Scleractinian Corals Research Articles

Exposure to pentachlorophenol destructs the symbiotic relationship between zooxanthellae and host and induces pathema in coral Porites lutea

Stress from chemical pollutants is among the key issues that have adverse impacts on coral reefs. As a persistent organic pollutant, pentachlorophenol (PCP) has been detected in the seawater of Weizhou Island and was proved to have significant adverse effects on aquatic animals. However, little is known about its effects on scleractinian coral. Therefore, we investigated the response of the coral Porites lutea to PCP stress. Coral bleaching, photosynthesis parameters and antioxidant enzyme activities of P. lutea under PCP exposure were documented. After 96 h of exposure, significant tissue loss and bleaching occurred when the PCP concentration exceeded 100 μg/L. The density of symbiotic zooxanthellae decreased from 2.06 × 106 cells/cm2 to 0.93 × 106 cells/cm2 when the PCP concentration increased from 1 μg/L- 1000 μg/L. Long-term exposure of 120 days to PCP at 0.1 μg/L also led to coral bleaching, the maximum photochemical quantum yield of PSII in P. lutea nubbins significantly decreased to 0.482. The analysis of microbial community distribution indicated that the increase of the pathogenic bacterium Citrobacter may be one of the inducers of coral bleaching. Conjoint analysis of transcriptomics and proteomics showed that the metabolism of amino acids and carbohydrates in zooxanthellae was abnormal, leading to the destruction of its symbiotic relationship with the host. The immune system of the host was disrupted, which could be linked to the prevalence of coral pathema. The toxic responses of PCP on both zooxanthellae and its host were further confirmed by the upregulation of the differential metabolites including 1-naphthylamine and phosphatidylcholine, etc.

Patterns of change in coral reef communities of a remote Maldivian atoll revisited after eleven years

Coral reefs are exposed worldwide to several global and local human pressures including climate change and coastal development. Assessing the effects of such pressures on coral reef communities and the changes they undergo over time is mandatory to understand their possible future trends. Nonetheless, some coral reefs receive no or little scientific attention, as in the case of Huvadhoo Atoll that is an under-studied region in the southernmost area of the Maldives (Indian Ocean). This study analyzes the changes occurring over time in eight coral reefs (four inner reefs within the atoll lagoon and four outer reefs on the ocean side) at Huvadhoo Atoll, firstly surveyed in 2009 and revisited in 2020 using the same field methods. The cover of 23 morphological benthic descriptors (including different growth forms of Acropora) was taken into account and then grouped into three categories (i.e., hard coral, other benthic taxa and abiotic descriptors) to analyze the change in the composition of the coral reef community. Significant changes (e.g., increase in hard coral cover and decrease in abiotic descriptors) were observed in the inner reefs as compared to the outer reefs, which showed less variability. A significant decrease in tabular Acropora cover was observed in both inner and outer reefs, with possible negative effects on reef complexity and functioning. By comparing two time periods and two reef types, this study provides novel information on the change over time in the community composition of Maldivian coral reefs.

Modern-type reef in ancient time - Palaeoecology of a Middle Devonian coral community from Madène el Mrakib (Anti-Atlas, Morocco)

The southernmost Devonian reefs formed along the north-western margin of Gondwana. One of the best-preserved reefal palaeoecosystems of this area is found in the Givetian of Madène el Mrakib (Anti-Atlas, Morocco), exposing a vast, at least ∼1.2 km2 area of reef strata. This contribution documents the ecological succession, taxonomical structure and palaeoecology of this exceptionally diverse reef community. Combined evidence from the sedimentary succession and faunal changes records a trend of progressive shallowing. The ecological succession is characterised by an upsection increase in the abundance and diversity of the reef-building biota, accompanied by a shift in the dominant morphotypes of tabulate corals from platy (pioneering and diversification stages) to branching and massive forms (climax stage). The exceptionally rich, shallow-water reef community occurs in the uppermost part of the succession. The climax community is dominated by extraordinarily large, branching tabulate corals (mostly Thamnopora), with the notable role of massive alveolitid, heliolitid and favositid tabulates, as well as large, solitary rugose corals. A surprising feature of this assemblage is the rather subordinate role of stromatoporoids, generally regarded as a main component of the shallow-water Devonian reefs. Remarkably, the observed community structure is closer to that typical of modern shallow-water reefs, dominated by branching scleractinian corals from the family Acroporidae, than to the archetypal Paleozoic reefs. These distinctive traits of the Madène el Mrakib community make it particularly suitable for comparative studies between Devonian and modern reef ecosystems, showing that these communities shared notable similarities in terms of their ecological successions, zonation patterns, dominance of branching corals and high morphological variability in shallow-water environments, and adaptations of corals to turbulent conditions.

