Development of Low Budget Survey Equipment and Techniques for Shallow Water Ecosystems: A Case Study of the Fal Estuary Seagrass beds
Clive Pollittt and Claire Eatock
Author’s biographical information Mr Clive Pollitt, FdSc Marine Science student. Falmouth Marine School. Falmouth, Cornwall, UK. clivepollitt@aol.com. Dr Claire Eatock. FdSc Marine Science lecturer. Falmouth Marine School. Falmouth, Cornwall, UK. Claire.eatock@falmouthmarineschool.ac.uk Claire Eatock is a lecturer and Clive Pollitt a foundation degree student at Falmouth Marine school. Clive is an engineer interested in promoting marine biology to the general public.
Falmouth Marine School Killigrew Street Falmouth Cornwall TR11 3QS United Kingdom Tel: 01326 310 310
1
Abstract Seagrass beds are one of the many shallow water benthic habitats that need to be regularly monitored. This project used the seagrass beds in the Fal estuary in Cornwall UK as a test case to develop inexpensive shallow water habitat surveying equipment that would be suitable for colleges and amateur conservationists. It came up with four devices; a simple glass bottomed box that could be mounted on the side of a boat; a video camera mounted on a long extending pole that could give close-up pictures of the benthos; a photo/video-quadrat made from industrial shelving material that could record statistical data for benthic habitats and finally an underwater towed video monitoring system that could be used to cover large benthic areas. With these pieces of equipment a successful baseline survey of the Fal estuary Seagrass beds was completed. Keywords Benthic, Survey, Seagrass, Volunteer Bio-monitoring.
Introduction
Surveying shallow marine benthic environments is important for conservation groups, environmental monitoring, water quality control, pollution monitoring and for monitoring global warming and ocean acidification. (Rhoads 2004) A large amount of marine life is within the shallow photic zone just beyond the shore and in the inter-tidal zone.
The costs associated with this type of surveying have become prohibitive due the sheer amount of area to be covered. This has resulted in large areas being infrequently surveyed, if at all, and environmental and planning decisions cannot be easily made with confidence if current coastal survey data is not available. An example of this is in the Fal estuary in Cornwall, England where a Special Area of Conservation (SAC) was established in 1992 as a result of the European Habitats Directive. The local harbor commissioners are one of the organizations who have been 2
made responsible for environmental monitoring of the estuary but have very little current data. This is a very typical situation in Britain and Europe at large. The reasons for this situation are the costs involved with environmental surveying which are often outside the budget of small environmental organizations. The Fal estuary was made a SAC largely because of the maerl and seagrass beds that are present within it. There is however very little current environmental habitat survey data available, the habitat map presently in use being more than 20 years old. (Kevan Cook, Lead Advisor, Marine, Truro, Natural England, personal communication, 23 September 2010)
Volunteer based monitoring programs have been designed and initiated by many organizations including Seagrass Watch, (McKenzie 2002) but many have found that these programs are difficult to sustain. This is largely due to the fact that most Seagrass is below the water for much of the time and qualified volunteer divers are required to do the surveying. (Short 2009) Different monitoring options are dependent on the structure and resources available, e.g. cumbersome methods are not practical for volunteer-based monitoring networks and also the adequacy of different methods for the various species, which requires knowledge of their growth rates and basic ecology. (Duarte 2003)
Many types of equipment have been used to overcome the difficulty of using professionally qualified divers. Professional surveying institutions often overcome this by the use of remotely deployed video equipment (Potts 1982), which has become a well established tool in many areas of marine research. (Holme 1984) Towed video sledge techniques provide a means to visually survey large areas of seafloor without the depth or time constraints usually associated with other techniques such as scuba diving. (Sisman 1982) In the past, techniques such as this have been used to monitor the condition of features in candidate Special Areas of Conservation (SAC) (Magorrian 1996) Towed video sledge data can 3
