Ocean Coral Reefs Research Articles

Depth structuring of pelagic copepod biodiversity in waters adjacent to an Eastern Indian Ocean coral reef

We compared pelagic copepod communities at three (400+ m) stations adjacent to Scott Reef (14°S), a shelf-break reef in Australia's Indian Ocean territory, with those within the shallow (c.50 m) atoll lagoon. The metazooplankton assemblage sampled by our 100-μm multinet system was dominated by small (< 1.0 mm) copepods. We identified over 220 copepod species, belonging to five of the nine orders. Of these, 68 (31%) are new records for Australian waters and at least 14 are likely to be undescribed. Redundancy analysis indicated that depth stratum was the most important determinant of community structure: distinct communities were associated with the epipelagic (within which the atoll lagoon community was further distinguished by reef-associated copepods), the chlorophyll maximum/thermocline, the upper mesopelagic and the hyper-benthos. The family Oncaeidae was highly speciose (> 52 taxa) and progressively more important with increasing depth.

The effects of sea surface temperature anomalies on oceanic coral reef systems in the southwestern tropical Atlantic

In 2010, high sea surface temperatures that were recorded in several parts of the world and caused coral bleaching and coral mortality were also recorded in the southwest Atlantic Ocean, between latitudes 0°S and 8°S. This paper reports on coral bleaching and diseases in Rocas Atoll and Fernando de Noronha archipelago and examines their relationship with sea surface temperature (SST) anomalies recorded by PIRATA buoys located at 8°S30°W, 0°S35°W, and 0°S23°W. Adjusted satellite data were used to derive SST climatological means at buoy sites and to derive anomalies at reef sites. The whole region was affected by the elevated temperature anomaly that persisted through 2010, reaching 1.67 °C above average at reef sites and 1.83 °C above average at buoys sites. A significant positive relationship was found between the percentage of coral bleaching that was observed on reef formations and the corresponding HotSpot SST anomaly recorded by both satellite and buoys. These results indicate that the warming observed in the ocean waters was followed by a warming at the reefs. The percentage of bleached corals persisting after the subsidence of the thermal stress, and disease prevalence increased through 2010, after two periods of thermal stress. The in situ temperature anomaly observed during the 2009–2010 El Nino event was equivalent to the anomaly observed during the 1997–1998 El Nino event, explaining similar bleaching intensity. Continued monitoring efforts are necessary to further assess the relationship between bleaching severity and PIRATA SST anomalies and improve the use of this new dataset in future regional bleaching predictions.

Ocean acidification and coral reefs

As the world's oceans continue to absorb atmospheric CO2, the resulting changes could adversely affect coral reefs. As the world's oceans continue to absorb atmospheric CO2, the resulting changes could adversely affect coral reefs.

Factors influencing microbial mat composition, distribution and dinitrogen fixation in three western Indian Ocean coral reefs

Cyanobacteria have been found to be important for primary production and nitrogen supply on coral reefs. Here, the distribution of cyanobacteria that dominate microbial mats (identified by using microscopic and molecular tools), their abundance, and specific contributions and timing of N2 fixation, were studied in two coral reef systems of the western Indian Ocean: Mayotte (Comoros) and Tulear (Toliara, Madagascar). The results were compared with previously published data from the reefs of La Réunion Island (Mascarenes). Variations in nutrient levels, temperature and light penetration (Secchi) were also measured and compared. The reefs in Mayotte are situated in oligotrophic ocean waters and support coral reefs in good condition. The reef of Tulear was overgrown by algae. The shallow lagoon and reef in La Réunion showed signs of eutrophication and coral degradation. All three reefs maintained a diverse population of benthic cyanobacterial mats. A total of 13 different cyanobacterial morphotypes were encountered, belonging mainly to the genera Anabaena, Hydrocoleum, Leptolyngbya and Lyngbya (as identified by morphotypes and 16 S RNA analyses), but with variable abundances. Twelve of the 13 dominant cyanobacteria observed in the three sites fixed dinitrogen with daily rates of up to 42 nmol N2 µg−1 Chl a. Maximum values were achieved by the heterocystous Anabaena sp. during daylight in Mayotte, which exhibited strongly light‐stimulated nitrogenase activity. Mats dominated by non‐heterocystous cyanobacteria fixed both during daylight and the night, with daily rates up to 38 nmol N2 µg−1 Chl a (by Lyngbya majuscula, Mayotte). Hydrocoleum‐dominated mats fixed N2 at rates between 0 (H. glutinosum, Tulear) and 23.4 nmol N2 µg−1 Chl a (H. coccineum, Mayotte). Cyanobacteria are normal constituents of the benthic microflora in tropical regions, but their abundance, diversity and species composition changes with environmental conditions and so do the rates of N2 fixation on the lagoon floors.

