Marine ecology topics

HO13 Tracking the recovery of a keystone urchin species and its role in reef restoration

Under natural conditions, the sea urchin (Diadema antillarum) is the most important herbivore on Caribbean coral reefs, and is therefore considered a keystone species. However, a disease in the 1980s caused the death of an estimated 98% of individuals throughout the region. This mass mortality event had a devastating effect on reef health, driving subsequent phase shifts to algal dominated benthic communities. Recovery has been extremely limited, with populations on most reefs still severely depleted, and Utila Island is a classic example of this. Remarkably, the Banco Capiro reef system in Tela Bay has a population density of D. antillarum at astonishingly high levels. It also boasts extremely high benthic reef health, despite historical overfishing leading to a complete collapse of the fishery. Since its recent discovery, Operation Wallacea scientists began detailed population studies in 2013 and this project will continue to build on this. The primary objective is to quantify changes in the abundance, biomass and population structure of D. antillarum on the reefs of Utila and Banco Capiro. Further data will assess the potential roles of competition, predation and environmental factors in driving the recovery on Banco Capiro.

Extended Project Summary

HO14 Managing the Caribbean lionfish invasion

Lionfish are an invasive species in the Caribbean and are having a devastating impact on local fish communities throughout the region. Introduced in the 1980s, believed to be by accident, lionfish have spread extremely quickly and are now found as far as New York City and Brazil. Their success is down to a number of factors, including their high reproductive rate, generalism in terms of both diet and habitat, and a lack of natural predators. They are now considered to be one of the greatest threats to the future of Caribbean coral reefs and their fish communities. Management approaches to dealing with the lionfish invasion are limited, with one of the most common being direct removal via spear fishing. This relies on regular visitation to individual reef sites, as studies have shown full recovery of lionfish populations only five months after complete removal. Baseline data will be collected on population densities of lionfish at sites of varying intensities of culling. Lionfish will subsequently be removed and morphometric measurements taken along with dissections for physiological and gut content assessments, which can link fish assessments to gauge prey availability. In addition, lionfish behavioural responses to divers, such as Flight Initiation Distance (FID) and Alert Distance (AD) can be assessed, which could also be expanded to include commercially valuable fish such as grouper.

Extended Project Summary

HO15 Interactions between reef health and fish communities

The ecological and economic value of coral reef fish communities makes them vital not only to ecosystem health but also to local food security and livelihoods. However, as consumers they are ultimately dependent on the abundance and composition of primary producers within the system, but also the provision of microhabitats for shelter. Competition for space on Caribbean reefs is extremely intense, with traditionally dominant hard corals increasingly being replaced in recent decades, primarily by macroalgae, but also soft corals and sponges. These phase shifts have significant impacts on benthic structure and function, with knock-on effects on dependent communities such as fish. Students on this project will conduct fish surveys on a wide range of reefs in both Utila and Tela using cutting edge stereo-video technology, which allows not only abundance and diversity measurements, but also accurate biomass estimates from published species-specific length:weight relationships. These data will be compared to benthic assessments using line intercept video transects and state of the art 3D computer modelling, to investigate how benthic health and structure impacts fish communities at the species, family and feeding guild level. With over three years of data already available, students can also incorporate a temporal component to explore long-term trends in benthic and fish community composition at key study sites.

Extended Project Summary

HO16 The dynamics of mutualistic cleaning interactions on Caribbean coral reefs

On coral reefs, the cleaning behaviour of certain species represents an important interspecific and mutualistic relationship that provides a vital ecological service to the wider reef fish community. In the Caribbean, cleaning is performed by both fish (primarily gobies of the genus Elacatinus) and invertebrates (primarily the Pederson cleaner shrimp, Ancylomenes pedersoni). Cleaner species occupy cleaning stations that are sought by client fish who perform set behaviours in order to initiate cleaning. The dynamics of these interactions are complex, and span the taxonomic spectrum of the reef fish community, with Pederson cleaner shrimp alone known to service over 20 families of fish. After mapping the cleaning stations present at a site, students will use remote video observations to explore patterns in cleaning behaviour involving shrimp, gobies or both. Projects could focus on drivers of clientele composition, or how cleaning frequency and duration varies between client species. Alternatively, projects could build on recent research demonstrating the impact of diver presence on the provision of cleaning behaviour through a combination of in water diver observations and remote videography.