Distinct coral environments shape the dynamic of planktonic Vibrio spp.

BackgroundCoral reefs are one of the most biodiverse and productive ecosystems, providing habitat for a vast of species. Reef-building scleractinian corals with a symbiotic microbiome, including bacteria, archaea, viruses and eukaryotic microbes, are referred to coral holobionts. Among them, coral diseases, mainly caused by Vibrio spp., have significantly contributed to the loss of coral cover and diversity. Habitat filtering across the globe has led to a variety structure of marine bacterial communities. Coral species, quantity and characteristics are significant differences between the Xisha Islands and Daya Bay (Guangdong Province). Thus, the Vibrio communities may be distinct between coral rich and poor areas.ResultsThrough comparison of Vibrio dynamics between coral-rich (Xisha Islands) and coral-poor (Daya Bay) locations, we uncovered differences in Vibrio abundance, diversity, community composition and assembly mechanisms associated with corals. The higher abundance of Vibrio in coral rich areas may indicate a strong interaction between vibrios and corals. V. campbellii, Paraphotobacterium marinum and V. caribbeanicus were widely distributed in both coral rich and poor areas, likely indicating weak species specificity in the coral-stimulated growth of Vibrio. Random-forest prediction revealed Vibrio species and Photobacterium species as potential microbial indicators in the coral rich and coral poor areas, respectively. Ecological drift rather than selection governed the Vibrio community assembly in the Xisha Islands. Comparatively, homogenizing selection was more important for the Daya Bay community, which may reflect a role of habitat filtration.ConclusionThis study revealed the different distribution pattern and assembly mechanism of Vibrio spp. between coral rich and poor areas, providing the background data for the research of Vibrio community in coral reef areas and may help the protection of coral reef at the biological level. The main reasons for the difference were different number and species of corals, environmental (e.g., temperature) and spatial factors. It reflected the strong interaction between Vibrio and corals, and provided a new perspective for the investigation of Vibrio in coral reef ecosystem.

Hoeflea poritis sp. nov., isolated from a bleached scleractinian coral Porites lutea.

A Gram-stain-negative, aerobic, rod-shaped, nonmotile and yellow-pigmented bacterium designated E7-10T was isolated from a bleached scleractinian coral Porites lutea. Strain E7-10T grew with 1.0-8.0 % (w/v) NaCl (optimum, 4.0 %), at 18-41 °C (optimum, 28 °C) and at pH 6.0-10.0 (optimum, pH 8.0). Phylogenetic analysis using 16S rRNA gene sequences revealed that E7-10T formed a lineage within the genus Hoeflea, but it was distinct from the closest species 'Hoeflea prorocentri' PM5-8T, showing 98.01 % sequence similarity. The predominant cellular fatty acids of E7-10T were summed feature 8 (26.7 %), C18 : 1 ω7c 11-methyl (26.2 %), C16 : 0 (20.8 %) and C19 : 0 cyclo ω8c (17.9 %). The major respiratory quinone was Q-10. The polar lipids mainly comprised phosphatidylethanolamine, two glycolipids and five phospholipids. The genome size of E7-10T was 5.58 Mb with G+C content 60.27 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between the genomes of strains E7-10T and PM5-8T were 19.50 and 75.95 %, respectively, which were both below the defined cutoff values (70 % and 95-96 %, respectively) for species delimitation. Thus, strain E7-10T represents a novel species within the genus Hoeflea, for which the name Hoeflea poritis sp. nov. is proposed. The type strain is E7-10T (=JCM 35852T=MCCC 1K08229T).

Vulnerability of six cold-water corals to sediment resuspension from bottom trawling fishing

Bottom trawling can significantly affect benthic communities, directly through immediate removal of sessile organisms and indirectly through sediment resuspension. Submarine canyons, often surrounded by fishing grounds, are important habitats for cold-water corals (CWC). Vulnerability of CWCs to increased suspended sediment concentration (SSC) is key to understanding the severity of bottom trawling effects on those communities. Here we show survival, growth, and physiological response of six CWCs from a Mediterranean submarine canyon (Dendrophyllia cornigera, Desmophyllum dianthus, Desmophyllum pertusum, Madrepora oculata, Leiopathes glaberrima and Muriceides lepida), exposed to a long-term, aquarium-based sedimentary disturbance experiment. Compared to cup coral and octocoral, which did not exhibit symptoms of distress, our data indicate that colonial scleractinian corals and black coral, which experienced substantial polyp mortality in enhanced SSC treatments, are more vulnerable. Indirect impact of bottom trawling could thus contribute to structural simplification of CWC communities posing an additional stressor alongside with global climate change.