Nutrient status in coral reefs of the Îles Eparses (Scattered Islands): comparison to nearby reefs subject to higher anthropogenic influences (Mozambique Channel and Mascarenes, Indian Ocean)

Abstract Indian Ocean coral reef environments off Mascarenes (Réunion and Rodrigues Islands), Comores archipelago (Mayotte) and Eparses atolls (Europa, Glorieuses, Juan de Nova and Tromelin), were sampled in 2007 and 2009 for environmental parameters and benthic diatoms studies. This preliminary note documents the nutrient concentrations [NO3−, NO2−, PO4− and Si(OH)4] of coastal waters in diverse sites and examines the possible relationship between nutrient concentration and anthropogenic pressure. The pool of data is restricted, but the marine coastal environments of Réunion, Rodrigues and Mayotte exhibit, on average, higher levels of nutrient concentration, as compared to Eparses atolls, probably in relation to the degree of urbanisation. A project based on the study of benthic diatom assemblages will offer the opportunity to search for possible anthropogenic signatures.

Theme section on “Ocean Acidification and Coral Reefs”

Theme section on “Ocean Acidification and Coral Reefs”

Western Indian Ocean coral communities: bleaching responses and susceptibility to extinction

A field study of coral bleaching and coral communities was undertaken spanning 8 countries and ~35° of latitude in 2005. This was combined with studies in southern Kenya and northeast Madagascar in 1998 and Mauritius in 2004 to develop a synoptic analysis of coral community structure, bleaching response, susceptibility of the communities to bleaching, and the relative risk of extinctions in western Indian Ocean coral reefs. Cluster analysis identified 8 distinct coral communities among the 91 sites sampled, with 2 distinct communities in northern South Africa and central Mozambique, a third in the central atolls of the Maldives, and 5 less differentiated groups, in a swath from southern Kenya to Mauritius, including Tanzania, the granitic islands of the Seychelles, northeast Madagascar, and Reunion. Massive Porites, Pavona, and Pocillopora dominated the central and northern Indian Ocean sites and, from historical records, replaced dominance by Acropora and Montipora. From southern Kenya to Mauritius, coral communities were less disturbed, with Acropora and Montipora dominating, and a mix of subdominants including branching Porites, Fungia, Galaxea, massive Porites, Pocillopora, and Synarea. The survey identified an area from southernmost Kenya to Tanzania as having the least disturbed and highest diversity reefs, and as being a regional priority for management. Taxa vulnerable to future extinction based on their response to warm water, population density, and commonness include largely low-diversity genera with narrow environmental ranges, such as Gyrosmilia interrupta, Plesiastrea versipora, Plerogyra sinuosa, and Physogyra lichtensteini.

Reproduction of the commercial sea cucumber Holothuria whitmaei [Holothuroidea: Aspidochirotida] in the Indian and Pacific Ocean regions of Australia

Seasonal trends in the gonad index (GI) of two widely separated populations of black teatfish, Holothuria whitmaei (formerly included in Holothuria nobilis), were investigated between Pacific (Great Barrier Reef) and Indian Ocean (Ningaloo Reef) coral reefs of Australia. Reproductive activity followed a similar annual trend, with the GI of both populations peaking typically between April and June. Macroscopic and histological analysis of Ningaloo Reef specimens revealed that large germinal tubules, positioned centrally on the gonad basis, progressed through four maturity stages: growing (II); mature (III); partly spawned (IV); and spent (V). Growing tubules dominated the central region of the gonad basis between January and March, followed by an increase in the number of mature tubules throughout the GI peak (April–June). The progressive appearance of partly spawned and spent tubules between June and October suggests that spawning in H. whitmaei continues intermittently over an extended period throughout the austral winter. The examination of the gonad structure of sexually mature male and female specimens identified five tubule size classes in total (C1 to C5), each of differing physical and gametogenic status. In females, smaller C1 tubules located at the anterior edge of the gonad basis contained pre- to early vitellogenic oocytes. Larger C2 and C3 tubule cohorts, positioned centrally on the gonad basis, contained mid- to late-stage vitellogenic oocytes. Smaller C4 and C5 tubules, located at the posterior edge, contained only relict oocytes. Similar physical and gametogenic differences were apparent between tubule cohorts in male specimens. We propose that these results, together with evidence of incomplete gonad resorption over the austral summer, indicate that gonad development in H. whitmaei conforms to the predictions of the Tubule Recruitment Model (TRM). The TRM is reported rarely among tropical aspidochirotes, and results presented here (1) provide the first direct evidence of this model in H. whitmaei, and (2) confirm that this species is one of the few winter-spawning tropical invertebrates.