Extended Project Summary

HO17 Coral reef SD complexity as a driver of ecosystem function and biodiversity

The structural complexity of an ecosystem is one of the primary drivers of biodiversity, and this is especially true for coral reefs. As ecosystem architects of tropical reefs, hard corals lay down structurally complex calcium carbonate skeletons, which in turn provide the range and quantity of microhabitats needed to support the staggering levels of reef biodiversity. However, recent decades have seen a significant loss of hard coral cover, particularly the more structurally complex branching growth forms, leading to a phenomenon known as reef flattening. The Caribbean has been particularly impacted, and the carrying capacity of associated fish and invertebrates has subsequently decreased. Students on this project will film areas of reef using GoPro cameras while diving, and use the footage to construct state of the art 3D computer models. These models are proportionally accurate and allow 3D complexity to be quantified like never before. Structural complexity measurements will then be linked to observational data of target species of fish and invertebrates to explore how 3D reef structure influences biodiversity and ecological processes.

Extended Project Summary

HO18 Designing an optimal monitoring strategy for Caribbean coral reefs using novel technological solutions

Global coral reef research and management remains heavily reliant on basic in water data collection by divers and snorkellers. However, data quality can vary enormously due to factors such as level of training, in water ability and observer bias. With the emergence of affordable underwater photography and videography, a new suite of techniques has become available to marine researchers that not only increases accuracy of data, but allows new questions to be addressed that would otherwise be impossible through traditional methods. Coral reef health can now be assessed using video transects, while cutting edge stereo-video surveys allow fish communities to be accurately assessed not only for abundance and diversity, but also the much more useful metric: biomass. Even more excitingly, a new collaboration between Opwall and Oxford University has developed a method of constructing accurate 3D computer models of areas of reef filmed using GoPro cameras. These models allow quantification of structural complexity, and have the potential to replace traditional benthic transect techniques. Students on this project will spend time carrying out each of the methods described above, conducting a thorough assessment of their strengths and weaknesses, to design an optimal approach for Caribbean reef monitoring for the modern era.

Extended Project Summary

HO19 Physiology and behaviour of the long-spined sea urchin, a keystone Caribbean coral reef herbivore

The long-spined sea urchin (Diadema antillarum), is responsible for the maintenance of coral reef health throughout the Caribbean. However, in the early 1980s a region wide epidemic reduced their populations by an average of 98%, which stimulated the widespread macroalgal phase-shifts that currently plague the Caribbean. Despite the fact that restoration of D. antillarum is widely believed to be a conservation priority we know surprisingly little about their physiology and behaviour. The aim of this project is therefore to explore the innate responses of this keystone species to numerous external environmental and physical factors, such as food and habitat availability, rising sea surface temperatures and ocean acidification, which may affect the success of targeted conservation efforts. These questions will be answered through a series of laboratory manipulations on urchin specimens collected from nearby reefs.

Extended Project Summary

HO20 The behaviour of invasive lionfish on Caribbean reefs

The invasion of lionfish in the Caribbean has developed into one of the greatest threats to the survival of the region’s coral reefs thanks to the devastating effect they have on native fish populations. Research has naturally focused on mapping the spread of lionfish, quantifying their ecological impacts, and exploring management interventions to reduce their numbers. However, improving our understanding of the behaviour of this species on non-native reefs is of particular interest to better grasp the underlying success of their invasion. This project will assess lionfish behaviour both on the reefs and in a small laboratory, where individuals will be captured and processed. Particular focuses of this work could include prey selectivity, and habitat preferences to investigate the cryptic nature of this species, and data can be linked to ecological characteristics of the reef itself.

