Researching the Reefs

Researching the

Reefs Dive into the world of marine conservation

Matthew G. Bassett

Reefs at Risk.................................................................................11

Coral Reef Biology..................................................................... 15

Support Systems & Threats.................................................... 20

A Delicate Balance................................................................... 26

Caribbean Reef Research.......................................................33

Challenges & Opportunities................................................... 39

Reef Health Check................................................................... 44

Dying Diadema.........................................................................52

Taming The Lion..................................................................... 64

Future Prospects.......................................................................76

Additional Resources.............................................................. 80

Further Reading......................................................................... 80

Technical Details....................................................................... 86

Acknowledgements................................................................. 88

Section 1

[6] Reefs at Risk

Section 1

SECTION 1

REEFS AT RISK Coral reefs exhibit some of the richest diversity of life in the world, providing a home to a myriad of weird and wonderful species, a tourist economy of almost unrivalled scale, and countless ecosystem services. Sadly these colourful, life-filled, charismatic systems are also amongst the most fragile in the world; and under greatest threat. The narrow window of conditions under which they can survive, dependence on other ecosystems to keep these conditions stable, and the apparent determination of humanity not to change our ways, are all contributing to this increasing fragility.

For the many people who dive on these beautiful reefs, the issues are well known and hotly debated. For the many more who either haven’t had the opportunity, or unfortunately do not care enough, they are hidden from view. Imagery therefore, is more important than ever in bringing these issues into the public eye. High profile media commentators such as David Attenborough and National Geographic magazine have done a great deal to highlight the risks, but more needs to be done if these unique systems are to be saved.

Reefs at Risk [7]

Section 1

[8] Reefs at Risk

Section 1

Like all damselfish, the bicolour damselfish (Stegastes partitus) is fiercely territorial, swimming aggresively at all who approach its home; in this case a small Agaricia tenuifolia coral.

Reefs at Risk [9]

Section 1

[10] Reefs at Risk

Section 1

Coral Reef Biology Coral reefs are truly remarkable systems, starting with tiny cnidarian polyps and building over centuries.

Individual corals slowly excrete calcium carbonate, growing to huge sizes and creating intricate structures; all eventually coming together over thousands of years to form large reef systems.

Corals are filter feeders, but of the energy they require, around 90% is produced by other means. Microscopic algae known as zooxanthellae make their home within the coral; in this mutually beneficial relationship, the corals receive food from the photosynthesising algae, while the zooxanthellae gain shelter.

Corals require a narrow range of specific conditions in order to thrive including a temperature (optimum growth occurs between 26-28°C) and clean, clear, oligotrophic saltwater (low in nutrients); if the nutrient concentration was high, the algae would bloom and smother the corals. Any dramatic or prolonged change to these conditions makes it incredibly difficult for the corals to survive.

The global coral reef area has been estimated at around 255,000 km2, but this has undoubtedly decreased over the last decade. Although taking up only a tiny portion of the oceans, they are home to a staggering proportion of its biota; estimates of the species diversity range from just under 600,000 to well over 9 million.

Regardless of the accurate number, coral reefs are highly significant ecosystems of global importance.

Reefs at Risk [11]

Section 1

Banded coral shrimp (Stenopus hispidus) taking shelter in a barrel sponge.

[12] Reefs at Risk

Section 1

Reefs at Risk [13]

Section 1

[14] Reefs at Risk

Section 1

French angelfish (Pomacanthus paru) are curious fish and will often approach divers to take a closer look.

Reefs at Risk [15]

Section 1

Support Systems & Threats When discussing coral reefs, it is often easy to get

complexity, distance from the coral reef, and relatively

carried away with the reef itself and forget about

turbidity of the water provides prey species with

the other habitats that contribute to the wellbeing

excellent protection from predators. When combined

and continuation of reef systems. For example,

with an abundance of food, this forms a perfect nursery

mangrove forests (or mangles) and seagrass beds are

environment for juvenile fish.

commonly associated with coral reefs. Significantly, the biodiversity of reefs associated with these related

Whilst clearly vital to reef health, both systems are

systems is significantly greater than on reefs without

under serious threat from deforestation in response to

these supportive habitats.

real-estate development and the expansion of intensive shrimp farming.

It is rare to see trees living so close to the sea due to the high salt content of the surrounding water. Mangroves

In addition to these conflicts with economic

are biological marvels, thriving in these most extreme

development and responses to stress induced by

of conditions. They have developed unique ways of

climate change, increased tourism and intensity of

dealing with the salt concentration, and often oxygen-

diving are also adding to the pressures on these visually

depleted soils, that comprise their habitat. These

and biologically spectacular ecosystems. Around the

include adaptions such as weird and wonderful root

Honduran island of Utila, it is common to see broken

shapes that reach up from the anoxic mud, leaves that

sponges caused by a careless fin kick, petrol leaking

appear to be frosted as they excrete the unwanted salt,

from boats, and plastic that may have drifted from the

and floating seeds (called propagules) that will only

mainland, or even from a local bin that was blown over

germinate when conditions are perfect.

in the wind. Even those who just paddle in the water may be causing harm; sunscreen is incredibly toxic to

Mangroves, along with seagrass beds, provide vital

corals, negatively affecting their growth when it washes

services to their associated coral reefs; their structural

off the skin of divers and beachgoers.

[16] Reefs at Risk

Section 1

The island of Utila has extensive mangrove forests, but deforestation has caused fragmentation into smaller mangles, like this one.

