Marine ecology topics

 

IH270 Sponge ecology and coral reef phase shifts in Indonesia (Weeks 2 – 8; need to have completed IH007 and be dive trained)

IH270 Summary

The high abundance of sponges on many coral reefs, along with their diverse functional roles mean changes in their distribution and abundance patterns have the potential to affect overall reef ecosystem functioning, particularly through their trophic relationships with other organisms. Of particular importance is the potential for declines in coral and fish to result in the increased abundance of other organisms, and for reef systems to undergo phase shifts in response to such degradation. Although the best described phase shifts are from coral- to algal-dominated systems, there also appears to be the potential for coral-dominated systems to become dominated by other organisms, including sponges. Understanding the causes and consequences of such phase shifts is critically important for coral reef management, as these changes can have profound effects on reef ecosystem function. This project will specifically document the spatial variation in the abundance and diversity (using a morphological surrogate) across sites in the Wakatobi, and assess the variation in total sponge abundance and that of key sponge species across environmental gradients in the Wakatobi. Given the expected declines in coral abundance in response to climate change and ocean acidification effects, there is every possibility that sponge-dominated reefs might become more abundant in the future, and this project will begin to assess how such reefs might function and if they can support similar levels of fish biomass and productivity as coral-dominated systems.

IH271 Competitive interactions between sponges and other reef organisms in Indonesia (Weeks 2 – 8; need to have completed IH007 and be dive trained)

IH271 Summary

Sponges are an important component of coral reefs across the world with a range of important functional roles. Given that sponges are one of the dominant components of reef fauna in many places and because space is generally limiting in healthy coral reef systems, sponges are likely to interact in a variety of ways with a range of organisms as they grow. Although limited space might be expected to result in intra- and inter-phyletic spatial competition between sponges, many earlier studies have highlighted how sponge survival can be facilitated by positive interactions with other organisms. Despite these positive interactions, other studies have clearly shown that sponges are effective spatial competitors with the ability to overgrow other reef organisms and cause the necrosis of tissue that has been overgrown. This project will investigate the spatial associations and potential competitive interactions between sponges and other organisms in order to assess how coral reef function may change as a result of future declines in corals.

IH272 The diversity, distribution and abundance of Nudibranchs in Indonesia (Weeks 2 – 8; need to have completed IH007 and be dive trained)

IH272 Summary

Molluscs are the most abundant group of animals on coral reefs, comprising up to 60% of all marine invertebrate species. Nudibranchs are one of the most diverse groups within the phylum but ecological knowledge of these charismatic species and specifically data concerning their true diversity, abundance and distribution is very limited. Studies in to the extremely photogenic Nudibranchs are extremely important to the Wakatobi which is increasingly becoming recognised as one of the best coral reef dive sites in the world particularly for underwater photographers. Unfortunately and before Operation Wallacea established their research facility on Hoga Island,  an expedition team removed many specimens for museum collections and since that point numbers have been low. Anecdotal evidence however suggests that populations are recovering and now represents the perfect opportunity to gain a much greater understanding of the ecological needs of Nudibranch species, their habitat preference, feeding ecology and those factors that drive their distribution as well as abundance. Due to their life history traits such as low fecundity and low dispersion, Nudibranchs are not very resilient and thus detailed knowledge of their ecology are needed so group specific conservation strategies can be produced and recommendations made to marine park authorities.

IH273 The role of territorial Damselfish in sculpturing coral reef biodiversity in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)

IH273 Summary

One of the most conspicuous groups of fish and certainly one of the most successful across reef systems are the Damselfish. Several species of Damselfish set up closely guarded territories and defend their resources through numerous aggressive behaviours. The degree of aggression varies between species and also with species most probably as a direct consequence of the surrounding fish community. Those individuals living in species rich and highly competitive environments may defend their territories with great vigour than individuals of the same species living on reefs with lower fish abundance. Regardless such Damselfish species are likely to influence fish assemblages in their immediate vicinity. The obvious influence would a negative one with Damselfish actively excluding other species, however research has demonstrated that some Damselfish may facilitate species richness through their active farming and managing of the benthic environment. This study will help understand how the complex fish communities of coral reefs are structured. 