be used to estimate the relative abundance of benthic species using the Visual Fast Count (VFC) technique. (Kimmel 1985) The main disadvantage of the towed video sledge system is the potential damage it can cause to the fragile seafloor habitat that it is recording. (Grizzle 2008) An alternative is to have a Drop Down Video System (DDVS) which is a camera mounted on a frame, often associated with a quadrat. (Holt, Sanderson 2001) This is lowered to the seafloor where it remains stationary whilst recording the benthos. The position is given by a Global Positioning System (GPS) receiver and the equipment is then moved to a new location often on a pre-set transect. DDVS recording techniques have been used in a variety of applications and are appropriate for the identification of seabed habitats. (Sanderson et al. 1999) An underwater Remotely Operated Vehicle (ROV) is a self propelled underwater camera system often with artificial lighting capable of descending to depths unreachable by divers and is considered suitable for biotype surveying and monitoring. (Arbour 2004) The ROV is usually connected to a surface support vessel via a tether cable which controls the ROV’s movements and passes the underwater video image to the operator for control and recording purposes. Due to their maneuverability these systems are able to acquire great detail of the biotype. Together with GPS equipment and on-board recorders these systems combine the flexibility of a diver together with the advantages of remote control. The disadvantage of ROV, towed and drop down video systems is the expense of the equipment and of the support vessel, deploying equipment and tethers and the need for highly trained personnel. (Epstein 2010) These factors usually place these survey techniques out of the reach of small, low budget surveying organizations and volunteer initiatives. (Short 1984)
The purpose of this project was to develop inexpensive and safe shallow benthic surveying equipment using basic skills and the recent development of inexpensive high definition digital video cameras and recording equipment. The Seagrass beds in the Fal estuary were chosen as a test case. 4
1) Aqua-scope
The first device developed was built along the lines of a glass bottomed boat. (See figure1) This piece of equipment was a large wooden box 75cm high by 75cm long and 40cm wide. The bottom of the box had a glass water-proof window installed with handles and boat attachment points placed along the sides of the box. The inside was painted matt black and a removable top with an observation port were added. It was named the Aqua-scope.
Deployment When the boat had reached the right location to be surveyed the position and depth were taken using the boats onboard fish finder and GPS. The Aqua-scope was then placed in position over the side of the boat and secured with its fastenings. Viewing of the seafloor was simply done by looking into the viewing port. The boat was allowed to drift and the depth, GPS positions and benthos were noted as it did so. Still camera and video photography was possible with the camera placed at the viewing port or lowered to the glass pane where a very wide field of view was possible.
Results General observation underwater to a depth of 4 to 5 meters in bright, calm conditions was possible at slack low tide. (See figure 2) The Aqua-scope was successfully used to map the position of the major sea-grass beds in the Fal and in particular the St. Mawes Eelgrass meadow near the Fal entrance. Four surveys were conducted in the summer months of June, July and September and three during March using the Aqua-scope. It was also used in conjunction with the other surveying equipment developed in the project to help observe the performance and deployment of the equipment. 5
Materials and Costs (See table 1)
Capabilities and limitations The data collected by the Aqua-scope could be considered to be equivalent to the data obtained from surface snorkeling i.e. a general visual survey of areas of the seafloor where the benthos type , coverage and location could be observed and recorded manually. The main limitation of the Aqua-scope was the limited depth to which it can be used and the inability of the boat to maneuver with it deployed. Any movement by the boat against the tide resulted in turbulence and bubbles around the observation glass. The weather conditions had to be bright and calm and the survey had to take place during slack tide, preferably spring low tide, when the water had the lowest turbidity conditions. A suggestion for its improvement would be to have a more streamlined design with strong attachment points to the boat that would make limited maneuverability possible.
2) Scubar
In order to have a closer look at the benthos, and in this case the seagrass, observed with the Aqua-scope it was necessary to develop a simple video system that could get within centre meters of the seagrass. A simple all-in-one water-proof video head- camera (Oregon Scientific Action Camera ATC-3k) was mounted on a 5 meter fiberglass extending window cleaning pole and used to place the camera into the desired position below the boat. This system was called the Scubar.
The camera was set to record and its timer synchronized with the boats onboard clock along with the GPS position and depth. This was blind recording but worked well where the general
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condition of the seagrass was required. The footage recorded was analyzed in conjunction with the recorded depth and position afterwards by re-synchronizing the results.