Reefs at Risk [17]

Section 1

Building on mangroves not only destroys these vital systems, but creates a huge amount of waste.

Whilst problematic, the issues caused by tourism tend

These conditional changes are highly stressful for the

to be localised and manageable, while the threats from

corals and, in severe cases, can lead to coral bleaching;

climate change are global and severe. Most of these

the zooxanthellae are expelled and the white calcium

climatic threats limit the conditional range in which

carbonate skeleton becomes exposed. Bleaching

corals can survive. Whilst these conditions have been

evolved as a short-term stress response; the coral

relatively stable since corals evolved, more recent

taking in stronger zooxanthellae that are better suited

changes are resulting in critical adjustments.

to the new conditions. However, with the increasing pace of climate change, raised sea temperature events

One obvious threat is that from rising sea temperatures;

are becoming more protracted and corals are invoking

As corals struggle to survive far outside their optimum

the bleaching response more frequently, often proving

growth temperature range of 26-28°C, the current

irreversible. This repetitive bleaching is becoming

predictions that sea temperatures may rise by at least

more common on reefs worldwide, causing high

4°C by 2100 will, if proved correct, result in widespread

mortality rates; reefs that were thought to be eternal

losses. Perhaps not so obvious, is the risk of rising

are fading fast. During 2016, Australia’s Great Barrier

acidity of the oceans caused by increasing carbon

Reef, the earth’s largest reef system, was decimated by a

dioxide levels in the atmosphere leading to higher

bleaching event so severe that many of the corals have

levels of CO2 dissolving in seawater. So, for organisms

yet to recover. Estimates suggest that 70% of shallow

such as coral, with structural skeletons comprised of

water coral had died in some areas and the longer-term

calcium carbonate, which readily dissolve in acidic

impact on the wider marine ecosystem has not yet

conditions, this acidification has the potential for

been determined.

catastrophic consequences.

[18] Reefs at Risk

Section 1

This development, currently just two villas, plans to extend further into the mangroves, destroying a habitat vital for reef health.

Reefs at Risk [19]

Section 1

Litter is one of the more obvious threats to reef systems. High winds and lidless bins exacerbate the problem.

[20] Reefs at Risk

Section 1

Reefs at Risk [21]

Section 2

SECTION 2

A DELICATE BALANCE

[22] A Delicate Balance

Section 2

A Delicate Balance [23]

Section 2

This Acropora cervicornis has healthy tips, but the darker patches are evidence of the plight of the reef as algae slowly takes over in a phase shift.

[24] A Delicate Balance

Section 2

Despite the vast range of life supported by the reefs, changes to the species composition can completely upset the delicate ecological balance.

Ecosystems undergo phase shifts when their core species, or group of species, changes. On coral reefs, a common change is from coral-dominated to algaedominated systems. Unfortunately algae-dominated reefs are much simpler structurally; less diverse, and much less ecologically and economically viable.

Phase shifts often occur when keystone species (important species that provide a vital service to the system’s survival) are removed from the system. Many of the keystone species on reefs are grazing animals, which feed on algae, keeping them at levels where they don’t bloom, smother the corals, and take over. If these species are removed, algal growth is no longer regulated; the reef undergoes a phase shift, becoming much less diverse in the process. Whilst the keystone grazers do limit algal growth, corals also depend on the low nutrient levels in the surrounding water. Removing systems, which effectively filter these nutrients (e.g. mangles and seagrasses), allows nutrient-rich water from the land to flow unhindered onto the reef. This enriched water provides ideal conditions for algal growth, and so an algae-dominated system develops at the expense of the coral. Whilst such phase shifts may be reversible, research and monitoring efforts must be continued to understand the complex interactions and evaluate solutions.

A Delicate Balance [25]

Section 2

[26] A Delicate Balance

Section 2

A Delicate Balance [27]

Section 3

[28] Caribbean Reef Research

Section 3

SECTION 3

CARIBBEAN REEF RESEARCH

Caribbean Reef Research [29]

Section 3

[30] Caribbean Reef Research

Section 3

Researcher Saskia van Dongen records measurements on reef health, adding to the extensive database of temporal data recorded in previous years.

Caribbean Reef Research [31]

Section 3

Lectures are part of the daily routine of the school groups that visit the research site.

A shady spot and quiet afternoon presents the perfect opportunity to catch up on data entry; an essential part of life on a research station.

The Mesoamerican Barrier Reef System (MBRS) runs

Education is one of the most important tools in the

throughout the Caribbean, stretching over 1000

conservationist’s arsenal, and Opwall gives high school

kilometres, and is one of the largest in the world,

and university students from around the world the

second only to the Great Barrier Reef of Australia.

opportunity to learn about, and contribute to, research

Whilst perhaps not as diverse as the Indo-Pacific’s

programmes addressing issues affecting the world’s

super-diverse coral triangle, it still boasts a vast range

fragile ecosystems.

of species. Unfortunately, in the last few decades the MBRS, along with many global reef systems, has been

One of the many sites studied by Opwall is the

under serious threat from climate change, overfishing,

Honduran island of Utila. Situated within the Bay

phase shifts, and invasive species. These threats have

Islands Marine Park, Utila boasts impressive fringing

led to many of the reefs that make up the MBRS to

reefs that are home to an extensive diving culture and

become critically degraded.

a thriving tourist economy. Opwall has several longterm monitoring projects centred on understanding

The threats facing coral reefs across the world need

the complex ecological processes on the Caribbean

urgent attention. Globally, teams of scientists are

reefs; controlling the spread of invasive lionfish species,

working tirelessly to learn as much as they can about

barriers to recovery of the long-spined sea urchin

the reefs and the threats they face in order to halt the

(Diadema antillarum), fish population health, and reef

advancing threat of extinction. One such organisation

complexity. All these projects are led by a group of

is Operation Wallacea (Opwall); this British company

dedicated scientists, passionate about protecting the

sends out teams of scientists to some of the most

reef for future generations.

biologically interesting ecosystems in the world.