Extended Project Summary

HO21 Assessing the population status of the Caribbean spiny lobster, Panullrus argus, on a unique coral reef ecosystem

As a mesopredator, the Caribbean spiny lobster (Panulirus argus) feeds upon a wide range of resources
including many species of snail, crustacean and sea urchin, but is also predated by numerous larger reefdwelling
organisms such as sharks, snappers and groupers. P. argus therefore sits at the centre of Caribbean
coral reef food webs, meaning that changes in population size can lead to dramatic trophic cascades affecting
the entirety of the reef system. As well as being ecologically important, lobsters are also hugely economically
valuable and it is estimated that over-harvesting has reduced P. argus populations by up to 50% in some parts
of the Caribbean since the 1950s. Despite these dramatic population declines, P. argus has been assessed as
‘data deficient’ by the IUCN and is therefore afforded little protection. Caribbean spiny lobsters in Honduras
have been largely neglected by the scientific community, but this project aims to redress this by using a
combination of in situ population surveys to assess their size-distribution structure and habitat selectivity, and
lab-based experiments to investigate basic facets of their behaviour and physiology. We hope these data will
ultimately be used to increase the degree of protection provided to the Caribbean spiny lobster and prevent
further declines to their population sizes.

Extended Project Summary

HO22 Exploring abiotic factors as drivers of a unique Caribbean coral reef system

The biotic components of any ecosystem are sculpted, at least in part, by the abiotic conditions they are
exposed to. Understanding the abiotic variables present in a system can therefore provide clues helping
to explain patterns in biodiversity, productivity, community composition and more. Located in Honduras’
mainland Tela Bay, Banco Capiro is a newly discovered reef system that boasts one of the highest covers of
healthy coral anywhere in the Caribbean. Yet at first glance Tela Bay seems an unlikely candidate for such a
natural wonder, thanks to increased turbidity and close proximity to a sizeable human settlement and riverine
input. The mystery behind this unique reef system is yet to be fully understood, and this project will quantify
a range of abiotic variables to shed light on the conditions Banco Capiro exists under. These data will be
combined with in situ habitat surveys to quantify spatial patterns of reef health, allowing students to tease
apart the relationships between individual abiotic and biotic variables.

IN124 The feeding behaviour of herbivorous fish and their role in maintaining the reef

Reef building corals are the foundations of coral reefs. They produce the physical structure and complexity
that provide habitat for the many thousands of species. However their abundance is greatly threatened and
as environmental conditions change we see other benthic taxa starting to outcompete corals and dominate
which can lead to new less biodiverse alternative ecological states. Shifts from one dominate state to
another are often termed phase shifts and knowledge of the key factors that increase and / or decrease the
probability of such phase shifts occurring are desperately needed so that direct conservation action can
intervene to prevent a net reduction in reef biodiversity. The shift from coral to algal dominance has been well
documented in the Caribbean and appears commonplace. However, on the mega biodiverse reefs of the coral
triangle there has been no such shift. One hypothesis is that the feeding rate and behaviour of herbivorous
fish reduce the ability of algae to become dominant. There is thus an urgent need to quantify the amount of
herbivory occurring on reefs of the Wakatobi using a combination of behavioural-based studies of specific
key herbivores and assessment of actual grazing rates occurring per unit area of reef. Recent research has
suggested that the presence of key predators of fish can influence herbivore-feeding behaviour. Therefore
further studies could also examine how the presence of large predators such as large emperors, snappers and giant-and/or blue fin trevally influence the behaviour of herbivores. Other studies could use caging experiments to examine how the removal of herbivore pressure influences changes in algal biomass. This is an extremely important piece of research that will help identify the key issues facing the reefs of this biodiversity hotspot. Information gained will feed directly in to predictions of future health and help inform effective conservation strategies.