Taxonomic patterns of bleaching within a South African coral assemblage

In 1998, the Indian Ocean coral reefs suffered a severe and extensive mass bleaching event. The thermal tolerances of corals were exceeded and their photosynthetic symbionts (zooxanthellae) lost. Mortalities of up to 90% were recorded on the reefs of Seychelles, Maldives, Kenya and Tanzania. South African coral reefs were among the few that largely escaped the 1998 mass bleaching event, but may be threatened in the future if global warming increases. This study assessed the extent of coral bleaching and partial recovery at Sodwana Bay, South Africa during 2000 and 2001. Bleaching levels in this study varied over the course of a year, which suggested that seasonally varying parameters such as sea temperature were the most likely cause of bleaching. Bleaching levels were highest at the shallowest site. However, these bleaching levels were very low in comparison with those of reefs elsewhere in the Indian Ocean. The greater volume of water over the relatively deeper reefs of Sodwana Bay may have protected the reefs from severe bleaching. Field measurements on the three reefs indicated that, although the reefs at Sodwana Bay are still healthy, bleaching increased from <1% in 1998 to 5–10% in 2002. Bleaching occurred in 26 coral genera. The Alcyonacea were highly susceptible to bleaching, especially Sarcophyton sp. Among the hard corals, Montipora spp. were the species most susceptible to bleaching. The sensitivity of these genera to early and slight increases in temperature suggests that they can forewarn of a possible greater bleaching event. In contrast, the coral genera Turbinaria and Stylophora were most resistant to bleaching.

Use of in situ and airborne reflectance for scaling-up spectral discrimination of coral reef macroalgae from species to communities

In principle, a priori knowledge of organism-scale spectral signatures for key ecological end-members is a basic requirement for identifying coral reef benthic communities using hyper- spectral remotely-sensed imagery. Spectral signatures of end-members are now relatively well known for predominant reef taxa (coral, algae) and for the background of the living communities (e.g. sediments). What remains unclear is whether the criteria for spectral discrimination between end- members at the millimeter or centimeter scale remain valid when attempting to process images at several meters resolution. In other words, is it possible to scale-up spectral criteria of identification from species/organisms to communities? We address this issue with in situ and 'compact airborne spectrometer imager' (CASI) hyperspectral measurements of the tropical marine flora of 2 South Pacific Ocean coral reefs. Targets were the dominant algal species and communities encountered in the shallow (0 to 3 m) barrier and fringing reefs of Moorea Island and the outer margin of the rim of Rangiroa Atoll (French Polynesia). Stepwise wavelength selection and linear discriminant analysis highlighted the key non-redundant wavelengths necessary to achieve good separation between the predefined ecological groups. Comparison of the wavelengths identified from in situ and airborne measurements allowed definition of a subset of common wavelengths that were robust to changes in spatial scale and still provided excellent discrimination and classification accuracy between the eco- logical groups. These results suggest that continuous spectral signatures acquired in situ at the centi- meter scale can be used to select key discrete wavelengths for remote-sensing observations of com- munities at the meter scale despite the spatial heterogeneity in benthic cover and the resulting spectral mixing.

A new species of the gobiid fish Trimma from the Western Pacific and Northern Indian Ocean coral reefs, with a description of its osteology

A new species of the genus Trimma is described. Trimma annosum is characterized by the presence of scales in the predorsal midline, non-elongate spines in the first dorsal fin, and a moderate interorbital trench. The fifth pelvic-fin ray is branched dichotomously once and is 40-65% the length of the fourth. When alive, Trimma annosum is bluish grey with 3 or 4 rows of large yellow blotches on the head and body. In addition to the northern Indian Ocean where it is apparently rare, the species is distributed eastward throughout Indonesia and the Philippines to China, Micronesia and Fiji. The osteology of this species is described and illustrated in some detail to form the basis for a series of phylogenetic studies of Trimma currently being undertaken.