An improvement of this system was to replace the head-camera with a waterproof closed circuit television (CCTV) camera that was connected to a boat mounted monitor and recorder via a long tether cable. A video monitor and a mini digital-video recorder were used. The monitoring and recording could be performed by a laptop computer with basic video recording web-cam software and video input adaptor. (The lap-top computer monitoring and recording system was used on the Delta-wing, see later) This allowed real time monitoring and a recording for later analysis.
Deployment
The Scubar was simply put over the side of the boat on arrival at the chosen survey location. The pole was extended to the required depth and held above the benthos by using the boats on-board depth meter and a graduated scale on the Scubar lowering pole. The Scubar was allowed to record the benthos for a preset time and then raised to the surface and the boat moved to the next location where the same procedure was repeated.
Results This system was very simple to use and required minimal set up and preparation. Being totally waterproof it was used on a small inflatable dinghy and canoe allowing access to areas not normally accessible to motorboats. This system was aided by the simultaneous use of the Aquascope to position and orientate the camera at the end of the pole. The CCTV system was more complicated, requiring external power for the monitor, camera and recorder. The length of the tether cable had an effect on the video signal quality and hence the recorded image.
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The Scubar was able to examine the outer limits of the Seagrass areas with more detail than with the Aqua-scope, when it was often unclear whether the seafloor coverage was seaweed or Seagrass. (See figure 3) The Scubar was able to positively identify the Seagrass and seaweed in these situations. Eight successful surveys of the Fal Seagrass beds were conducted with the Scubar in June, July, September and October in 2010 and in March 2011.
Materials and Costs (See tables 2 and 3)
Capabilities and Limitations The data collected by the Scubar could be considered to be equivalent to the data obtained from scuba diving down to 5 meters, i.e. a close visual survey of the seafloor where the benthos type, coverage and position could be observed and recorded manually in detail. The limitation of the Scubar was the inability of the boat to maneuver with it deployed. The boat was only able to drift with the tide, as to maneuver the boat with the pole extended, threatened to break the pole. A drifting transect was possible but not a preset transect. The Scubar had to be used as part of a fixed point survey method where it was deployed and recovered between preset way-points. Another limitation of the Scubar was the limited depth to which it could be used. Like the Aquascope, the weather conditions had to be bright and calm and the survey had to take place during slack tide, preferably spring low tide, when the water had the lowest turbidity conditions. The Scubar was also limited to the depth rating of the camera used. A suggestion for improvement would be for a sturdier pole with a boat mounting to hold it in position and a high definition camera with lighting to enable deeper surveys in darker conditions.
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3) Photo-quadrat.
In order to collect data that could be statistically analyzed a Photo-quadrat system was developed. This survey would traditionally be undertaken by a diver with a quadrat and possibly an underwater camera. The Photo-quadrat was a metal cage fitted with an underwater digital stills camera, connected to a remote triggering system. The cage was lowered to the seabed and the camera triggered from the boat above. The cage had a 0.5m square base and was one meter tall with a grid pattern built into the base. (See figure 4) It was constructed of galvanized metal “Dexion�, an industrial shelf rack system that can be used for construction of framework due to its narrow (3cm) L section, long lengths and its multiple pre-drilled mounting holes. The grid pattern was made of fine nylon cord that was laced at measured intervals along the bottom of the cage. The cage was held together with nuts and bolts through the multiple holes in the Dexion lengths. Small half Kilogram zinc weights were added to the base to provide better stability. The camera was mounted on the top of the cage using its tripod fitting and was positioned pointing towards the base. The trigger release mechanism was a small water-proofed electric solenoid positioned on the frame to activate the camera shutter via the solenoid’s plunger. (See figure 5) The solenoid was connected via a long cable connected to a 12v battery and activation trigger on the boat.
Deployment The camera was pre-focused on the Photo-quadrat base and lowered to the seafloor whilst the GPS position and depth were recorded from the boats instruments. Once the Photo-quadrat had reached the bottom, it was left for a couple of minutes for any disturbed sediment to settle and the camera trigger activated. The equipment was then raised to the surface and moved to the next point and the process repeated. 9
A further development of the Photo-quadrat was the substitution of the still camera with an underwater high definition (HD) video camera. This camera was attached to the Photo-qaudrat in the same way as the stills camera and lowered to the seabed. The camera was set to record before it was lowered as it required no trigger release mechanism and could be left on the seafloor unattached to the boat. The lowering rope could be tied off to a buoy on the surface for collection when the recording was complete. This system was very inexpensive and simple to construct and was easy to adjust for cameras of different focal lengths due the multiple fixing holes in the Dexion material.