IH274 Resource utilisation of reef fish across environmental gradients in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)

IH274 Summary

As reef habitats become more degraded, resident fish species will have to constantly adapt to the changing environment. Arguably, it is the species that are most plastic in their behaviour that will fare best but the numbers of studies that examine the variety of species behaviours across reefs of different quality are rare.  We therefore have little idea on how specialised species are able to alter their behaviour and ecological niche to be able to exist across reefs of different quality. Studies could examine the variation in the behavioural ecology and therefore the degree of plasticity that exists between two coral dependent butterflyfish namely Chaetodon baronessa and  Chaetodon lunulatus across reef sites of varying qualities through the use of scuba, snorkelling or a combination of both. Specifically researchers could examine whether the species’ preferred prey (coral species) changes across reefs and whether the selectivity of species alters depending on the availability of coral species. Such research will greatly increase our understanding of how adaptable reef fish species are and how specialised species with an apparent restricted ecological niche, may fare under conditions of reduced habitat quality.

IH275 The ecology of Anemonefish in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)

IH275 Summary

One of the more conspicuous groups of fish on tropical reefs is the anemone fish. Anemone fish are heavily collected for the aquarium trade and have a mutualistic relationship with their host anemones. However, preliminary investigations have shown that this relationship is much more plastic than first thought and may be dependent on the availability of different anemone species across different reef sites with more dominant anemone fish species being more selective than less aggressive species. Further investigations have also shown that some species co-inhabit single host anemones; but what dictates this dual association? Surprisingly little research has been carried out that adequately details the association between fish and anemones and, at present, it is not possible to identify the key ecological drivers of the partnership. Research could also include detailed investigations in to the behavioural ecology of different Anemonefish and the degree to which they defend their resource. The question then arises as to whether or not the presence of Anemonefish on a reef exclude others. There is much to learn about the Anemonefish and insights in to their ecology will enhance our understanding of the key drivers of reef biodiversity.

IH276 The ecological impact of smothering sponge and ascidians on coral reefs in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)
In recent years, an aggressive colonial ascidian (tunicate) and a smothering sheet like sponge has increased in abundance on reefs surrounding Hoga Island, particularly reefs that are impacted by high sedimentation. This ascidian is unique in that it is able to colonize live coral resulting in colony death whereas it is uncertain whther the sponge species colonises live or dead coral colonies.  To date, no research has been undertaken on this ascidian or the sponge species despite the fact that they are causing significant mortality on reefs of the Indo-Pacific and have the potential to dramatically alter the ecology of the system by degreasing biological and physical complexity. . Research is urgently required to assess the ecology of these two species and in particular to examine their abundance, distribution, environmentally regulated growth, and also to determine the coral species that are most affected and under water set of environmental conditions. This research is only suitable for scuba divers and will involve extensive field surveys coupled with repeated measures of colonies affected across environmental gradients so that site-specific progression rates can be calculated.

IH277 The behaviour and functional role of reef fish cleaners in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)

IH277 Summary

The Wakatobi Marine National Park is unusual in that three species of cleaner wrasse are present on its reefs and a number of cleaner shrimps. The Bluestreak Cleaner Wrasse (Labroides dimidiatus) has been well studies but few studies have focused on the behaviour and ecology of the other two cleaner wrasse species: the Blackspot (Labroides pectoralis) and Bicolour (Labroides bicolor) and the numerous cleaner shrimps. This study could be divided in to a number of different research projects that aim to fully characterise the ecology of the different cleaner species and the relative role they play on reefs of different quality. In particular researchers may which to compare and contrast the clients of the different species and whether or not one species is more important than another in terms of the functional roles they play. To achieve this research could examine variation in time spent cleaning, differences in the clientele, the relative worth of different clients to the various cleaner species and whether this value alters across environmental gradients.