IN125 The prevalence of coral diseases and their impacts on reef biodiversity

Reef building corals are the key ecosystem architects that produce the complex physical structure that
provides habitat for the many thousands of species inhabiting reefs. Like every other animal, corals are
impacted by disease, caused by many different microbes. The extent of the threat caused by coral diseases to
reef ecosystem health is largely dictated by environmental conditions both past and present. In the majority
of reef systems, including those of the coral triangle, environmental quality is decreasing, resulting in corals
being put under increasing pressure. The environmental conditions thought to increase disease include
sedimentation and pollution. The vulnerability of corals to diseases is also increased when they are put
under physiological stress. During 2016 the global thermal event, commonly termed the Godzilla El Niño,
devastated the world’s reefs and although corals of the Wakatobi demonstrated remarkable resilience, the
prolonged physiological stress caused by the El Niño could have increased long term vulnerability to disease.
Therefore there is urgent need to understand the current prevalence of disease, the key diseases present in
the Wakatobi, the species of corals affected and how diseases are spatially distributed across reefs of different
environmental conditions. Data gained from this research are paramount for marine park managers and will
greatly add conservation efforts. Research can also be compared to original data published over a decade ago
to determine how diseases have changed over time.

IN126 Hide and seek: behavioural characteristics of fish living within coral colonies

Many species of fish live within the colonies of branching and tabulate corals. These fish often belonging to
the damselfish family, most often live in large groups and seek refuge within the complex structures provided
by these colonies. Such colonies, most often belonging to the genus Acropora are vulnerable to thermal
events, sedimentation and turbidity. There is a need to understand the specific relationship between corals
and their resident fish, in particular how environmental conditions influence coral colony morphology and
how this influences the resident fish assemblage. Many species that inhabit coral colonies are juvenile or
sub adults, whilst other species inhabit colonies throughout all life stages. The behaviour of different species
and how this varies with life stage is of scientific interest as such behaviour is key to the success of these
fish within reef systems. The flight response of fish and how this varies across environments will enable
researchers to gain a better understanding of the importance of coral colonies for the ecological success of
fish as well as providing new insights in to the behavioural ecology of key fish species. This research could
examine the distribution of different reef fish species that inhabit branching and table corals and how this
varies across with colony morphology. Other projects could examine the flight response of the resident fish
by examining the speed and patterns of escape from potential threats. Preliminary investigations suggest that the flight response of juveniles differs greatly from adults particularly as it concerns the time it takes for fish to emerge from the coral colony when a threat is removed or how close a threat needs to be to elicit a flight response of fish which retreat in to the coral to seek refuge. This project offers a unique opportunity to examine specific behavioural traits, how they vary across species and life stages and to examine the unique and complex interactions between fish and reef building corals on the most biodiverse reef system in the world.

IN27 Behavioural adaptations of dwarf cuttlefish, Septa bandensis

As a group, cephalopods display a high level of nervous integration resulting in complex behavioural responses and social interactions that rival those seen in higher vertebrates. The Wakatobi National Park is home to at least 30 cephalopod species, many of which can be found inhabiting reef and reef-associated habitats. The dwarf cuttlefish (Sepia bandensis) is the most abundant cephalopod species found in the park, occurring in large numbers near rocky shorelines, on coral rubble, in seagrass meadows and at mangrove margins. While the species has some minor commercial value in local artisanal markets, its major importance lies in their ability to shape habitat ecology by indiscriminately preying on large numbers of small to medium sized crustaceans. In spite of their ecological importance, little is known about the feeding behaviour or social interactions in this species. The primary objective of dissertation projects could include aspects of feeding behaviour, effects of competition, and social interactions between individuals of different gender and/or size. Other studies may be considered but require approval of the field supervisor. All studies would be conducted using captive animals housed in the Hoga Island Research Laboratory and proposed studies must be non-lethal. Students must also check with their university advisor regarding their universities policies and procedures for working with cephalopod animals. Students are strongly encouraged to contact their project field supervisor early in the proposal development process.

