Ocean Coral Reefs Research Articles

Corresponding planktivore and predator spatial distributions in an oceanic coral reef system

Understanding the drivers of food web community structure is a fundamental goal in ecology. While studies indicate that many coral reef predators depend on pelagic subsidies, the mechanism through which this occurs remains elusive. As many of these species are important fishery targets, a better understanding of their trophodynamics is needed. To address these gaps, we employed a comprehensive structural equation modelling approach using extensive surveys of the reef community to explore relationships between groupers and snappers, their prey, and the surrounding habitat in an oceanic coral reef system. There were significant positive relationships between site-attached and transient planktivores and grouper and snapper biomass, respectively, indicating that pelagic subsidies are transferred to upper trophic levels through planktivores. Contrary to previous studies, habitat complexity and depth were not important for predators or prey. Instead, corallivores and site-attached and transient planktivores were primarily associated with live habitat and coral cover. This indicates that a decline in coral cover could have severe direct and indirect impacts on the structure and functioning of multiple levels of the reef food web. While pelagic reliance may suggest that predators are resilient to bleaching-related habitat loss, the associations of their planktivorous prey with live coral suggest that both benthic and pelagic pathways should be preserved for continued resilience of these food webs and their fisheries. By considering direct and indirect relationships, our study generated insights not only on the complex dynamics of coral reef ecosystems, but also on how they may respond to environmental change.

Host specificity of coral-associated fauna and its relevance for coral reef biodiversity

Coral-associated fauna predominantly consists of invertebrates and constitutes an important component of coral reef biodiversity. The symbionts depend on their hosts for food, shelter and substrate. They may act as parasites by feeding on their hosts, by overgowing their polyps, or by excavating their skeletons. Because some of these species partly reside inside their hosts, they may be cryptic and can easily be overlooked in biodiversity surveys. Since no quantitative overview is available about these inter-specific relationships, this present study adresses variation in host ranges and specificity across four large coral-associated taxa and between the Atlantic and Indo-Pacific oceans. These taxa are: coral barnacles (Pyrgomatidae, n = 95), coral gall crabs (Cryptochiridae, n = 54), tubeworms (Serpulidae, n = 31), and date mussels (Lithophaginae, n = 23). A total of 335 host coral species was recorded. An index of host specificity (STD) was calculated per symbiont species, based on distinctness in taxonomic host range levels (species, genus, family, etc.). Mean indices were statistically compared among the four associated taxa and the two oceanic coral reef regions. Barnacles were the most host-specific, tubeworms the least. Indo-Pacific associates were approximately 10 times richer in species and two times more host-specific than their Atlantic counterparts. Coral families varied in the number of associates, with some hosting none. This variation could be linked to host traits (coral growth form, maximum host size) and is most probably also a result of the evolutionary history of the interspecific relationships.

Multivariate environment-fish biomass model informs sustainability and lost income in Indian Ocean coral reefs

Multivariate environment-fish biomass model informs sustainability and lost income in Indian Ocean coral reefs

Mapping coral reef habitats of Apo Reef Natural Park, Sablayan, Occidental Mindoro, Philippines

Limited spatial information on Philippine oceanic coral reef resources poses a challenge to conservation and management. In the face of an increased occurrence of natural disturbances, repetitive, broad-scale spatial information is critical in determining large-scale patterns that help managers resolve the potential trajectory of the coral reef ecosystems, elucidating whether it will recover or continue to decline. In this study, we provide a decent habitat map of Apo Reef Natural Park using freely available Sentinel-2 data using the Google Earth Engine (GEE) cloud computing platform. Through the use of training and validation data, we implemented supervised classification via the classification and regression trees (CART) algorithm. The results successfully delineated four major habitat classes across ARNP with an acceptable level of accuracy (58.8%). These habitat classes are: Mixed Live Coral and DCA habitat, DCA habitat, Mixed Rubble and DCA habitat, and Sand habitat. In total, we mapped over 6,000 hectares of shallow subtidal habitats across a 27,000-hectare protected area. Among the classes, sand-dominated habitats had the largest coverage in the shallow subtidal section of the reef complex. The total hard coralline substrate was estimated to cover over 3,800 hectares. The impact of consecutive, high-intensity disturbances that hit ARNP resulted in the predominance of algae-covered habitat types, which in turn resulted in relatively high classification errors of DCA habitats, and Mixed Live Coral and DCA habitats. It is expected that as the reef recovers, accuracy in discerning these habitat types will eventually increase. The study shows the utility of the GEE platform in conducting low-cost, broad-scale monitoring of oceanic reef complexes at a resolution that is acceptable for management purposes.