IH278 The abundance and impact of coral bio-eroding invertebrates across environmental gradients in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)

IH278 Summary

The growth of a coral reef is dependent on the balance between processes of accretion and erosion. In a healthy system, there is generally net growth as those organisms contributing to the physical structure of a reef (e.g. hard corals, coralline algae) are more dominant than abiotic physical erosive forces (e.g. wave energy), anthropogenic destruction (mining, blast finishing and anchor damage) and bio-eroding.  This balance can be changed by prevailing environmental conditions, and in particular light and temperature by reducing reef accretion rates, but reef growth can also be reduced by variations in the abundance of those organisms that can actively remove material, ie bio-eroders. Many species are capable of bio-eroding corals, either during predation activities (e.g. Parrotfish) or during burrowing activities (e.g. several species of molluscs). It would seem likely that the abundance of these organisms may also be regulated by prevailing environmental conditions and therefore if the processes that reduce coral growth are the same that stimulate greater bio-erosions, reefs could be severely threatened. Therefore research is required to determine the relative abundance and selectivity of bio-eroding species and how environmental conditions regulate this activity.

IH279 The ecology and biology of shallow subtidal patch reefs in Indonesia (Weeks 2 – 8; need to have completed IH007 or IH008 and be dive trained if incorporating a diving element)

IH279 Summary

How stable are reef communities over time? What changes are occurring and over what time scales? What are the responses of fish communities to changes in benthic cover? Coral reefs are dynamic ecosystems and may actually exist in multiple stable states.  Permanent transects have been used to successfully document changes in benthic cover, but assessing changes in mobile organisms are more difficult.  However, smaller patch reefs sometimes referred to as bommies provide an ideal template to evaluate changes in mobile organisms, as they tend to house a greater number of resident species. Coral patch reefs situated in lagoonal areas backward of the main reefs may also facilitate the daily migration of reef fish to other coastal habitats such as seagrass and mangrove forests. Consequently and apart from being an ideal model system to investigate the drivers of reef biodiversity, these patch reefs are of major ecological importance. Several research projects could be developed in this field to assess the ecological and functional roles of such patch reefs and also to identify the key environmental and biological drivers of reef biodiversity. This research is increasingly becoming more important as such patch reefs are often targeted for coral mining activities and are therefore are at real threat from human induced degradation.

IH280 Methods of reef assessment and the effect different survey techniques have on estimations of reef fish abundance and functional biomass in Indonesia (Weeks 2 – 8: need to have completed IH007 and be dive trained)

IH280 Summary

This research project, which is fundamental to conservation research, aims to compare techniques and protocols most commonly used within reef monitoring programmes, and will assess the variability between techniques, the relative cost of each technique, and how all of these vary across sites of different quality and habitat structure. The ultimate goal of the study is to produce an output in the form of a standardised and validated set of protocols which will be recommended for all agencies to use. For example, obtaining true estimates of fish abundance and biomass is key to reef management, conservation and monitoring programmes. Several techniques are widely used although we have little appreciation of how the techniques used influence the data obtained and whether or not it is possible to directly compare data collected by different techniques. It is most likely that the different techniques return different data and evaluating the levels of variation between methods is extremely important particularly when scientists and managers need to compare data obtained between sites or within a site over successive years when different protocols have been used. We also need to identify best practises and identify those techniques and protocols that return the most reliable and robust data. Furthermore it would be most desirable to identify the techniques which are most cost effective, in terms of time, to use when undertaking reef assessment. The best practises will therefore be those methods that return the most scientifically robust data for minimum effort.

IH281 Conservation of herbivore biomass and functional biology of reef systems (Weeks 2 – 8: need to have completed IH007 and be dive trained)

IH281 Summary

Of key concern to conservation biologists are those species that play important functional roles and the potential loss of those species from the system as a result of over exploitation.  The removal of algae from coral reefs is an extremely important functional role and influences successful coral recruitment and coral growth. Herbivores are a key functional group whose characteristics (e.g. species and abundance) influence the structure and biodiversity of coral reefs and therefore help sculpture the environment.  In reefs of the Caribbean, removal of grazing fish (Parrotfish) following the demise of grazing Diadema populations, has resulted in a phase shift from a once coral dominated system to an algal dominated system with major consequences for biodiversity. Within the Indo-Pacific region, there are many more grazing species and consequently a higher degree of functional redundancy. However, limited information exists on the relative importance of different herbivores. Research is thus needed that evaluates the relative importance of different herbivore groups by examining their feeding behaviour, abundance, biomass and distribution across sites of different habitat quality. Biomass can be very accurately estimated through the use of stereo videography and through the construction of length to biomass relationships from fish caught in local fisheries markets.