[32] Caribbean Reef Research

Section 3

Caribbean Reef Research [33]

Section 3

Work carries on above the water as quadrats are prepared for the next dive

Waterproof transect tapes are essential equipment for marine research

[34] Caribbean Reef Research

Section 3

Challenges & Opportunities It is said that we know more about space than we do

that can be completed during a single dive. Methods

about our own oceans; we have even mapped more

allowing extended dive time and depth beyond that of

of the moon’s surface than our own seas. Despite

recreational limits, such as rebreathers and technical

this, marine research is making steady progress; our

diving, are highly specialised and so require expensive

understanding of the complex interrelationships in

training and equipment. In response, researchers are

these ecosystems is improving as research techniques

constantly developing new equipment. Most is not

are developed and refined.

necessarily research-specific, but relies on adapting newly developed leisure equipment. For example, the

In marine research’s infancy, boats and trawls allowed

advent of action cameras such as GoPros, has meant

scientists to gather basic data on the marine world, but

techniques such as stereo-video surveys, 3D modelling,

it was the advent of scuba (Self Contained Underwater

and behavioural studies have suddenly become much

Breathing Apparatus) that allowed the field of marine

more accessible and affordable.

research to make real progress. Being able to stay submerged and take measurements in situ allowed

Whilst apparently simple, assessing moving fish in the

scientists to achieve a new level of understanding of

3D marine environment presents practical challenges.

the marine world.

In particular, the distorting effect of light underwater can lead to inaccurate results when filming transects,

Life on a marine research station requires a certain

as fish may appear closer or further away depending on

level of inventiveness; resources may not be as readily

conditions. To counteract this distortion, researchers

available as in a university research lab. Projects that

use two cameras in a technique known as stereo

may have progressed smoothly at home may not

video surveying (or SVS). Twin recordings are made

necessarily go as well on site. Resourceful scientists

across transects by divers reeling out a transect tape

may also need to respond to a range of practical

behind the camera to reduce the disturbance to fish.

challenges resulting from working in remote and

Then, when the recordings are analysed back in the

challenging environments, often having to deal with

laboratory, the two videos are arranged side-by-side

broken equipment and technical faults.

using specific software. When a fish appears and is detected in both videos, the software then makes a

Whilst there are significant differences of course,

more accurate measurement than would be possible

conducting research underwater has many parallels

using only a single recording. Whilst early attempts

with terrestrial investigations. Both are heavily reliant

with this technique were burdened with heavy,

on transects; measuring and collecting data within

cumbersome, and expensive equipment, the reduced

a defined area. However, differences appear as the

weight of action cameras has made SVS a much more

time and depth constraints inherent in diving begin to

accessible and practical technique for both research

limit activities; notably air supply restricting the tasks

and on-going monitoring.

Caribbean Reef Research [35]

Section 3

[36] Caribbean Reef Research

Section 3

Black margate (Anisotremus surinamensis) schooling around a coral bommy.

Nearing the end of the dive, researcher Gina Wright reels back in one of the many transects needed for the stereo-video surveying.

Stereo-video equipment has advanced in recent years.

The smaller system at the front is much easier to use, compared to the larger, more cumbersome camera system behind.

Caribbean Reef Research [37]

Section 3

[38] Caribbean Reef Research

Section 3

Researcher Adam Southern untucks a transect tape from the reef whilst his student reels it in on completion of a dive.

Caribbean Reef Research [39]

Section 4

SECTION 4

REEF HEALTH CHECK

[40] Reef Health Check

Section 4

Reef Health Check [41]

Section 4

In addition to detailed research on specific issues, scientists are also checking developments on reefs over the longer-term. Monitoring animal populations and tracking the changing composition of the reefs are particularly important in assessing reef health and providing early warning of any developing problems.

Key indicators of reef health are the number, diversity, and size of fish populations. Diverse populations with high numbers of large species indicate that a reef is healthy; those with large sharks, groupers and other predators are much more dynamic than those without.

Monitoring these populations over a long period of time provides consistent and large datasets, which can provide a baseline for many of the other projects being studied by scientists. For example, invasive lionfish numbers can be plotted against current and historic fish populations to make inferences about their overall impact and the effect of any interventions.

In the past, unless scientists had access to particularly sophisticated and expensive equipment, techniques used to measure complexity of a reef system were relatively basic. Ecologists often use a basic measure of complexity known as rugosity; a rough estimate of the amount of habitat space available for both sessile and mobile organisms. Traditionally it was measured by placing a chain of known length (usually one metre) on the reef. As the chain fell into the troughs and depressions in the seabed, its overall length would shorten and could then be recorded when the chain was subsequently removed and straightened.

Habitat assessment scores (or HAS) are also standard ecological evaluations, made without specialised equipment, to produce assessments of key indicators including rugosity, variety of growth forms, average height, size of refuges (holes or gaps), how much is covered by life, and percentage of hard substratum.