Results The Photo-quadrat system allowed close inspection of the seabed in high definition still image snapshots but also close observation of the seabed in 10 minute video recordings showing transitions and activity during that time. The GPS position, its depth and other data could be recorded from the boats instruments as the Photo-quadrat was lowered. The grid pattern on the Photo-quadrat base allowed accurate data collection for quantitative statistical analysis. The percentage coverage could be measured together with individual measurement of leaf, rhizomes and flower size and quantity. (See figure 6)
Materials and costs ( See table 4)
Capabilities/ Limitations This system was successfully tested in two surveys in October 2010. A problem encountered with the still camera system was the camera lens became fogged from the sunlight when the Photo-quadrat was brought to the surface between deployments. This was remedied by placing a dark, wet towel over the camera when it was lifted clear of the water. Another problem encountered was that the rate of drift of the boat was often rapid, allowing insufficient time for 10
the sediment to settle around the Photo-quadrat before a photograph could be taken. This could be rectified by having a longer cable for the trigger release mechanism. The waterproof HD video camera system also suffered lens fogging problems between deployments and limited camera battery life. A large battery would be required for meaningful surveys.
4) Delta-wing
To overcome the boat maneuverability limitations of the Aqua-scope and Scubar, a towed video camera system was developed. This allowed continuous close-up monitoring of the seabed at greater depths, over a large area whilst travelling along a pre-set transect. This required a waterproof CCTV camera connected to a devise that kept the camera approximately a meter above the seabed. It was required to be stable when towed below the boat whilst being connected to a boat mounted monitor and recorder. It was important that the devise could give accurate GPS positions and depths of what was being recorded. In order for this to happen, the devise needed to be towed directly beneath the boat. This devise was named the Delta-wing. This system would give similar results to that obtained from an ROV system. The Delta-wing was a one meter triangular wing shaped piece of 6mm ply-wood with 30cm triangular vertical stabilizing fin and a 10 kg metal weight bolted to the underside of the wing. (See figure 7) The camera was mounted at the front of the wing and a tow rope attached in such a position that the Delta-wing pointed 30 degrees down from the horizontal when towed. The Delta-wing was tested using a lap-top computer to monitor and record the benthos. The depth of the Delta-wing was monitored from markings on the tether rope whilst the depth of the water and position and speed were measured using the boats onboard fish finder, log and GPS.
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Deployment The Delta-wing was lowered over the side of the stationary boat with the tether rope together with the electric cable. The depth of the Delta-wing was indicated by measurements on the tether rope. The lap-top video recording was started and the depth, position and times were all noted. The boat moved forward until the Delta-wing had orientated itself in the direction of travel and a steady course steered along a transect at approximately 4 kph.
Results Three successful transect surveys were conducted in March 2011 over the seagrass beds in the Fal Estuary at approximately a meter above the seafloor. The boat was moving at approximately 4 kph and good quality images could be observed and were recorded. The boat speed had to be adjusted when the Delta-wing was moved closer to the seafloor as the image on the monitor was moving too rapidly for accurate identification. The advantage of the system was that when a particular area of interest came into view the boat could stop for closer analysis and the Deltawing could even be lowered onto the seafloor. The Delta-wing orientated itself well in the direction of travel and could be positioned directly below the boat at 4 kph giving an accurate GPS position and depth. The Delta-wing could be used to cover large areas more rapidly by raising it to give a broader field of view and increasing the boat speed. An extra light was fitted to the Delta-wing but it was found to be unnecessary. The value of the Delta-wing was shown by the discovery of two other wise undetected seagrass beds. The Aqua-scope and Scubar were unable to detect these very small sparsely populated beds using the point survey system. The Delta-wing however using continuous recording was able to detect these thinly populated Seagrass beds easily amidst a large area of deserted seabed. (See figure 8)
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Materials and Costs (See table 5)
Capabilities/Limitations The Delta-wing was heavy and cumbersome to use. Lowering and raising it was strenuous work and the tether rope, electric cables and connections to the lap-top and battery were awkward. A boat with sufficient deck space was necessary. It was found that for extended recording the computer lap-top method of monitoring and recording was the most satisfactory however the laptop needed extra battery power. Connecting this particular lap-top to the boats 12v power source caused interference from the boats alternator which affecting the CCTV camera timing signal.