Multivariate environment-fish biomass model informs sustainability and lost income in Indian Ocean coral reefs

Many tropical reef fisheries are underperforming relative to maximum sustained yields despite their importance for the economies and food security of natural resource dependent people. Assessments of fisheries in tropical reefs have been hampered by the logistic difficulty and costs of making empirical estimates of sustainable yields in multi-species fisheries. To overcome this limitation, we used empirical fish biomass recovery data in high-compliance closures to create a production curve estimate that established biomass and yields at maximum sustained yield (Bmsy). A multivariate machine learning model using environmental and human influence proxies made biomass and yield estimates in 10,815 ∼6.25 km2 Indian Ocean cells. Subsequent analyses determined the national over- and under-fishing status. Identified proxies of travel time from markets, depth, and fisheries management were the main drivers of biomass and subsequent status. The East African countries of Kenya, Tanzania, and Mozambique had 18,500 km2 of reef and the lowest regional estimated biomass - losing 17,600 tons of commercial target fish per year. Therefore, the estimated loss is between US$ 50–150 million per year depending on the worth in the fisheries trade’s value chain The more populated islands of Reunion, Mauritius, Mayotte, and Comoros have smaller areas (5000 km2) and losing 3000 tons/year, and >US$ 9 million per year. Madagascar has many reefs (13,700 km2) and larger variation in yields with an estimated loss of ∼6000 tons/y. Increased restrictions could greatly increase the value of Indian Ocean fisheries by promoting the recovery of target biomass and recovering lost income.

Body shape and mode of propulsion do not constrain routine swimming in coral reef fishes

AbstractIt is widely believed that because of biomechanical trade‐offs, fish body shape and the mode of propulsion are strong predictors of swimming performance, with the best cruisers, maneuverers and accelerators having different body forms and emphasizing different propulsion mechanisms. This paradigm is regularly projected onto routine swimming behaviour and dominates the ecomorphological literature, despite the paucity of field measurements.In this study, we measured variation in swimming behaviour among 48 species of Indian Ocean coral reef fishes using recordings from a remote stereo video system. We measured average swimming speed, average swimming bout distance, frequency of turns and percent of time spent station‐holding and looked for the predicted trade‐offs between them.We find little evidence of the expected relationships between swimming behaviours across species, little evidence that body shape affects swimming and few differences between species that swim by undulating the body and those that emphasize the use of median and paired fins. Taxa widely thought of as archetypical maneuverers (Chaetodon) and cruisers (Caranx) were not outliers in any behaviours.Our results indicate that swimming behaviour is not easily predicted from simple measures of body shape and that alternative swimming modes can produce comparable behavioural profiles.Read the freePlain Language Summaryfor this article on the Journal blog.