HAS scores are standardised as much as possible, but there is a significant amount of researcher bias, so steps are being made to improve the accuracy of these complexity studies.

[42] Reef Health Check

Section 4

Student Duncan O’Brien films a quadrat as part of his undergraduate dissertation into 3D modelling of the reef.

Reef Health Check [43]

Section 4

Student Sophie Carolan measures the rugosity of the habitat within a quadrat.

Students record data for their dissertation projects, hoping to answer questions about reef complexity and 3D modelling.

In recent years, efforts have been made to improve techniques, again by utilising new equipment such as action cameras with sophisticated computer software, and combining this with traditional and proven methods of sampling using quadrats. This approach has drastically improved complexity studies by allowing quick and relatively simple modelling of reefs. The actual methodology of the technique is relatively straightforward, allowing multiple quadrats to be surveyed within the limited dive time available.

•

Two metre squared quadrats made from PVC

•

piping are placed on the reef.

Back in the lab, individual images (or frames) are taken from the video and aligned using specialised modelling software to create a

•

The quadrats are then filmed with an action

model of the reef surveyed within the quadrat.

camera; starting from the bottom left corner, divers swim up and down the quadrat until the top right corner is reached.

•

This model allows the researcher to calculate rugosity, but also more detailed complexity measures to reveal further information on the

•

The divers then turn 90 degrees and film the quadrats again swimming at right angles to the previous path.

[44] Reef Health Check

reef composition

Section 4

Reef Health Check [45]

Section 4

[46] Reef Health Check

Section 4

Reef Health Check [47]

Section 5

SECTION 5

DYING DIADEMA

[48] Dying Diadema

Section 5

Dying Diadema [49]

Section 5

One keystone species in the Caribbean receiving significant research attention, is the long-spined sea urchin (Diadema antillarum); so-called because of the exceptionally long black spines that grow from the test (main spherical body), which provide protection from predators, such as Panulirus argus (the spiny lobster).

D. antillarum occurs as three distinct colour morphs: black, black and white, or white. When present in large numbers, these echinoderms consume huge quantities of macroalgae, preventing excess growth and creating conditions favouring the growth of hard corals. Hard corals create reef areas with high species complexity, resulting in much healthier reef systems. If the algae are not controlled, major phase shifts occur that impact this ecological diversity; often dramatically.

In the 1980s, populations of D. antillarum in the Caribbean were decimated by an unknown pathogen.

Local losses of up to 99% caused catastrophic changes to their associated reef habitats. The species occupies an important ecological niche as a prolific grazer.

So, following mass mortality caused by the disease outbreak, growth of algae became virtually unregulated.

Monitoring assessments showed that following the epidemic, macroalgal cover increased by up to 70% at the expense of coral. Furthermore, studies conducted prior to the mortality event reinforced their ecological importance as a keystone species; experimental removal of D. antillarum from a reef study area resulted in a reduction in primary productivity of 20-40% within just five days.

[50] Dying Diadema

Section 5

Researcher Natalie Lubbock collecting temporal data for her research on Diadema antillarum

Dying Diadema [51]

Section 5

Diadema antillarum unwisely sharing its shelter with the spiny lobster (Panulirus argus), one of its main predators.

[52] Dying Diadema

Section 5

Dying Diadema [53]

Section 5

Equally worrying, is the observation that populations

in other taxonomic groups. Typical UVC records

of urchins have still not recovered from the mass

for this research include the four main herbivore

mortality event. Several hypotheses have been

groups competing with D. antillarum (surgeonfish,

advanced to explain this phenomenon including

damselfish, butterflyfish, and parrotfish) and the three

increased competition, predation, and changing

main predator fish groups (triggerfish, grunts, and

food composition. Since reefs with both fish and

wrasse). Since competition for space and food may

urchin grazers have greater productivity and greater

be a contributory factor in population recovery, other

biodiversity than those with only fish grazers, the

urchin species competing directly with D. antillarum

resulting change from coral-dominated to algae-

are also recorded, notably common, slate pencil,

dominated systems is reducing biodiversity, ecosystem

boring, west Indian sea egg, and jewel urchins. One

function, and productivity throughout the Caribbean.

of the predators of D. antillarum, the spiny lobster, has not been recorded routinely in the past because of it

This seeming inability of D. antillarum to recover from

challenging behaviour (rapid mobility and nocturnal

the mass mortality event has focussed research efforts

habit). However, its importance as a prolific predator

by the research team on Utila to understand these

has led to inclusion in the current year’s programme.

unknown barriers to urchin population recovery. A long-term monitoring project is studying the different

Specific research work is investigating the contribution

components that may be contributing to the problem;

of reef complexity as a barrier to recovery of D.

focusing particularly on competition, predation, and

antillarum. Low reef complexity, as determined by

reef complexity.

habitat assessment scores, is generally an indication of lower reef biodiversity. So for D. antillarum, which

Monitoring techniques for these studies involve

uses cracks and spaces within the reef to hide from

recording observations along 50m transects established

predators, low reef complexity could be a significant

on the reefs. For specific research on aspects of

factor hindering population recovery. Similarly, reef

competition and predation, underwater visual surveys

resilience is being monitored by studying juvenile

(UVC) are conducted to record target organisms

coral recruits. Defined as any coral less than 4cm

[54] Dying Diadema

Section 5

Researcher Saskia van Dongen collecting temporal data on Diadema antillarum with help from Operation Wallacea students.