Overall equipment comparisons (See tables 6,7,8)
Discussion
In line with the project’s objective, it has been shown that inexpensive home built surveying equipment can be developed and used successfully for shallow benthic habitat surveying that could be performed by colleges, enthusiasts, clubs and boatmen to a scientifically robust standard. (Holt 2001) The costs can be kept low due to the use of equipment already available like under water cameras, lap-top computers and standard on board boat equipment like fish finders and GPS. Other factors not included in this report were the size and type of boats used, the fuel and boat costs, the detailed health and safety issues with each different system, the affect of time and seasons on the surveys and the qualifications of the participants in the project. The Aqua-scope was the most user-friendly, easiest to build and deploy and gave good enough results to establish a basic presence to a depth of 5 meters on sunny days at low slack tide. The 13
Scubar made it possible to refine the perimeters of the Seagrass beds and examine the general condition of the Seagrass but was more difficult to use. The Photo-quadrat produced quantitative data making it possible to perform statistics on the Seagrass beds and the Delta-wing made it possible to search larger areas for new Seagrass beds although it was the most complicated to use. The ability of the Delta-wing was proved by the discovery of two previously undetected seagrass beds. The surveys conducted during this project using this equipment developed has formed a baseline survey of the Fal estuary Seagrass beds that can be built upon by further use of the same equipment or for more detailed professional surveys in the future.
3691 words including abstract.
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References cited Arbour A. 2004. Applications for Mini-ROV sustems for coastal and estuarine monitoring. Alliance for coastal technologies. UMCES Technical Report Series: TS-463-04-CBL / Ref. No. [UMCES]CBL 04-128. (Novenber 2010. www.actus.info/download/workshop_reports/ACT_WR04-07_Mini_ROV.pdf )
Duarte CM. Krause Jensen D et al. 2003. European seagrasses: An introduction to monitoring and management. The M&MS project. ( November 2010; www.seagrasses.org)
Epstein J. 2010. Hawkes Unveils New ROV Class. Marine Technology reporter. October 2010. (November 2010. http://dwp.marinelink.com/pubs/nwm/mt/201010/ )
FHC 2011 . Falmouth Harbour Commissioners . (March 2011. www.falmouthport.co.uk)
Grizzle R E et al. 2008. Bottom habitat mapping using towed underwater videography: subtidal oyster reefs as an example application. Journal of Coastal Research: volume 24.
Holme N A. MacIntyre A D.1984. Methods for the study of marine benthos 2nd edn. Oxford: Blackwell Scientific Publications, for International Biological Program. [IBP Hanbook, no. 16].
Holt R. Sanderson B. 2001. JNCC Marine Monitoring Handbook March 2001, Procedural Guideline No. 3-5 Identifying biotopes using video recording. ( November 2010. www.jncc.gov.uk/PDF/MMH-Pg%203-5.pdf )
Kimmel J. 1985. A New species-time method for visual assessment of fishes and its comparison with established methods. Environmental Biology of Fishes 12. 15
Magorrian BH. Service M.1996. An acoustic bottom-classification survey of Strangford Lough, Northern Ireland. Journal of the Marine Biological Association of the United Kingdom 1995.75.
McKenzie L J. Campbell S J. 2002. Manual for Community(citizen) Monitoring of Seagrass Habitat – Western Pacific Edition. Seagrasswatch. Townsville. Australia. (November 2010. www.seagrasswatch.org/Methods/Manuals/SeagrassWatchWesternPacific_Manual.pdf )
Potts G W et al.1982. Scuba diver-operated low-light-level video system for use in underwater research and survey. Journal of the Marine Biological Association of the United Kingdom , 67.
Rhoads D C. Germano J D. 2004. Interpreting long-term changes in benthic community structure: a new protocol. Hydrobiologia Volume 142.