A comparison of the ecology of shallow subtidal gastropods between western Indian Ocean and Caribbean coral reefs

I studied the ecology of snails inhabiting shallow wave-protected subtidal coral reef seascapes on the down-welling eastern edge of the American (Florida Keys and Belize) and African (Kenya and Madagascar) continents. Snail population abundance (CPUE), body sizes, modes of feeding, numbers of species, and species diversity were compared between regions and ocean basins. The Caribbean region had a third the number of species above 50 h or 5,000 individuals of sampling and higher dominance. When analyzed as numbers of individuals, the Caribbean community had a greater abundance of herbivorous and detritivorous individuals compared to the western Indian Ocean region. When analyzed as a percentage of species, there were no trophic differences, with two thirds of the species being carnivorous and one third herbivorous or detritivorous in both ocean basins. Body sizes were also not different in analyses based on either species or population abundance, but the Caribbean sites had higher variation in body size than the western Indian Ocean. The trophic, dominance, and species richness data suggest that the Caribbean assemblage has been influenced by environmental stress, but body-size data do not reflect this pattern unless stress increases variation rather than decreases body size. Recent environmental conditions may account for differences in the population dominance of trophic categories, but differences in species richness has required many millions of years of differential species origination and extinction.

Endobionts of the Coral Reef Sponge Theonella swinhoei (Porifera, Demospongiae)

Endobionts associated with the coral reef sponge Theonella swinhoei (Lithistida, Demospongiae), from the Red Sea and Indian Ocean, were characterized through histological and ultrastructural investigations. Prokaryotes included unicellular heterotrophic bacteria (mean concentration, 20% of the sponge tissue), unicellular cyanobacteria (Aphanocapsa feldmanni, 15% of the sponge tissue), and non-photosynthetic filamentous forms, probably in the Beggiatoa-group (sulfur bacteria, family Beggiatoaceae, 40% of the sponge tissue). Evidence of ingestion of small pieces of filamentous bacteria by sponge cells was observed. The worm Haplosyllis spongicola (Syllidae, Polychaeta) inhabited the canals of the sponge aquiferous system (mean density, 73 worms/cm3). The abundance and distribution of the endobionts living in T. swinhoei from different localities are presented and discussed in comparison with those of other sponge species reported in literature. Additional key words: polychaetes, filamentous bacteria, cyanobacteria Sponges present an astonishing landscape of associations with various kinds of autotrophic and heterotrophic organisms (Pearse 1932; Pansini 1970; Ilan et al. 1994). The various parts of a sponge, especially the endosome, contain large populations of extracellular bacteria (Vacelet 1975; Vacelet & Donadey 1977), which may greatly differ from the bacterial population in the water surrounding the same sponge (Wilkinson 1978b). The presence of cyanobacteria or other photosynthetic organisms is less frequent. Even though the autotrophic organisms inhabit the more superficial layers in order to fulfill their metabolic needs, some peculiar localizations inside the skeletal fibers (Riitzler 1990) and along the siliceous spicule bundles (Gaino & Sara 1994) have been observed. In this last condition, siliceous spicules, acting as a light-conducting system (Cattaneo-Vietti et al. 1996), enhance photosynthesis. Since the first observations of Feldmann (1933), many ultrastructural studies have stressed the presence of cyanobacteria in sponges of both Mediterranean and tropical origin (Sara 1971; Vacelet 1971; Vacelet & Donadey 1977; Wilkinson 1978a,c; Rutzler 1990). In some cases symbionts are so tightly associated with the sponge tissues as to constitute a symbiocortex (Simpson 1984, pp. 114-123). Cyanobacteria protect a Author for correspondence. E-mail: zoologia@unige.it sponges from excessive solar radiation (Sara & Vacelet 1973; Wilkinson 1980) and variations in the photosynthetic symbiont concentration may effect changes in the color of the sponge surface (Gaino et al. 1977). Direct feeding on cyanobacteria has been frequently suggested but observed only for unicellular types (Sara 1966; Wilkinson 1980; Berthold et al. 1982; Rutzler 1990). The translocation of glycerol, fixed nitrogen, and other photosynthetically fixed nutrients represents a trophic advantage for the sponge host (Wilkinson 1979; Wilkinson & Fay 1979), mainly in coral reefs and other tropical environments where the low levels of available nutrients favor these associations (Wilkinson 1987). So far, only two species of unicellular cyanobacteria have been frequently described in association with sponges: Aphanocapsa feldmanni and A. raspaigellae (Sara 1966; Gaino et al. 1976; Wilkinson 1980; Rutzler 1990). A few reports treat filamentous multicellular cyanobacteria, differing in dimension and shape, most commonly Oscillatoria spongeliae (Sara 1966) and Phormidium spongeliae (Wilkinson 1980). Nonetheless, Bewley et al. (1996), in ultrastructural observations, reported the lack of a photosynthetic system in some prokaryotic filaments, previously attributed to the above mentioned cyanobacteria. In addition, sponges serve as hosts to a number of other heterotrophic organisms, providing food and shelter to species from many taxa. Polychaetes have This content downloaded from 157.55.39.153 on Mon, 19 Sep 2016 04:41:51 UTC All use subject to http://about.jstor.org/terms Magnino, Sara, Lancioni, & Gaino been commonly observed in sponges (Pearse 1950; Pawlik 1983; Koukouras et al. 1996; Martin 1996; Rutzler, 1997). In particular, the polychaete Haplosyllis spongicola (GRUBE 1855), family Syllidae, is an abundant inhabitant of sponges. Fauchald & Jumars (1979) proposed that this worm grazes on the sponge surface. A more intimate relationship with its host has been directly observed by Tsurumi & Reiswig (1997), who reported that H. spongicola feeds on the tissues surrounding the sponge water canals, within which it lives. It is often difficult to establish the correct relationship between sponges and their endobionts. The sponge Theonella swinhoei GRAY 1868 (order Lithistida) is a remarkable component of the sponge populations in coral reef communities. Heterospecific associations, representing many types of adaptive interactions, are very common in this peculiar environment (Wilkinson 1987; Castro 1988). Previous studies on T. swinhoei from the Red Sea showed the unicellular symbionts A. feldmanni associated with sponge tissues (Wilkinson 1979, 1980; Bewley et al. 1996). Here we document that specimens of T. swinhoei, from both Red Sea and Indian Ocean coral reefs, constitute a further example of how sponges may represent a suitable micro-environment for the development of various kinds of autotrophic and heterotrophic organisms, which inhabit different parts of the sponge body.