Tempestichthys bettyae, a new genus and species of ocean sleeper (Gobiiformes, Thalasseleotrididae) from the central Coral Sea

The Thalasseleotrididae is a small family of exclusively marine gobioids. They form a sister taxon to the Gobiidae and Oxudercidae and are distinguished from most species in these families by having six branchiostegal rays and a membrane linking the hyoid arch to the first ceratobranchial. Here we use micro-CT informed morphological data and molecular phylogenetics to describe a new genus and species of thalasseleotridid discovered on a tropical oceanic coral reef in the central Coral Sea. Tempestichthys bettyae gen. et sp. nov. is the first tropical thalasseleotridid and differs from other members of the Thalasseleotrididae by having a T-shaped palatine and a distinctive shape and colouration. The three previously described thalasseleotridid species are endemic to temperate coastal waters of southern Australia and New Zealand and are all translucent brown with dorsoventrally compressed heads. However, Tempestichthys bettyae is laterally compressed with a pointed snout and is translucent white with opaque white and crimson red markings and a largely crimson iris. We discuss the unique characters of this new genus, including its distribution, form, colouration and diminutive size, and highlight the potential of there being undescribed diversity in the Thalasseleotrididae. http://zoobank.org/urn:lsid:zoobank.org:pub:3F584DD6-0B33-4E69-98A7-22D68EE1A1B8

Spatial covariation in nutrient enrichment and fishing of herbivores in an oceanic coral reef ecosystem.

Both natural and anthropogenic stressors are increasing on coral reefs, resulting in large‐scale loss of coral and potential shifts from coral‐ to macroalgae‐dominated community states. Two factors implicated in shifts to macroalgae are nutrient enrichment and fishing of reef herbivores. Although either of these factors alone could facilitate establishment of macroalgae, reefs may be particularly vulnerable to coral‐to‐algae phase shifts in which strong bottom‐up forcing from nutrient enrichment is accompanied by a weakening of herbivore control of macroalgae via intense fishing. We explored spatial heterogeneity and covariance in these drivers on reefs in the lagoons of Moorea, French Polynesia, where the local fishery heavily targets herbivorous fishes and there are spatially variable inputs of nutrients from agricultural fertilizers and wastewater systems. Spatial patterns of fishing and nutrient enrichment were not correlated at the two landscape scales we examined: among the 11 interconnected lagoons around the island or among major habitats (fringing reef, mid‐lagoon, back reef) within a lagoon. This decoupling at the landscape scale resulted from patterns of covariation between enrichment and fishing that differed qualitatively between cross‐shore and long‐shore directions. At the cross‐shore scale, nutrient enrichment declined but fishing increased from shore to the crest of the barrier reef. By contrast, nutrient enrichment and fishing were positively correlated in the long‐shore direction, with both increasing with proximity to a pass in the barrier reef. Contrary to widespread assumptions in the scientific literature that human coastal population density correlates with impact on marine ecosystems and that fishing effort declines linearly with distance from the shore, these local stressors produced a complex spatial mosaic of reef vulnerabilities. Our findings support spatially explicit management involving the control of anthropogenic nutrients and strategic reductions in fishing pressure on herbivores by highlighting specific areas to target for management actions.

Conservation implications of forage base requirements of a marine predator population at carrying capacity

SummaryPrey depletion may contribute to marine predator declines, yet the forage base required to sustain an unfished population of predatory fish at carrying capacity is unknown. We integrated demographic and physiological data within a Bayesian bioenergetic model to estimate annual consumption of a gray reef shark (Carcharhinus amblyrhynchos) population at a remote Pacific atoll (Palmyra Atoll) that are at carrying capacity. Furthermore, we estimated the proportion of the atoll's reef fish biomass production consumed by the gray reef sharks, assuming sharks either partially foraged pelagically (mean 7%), or solely within the reef environment (mean 52%). We then predicted the gray reef shark population potential of other, less remote Pacific Ocean coral reef islands, illustrating that current populations are substantially smaller than could be supported by their forage base. Our research highlights the utility of modeling how far predator population sizes are from their expected carrying capacity in informing marine conservation.