Extended Project Summary

IN28 The complex behaviour of coral reef fish in a mega biodiversity hotspot

The behavioural characteristics of reef fish are complex and largely dictate the success of a species
within the highly competitive reef systems of the coral triangle. Behaviour is plastic, varies in response to
environmental conditions and has evolved to enhance the fitness of the individual. An evolutionary strategy
for many species existing within mega biodiversity hotspots such as those of the Wakatobi is to form
mutualistic relationships with other species. Mutualistic relationships appear commonplace but perhaps the
clearest example are those that exists between anemones and their inhabiting anemonefish species. A recent
study demonstrated that reefs of the Wakatobi have unique levels of cohabitation of anemonefish within a
single host anemone. On reefs surrounding Hoga the prevalence of cohabitation is the highest in the world
but the costs and possible benefits of cohabitation is yet to be ascertained. Research could examine the
implications of cohabitation as it concerns reactions to predators or opportunities for anemonefish species
to defend larger territories. Another common mutualistic relationship between fish species are the complex
interactions between cleaner species and their clients. The reefs of the Wakatobi have several cleaner fish
species as well as cleaner shrimps but it is uncertain whether these different cleaners partition their clients
or whether the most abundant cleaning species i.e. the bluestreak cleaner wrasse is dominant because it provides the highest quality service to its clients. The implications of degrading habitats on cleaner density and service provision is also unknown although it may be expected, unlike most other species, that cleaner abundance may actually benefit from a degraded system. The more researchers examine species of reef fish the more complex behavioural traits are
discovered. For example recent preliminary research has demonstrated the diverse behaviour of the commonly encountered trumpetfish previously considered to be a relatively sedate species. However it now appears that trumpetfish commonly display a range of complex behaviours which include ambush predation, utilising other fish species to hide whilst stalking prey, using colour changes to hide from prey items and utilising stealth and ambush feeding strategies. However research is preliminary and further studies are required to really describe the behavioural ecology of this charismatic species. Overall dissertations in this research area will provide great insight in to the strategies employed by resident species to increase their chance of survival in the most biodiverse and
competitive coral reef systems in the world.

IN129 The biodiversity of coral patch reefs and their conservation value

Located within the zone separating the reef flat from seagrass beds of the Wakatobi are numerous coral patch
reefs. These patches range in size as well as distance from the main reef system (reef crest) and represent
a unique opportunity to examine the ecology of coral reefs that have different levels of isolation. The locally
termed coral bommies, are home to numerous fish species and have very different levels of biodiversity.
It appears most likely that the patch reefs represent important species rich “islands” but the factors that
influence fish species richness and the stability of resident fish assemblages remain largely unknown. It
appears likely that larger patches will house greater species richness as will those patches that are closer to
the main reef system. But it is also possible that other factors such as the biological and physical complexity
of the patches are more important, or that coral patches close together could act as a single patch for resident
fish. The patches may be extremely important for juvenile reef fish seeking refuge from the high predatory
pressure common to the main reef system and it is likely that such predatory pressure will decrease with
increasing distance from the reef crest. Therefore there are a number of different factors that may influence the
community ecology of reef fish utilising coral patches and this research could take a number of approaches
to examine the physical and biological attributes of reef patches, the factors that drive reef biodiversity and the importance of reef patches located in this transition zone for the main reef system. A high degree of juveniles would mean that such patches have high conservation value although they are currently given little if any attention from reef managers. Therefore as well as addressing fundamental ecological questions, research within this subject area has direct conservation implications and may lead to recommendations for conservation intervention to increase the availability of these habitats.

IN30 Will coral reefs become sponge reefs?

