: 888–897. Underwood AJ, Chapman MG and Connell SD. (2000). Observations in ecology: you can’t make progress on processes without understanding the patterns. Journal of Experimental Marine Biology and Ecology 250: 97–115. van Rein H, Schoeman DS, Brown CJ, Quinn R and Breen J. (2011). Development of benthic monitoring methods using photoquadrats and scuba on heterogeneous hardsubstrata: A boulder-slope community case study. Aquatic Conservation: Marine and Freshwater Ecosystems 21: 676–689. Williams ID, Couch CS, Beijbom O, Oliver TA, Vargas-angel B, Schumacher BD and Brainard RE. (2019). Leveraging automated image analysis tools to transform our capacity to assess status and trends of coral reefs. Frontiers in Marine Science 6: 1–14.

Routledge Handbook of National and Regional Ocean Policies Edited by Biliana Cicin-Sain, David L. VanderZwaag and Miriam C. Balgos Published by Routledge eBook edition, 2015 ISBN: 978-1-315-76564-8 682 pages To write a review in 2021 of a book first published in 2015 may seem like an unusual activity. The reasons for the delayed review are two-fold. Firstly, this review aims to test the continuing utility of the handbook, which endeavours to ‘provide succinct lessons learned and emerging best practices, which are directly relevant to the growing number of nations and regions that are also beginning to pursue integrated ocean policies’, and that ‘should be useful to governmental, non-governmental, and private sector practitioners involved in ocean and coastal management around the world, as well as to graduate and undergraduate students in marine and environmental policy.’ Secondly, this review aims to assess if, during the interregnum between the date of the book’s publication and now, the acknowledgement by the book’s contributors that ‘the pace at which management and governance of

the oceans is proceeding does not match the pace of the degradation of the marine environment and its resources’ has occurred, and to assess the impact of this on the ongoing utility of the handbook. The book is one of the main products of an international programme of research on national and regional ocean policies underwritten by philanthropic funding from the Nippon Foundation. The programme spanned from 2004 to 2007. During this time, the programme undertook two workshops in Tokyo and New York in 2004, and an international meeting, ‘The Ocean Policy Summit: International Conference on Integrated Ocean Policy: National and Regional Experiences, Prospects, and Emerging Practices’ (TOPS) in Lisbon in 2005. The aims of the programme were to: • ‘develop a framework for cross-national analysis of national and regional ocean policies, and for drawing lessons useful to other cases in other countries/regions’; • ‘carry out systematic comparative analyses of national and regional ocean policies in a selected number of countries/ regions on principles embodied, institutional arrangements, and other governance variables’; • ‘draw lessons from the comparative analyses and develop suggested guidance for other nations/regions contemplating national/regional ocean policy formulation and implementation’; and • ‘disseminate the results of the research work broadly’. The book was edited by three internationally recognised marine

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law and policy practitioners: Biliana Cicin-Sain, Director of the Gerard J. Mangone Center for Marine Policy and Professor of Marine Policy at the University of Delaware; David L. VanderZwaag, Professor of Law and the Canada Research Chair in Ocean Law and Governance at the Marine and Environmental Law Institute, Dalhousie University, Canada; and Miriam C. Balgos, Associate Scientist at the College of Earth, Ocean, and Environment, University of Delaware, and Program Coordinator for the Global Ocean Forum. The three editors were part of a sixty-strong mixture of international academics and practitioners in the areas of marine law and ocean policy. That pool included expertise from Australia, Brazil, Canada, India, Jamaica, Mexico, New Zealand, Norway, Philippines, Portugal, Russian Federation, United Kingdom, United States and Vietnam. Contributors to the book were also drawn from four regional organisations: East Asian Seas, the European Union, Pacific Islands and SubSaharan Africa. The contents of the handbook comprise twenty-one chapters and four appendices. The chapters are divided into: Part I: Introduction (Chapters 1 to 2); Part II: National Ocean Policies (Chapters 3 to 17); and Part III: Regional Ocean Policies (Chapters 18 to 21). The practice of, and research into, ocean governance continues to grow exponentially, with an increased interest in careers in this area by new entry job seekers. Since the publication of this book in 2015, there has been a significant interest in the development and application of