Dying Diadema [55]

Section 5

in diameter, these are the species that would ensure

of morphological type (colour), test size, oral cavity

the reef’s continued existence in the event of a major

diameter, and weight. Since genetics is a relatively

tropical storm or other large disturbance event. These

new area of study, it is not yet known which part of the

studies of reef structure, when combined with records

urchin is best suited for testing. So genetic testing is

of D. antillarum abundance and population structure,

currently being evaluated on samples from spines, soft

will hopefully shed light on the causes of the rise and

tissues, and tubular feet. It is unknown whether the

fall of this keystone species.

colour morphs contribute to the ability of population to bounce back from catastrophic events, but preliminary

For effective research into barriers to recovery from

observations indicate a higher percentage of white

mass mortality, it is important to compare results

forms of D. antillarum in Banco Capiro than on Utila.

with a stable population. Parallel studies are therefore

So this ongoing research is attempting to determine

being undertaken on another reef system, Banco

whether there are there are morphological and genetic

Capiro, located 8 km offshore from the bay of Tela,

differences between populations at the two sites.

approximately 60 km from Utila. D. antillarum populations are much more stable there than those

Looking further ahead, an exciting new research

seen on many other Caribbean reefs. Operation

project into reef complexity has just begun. This long-

Wallacea is using this site to investigate why

term study involves the installation of artificial cement

populations are so successful there compared with

caves at depths of about 10m on the reef where D.

other Caribbean sites, more specifically Utila, and to

antillarum are rarely found. It is hoped that increasing

act as a benchmark for studies on factors influencing

the complexity of the reefs at these depths will entice

population recovery. In parallel with this ecological

D. antillarum to recolonise these areas of the reef, and

research, Opwall is also conducting detailed studies to

reveal further insights into the role of reef complexity

gain greater understanding of the anatomy, physiology,

on population recovery.

and genetics of the urchins, including comparisons

[56] Dying Diadema

Section 5

Artificial cave placed on the reef to increase complexity, in hope that it will aid the recovery of Diadema antillarum

Researcher Natalie Lubbock collecting Diadema antillarum, assisted by an Operation Wallacea student

Dying Diadema [57]

Section 5

[58] Dying Diadema

Section 5

Artificial caves housing Diadema antillarum.

It is hoped the urchins will stay at this depth and start to recolonise other areas of the reef.

Dying Diadema [59]

Section 6

SECTION 5

TAMING THE LION

[60] Taming the Lion

Section 6

Taming the Lion [61]

Section 6

In 1985, a fisherman off the coast of Florida reported a strange catch; during subsequent years, more and more sightings of this strange new fish were being reported. By the late 1990’s and early 2000’s, this new arrival had established populations along the Atlantic Coast of the United States as far as North Carolina.

By 2010, two species of lionfish (Pterois miles and P. volitans) had spread rapidly through the Caribbean, and were wreaking havoc on its reefs. Whilst they are now thoroughly established, substantial research effort is being directed at curbing their impact.

Several theories have been proposed to explain how they became established so readily. Some have suggested introductions were caused by discharged ship ballast water containing viable eggs, or mature lionfish may have been unintentionally introduced to non-native areas. In reality, the most likely cause is accidental or deliberate release from aquaria. Lionfish are popular, charismatic aquarium fish, but they are voracious predators. Once owners realise they have nothing in their aquaria except single, happy, and fat lionfish, they will probably be less inclined to keep them. There are reports of lionfish escaping during the chaos caused by Hurricane Andrew, a Category 5 Atlantic hurricane that struck South Florida in August 1992, but these reports have been widely contested.

Introducing any non-indigenous species to a new area is potentially catastrophic. The consequences of the lionfish invasion have been dramatic, and the delicate ecological balance on Caribbean reefs has been seriously disrupted.

[62] Taming the Lion

Section 6

Lionfish like to hide away within the reef, so divers hoping to spear the invasive fish have to look everywhere

Taming the Lion [63]

Section 6

[64] Taming the Lion

Section 6

Although smaller groupers, such as this graysby (Cephalopholis cruentata), are commonly seen on Caribbean reefs, overfishing of the larger groupers may have been instrumental in the success of the invasion, removing competition for the new fish.

Taming the Lion [65]

Section 6

In their native ranges, Lionfish are under pressure from

reach sexual maturity. In areas of reduced predation,

predation, disease, and competition. It is therefore in

populations of R-selected species such as lionfish can

their best interests to eat as much as possible to reach

therefore increase dramatically.

sexual maturity quickly and start producing young.

Avoiding predators and dealing with competition

Invasive species often have advantages in a new

means they cannot feed constantly. However in

environment because they are unfamiliar to existing

their new invasive ranges, the absence of specific

residents. Usually, predators and prey species develop

predators and consequent need to avoid predation

selective behaviour and learn to choose safe food

means lionfish are reaching sexual maturity quicker

while avoiding harmful alternatives. Lionfish display

than normally expected in their native ranges. This

venomous spines and bright aposematic colouration to

lack of predation has also allowed invasive populations

warn potential predators of the danger; so established

to breed at a rate many times greater than their native

reef predators in their Indo-Pacific territory avoid

relatives, spawning every four days throughout the

them. Conversely, however, prey species in their new

year, and producing around 2 million eggs annually.