Zoogeography of the coral reef fishes of the Socotra Archipelago

Fish communities and habitats were studied at the Socotra archipelago (Gulf of Aden, ≈12°N 54°E). Extensive and unexpected hermatypic coral communities were recorded, at the centre of a 2200 km gap in knowledge of species and habitat distributions which coincides with a change from a western Indian Ocean coral reef fauna to an Arabian one. The fish assemblage associated with the Socotra archipelago corals is predominantly south Arabian. An east African influence, minimal on the mainland coasts of Arabia, is more evident here, and results in previously unrecorded sympatry between Arabian endemic species and their Indian Ocean sister taxa. A study of distributions of Chaetodontidae (butterflyfishes) in the north‐western Indian Ocean reveals a number of distinct patterns, with a trend for species replacement along a track from the northern Red Sea to the Indian Ocean. A major feature of the reef fish zoogeography of the region is found to be a distinct south Arabian area, characterized by a ‘pseudo‐high latitude effect’ which results from seasonal cold water upwelling along the Arabian sea coasts of Yemen and Oman and the Indian Ocean coast of Somalia. This south Arabian feature is consistent across a wide range of fish families. It is most pronounced in Oman and Yemen, and although it is the dominant influence at Socotra it is slightly ‘diluted’ here by the east African influence. The south Arabian area wholly or partly accounts for most of the major marine zoogeographic features around Arabia, and is the principal feature fragmenting Arabian coastal fish assemblages, and separating them from those of the wider Indo‐west Pacific.

Species Records and Distribution of Shallow-water Coralline Algae in a Western Indian Ocean Coral Reef (Trou d’Eau Douce, Mauritius)

Article Species Records and Distribution of Shallow-water Coralline Algae in a Western Indian Ocean Coral Reef (Trou d’Eau Douce, Mauritius) was published on January 1, 1995 in the journal Botanica Marina (volume 38, issue 1-6).

Predictable spatial escapes from herbivory: how do these affect the evolution of herbivore resistance in tropical marine communities?