Sanderson et al. 1999. The Human Footprint and the Last of the Wild. BioScience . Vol. 52.
Short F T.1984. Seagrass-Watch Western Pacific Manual for Community (citizen) Monitoring of Seagrass Habitat .(November 2010. www.seagrasswatch.org)
Short FT.2009. SeagrassNet Final Report: 2005 – 2009. Seagrass-Watch. USA .(November 2010. www.seagrasswatch.org) Sisman D. 1982. The Professional Diver's Handbook. Submex. London .
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Figure 1. The Aqua-scope
Figure 2. View through the Aqua-scope.
C Pollitt 2010
C Pollitt 2010
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Figure 3. Seagrass recorded by the Scubar. C Pollitt 2010
Figure 4. Photo-quadrat with still waterproof camera. C Pollitt 2010
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Figure 5. Waterproof, still camera, trigger release mechanism.
Figure 6. Photo-quadrat picture.
C Pollitt 2010
C Pollitt 2010
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Figure7. The Delta-wing
C Pollitt 2011
Figure 8. The Delta-wing recording
C Pollitt 2011
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Table1. Materials and Costs of the Aqua-scope Material
Measurements
Used for
Number
Cost
Supplier
6mm, Exterior
Sheet, 1220cm
Aqua-scope
1
£30
Hardware
plywood
x 2440cm
body
Wood
250 ml
supplier. £4
Adhesive.
Hardware supplier
Everbuild 502 Pine
Glass pane
12mm x 12mm
Body
1
£10
Hardware
x 3m long
construction
6mm thick
Window
1
£10
Glazier
Aqua-scope
1
£6
Hardware
supplier.
60cm x 30cm Exterior white
1 liter
Gloss Paint Silicon Sealer
exterior 310 ml
Unibond 2580 Aluminum
Waterproofing 1
£8
window 15cm x 3cm
Handles 20cm
supplier.
Hand
supplier. 2
£5
Mounting 3m length
Boat
Hardware
Hardware supplier.
1
£10
C&S Non-
diameter
mounting and
ferrous
Aluminum
supports
metals. Metal
tube Matt Black
supplier 750 ml
Paint Wood screws
Inside Aqua-
1
£5
scope 12mm
Aqua-scope
supplier. 50
£10
Body Total cost
Hardware
Hardware supplier.
£98 21
Table 2. Materials and costs for the basic blind Scubar system Material
Measurements Used for/in
Number
Cost
Supplier
Extending
5 meters x
Underwater
1
£50
Window
Fibreglass
50mm
camera
cleaning
pole
diameter
mounting
suppliers
Head Camera 10cm x 5cn
Underwater
Oregon
image
equipment
recording
supplier
diameter
Scientific
1
£80
Sports
atc-3k Extra strong Cable ties
Total cost
30cm
Securing
5
£3
Hardware
camera to
supplier.
pole
Trago mills £133
22
Table 3. Materials and costs for the real time CCTV Scubar system Material
Measurements Used for/in
Number
Cost
Supplier
Extending
5 meters x
Underwater
1
£50
Window
Fiberglass
50mm
camera
cleaning
pole
diameter
mounting
suppliers
Swann
Color, 380 tv
Underwater
CCTV
lines, 1/3 inch
monitoring
camera
cmos. 12 v.
12v battery
12v
1
£30
Electronic security supplier
Powering
1
£15
cctv camera
Electronic supplier
7” color
Phono (RCA)
Monitoring
video
or s-video
cctv camera
Electroncs
monitor
compatible
images
supplier
DV recorder
2Gb Sd card
Recording
recording
CCTV
Electroncs
media.
images
supplier
20 meters
Transferring
3 core
1
1
1
£70
£70
Consumer
Consumer
£20
13 amp
images from
Electrical
mains cable
CCTV to
supplier
monitor.