There are reports from across the world of coral regime shifts, whereby declines in coral result in increased
abundance of other benthic groups. Throughout the Caribbean these changes are typically to reefs dominated
by algae, but in the Indo-Pacific changes to reefs dominated by other animal groups are more common. In
the last few years there has been particular interest in the sponges as these are one group of organisms that
have been identified as potential ‘winners’ in the face of environmental degradation and climate change.
Within the Wakatobi a transition has occurred on one major reef system, Sampela, where coral abundance
has declined over the last 10 years to very low levels, but sponge abundance appears to be increasing. In
particular, this site is dominated by the giant barrel sponge, Xestospongia spp. and the encrusting sponge,
Lamellodysidea herbacea; these have also been reported as increasing in abundance in other parts of the
Indo-Pacific. In addition, recent experimental evidence has shown that sponges appear much more resilient
to ocean warming and acidification than coral, so are likely to be a greater feature of coral reefs in the
future. Dissertations in this area will build on long term datasets to track this shift in dominance and explore
the ecosystem level effects. Projects might also include behaviour based studies to understand levels of
spongivory and which species of reef fish are able to utilise sponges as a food source. Further studies should examine the competitive interactions between corals and sponges, the later being known to utilise a number of competitive techniques including direct overgrowing as well as chemical attack. Therefore research could also utilise an experimental approach to examine implications of sponge-derived chemicals for coral productivity. It is undoubtedly the case that greater effort is needed to understand the interactions between corals and sponge and the consequences of sponge dominated systems for coral reef biodiversity. Research activity will also allow us to explore the potential management interventions needed to prevent future regime shifts.

IN31 Evaluating potential effects of rising environmental temperatures on thermal ecology of fiddler crabs, Uca spp. 

(start dates 13 June or 27 June)

Often exhibiting high levels of biodiversity and endemism, mangrove forests demonstrate a remarkable interdependence between local flora and fauna such that a loss of diversity or density in one group has marked adverse effects on the other. Declines in burrowing crustacean populations, for example, have been shown to result in reduced organic turnover, decreased nutrient and energy cycling, and diminished primary productivity in mangrove species. Fiddler crabs (Uca species) are one of several semi-terrestrial, burrowing, mangrove decapods making up a keystone group commonly referred to as engineers. Indonesia boasts the highest diversity of fiddler crab species of any country in the world with 14 total species, seven of which can be found within an area of 4-square meters within the Ambeua Mangrove near Hoga Island. Previous research at the Hoga Marine Laboratory has shown that local fiddler crab populations are relatively tolerant of high temperatures; however, with environmental temperatures across the Malay Archipelago expected to increase by up to 4°C in coming decades, it is unclear how fiddler crab populations and ultimately mangrove ecosystems, may be affected. Potential dissertation projects could evaluate differences in thermal adaptations of Uca spp. occupying different intertidal regions, or may look at acclimation responses of a single Uca species. All studies would include a field observation component, though most of the empirical work would take place in the Hoga Island Research Laboratory. Students are strongly encouraged to contact their project field supervisor early in the proposal development process.

Extended Project Summary

IN32 Using the past to predict the future: long-term changes in the community ecology of coral reefs

The global demise of coral reefs has been well documented in the scientific literature. The reefs of the Wakatobi have been assessed by Operation Wallacea for the past 15 years. The abundance of reef building corals has declined but other functional benthic taxa, such as soft corals, have increased. As well as an overall decrease in reef building corals, the types of corals present, both in terms of species and colony structure have also changed. Where once reefs in the region harboured a mix of different colony growth forms (including branching, table, and foliose corals), the system today is dominated by massive (boulder-like) and encrusting corals. The physical form of the reef is therefore changing which has implications for resident and transient fish communities. During 2017 the research teams would like to complete the monitoring of reefs around the Wakatobi and use previous data combined with the final year of data collection, to determine how fish communities respond to changes in biological and physical structure of reefs. The detailed data set across six sites and three reef zones will allow managers to identify the likely consequences of long term changes in habitat quality for both biodiversity and food productivity. The relationship between benthic structure and fish community is a complex one but if habitats are to be actively restored we need to know how the fish community is likely to respond. Projects here could focus on the system as a whole, or could identify particular fish taxa that have changed and examine their interaction with specific reef structures across different spatial scales. For example we would predict that larger predatory fish respond to complex reef structures over larger spatial scales than smaller residential fish but that complexity of habitat may be needed at every spatial scale to support a healthy, biodiverse and productive fish community. Projects could therefore utilise a large historical data set, further assessment of varied reef sites and could include taxa specific assessment utilising behavioural studies. Data collected will be used to define future protective and active management intervention.