Deep reef ecosystems of the Western Indian Ocean: addressing the great unknown

Indian Ocean coral reef ecosystems are some of the least explored, least funded and least protected worldwide. "First Descent: Indian Ocean" represents a series of research expeditions undertaken by Nekton between 2018-2022 in partnership with Governments in the Indian Ocean region to contribute to establishing a baseline of marine life and catalyse 30% protection by 2030. Two recent expeditions, the 2018 WILDOCEANS/ACEP Comoros Mesophotic Biodiversity Expedition (led by WILDTRUST), and the 2019 First Descent: Seychelles (led by Nekton Foundation) systematically surveyed deeper reef ecosystems in those areas, resulting in collections of biological meterial and underwater footage. In August 2019, taxonomic experts from across the globe, attended a workshop in order to identify the collected material and provide a first snapshot of the diversity of the surveyed habitats. Part of the workshop also focused on providing taxonomic training to host nation scientists and early career researchers. This document is a report on the proceedings and some of the first outcomes of this workshop.

Genomic and ecological attributes of marine bacteriophages encoding bacterial virulence genes

BackgroundBacteriophages encode genes that modify bacterial functions during infection. The acquisition of phage-encoded virulence genes is a major mechanism for the rise of bacterial pathogens. In coral reefs, high bacterial density and lysogeny has been proposed to exacerbate reef decline through the transfer of phage-encoded virulence genes. However, the functions and distribution of these genes in phage virions on the reef remain unknown.ResultsHere, over 28,000 assembled viral genomes from the free viral community in Atlantic and Pacific Ocean coral reefs were queried against a curated database of virulence genes. The diversity of virulence genes encoded in the viral genomes was tested for relationships with host taxonomy and bacterial density in the environment. These analyses showed that bacterial density predicted the profile of virulence genes encoded by phages. The Shannon diversity of virulence-encoding phages was negatively related with bacterial density, leading to dominance of fewer genes at high bacterial abundances. A statistical learning analysis showed that reefs with high microbial density were enriched in viruses encoding genes enabling bacterial recognition and invasion of metazoan epithelium. Over 60% of phages could not have their hosts identified due to limitations of host prediction tools; for those which hosts were identified, host taxonomy was not an indicator of the presence of virulence genes.ConclusionsThis study described bacterial virulence factors encoded in the genomes of bacteriophages at the community level. The results showed that the increase in microbial densities that occurs during coral reef degradation is associated with a change in the genomic repertoire of bacteriophages, specifically in the diversity and distribution of bacterial virulence genes. This suggests that phages are implicated in the rise of pathogens in disturbed marine ecosystems.

Estimating Connectivity Through Larval Dispersal in the Western Indian Ocean

AbstractThe health and functioning of coral reef ecosystems in the Western Indian Ocean are in decline due to anthropogenic stress, and the rate of decline is set to accelerate. Marine reserves have become important tools in mitigating these pressures, and one of the most critical factors in determining their spatial design is the degree of connectivity among populations. However, the spatial scale and strength at which populations are potentially connected by dispersal remain uncertain. In this paper, the potential connectivity of corals was assessed through a Lagrangian particle‐tracking algorithm coupled offline with an ocean circulation numerical model. Connectivity metrics and graph theory were used to analyze the networks and highlight those reefs that are critical for maintaining the connectivity of corals across the region. Western Indian Ocean coral reefs formed about 13 clusters for larvae with short pelagic larval duration (PLD; 5 days) but grouped into stable larger clusters at 15, 30, and 60 days PLDs, with strong westward dispersal from the northern tip of Madagascar and Comoro Islands toward the East African coast. Reefs at Mafia‐Latham Island (Tanzania), Angoche‐Nacala and Pemba‐Mucufi (Mozambique), Anjouan and Ngazidja (Comoros), and Glorieuses (France) were the most significant for multigenerational connectivity, as measured by betweenness centrality. The small islands Agalega and Tromelin were completely disconnected from other sites at all PLDs. These findings identify priority conservation areas and actions to help support coral reef resilience through a connected network of marine protected areas.