HT282 Uncovering the unique coral reef ecosystems of Tela Bay (Weeks 3 – 9; need to be dive trained and have completed HT009)

HT282 Summary

The coral reefs of TelaBay are truly unique, and pose a number of ecological questions with important implications for coral reef conservation throughout Honduras and the rest of the Caribbean. The main reef in the bay, known as Banco Capiro, boasts a coral cover of approximately 70%, which is higher than almost anywhere else in the entire Caribbean and even higher than many reefs in the Indo-Pacific. Nearby patch reef systems, however, are more representative of Caribbean reefs, being dominated by macroalgae after the occurrence of phase shifts, although even these sites are showing early signs of recovery. Another distinct difference between the reefs of TelaBay and elsewhere is the increased turbidity, which reduces visibility but importantly reduces the quantity and quality of light reaching the benthic community. This phenomenon is believed to protect sensitive corals from the dangers of high light stress, an idea known as the refuge hypothesis. In short, the reefs of TelaBay are ecologically mysterious, and this project will attempt to better our understanding of the biological and ecological processes taking place on the coral reefs of TelaBay, in order to better inform conservation managers of how the corals are able to thrive to such an extent. Data will include a benthic assessment of a number of reef sites to investigate patterns in benthic cover, coral species diversity, and variation in environmental conditions. A more detailed assessment of the physiology of corals in TelaBay could also be carried out using fluorometry techniques to assess patterns in photosynthetic efficiency.

HU283 Depth distributions and bathymetric connectivity of coral reef fish (Weeks 2 – 9; need to be dive trained and have completed HU007)

HU283 Summary

Most coral reef research focuses on shallow water habitats and their ecological processes. A good example of this is the habitat connectivity exhibited by fish migrations between coral reef, seagrass and mangrove ecosystems. However, coral reefs extend beyond the limits of recreational diving, with mesophotic coral reef ecosystems (MCEs), extending in some areas to over 100m depth. These reefs are beyond the logistical abilities of most researchers, and therefore very little is known of the community structure at these depths, and what level of habitat connectivity exists between MCEs and their shallow counterparts. By working alongside a small team of technical divers able to sample MCEs, students on this project will collect the shallow data component through a range of fish and benthic monitoring techniques, and ultimately have access to both data sets for use in their dissertations. Specific questions could include an assessment of total biomass at varying depths, or a more detailed analysis of fish community structure between a range of habitats. The ultimate aim of this project is to investigate the importance of deeper coral reef habitats for conservation management, and data collected will be used to inform the conservation framework on Utila.

HB284 The ecological restoration offered by keystone species: Sea urchins in Tela Bay (Utila: Weeks 2 – 4, Tela: Weeks 5 – 9; need to be dive trained and have completed HU007 or HT009)

HB284 Summary

Under natural conditions, sea urchins (specifically Diadema antillarum) are the most important herbivores on Caribbean coral reefs, and are 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 limited throughout the Caribbean, with populations on most reefs still severely depleted, and Utila is a classic example of this. Remarkably, a reef system in Tela Bay known as Banco Capiro 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. In 2013, a significant colonisation of D. antillarum was observed on a heavily degraded reef system in Tela Bay, known as La Ensanada, which seems to support the theory that Banco Capiro can act as a seeder population for future reef recovery along the Honduran coast. This project will assess the populations of D. antillarum and other urchins on Honduran coral reefs, and investigate their ecological impact on degraded reefs after re-colonisation. In addition, students could investigate why the population of urchins in TelaBay has been so successful compared to nearby Utila.