IN33 Fisheries research in local communities

Opwall have been working with local fishing communities in the Wakatobi for almost 20 years, developing a deep understanding of the conservation issues associated with declining fish stocks and producing several award winning dissertations along the way. Opportunities exist for students to build on this extensive experience by completing dissertation projects focusing on artisanal fishing pressure by working alongside Opwall staff and local Indonesian partners in small fishing communities on and around Kaledupa island. To talk about this opportunity, and how it might be suitable for your undergraduate or masters dissertation research, please email Dr Dan Exton:


IN34 Role of mangroves in marine ecosystems

The mangroves and associated seagrass beds around the island of Kaledupa and Hoga provide an excellent
laboratory to study some of the effects of mangroves on the marine environment. Some of the mangroves
suffer from harvesting and one project could look at the effects of this harvesting on the mangrove biota (both
infauna diversity – species that bore) and epiphytes in mangroves with different levels of exploitation. Another
project could compare the effectiveness of mangroves that have been partially damaged from harvesting with
more pristine areas in depositing sediment from the water column. Note this study could be extended to the
adjacent seagrass areas and coral to assess their impact on sediment settlement. Another project could look
at the processes which affect carbon release from mangroves. Different guilds of biodegrading organisms
(e.g. bracket fungi, beetle larvae, termites and shipworms) process wood but their relative contribution to
this process varies according to the length of time the woody detritus is submerged on a tidal cycle and the
salinity levels. This could be examined by studying the biodegrading organisms on mangrove wood detritus
at different distances form the strandline.

ME54 A comparison of pristine and degraded mangroves in Akumal and theimpact of mangrove degradation on adjacent seagrasses and coral reefs

Mangrove forests are highly productive marine ecosystems that are essential for the health of adjacent ecosystems e.g. sea grass beds and coral reefs. Yet, as much as 1 – 2% of the global mangrove forests are lost per year. Mangroves draw down atmospheric CO2 sequester and trap fine sediments, facilitate vital biodiversity mechanisms (e.g. fish nurseries) and improve fishery productivity. Despite the obvious importance of mangroves, mangrove forests in the Yucatan Peninsula have been under considerable anthropogenic impact from harvesting, causing a reduction in important habitat and biodiversity, carbon sequestration, and the productivity of adjacent sea grass and coral reef ecosystems. If the ecosystem services that mangroves provide can be quantified, then there is scope to develop a mangrove equivalent of the REDD programme in which fishing communities could receive economic investment in exchange for continued protection of the mangroves. Projects could therefore focus on a comparison of the structure, function, and faunal diversity of pristine and degraded mangroves, or an investigation of wood degradation processes across mangroves of differing quality. In addition, projects could investigate health and diversity of seagrasses and coral reefs in relation to the level of degradation of adjacent mangroves. Belt transects and permanent plots will be used to record tree composition, basal areas and tree densities. Biodiversity assessments will be conducted by investigation of the available mangrove substrata. Snorkel and dive based transect and quadrat surveys may be used to assess diversity and coverage of seagrasses, hard corals and algae.