Coral larval settlement induction using tissue-associated and exuded coralline algae metabolites and the identification of putative chemical cues.

Reef-building crustose coralline algae (CCA) are known to facilitate the settlement and metamorphosis of scleractinian coral larvae. In recent decades, CCA coverage has fallen globally and degrading environmental conditions continue to reduce coral survivorship, spurring new restoration interventions to rebuild coral reef health. In this study, naturally produced chemical compounds (metabolites) were collected from two pantropical CCA genera to isolate and classify those that induce coral settlement. In experiments using four ecologically important Caribbean coral species, we demonstrate the applicability of extracted, CCA-derived metabolites to improve larval settlement success in coral breeding and restoration efforts. Tissue-associated CCA metabolites induced settlement of one coral species, Orbicella faveolata, while metabolites exuded by CCA (exometabolites) induced settlement of three species: Acropora palmata, Colpophyllia natans and Orbicella faveolata. In a follow-up experiment, CCA exometabolites fractionated and preserved using two different extraction resins induced the same level of larval settlement as the unfractionated positive control exometabolites. The fractionated CCA exometabolite pools were characterized using liquid chromatography tandem mass spectrometry, yielding 145 distinct molecular subnetworks that were statistically defined as CCA-derived and could be classified into 10 broad chemical classes. Identifying these compounds can reveal their natural prevalence in coral reef habitats and facilitate the development of new applications to enhance larval settlement and the survival of coral juveniles.

In situ observation of circadian rhythm of polyps’ opening and closing of the coral Dendrophyllia ramea (Linnaeus, 1758)

A widespread population of the coral Dendrophyllia ramea has been revealed southeast of Syracuse (East Sicily, Italy) at around 75 m depth. Dendrophyllia ramea is an arborescent scleractinian coral, classified as “Vulnerable” in the Mediterranean IUCN Red List and listed in Annex B of the Barcelona Convention. It is considered rare because it is seldom recorded on the Mediterranean seabed. In situ observations of two selected colonies were carried out over three months using a custom-made underwater video recording system to increase knowledge about the ecology of the species, specifically its circadian rhythm. The area was also surveyed using a special navigation system integrated into a diver propulsion vehicle to map the colonies’ position and distribution. The rhythms of the opening and closing of Dendrophyllia ramea’s polyps during the day were studied and linked to environmental factors, such as temperature, water flow, and direction. The results show that Dendrophyllia ramea opens and closes its polyps according to its circadian rhythm and water flow in analogy with other anthozoans in different environments. The opening/closing frequency analysis showed that both colonies closed at least once daily with different periodicity; one colony closed on average a few hours earlier. This project gathered important information on D. ramea’s circadian rhythm, which is relevant for improving knowledge about the ecology of this species since it provides insights into its feeding behavior, reproduction seasonality, response to environmental changes, interactions with other species, and conservation needs.

First Report of Diseases and Compromised Health Conditions on Hard Corals around Rodrigues Island, Southwest Indian Ocean

Coral diseases represent a prominent menace to coral reefs and to the associated ecological services they provide to the surrounding coastal communities. Studies on diseases and compromised health conditions (CHCs) on hard corals in the Southwest Indian Ocean (SWIO) are scarce, and their consequences are often overlooked. This study aimed to establish the baseline prevalence of diseases and CHC of hard corals around Rodrigues Island. Coral disease and CHC prevalence were visually assessed using 2 m × 50 m belt transects at eight sites around the island. This is the first report of four coral diseases, namely White Plague (WP), White Syndrome (WS), Black Band (BB), and Growth Anomalies (GA), and two CHCs, two forms of Pink Pigmentation Responses (PPR)—Pink Patches (PP) and Pink Line Syndrome (PLS)—observed on six genera of hard corals from the island of Rodrigues. PP on Fungia (15.92 ± 5.65%), followed by the WS on Montipora (4.67 ± 3.72%) and GA on Gardineroseris (4.16 ± 4.16%), so far unreported from the SWIO, were the most prevalent around the island. The least prevalent disease was BB on Montipora (0.13 ± 0.13%). Although the overall disease and CHC prevalence for Rodrigues Island (0.98 ± 0.30%) were much lower than the surrounding islands in the SWIO, the observations of these diseases and CHCs on hard corals and relevant environmental parameters warrant further in-depth characterization to better inform coral reefs management and conservation actions.

Gas Chromatography-Mass Spectrometry-Based Targeted Metabolomics of Hard Coral Samples.