Los Roques and Las Aves Archipelagos, Venezuela: A Marine Ecological and Conservation Reconnaissance of Two Little-Known Southeastern Caribbean Oceanic Archipelagos

The Los Roques and Las Aves oceanic coral reef archipelagos of Venezuela lie in a biogeographically unique and biologically diverse area of the Caribbean and possess extensive coral reefs, seagrass beds, mangroves and shallow macroalgae meadows. The geographic location of these archipelagos safeguards them from most Western Atlantic hurricane damage as well as the most severe Caribbean coral bleaching episodes. While the Aves islands remain uninhabited and are an area of low accessibility, Los Roques has been a managed national park since 1972. We here present an updated synthesis of recent research for these archipelagos as an aid to scientists and conservationists interested in these island groups for which no recent ecological reviews are available. Los Roques has been much better documented than Las Aves and is the largest coral reef marine protected area of Venezuela. It has about 1,500 inhabitants living principally from tourism and fisheries. Studies show that Los Roques possesses fish populations that suffer comparatively less fishing pressure and may serve as a rare benchmark for pristine fish communities elsewhere in the Caribbean. It has also successfully maintained its importance to seabird colonies for the last five decades, notwithstanding serious marine park funding and staffing shortages. A new baseline biological inventory for Las Aves is particulary critical considering the fragmentary information available for this archipelago. The relatively intact and resilient oceanic coral reef systems of Los Roques and Las Aves are of regionally significant conservation value and deserve much more conservation and biodiversity attention than so far accorded.

Geography and island geomorphology shape fish assemblage structure on isolated coral reef systems.

We quantify the relative importance of multi‐scale drivers of reef fish assemblage structure on isolated coral reefs at the intersection of the Indian and Indo‐Pacific biogeographical provinces. Large (>30 cm), functionally‐important and commonly targeted species of fish, were surveyed on the outer reef crest/front at 38 coral reef sites spread across three oceanic coral reef systems (i.e. Christmas Island, Cocos (Keeling) Islands and the Rowley Shoals), in the tropical Indian Ocean (c. 1.126 x 106 km2). The effects of coral cover, exposure, fishing pressure, lagoon size and geographical context, on observed patterns of fish assemblage structure were modelled using Multivariate Regression Trees. Reef fish assemblages were clearly separated in space with geographical location explaining ~53 % of the observed variation. Lagoon size, within each isolated reef system was an equally effective proxy for explaining fish assemblage structure. Among local‐scale variables, ‘distance from port’, a proxy for the influence of fishing, explained 5.2% of total variation and separated the four most isolated reefs from Cocos (Keeling) Island, from reefs with closer boating access. Other factors were not significant. Major divisions in assemblage structure were driven by sister taxa that displayed little geographical overlap between reef systems and low abundances of several species on Christmas Island corresponding to small lagoon habitats. Exclusion of geographical context from the analysis resulted in local processes explaining 47.3% of the variation, highlighting the importance of controlling for spatial correlation to understand the drivers of fish assemblage structure. Our results suggest reef fish assemblage structure on remote coral reef systems in the tropical eastern Indian Ocean reflects a biogeographical legacy of isolation between Indian and Pacific fish faunas and geomorphological variation within the region, more than local fishing pressure or reef condition. Our findings re‐emphasise the importance that historical processes play in structuring contemporary biotic communities.

Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 560:87-103 (2016) - DOI: https://doi.org/10.3354/meps11921 Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs Timothy R. McClanahan1,*, Nyawira A. Muthiga1,2 1Wildlife Conservation Society, Marine Programs, 2300 Southern Boulevard, Bronx, NY, 10460 2Wildlife Conservation Society, Marine Programs, POB 99470, Kenya, 80107 *Corresponding author: tmcclanahan@wcs.org ABSTRACT: Calcification and reef growth processes dominated by corals and calcifying algae are threatened by climate and fishing disturbances. Twenty-seven environmental, habitat, and species interaction variables were tested for their influence on coral and calcifier cover in 201 western Indian Ocean coral reefs distributed across ~20° of latitude and longitude and up to 20 m deep. These variables predicted more of the total between-site variance of calcifying organism cover (~50%) than coral cover (~20%). Satellite-derived environmental variables of temperature, light, and water quality predicted more of the coral and calcifier cover than feeding interactions when groups of related variables were analyzed separately. Nevertheless, when simultaneously evaluating all variables, the environmental variables better predicted coral cover, but proxies of feeding interactions better predicted calcifier cover. Coral and calcifier cover were most consistently negatively influenced by sea surface temperature distributions (right skewness), but the orange-lined triggerfish Balistapus undulatus consistently had a strong positive association with coral and calcifier cover. Herbivorous fish and Diadematidae sea urchins were not positively associated with coral and calcifier cover. A primary prey of B. undulatus, the rock-boring sea urchin Echinometra mathaei, had a strong negative association with coral cover and particularly calcifier cover. Island reefs had higher calcifier abundance than fringing reefs, which probably results from high Acropora and B. undulatus but low E. mathaei abundance. When comparing all variables and models, these taxonomic associations had more influence than environmental stress variables on calcifiers. Given the important predatory role of B. undulatus in controlling E. mathaei populations, fishing restrictions on this species could help attenuate calcification losses predicted by climate change. KEY WORDS: Benthic cover · Calcium carbonate · Ecosystem-based management · Climate change · Predation · Resilience Full text in pdf format Supplementary material PreviousNextCite this article as: McClanahan TR, Muthiga NA (2016) Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs. Mar Ecol Prog Ser 560:87-103. https://doi.org/10.3354/meps11921 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 560. Online publication date: November 24, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Morphology of Biddulphia seychellensis (Grunow in Van Heurck) F.W. Mills and the generic limits of Biddulphia Gray

In this paper presented are the res ults of light and e lectron microscopie studies on a marine diatom species Biddulphia seychellensis. The species turned out to be abundant in some samples from the west coast of South Africa and from the western Indian Ocean coral reefs ofScattered Islands (Eparses). Unlike most representatives of the genus, B. seychellensis forms tripolar to square valves, but smallest specimens can be almost circular. The species shares a few features with the generitype, e.g., pseudocelli, few rimoportulae, areolae occluded with cribra and occas ional simple pores. Unlike in the generitype, however, the valve face in B. seychellensis is always flat, pseudocelli indistinct and never raised above the valve level, valvocopula is open, and the marg inal ridge is miss ing. Biddulphia seychellensis has been abundantly observed in warm oceanic waters with somewhat increased salini ty. In addition data on the di stribution in marine littoral are provided.

Identification and prevalence of coral diseases on three Western Indian Ocean coral reefs.

Coral diseases have caused a substantial decline in the biodiversity and abundance of reef-building corals. To date, more than 30 distinct diseases of scleractinian corals have been reported, which cause progressive tissue loss and/or affect coral growth, reproductive capacity, recruitment, species diversity and the abundance of reef-associated organisms. While coral disease research has increased over the last 4 decades, very little is known about coral diseases in the Western Indian Ocean. Surveys conducted at multiple sites in Reunion, South Africa and Mayotte between August 2010 and June 2012 revealed the presence of 6 main coral diseases: black band disease (BBD), white syndrome (WS), pink line syndrome (PLS), growth anomalies (GA), skeleton eroding band (SEB) and Porites white patch syndrome (PWPS). Overall, disease prevalence was higher in Reunion (7.5 ± 2.2%; mean ± SE) compared to South Africa (3.9 ± 0.8%) and Mayotte (2.7 ± 0.3%). Across locations, Acropora and Porites were the genera most susceptible to disease. Spatial variability was detected in both Reunion and South Africa, with BBD and WS more prevalent on shallow than deep reefs. There was also evidence of seasonality in 2 diseases: the prevalence of BBD and WS was higher in summer than winter. This was the first study to investigate the ecology of coral diseases, providing both qualitative and quantitative data, on Western Indian Ocean reefs, and surveys should be expanded to confirm these patterns.