Caribbean ranges have not yet learnt that lionfish

Lionfish are therefore exhibiting a life history strategy

are predators. As an example, local damselfishes

known as R-selection; giving birth to many offspring

(Pomacentridae) are a highly territorial group, and often

whilst showing little, if any, parental care. This

swim aggressively at divers when they get too close. As

approach contrasts with K-selected organisms, shown

they are unaware of the predatory danger from the new

by mammals such as humpback whales, which

invader, this behaviour often leads to their downfall;

produce few offspring but stay with them until they

they attack the lionfish with fatal consequences.

[66] Taming the Lion

Section 6

Public dissections are a great way to spread the word about the problem of lionfish, and get others involved in the research that’s taking place.

Prior to the lionfish invasion, relatively little was

a food source. Examples were reported of aggressive

known about their biology and life history strategies.

attention from sharks approaching divers, and even

Whilst native to the Indo-Pacific, with a reputation as

moray eels taking lionfish directly from spear guns.

voracious generalist predators, surprisingly little was known about the natural enemies in their home range.

Due to the sensitive nature of coral reefs, mass catching

Predictions about the predator/prey relationships

or killing of lionfish is not feasible. Pathogens or

in new territories were therefore difficult. Since the

other biological control agents released into the water

subsequent scale of population growth and impact

without intensive testing could have catastrophic

on the local ecology became apparent, research into

consequences. Encouraging other predators has also

all aspects of the lionfish’s biology, behaviour, and life

resulted in limited success; the reliability of accounts

history has intensified.

of groupers eating lionfish has not been substantiated.

Seemingly the only viable option to-date has been

The success, scale and speed of the colonisation

systematic removal or culling. Spear fishing is illegal

of new territories by lionfish have presented major

on many of the protected reefs but the use of Hawaiian

challenges for control and mitigation of the problem.

slings is permitted. These devices operate in a similar

Unsuccessful efforts have included ‘training’ top

way to a bow and arrow on land with energy stored in

predators such as sharks and moray eels to hunt

rubber tubing rather than a flexible bow. In practice,

the lionfish by feeding them speared lionfish. This

divers descend with one or two Hawaiian slings, and

approach was abandoned when the predators began

a ‘lionfish containment unit’; a PVC tube in which

to associate divers (not just those with spear guns) with

to store the lionfish safely by preventing spines from

Taming the Lion [67]

Section 6

Exciting new research into aggregation behaviour using 3D printed models may have serious implications on lionfish control stratergies.

Even out of water lionfish spines can be painful; removing these spines is the first step in a dissection.

[68] Taming the Lion

Section 6

protruding. On the Honduran island of Utila, the Bay

With recent improvements in 3D modelling

Islands Conservation Association (BICA) has taken

techniques, researchers are now able to address

steps to manage the culling program by requiring a

additional questions regarding reef complexity and

licence for those wishing to hunt.

lionfish habitat preference. Initial studies indicate that lionfish seem to prefer more complex habitats in

Public engagement is instrumental to success of

areas with heavy spear fishing pressure such as Utila,

many conservation programmes; generating research

when compared with reefs such as Banco Caprio with

funds or, in the case of lionfish, active participation

much less fishing. Whilst only preliminary data, these

in projects. Considerable efforts by conservation

observations suggest that lionfish may become wary of

organisations have been made to promote lionfish

divers and take refuge in more complex reef habitats.

culls; a quick search on YouTube yields hundreds of videos of people hunting them. Support for this

Two closely related aspects of research into aggregation

activity is greatly enhanced by the edibility of lionfish.

are now being pursued. Firstly, whenever lionfish are

The versatility of lionfish as a food ingredient has

found in aggregations, the individuals are speared,

been instrumental in the success, with many local

dissected, and morphometric data compared. The aim

restaurants promoting lionfish on their menus; lionfish

is to establish whether there are similarities between

ceviche, burgers, and carpaccio are often seen in

members of the aggregation, which may prove helpful

coastal Honduran restaurants.

in improving management techniques. For example, if the individuals in an aggregation are predominantly

Utila has a well-established culling program, with active

females about to spawn, culling the group will have a

support from all the local dive shops. Mass culling

greater impact on reproductive capacity than removing

events are a particularly effective way of collecting

single lionfish. The next step is to try and stimulate

a significant volume of data whilst encouraging

this aggregation behaviour by introducing 3D printed

widespread public involvement. Regular ‘Lionfish

lionfish models to the reef; preliminary observations

Derbies’ are held on Utila and have become very

show lionfish showing interest in the models. If

popular. A typical Derby will involve all the local dive

these early findings are confirmed and lionfish can

shops catching as many lionfish as possible on a

be encouraged to aggregate in selected areas, this will

given day. On returning to the dock, all lionfish are

have major implications for future control strategies.

numbered and dissected by research volunteers from

For example, the fragility of reef habitats and the non-

Operation Wallacea, BICA, and The Whale Shark &

selective properties of traps have limited widespread

Oceanic Research Centre (WSORC) with records made

use of trapping to-date. However this approach may

of size, weight, stomach content, and sex. Events

now become a practical option. Lionfish present a

such as these make a significant contribution to the

major risk to reef health in the Caribbean, but it is

expanding database of temporal data whilst also

important to remember that they are merely doing

maintaining public interest in ‘citizen science’ and

what all animals do: trying to pass on their genes. Yes,

raising the profile of the challenge. The post event

we need to regulate their numbers, as they are causing

‘cook-off’ certainly cpublic engagement!

real damage to the reef systems, but we must do this as humanely as possible. Lionfish should not be made to

Within their invasive ranges, lionfish have been

suffer merely because they are successful at breeding.

reported to come together in aggregations. Current research is focusing on the implications of these aggregations and how this could be used to improve management strategies.