Gas chromatography-mass spectrometry (GC-MS)-based approaches have proven to be powerful for elucidating the metabolic basis of the cnidarian-dinoflagellate symbiosis and how coral responds to stress (i.e., during temperature-induced bleaching). Steady-state metabolite profiling of the coral holobiont, which comprises the cnidarian host and its associated microbes (Symbiodiniaceae and other protists, bacteria, archaea, fungi, and viruses), has been successfully applied under ambient and stress conditions to characterize the holistic metabolic status of the coral. However, to answer questions surrounding the symbiotic interactions, it is necessary to analyze the metabolite profiles of the coral host and its algal symbionts independently, which can only be achieved by physical separation and isolation of the tissues, followed by independent extraction and analysis. While the application of metabolomics is relatively new to the coral field, the sustained efforts of research groups have resulted in the development of robust methods for analyzing metabolites in corals, including the separation of the coral host tissue and algal symbionts. This paper presents a step-by-step guide for holobiont separation and the extraction of metabolites for GC-MS analysis, including key optimization steps for consideration. We demonstrate how, once analyzed independently, the combined metabolite profile of the two fractions (coral and Symbiodiniaceae) is similar to the profile of the whole (holobiont), but by separating the tissues, we can also obtain key information about the metabolism of and interactions between the two partners that cannot be obtained from the whole alone.

Corallite sizes of reef corals: decoupling of evolutionary and ecological trends

AbstractCorallite sizes reflect a continuum in the efficacy of photosymbiosis in colonial reef corals, with smaller corallite sizes generally associated with higher autotrophy. Using a large compilation of reef-coral traits and corallite diameters as a proxy, we test here the hypothesis that photosymbiotic efficacy has increased over the evolutionary history of scleractinian corals. To gain a more comprehensive understanding of the evolutionary versus ecological patterns of corallite sizes of reef corals, we used three analytical methods: (1) occurrences-weighted within-bin analyses as a proxy for abundance or ecological dominance to depict ecological patterns; (2) unweighted range-through analyses; and (3) unweighted sampled-in-bin analyses to represent diversity in terms of taxonomic richness, enabling us to trace evolutionary patterns. By-genus, range-through analysis indicates a slightly positive trend of corallite sizes toward the Recent. However, the occurrences-weighted assessment shows a pronounced negative trend of corallite sizes in colonial corals since the Mesozoic. Random walk and directional evolution are both statistically supported to explain this long-term decrease. A driven trend is evolutionarily plausible, giving reef corals a selective advantage in the oligotrophic environments they largely occupy today.

Ocean warming and acidification detrimentally affect coral tissue regeneration at a Mediterranean CO2 vent

Among the main phenomena that are causing significant changes in ocean waters are warming and acidification, largely due to anthropogenic activities. Growing evidence suggests that climate change is having more substantial and rapid effects on marine communities than on terrestrial ones, triggering several physiological responses in these organisms, including in corals. Here we investigated, for first time in the field, the combined effect of increasing seawater acidification and warming on tissue regeneration rate of three Mediterranean scleractinian coral species characterized by different trophic strategies and growth modes. Balanophyllia europaea (solitary, zooxanthellate), Leptopsammia pruvoti (solitary, non-zooxanthellate) and Astroides calycularis (colonial, non-zooxanthellate) specimens were transplanted, during a cold, intermediate, and warm period, along a natural pH gradient generated by an underwater volcanic crater at Panarea Island (Mediterranean Sea, Italy), characterized by continuous and localized CO2 emissions at ambient temperature. Our results show a decrease in regenerative capacity, especially in the zooxanthellate species, with increasing seawater temperature and acidification, with demonstrated species-specific differences. This finding suggests that increasing seawater temperature and acidification could have a compounding effect on coral regeneration following injury, potentially hindering the capacity of corals to recover following physical disturbance under predicted climate change.

Photoacclimation dynamics in coral holobionts responding to thermal and irradiance changes correlate with photon pressure per symbiont

AbstractPhotoacclimation is a key homeostatic process that enables photosymbiotic reef corals to flourish within highly variable light environments. However, the temporal dynamics of photoacclimation remain poorly characterized. We studied photoacclimation at several time points over 24 d in two scleractinian coral taxa (mounding Porites spp. and branching Acropora muricata). Coral specimens preacclimated at 24°C and 171 μmol quanta m−2 s−1 were exposed to three light levels (−32%, +27%, and +65% relative to that of the acclimation period) at two temperatures (control, 24°C; mildly stressful, 29°C). Intra‐tissue light environment—specifically, photon pressure per symbiont—increased dramatically with each additional light dose and again with increasing temperature in Porites spp.; net photosynthesis (Pnet) rates continued to change for at least 2 weeks following light increase but not light reduction, and vice versa for symbiont densities. Intra‐tissue light environments were substantially dimmer and more homogeneous among all light treatments in A. muricata, which continued to increase its light‐use efficiency and Pnet through time in most or all treatments. Consequently, prolonged change in Fv/Fm at elevated temperature in Porites spp. but not A. muricata may have been caused by differing photodamage loads. Moderation of light levels by conditions within the coral tissue seems to affect the temporal dynamics of the photoacclimation response, and this finding emphasizes new avenues for photoacclimation research.