HU285 Herbivore ecology and feeding behaviour on algal dominated reefs around Utila (Weeks 2 – 8; need to be dive trained and have completed HU007)

HU285 Summary

Many coral reefs are currently under threat from phase shifts which lead to a move from a coral-dominated to an algal-dominated system. The consequences of these changes in stable state can be enormous, both ecologically and economically, including a large reduction in carrying capacity for the associated fishery. Traditionally, macroalgal density is kept low through a lack of nutrients in the water combined with consumption by herbivores. However many reefs are now polluted, which leads to an increase in nutrients required for algal growth, whilst overfishing has greatly reduced the biomass of herbivorous fish. In the Caribbean an important grazing organism is the urchin Diadema antillarum, which naturally occurs on reefs in high numbers. In the 1980s a disease decimated the population throughout the Caribbean, and numbers around Utila have still shown no signs of significant recovery. This combination of factors has left Caribbean reefs like those around Utila even more vulnerable to phase shifts, and this dissertation will study herbivore activity around the island. Data could include bite rates of herbivorous fish normalised to biomass, focusing on differences in herbivory rates between species and in response to changes in habitat quality.

HB286 Influences on reef fish populations on contrasting reef systems in Honduras (Utila: Weeks 2 – 6, Tela: Weeks 7 – 9; need to be dive trained and have completed HU007)
The reefs around Utila and TelaBay offer a unique opportunity to study various aspects of fish community structure and population dynamics on Caribbean coral reefs. Reef fish populations are subjected to a huge variety of different pressures and variables, both natural and human, that dictates their abundance and diversity and many of these variables are little understood.  Specific influences that are particularly important in Honduras are those of fishing, coral/algal coverage on reefs and the role of mangrove systems as nursery grounds for juvenile reef fish species. On Utila, overfishing has long been a problem, whilst degraded reef habitats have limited the carrying capacity for fishery recovery. However, the island boasts a gradient of reef habitats to explore the drivers of fish population density and community structure. The reefs of TelaBay have been subjected to extreme overfishing in the past, which has led to a complete collapse of the fishery. This ultimately led to fishing pressure significantly decreasing as fishers sought alternative livelihoods which, along with the extensive mangrove systems in the bay, has provided Tela with the potential for rapid fish biomass recovery. Dissertation projects will use cutting edge stereo-video technology, which allows accurate biomass assessments of reef fish communities. These data will be combined with additional data on benthic habitat quality and abiotic factors to investigate the main drivers of variation in reef fish community structure, and to identify temporal trends in overall fish biomass at both sites.

HU287  Interactions between benthic organisms on coral reefs around Utila (Weeks 2 – 9; need to be dive trained and have completed HU007)

HU287 Summary

Scleractinian corals are the ecosystem architects of highly biodiverse and productive coral reef biomes. However, on many reefs around the Caribbean, numerous factors have negatively impacted the ability of corals to thrive as they once did, which has severely altered the way competition for space takes place on these reefs. In particular this has commonly led to an overgrowth of macroalgae and the threat of an ultimate phase shift to an alternative stable state lacking the structural complexity to support the high diversity of fish and invertebrates which a healthy coral reef is famous for. This dissertation will therefore study the interactions between key groups of benthic organisms such as Scleractinian corals, macroalgae, sponges and soft corals to assess how these interactions are varying between reefs with different levels of impact. It could also focus specifically on the coral community, and study how competition between coral colonies varies with increasing impacts to try and gauge which corals are most likely to dominate the system in future years.

MM288 Reef fish and coral communities in Nosy Be, Madagascar (Weeks 2 – 8)
For this topic students need to be dive trained and also to have completed an identification course on reef fish and coral species likely to be encountered. These courses will be running in weeks 2 and 3 and from weeks 4 – 8 students will be able to work on their dissertation topic which utilises the stereo video and benthic video data being collected on all the reefs around the Lokobe Reserve and adjacent areas. Repeat stereo video surveys will be completed at different depths and the images analysed back at the research centre. The software available in camp allows the length of each fish within the study area to be measured accurately so precise biomass estimates can be made as well as details on the species communities. The benthic video data is collected by laying a 50m tape along a depth contour and then the benthic communities are filmed by swimming along with a video under your right shoulder and holding the tape in your left hand.  The video data is then analysed back at the research centre to calculate total coral cover, hard and soft coral community composition and levels of bleaching and disease. The data from this topic could a be analysed to assess the relative effectiveness of utilising different length transects or how coral cover, coral communities or fish communities and size groups change with depth.  For those students at universities where completion of their dissertation/thesis outside of term time is not allowed, this topic provides an opportunity to gain experience in conducting fieldwork and a guaranteed data set for later analysis.