Between-habitat differences in macrophyte consumption by herbivorous fishes were examined on three Caribbean and two Indian Ocean coral reefs. Transplanted sections of seagrasses were used as a bioassay to compare removal rates in reef-slope, reef-flat, sand-plain, and lagoon habitats. Herbivore susceptibility of fifty-two species of seaweeds from these habitats was also measured in the field. Seagrass consumption on shallow reef slopes was always significantly greater than on shallow reef flats, deep sand plains, or sandy lagoons. Reef-slope seaweeds were consistently resistant to herbivory while reef-flat seaweeds were consistently very susceptible to herbivory. This pattern supports the hypothesis that defenses against herbivores are costly in terms of fitness and are selected against in habitats with predictably low rates of herbivory.Sand-plain and lagoon seaweeds showed a mixed response when placed in habitats with high herbivore pressure; most fleshy red seaweeds were eaten rapidly, most fleshy green seaweeds were eaten at intermediate rates, and most calcified green seaweeds were avoided or eaten at very low rates. Differences in susceptibility between red and green seaweeds from sand-plain or lagoon habitats may result from differential competitive pressures experienced by these seaweed groups or from the differential probability of being encountered by herbivores. The susceptibility of a species to removal by herbivorous fishes was relatively consistent between reefs. Preferences of the sea urchin Diadema antillarum were also similar to those of the fish guilds.Unique secondary metabolites were characteristic of almost all of the most herbivore resistant seaweeds. However, some of the herbivore susceptible species also contain chemicals that have been proposed as defensive compounds. Genera such as Sargassum, Turbinaria, Thalassia, Halodule, and Thalassodendron, which produce polyphenolics or phenolic acids, were consumed at high to intermediate rates, suggesting that these compounds are not effective deterrents for some herbivorous fishes. Additionally, potential for the production of the compounds caulerpin, caulerpicin and caulerpenyne in various species of Caulerpa did not assure low susceptibility to herbivory.Heavily calcified seaweeds were very resistant to herbivory, but all of these species also produce toxic secondary metabolites which makes it difficult to distinguish between the effects of morphological and chemical defenses. Predictions of susceptibility to herbivory based on algal toughness and external morphology were of limited value in explaining differing resistances to herbivory.

The Foraging Strategy of Vermivorous Conid Gastropods

A heuristic model, developed from simple assumptions, generates testable hypotheses that predict the foraging patterns of predators which invest a significantly greater amount of energy in search for, as compared to pursuit and handling of, prey. Given: (1) the environmental distribution of potential food size, (2) the environmental distribution of potential food diversity within food size, and (3) the manner in which the limits of consumable food size vary with predator size; food and microhabitat niche breadths as a function of predator size can be predicted. The assumptions and derived hypotheses of the model are tested with data from vermivorous prosobranch gastropods of the genus Conus, ubiquitous associates of tropical Pacific Ocean and Indian Ocean coral reefs. Predictions are: (1) small Conus (&lt;10 mm shell length) are trophic specialists; (2) medium—sized Conus (10—25 mm shell length), trophic generalists; and (3) large Conus (&gt; 25 mm shell length), trophic specialists. This pattern is supported by both within— and between—species comparisons of Conus populations of different mean sizes. Relationships of food niche breadth with predator size are interpreted in light of the marked behavioral and morphological stereotypy of Conus, probably evolved in response to evolutionary and proximate predictability of available prey.

Regional Variation in Indian Ocean Coral Reefs. D. R. Stoddart , Maurice Yonge

<i>Regional Variation in Indian Ocean Coral Reefs</i>. D. R. Stoddart , Maurice Yonge

Polychaetes of Truncated Reef Limestone Substrates on Eastern Indian Ocean Coral Reefs: Diversity, Abundance, and Taxonomy

AbstractThis study provides the first evaluation of abundance and diversity of polychaete annelid assemblages of coral reefs. Quantitative analyses of the polychaete fauna of truncated coral reef limestone platforms off Sumatra and Thailand revealed a total of 76 species (13 reported for the first time from the tropical Indian Ocean) and average population densities of 49,000/m2. The number of species in a single sample ranged from 16 to 32, and species diversity (H) ranged from 1.9 to 2.5. Three species of Syllidae, Palola siciliensis, and Dodecaceria laddi occurred in all samples. The syllids dominated numerically in all samples but were quite small, mainly 2–10 mm long and 0.01–0.04 mg dry weight. Samples from the same station were essentially identical in species composition and relative abundance. Similarity decreased with increasing distance between stations. With respect to number of species, population density, and dominance of syllids, the assemblages studied resemble those associated with limestone substrates in marine caves in the Mediterranean.

Indian Ocean Coral Reefs: Reviews

Indian Ocean Coral Reefs: Reviews