Taming the Lion [69]

Section 6

Once the spines have been removed, the fish is weighed and cut open. Then, various parts are removed, weighed, and recorded.

[70] Taming the Lion

Section 6

Taming the Lion [71]

Section 7

SECTION 7

FUTURE PROSPECTS

[72] Future Prospects

Section 7

Coral reefs are in trouble; there is no doubt about

Caribbean Sea, and now as far as Brazil. As generalist

that. On a global scale, climate change is driving up

feeders, lionfish are decimating the populations of

sea temperatures and ocean acidification, hampering

vitally important herbivorous reef fish, exacerbating the

growth and stressing corals to the point of bleaching.

problems of the phase shifts caused by D. antillarum

Plastics are smothering our marine life and becoming

mass mortality.

ubiquitous; it is predicted that, by 2050, there will be a greater weight of plastic in the oceans than fish!

Despite all these issues, there is cause for hope. Teams of scientists are working tirelessly to improve our

In the Caribbean, Diadema antillarum kept the fast

understanding of these sensitive habitats and how we

growing macroalgae at a safe level, ensuring it did

can prevent further damage. More and more countries

not get out of control and smother the slow growing

are phasing out our dependence on petrol and diesel,

corals. When they were nearly wiped out by disease,

and banning use of microbeads and microplastics.

algae were allowed to grow practically unchecked, and although it appears that the pathogen that caused

One of the most important things we can do is to

the mortality has gone, D. antillarum populations are

educate. By informing the younger generations of the

still not recovering. To exacerbate these problems,

importance and wonder of these habitats, we can instil

Caribbean reefs are suffering from invasion by non-

a passion that will stay with them and hopefully pass on

indigenous lionfish. Since the 1980s these remarkable

to future generations.

fish have spread throughout the Gulf of Mexico,

Future Prospects [73]

Section 7

[74] Future Prospects

Section 7

Future Prospects [75]

Further Reading...

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Honda, K., Nakamura, Y., Nakaoka, M., Uy, W.H.,

growth. Nature 286, 249–252.

Fortes, M.D., 2013. Habitat Use by Fishes in Coral Reefs, Seagrass Beds and Mangrove Habitats in the

Downs, C.A., Kramarsky-Winter, E., Fauth, J.E., Segal,

Philippines. PLOS ONE 8, e65735.

R., Bronstein, O., Jeger, R., Lichtenfeld, Y., Woodley, C.M., Pennington, P., Kushmaro, A., Loya, Y., 2014.

Horton, H., 2016. Great Barrier Reef is “almost dead”, say

Toxicological effects of the sunscreen UV filter,

scientists. The Telegraph.

benzophenone-2, on planulae and in vitro cells of the coral, Stylophora pistillata. Ecotoxicology 23, 175–191.

Huitric, M., Folke, C., Kautsky, N., 2002. Development and government policies of the shrimp farming

Fitt, W.K., Gates, R.D., Hoegh-Guldberg, O., Bythell,

industry in Thailand in relation to mangrove

J.C., Jatkar, A., Grottoli, A.G., Gomez, M., Fisher, P.,

ecosystems. Ecol. Econ. 40, 441–455.

Lajuenesse, T.C., Pantos, O., Iglesias-Prieto, R., Franklin, D.J., Rodrigues, L.J., Torregiani, J.M., van Woesik,

Jambeck, J.R., Geyer, R., Wilcox, C., Siegler, T.R.,

R., Lesser, M.P., 2009. Response of two species of

Perryman, M., Andrady, A., Narayan, R., Law, K.L., 2015.

Indo-Pacific corals, Porites cylindrica and Stylophora

Plastic waste inputs from land into the ocean. Science

pistillata, to short-term thermal stress: The host does

347, 768–771. Lamb, J.B., True, J.D., Piromvaragorn, S.,

matter in determining the tolerance of corals to

Willis, B.L., 2014. Scuba diving damage and intensity

bleaching. J. Exp. Mar. Biol. Ecol. 373, 102–110.

of tourist activities increases coral disease prevalence.

Biol. Conserv. 178, 88–96.

France, R., Holmquist, J., Chandler, M., Cattaneo, A., 1998. 15N evidence for nitrogen fixation associated

McCoshum, S.M., Schlarb, A.M., Baum, K.A., 2016.

with macroalgae from a seagrass-mangrove-coral reef

Direct and indirect effects of sunscreen exposure for

system. Mar. Ecol. Prog. Ser. 167, 297–299.

reef biota. Hydrobiologia 776, 139–146.

Hoegh-Guldberg, O., Bruno, J.F., 2010. The Impact of

Mumby, P.J., Edwards, A.J., Arias-Gonzalez, J.E.,

Climate Change on the World’s Marine Ecosystems.

Lindeman, K.C., Blackwell, P.G., Gall, A., Gorczynska,

Science 328, 1523–1528.

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C.C.C., Llewellyn, G., 2004. Mangroves enhance

The New Plastics Economy - Rethinking the future of

the biomass of coral reef fish communities in the

plastics, 2016. World Econ. Forum.