Book Review

doi:10.3723/ut.38.025 Underwater Technology, Vol. 38, No. 1, pp. 25–26, 2021

Biliana Cicin-Sain et al. Routledge Handbook of National and Regional Ocean Policies

marine policies by international bodies (e.g. Organisation for Economic Co-operation and Development [OECD]) and regional bodies (e.g. European Marine Board). The Group of Seven (G7) and the Group of Twenty-Two (G22) have all added marine policy objectives to their regular meeting agendas. In the case of the G7, this has been by means of The Future of Seas and Oceans Flagship Initiative that looks, amongst other things, at the governance of sustained observations of the ocean. In 2019, the G22 added the policy objective to achieve a net zero goal for marine plastics disposal in the world’s oceans. The book shows its strength as a useful handbook that provides applicable lessons learned and sources of pertinent best practices. In addition, its utility as a handbook still extends to both the practitioner and the student

of ocean policies at national and regional levels. The only weakness of the book is one that its authors acknowledged, which was described at the start of this review: that ocean policy issues have continued to grow apace, remaining ahead of states’ and regional bodies’ ability to formulate integrated and harmonised marine policies, and associated regulations to address these issues. Some examples of these emerging issues are: • managing ocean acidification; • controlling illegal and unregulated fishing on the high seas; • managing the impact of the exploitation of marine genetic resources; • achieving net zero in respect to marine litter; • managing the impacts of deep sea mining; • remediating the continued warming of the oceans giving

rise to the melting of the polar ice caps; and • managing the impacts of carbon sequestration in the oceans. Since the publication of the book in 2015, the world has seen increases in regional ocean geopolitical tensions. These events are and will impact on both national and regional ocean policies. This book still has a place in academic libraries and in individual practitioners’ bookcases. That said, in recognition of the book’s own acknowledgment of the need to keep up with the changes in the seascape of ocean policy issues, the authors and publishers should consider commissioning a second edition to cover these new issues. (Reviewed by Roland Rogers, FSUT Writer and Researcher in Ocean Governance)

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Educational Support Fund Sponsorship for Gifted Students in Marine Science, Technology and Engineering to meet industry’s critical shortage of suitably qualified entrants.

SUT sponsors UK and overseas students (studying in the UK and abroad) at undergraduate and MSc level who have an interest in marine science, technology and engineering. Students are supported who are studying subjects such as:

Offshore and Ocean Technology Subsea Engineering Oceanography Marine Biology Ship Science and Naval Architecture Meteorology and Oceanography The SUT annual awards are £2,000 per annum for an undergraduate, and £4,000 for a one-year postgraduate course. (Part-time postgraduate studies funding available.) As one of the largest non-governmental sources of sponsorship, the SUT has donated grants totaling almost half a million pounds to over 270 students since the launch of the fund in 1990.

For further information please contact us t +44 (0)20 3405 9035

e info@sut.org

or visit our website

www.sut.org

UT2 and UT3 The magazines of the Society for Underwater Technology

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UT2 covers a focused range of underwater subjects including offshore, marine renewables, subsea engineering, ocean resources, diving and manned submersibles, underwater science and robotics. The magazine is represented at all the many exhibitions around the world at which the Society both co-organises and attends. Furthermore, the magazine is distributed at the many subsea training courses that are organised by the Society, ensuring it reaches tomorrow’s engineers and technologists.

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It consists of the content of the print magazine UT2, greatly expanded with other information.

UT2 and UT3 are available online at http://issuu.com/ut-2_publication www.sut.org

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Organised by

Underwater Technology 38.1

Articles inside

Book Review Routledge Handbook of

Monitoring rocky reef biodiversity by underwater geo-referenced

Attenuation of airborne noise by wet and dry neoprene diving hoods

Non-linear finite element analysis of a Ti6Al4V/Inconel 625 joint

A Personal View... Sustainable ocean use