B&Q
power Total cost
£255
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Table 4. Materials and costs of the Photo-quadrat Material
Measurements Used for/in
Number
Cost
Supplier
Galvanised
3cm L section
10 meters
£50
Industrial
Dexion
Frame construction
shelving
shelving
supplier
material Dexion nuts,
1 x 50 pack
Frame
bolts and
8mm x 15mm
construction
1x 50 pack
£10
shelving
washers
supplier
12v car door
12v, generic
Remote
locking
20mm plunger
shutter
solenoid
travel
activation
2 Core,
7 meters
Remote
5 amp cable
10 mm
Industrial
10 meters
1
£10
Car parts supplier
1
£10
Electrical
shutter
supplier
trigger
B&Q
Deployment
1
£10
Hardware
diameter
of Photo-
supplier
nylon rope
quadrat
B&Q
Zinc weights
0.5 kg
Frame base
4
£10
stabilization 12v battery
12v, 1ah
Solenoid
supplier 1
£15
power Total cost
Hardware
Electronics supplier
£115
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Table 5. Materials and costs of the Delta-wing Material
Measurements Used for/in
Number
Cost
Supplier
6mm
1 meter square
1
£10
Hardware
plywood
Delta-wing body and fins
Zinc
10 Kg – Boat
stabilization
Weights
engine anode
and ballast
Swann
Color, 380 tv
Underwater
CCTV
lines, 1/3 inch
monitoring
camera
cmos. 12 v.
12v battery
12v , 1ah
Powering
supplier 1
£30
Boat Chandler
1
£30
Electronics supplier
1
£15
cctv camera
Electronics supplier
7” colour
Phono (RCA)
Monitoring
video
or s-video
cctv camera
electronics
monitor
compatible
images
supplier
DV recorder
2Gb Sd card
Recording
recording
CCTV
electronics
media.
images
supplier
20 meters
Transferring
3 core 13A cable Galvanised
1
1
1
£70
£70
£20
images 3cm L section
Dexion
Frame
Consumer
Hardware supplier
0.5 meters
£2.50
construction
Industrial shelving
shelving
supplier
Dexion nuts,
I x 10 pack
Frame
bolts and
8mm x 15mm
construction
1x 50 pack
£2.50
Industrial shelving
washers Total cost
Consumer
supplier £250 25
Table 6. Comparison of Aqua-scope with Snorkeling Aqua-scope
Snorkeling
Advantages
Disadvantages
Costs
Advantages
Disadvantages Costs
General
Boat
ÂŁ98
General
Trained and
Snorkel
visual
Maneuverability + boat
visual
Qualified
equipment
benthic
when deployed
survey of
personnel
ÂŁ30
the seafloor
required.
survey Minimal
Weather and
Can be
Stringent
Health and
tide dependant
conducted
health and
safety, and
from the
safety and
insurance
shore
insurance
requirements
requirements
No formal
Limited field of
Wide field
Position and
training.
view.
of view
depth
Large groups
recording
possible
difficult
Simply
Requires
adaptable for
under water
non-
photo and
waterproof
video
video/ photo
recording
recording
equipment Weather and tide dependant
26
Table 7. Comparison of the Photo-quadrat and a diver quadrat survey Photo-quadrat Advantages
Diver Quadrat Disadvantages Costs
Advantages
Disadvantages Costs
Accuracy
Stringent
ÂŁ1000 for
Minimal
ÂŁ115
Health and
without still
health and
basic diving
safety, and
or video
safety and
package
insurance
camera
insurance
requirements
requirements
No formal
Blind quadrat
Preset
Trained and
training
positioning
quadrat
Qualified
required
and
positioning
personnel
orientation
and
required.
orientation Large groups
large groups
possible
difficult.
Weather and
Weather and
tide
tide
dependant
dependant
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Table 8. Comparison of the Delta-wing and an ROV Delta-wing
ROV
Advantages
Disadvantages
Costs
Advantages
Disadvantages Costs
Easily
Depth
£250
Highly
Professional
£60 000
deployed by
limitation
accurate data
trained and
initial cost .
untrained
gathered and
qualified
Rental £1000
personnel
recorded
personnel
per day
required
including operator
Accurate,
Limited
Highly
Professional
recorded
maneuverability
maneuverable
Personnel
data
hire £300 per day
Suitable for
Suitable for
detailed and
detailed and
extensive
extensive
surveying
surveying
Can be
Can achieve
modified for
great depth
other camera
surveys
systems
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