Extended Project Summary

ME55 Understanding the non-conventional cenote-mangrove forest system

The Yucatan Peninsula is formed of limestone karst substrate that was once coral reef. As limestone is porous, rainwater seeps through the rock surface to form an extensive network of underground rivers accessed from the surface by sink holes, known locally as cenotes. Mangrove forests associated with cenotes in coastal regions are not new, but research of them is. This novel project aims to investigate the driving forces behind the structure and function of these unusual mangrove ecosystems and to investigate differences of animal community structure in comparison with coastal mangrove forests. The majority of mangrove animals exploit the available hard substrata within mangrove ecosystems. Areas such as mangrove prop roots and in particular large wood detritus (LWD) are favourable for most mangrove fauna, but nothing is known about the organisms that process the fixed carbon in cenote mangrove forests. Projects may highlight new and unreported information from forest structure and function, to mangrove fauna diversity and niche separation. Continuous belt transects and plots will be used to establish the tree structure, composition and basal areas with the cenote mangrove forests. Biodiversity assessments of the fauna upon mangrove roots, substratum and LWD will be made, and animal observations will be employed. Degradation processes of LWD will be recorded in the forests and compared with those from conventional mangrove forests.

Extended Project Summary

ME56 How do mangrove trees reduce thermal stress and provide environmental buffering for fish in a Caribbean mangrove forest?

Mangrove forests are well known for their functional traits, particularly the nursery function enhanced by the
complexity of Rhizophora prop roots. A less understood functional trait is how mangrove trees may benefit
biodiversity mechanisms through environmental buffering and how such traits may influence fish behaviour.
Rhizophora mangle trees will investigated for their biodiversity function of reducing thermal stress for the
mosquitofish, Gambusia affinis. Diurnal distributions of fish populations between open channels and shaded
tree areas will be investigated. During the morning, when temperatures are cooler, and in the afternoons
when temperatures are at their most extreme, fish behaviour will be studied. This study will also investigate
the critical point when fish populations switch from being exposed in the channels to moving in areas of
more shade, which offer reduced thermal stresses to the fish. Environmental variables will be measured,
temperature and salinity, and then correlated to patterns of fish movements within the mangroves. Size
distributions of fish populations will also be made to determine if the fish are mature adults, immature or juveniles. If the fish are immature, then potentially, the thermal stresses caused by the excessive channel temperatures may impose serious developmental impacts that would be reduced by occupying the shaded tree areas. Thus, the mangrove tree may provide a little known refuge of environmental buffering for juvenile and adult fish, which would otherwise be exposed to lethal thermal stress.

ME57 The conservation of and improvement of Caribbean coral reefs: Reef restoration through plantation of Acropora cervicornis

Acropora is one of the most important Caribbean corals in terms of its contribution to reef growth and fishery habitat. Acroporid species are the Caribbean’s fastest growing reef-building corals. Since the 1970s, Caribbean acroporid populations have been decimated by disease outbreak. Their recovery has been impaired by the general poor health of Caribbean coastal ecosystems. In Akumal this decline is estimated at >90%, although it is unlikely that this truly represents the loss of coral due to the lack of reliable data. Coral restoration is increasingly considered to be a viable recovery plan. In Akumal preliminary research has been conducted to trial success rates of coral nurseries where Acropora cervicornis is grown, propagated and then transplanted onto the reef. The methods used are minimally invasive and require cheap materials. The trials have proved to be successful, with doubling of live tissue from dying rescued fragments within one year, combined with successful fusion and growth of transplanted colonies onto the reef. In order to measure the impact of coral restoration work, it is essential to develop baseline data from which to measure the successful colonies that have grown as a result of the restoration work. Using continuous belt transects on the reef, the mapping of acroporid colonies will be conducted to assess the distribution, abundance and surface area of the colonies. Coral frags will be out-planted at various distances from the mother colony to measure successful recruitment and growth at different sites from that of the mother colony. Reef fish assemblages, particularly juveniles, will be assessed on reefs with none or few acroporid colonies. Established acroporid frags will then be planted onto those reefs and re-assessed. These data will be compared to reefs with a high density of acroprids.

Extended Project Summary