Caribbean. Nature 427, 533–536.

Unsworth, R.K.F., Collier, C.J., Henderson, G.M., Muscatine, L., 1999. The role of symbiotic algae in

McKenzie, L.J., 2012. Tropical seagrass meadows

carbon and energy flux in coral reefs. Coral Reefs

modify seawater carbon chemistry: implications for

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coral reefs impacted by ocean acidification. Environ.

Res. Lett. 7, 24026.

Nagelkerken, I., van der Velde, G., Gorissen, M.W., Meijer, G.J., Van’t Hof, T., den Hartog, C., 2000.

Unsworth, R.K.F., Cullen, L.C., 2010. Recognising the

Importance of Mangroves, Seagrass Beds and the

necessity for Indo-Pacific seagrass conservation.

Shallow Coral Reef as a Nursery for Important Coral

Conserv. Lett. 3, 63–73.

Reef Fishes, Using a Visual Census Technique. Estuar.

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Plaisance, L., Caley, M.J., Brainard, R.E., Knowlton, N., 2011. The Diversity of Coral Reefs: What Are We Missing? PLOS ONE 6, e25026. doi:10.1371/journal. pone.0025026 Precht, W.F., Aronson, R.B., 2004. Climate flickers and range shifts of reef corals. Front. Ecol. Environ. 2, 307–314.

Spalding, M.D., Grenfell, A.M., 1997. New estimates of global and regional coral reef areas. Coral Reefs 16, 225–230.

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A Delicate Balance

Reef Health Check

Cramer, K.L., O’Dea, A., Clark, T.R., Zhao, J., Norris, R.D.,

Gratwicke, B., Speight, M.R., 2005. The relationship

2017. Prehistorical and historical declines in Caribbean

between fish species richness, abundance and habitat

coral reef accretion rates driven by loss of parrotfish.

complexity in a range of shallow tropical marine

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Scheffer, M., Carpenter, S., Foley, J.A., Folke, C., Walker,

Risk, M.J., 1972. Fish diversity on a coral reef in the

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591–596.

Dying Diadema Vergés, A., Steinberg, P.D., Hay, M.E., Poore, A.G.B., Campbell, A.H., Ballesteros, E., Heck, K.L., Booth, D.J.,

Bodmer, M. D. V.; Wheeler, P. M.; Hendrix, A. M.;

Coleman, M.A., Feary, D.A., Figueira, W., Langlois, T.,

Cesarano, D. N.; East, A. S. and Exton, D. A. (2017).

Marzinelli, E.M., Mizerek, T., Mumby, P.J., Nakamura,

Interacting effects of temperature, habitat and

Y., Roughan, M., Sebille, E. van, Gupta, A.S., Smale,

phenotype on predator avoidance behaviour in

D.A., Tomas, F., Wernberg, T., Wilson, S.K., 2014. The

Diadema antillarum: implications for restorative

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conservation. Marine Ecology Progress Series, 566 pp.

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Bodmer, M.D.V., Rogers, A.D., Speight, M.R., Lubbock,

Caribbean Reef Research

N., Exton, D.A., 2015. Using an isolated population boom to explore barriers to recovery in the keystone

Just how little do we know about the ocean floor?

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Coral Reefs 34, 1011–1021.

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Campbell, A.H., Ballesteros, E., Heck, K.L., Booth, D.J.,

Bruno, J., 2016. Prey naiveté to invasive lionfish Pterois

Coleman, M.A., Feary, D.A., Figueira, W., Langlois, T.,

volitans on Caribbean coral reefs. Mar. Ecol. Prog. Ser.

Marzinelli, E.M., Mizerek, T., Mumby, P.J., Nakamura,

544, 257–269.

Y., Roughan, M., Sebille, E. van, Gupta, A.S., Smale, D.A., Tomas, F., Wernberg, T., Wilson, S.K., 2014. The

Betancur-R., R., Hines, A., Acero P., A., Ortí, G., Wilbur,

tropicalization of temperate marine ecosystems:

A.E., Freshwater, D.W., 2011. Reconstructing the

climate-mediated changes in herbivory and

lionfish invasion: insights into Greater Caribbean

community phase shifts. Proc R Soc B 281

biogeography. J. Biogeogr. 38, 1281–1293.

Taming the Lion

Choi, C., 2011. Taming the Lionfish: Can Predators Be Trained to Control an Invasive Species? Time.

Albins, M., Hixon, M., 2008. Invasive Indo-Pacific lionfish Pterois volitans reduce recruitment of Atlantic

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Barbosa, M.C., Rocha, C.R., Rocha, L.A., 2015. First Record of Invasive Lionfish (Pterois volitans) for the

Albins, M.A., Hixon, M.A., 2013. Worst case scenario:

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[79]

THANK YOUS

This book is the culmination of a huge amount of work, and is something I have wanted to do ever since I started diving in 2013. However it is not something I could have accomplished alone, and there are several people I must thank.

Huge thanks must go to Operation Wallacea for allowing me to accompany them on their 2017 expedition, and all their staff and students who allowed me to photograph them whilst they worked.

Thank you also to David McMahon, Steve Galloway, and Thomas Hartman, for their teaching, and to my classmates for their continued support, throughout the year.

Finally, my family have supported my throughout my education, especially this year, and I am eternally grateful for all they have done for me.

Technical Details...

All images in this book were taken on the Honduran island of Utila 42

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Researching the

Reefs