The Effects of Meteorological Factors Anomalies on Oceanic Coral Reef Systems in the Northwestern South China Sea

Climate warming, variation of East Asian atmospheric system have affected the Chinese offshore environment through the air-sea interaction, the coastal waters of South China Sea had been influenced, leading a corresponding impact on the coral reef growth. This paper reports on coral coverage and dominant coral species changes in Xu wen National Coral Reef Nature Reserve, examines their relationship with meteorological factors anomalies recorded by satellite. The study reveals that: compared to the period from 1979 to 2003, the temperature of surface coastal water dropped significantly in South China Sea in 2004-2008, the divergence of low layer of atmosphere over it strengthened, produced a zonal westerly anomaly field, which had an opposite direction to the local northeastern trade wind. The increasing of suspended matter in water, the decreasing of down welling in northwestern South China Sea, made the water quality deteriorating, water transparency decreased significantly, coral reef survival environment worsened, which would cause adverse effects on coral reef building capacity in the Reserve. Continued monitoring efforts are necessary to further assess the relationship between coral building capacity and in situ meteorological factors anomalies and improve the use of the dataset in future regional degradation predictions.

Video transects are the most appropriate underwater visual census method for surveying high-latitude coral reef fishes in the southwestern Indian Ocean

Pilot studies are used to assess different sampling and monitoring protocols when developing long-term monitoring programs (LTMPs). Considering that the ultimate goal of LTMPs is preservation-orientated, non-destructive sampling methods are favoured. For coral reef fishes, underwater visual censuses (UVCs) have become the method of choice for surveying shallow, highly-diverse reefs. This study assessed three different UVC transect types to monitor high-latitude western Indian Ocean coral reefs; these were slate, photo and video transects. Slate data were analysed with CountN (all fish observed), while footage from reviewable photo and video transects was analysed by both CountN and MaxN (a single frame with the most fish per species), resulting in an assessment of five transect-type analysis technique combinations; slate, photo-CountN, video-CountN, photo-MaxN and video-MaxN. Video-CountN transects had the highest estimates of richness and abundance, the lowest variability, and the most representative diversity. Video-CountN transects were also the most efficient in that the time taken to analyse footage was comparable to the other combinations considered, the proportion of unidentifiable individuals was low, and it required the lowest sample size to achieve an acceptable statistical power. Video-CountN transecting is therefore recommended as the most appropriate method for conducting UVCs of high-latitude coral reef fishes in the southwestern Indian Ocean.

Bacterial Communities Associated with Porites White Patch Syndrome (PWPS) on Three Western Indian Ocean (WIO) Coral Reefs

The scleractinian coral Porites lutea, an important reef-building coral on western Indian Ocean reefs (WIO), is affected by a newly-reported white syndrome (WS) the Porites white patch syndrome (PWPS). Histopathology and culture-independent molecular techniques were used to characterise the microbial communities associated with this emerging disease. Microscopy showed extensive tissue fragmentation generally associated with ovoid basophilic bodies resembling bacterial aggregates. Results of 16S rRNA sequence analysis revealed a high variability between bacterial communities associated with PWPS-infected and healthy tissues in P. lutea, a pattern previously reported in other coral diseases such as black band disease (BBD), white band disease (WBD) and white plague diseases (WPD). Furthermore, substantial variations in bacterial communities were observed at the different sampling locations, suggesting that there is no strong bacterial association in Porites lutea on WIO reefs. Several sequences affiliated with potential pathogens belonging to the Vibrionaceae and Rhodobacteraceae were identified, mainly in PWPS-infected coral tissues. Among them, only two ribotypes affiliated to Shimia marina (NR043300.1) and Vibrio hepatarius (NR025575.1) were consistently found in diseased tissues from the three geographically distant sampling localities. The role of these bacterial species in PWPS needs to be tested experimentally.