Whole genome assembly and annotation of the endangered Caribbean coral Acropora cervicornis.

Coral species in the genus Acropora are key ecological components of coral reefs worldwide and represent the most diverse genus of scleractinian corals. While key species of Indo-Pacific Acropora have annotated genomes, no annotated genome has been published for either of the two species of Caribbean Acropora. Here we present the first fully annotated genome of the endangered Caribbean staghorn coral, Acropora cervicornis. We assembled and annotated this genome using high-fidelity nanopore long-read sequencing with gene annotations validated with mRNA sequencing. The assembled genome size is 318 Mb, with 28,059 validated genes. Comparative genomic analyses with other Acropora revealed unique features in A. cervicornis, including contractions in immune pathways and expansions in signaling pathways. Phylogenetic analysis confirms previous findings showing that A. cervicornis diverged from Indo-Pacific relatives around 41 million years ago, with the closure of the western Tethys Sea, prior to the primary radiation of Indo-Pacific Acropora. This new A. cervicornis genome enriches our understanding of the speciose Acropora and addresses evolutionary inquiries concerning speciation and hybridization in this diverse clade.

Hard coral cover in the Halmahera waters: Spatial distribution and environmental factors

Differences in the geographical location and geomorphology of small islands contribute to variations in aquatic environmental factors, spatial distribution of corals, and percentage of hard coral cover. This study was conducted in the open waters of the Termadoreh Islands in the middle of the Maluku Sea, and the semi-enclosed waters of Buli Bay. This study aimed to examine the distribution of hard coral cover in the Halmahera coral ecoregion with respect to differences in geographic location, geomorphology and water quality. This study found that the spatial distribution of hard corals differed among sites. Spatially, the total area of shallow water habitat at the study site showed the largest area of coral habitat in Termadoreh, at 1313.99 ha. Hard coral cover and coral diversity differed between sites and depths. Higher hard coral cover was found on the coral islands of Teluk Buli and lower on the volcanic islands of the Termadoreh Archipelago. The highest percentage of hard coral cover per site was found on Maitara Island (site MaT05) at 71.60%, and the lowest percentage of cover was found on Tidore Island (site TiT08) at 14.9%. An optimal temperature, salinity, and brightness parameters support the high percentage of hard coral cover. The highest coral diversity value in the Termadoreh Islands correlated with water brightness. This study is important for recording the conditions of hard corals in the Halmahera reef ecoregion. The results of this study provide data on the benefits of a coral reef management plan for the Halmahera coral ecoregion. We also provide recommendations regarding the life forms of hard corals that are appropriate for making coral seeds to restore and rehabilitate coral reef ecosystems at the research sites.

Polycladospora coralii gen. nov., sp. nov., a novel member of the family Thermoactinomycetaceae isolated from stony coral in the South China Sea.

Two novel filamentous bacteria, designated as IB182353T and IB182357, were isolated from stony coral of the South China Sea. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains IB182353T and IB182357 were closely related to Hazenella coriacea DSM 45707T (with 93.4 and 93.5% similarity, respectively). The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization results showed that the pairwise similarities between isolate IB182353T and the other recognized Thermoactinomycetaceae species were less than 68.9, 60.5 and 21.1 %, respectively. Both strains produced aerial and substrate mycelia, grew optimally at 25-30 °C, pH 8.0-9.0 and with 2-3 % (w/v) NaCl. The cell-wall peptidoglycan type was meso-DAP and the whole-cell hydrolysates contained ribose. The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminophospholipid and three unidentified phospholipids. The genomic DNA G+C content was 39.5 mol%. Strain IB182353T was distinguishable from its related type strains by the contents of two fatty acids, iso-C15 : 0 and iso-C17 : 1 ω10c. Based on polyphasic taxonomic characterization, we propose that strains IB182353T and IB182357 represent a novel genus and species within the family Thermoactinomycetaceae, for which the name Polycladospora coralii gen. nov. sp. nov. is proposed. The type strain is IB182353T (=MCCC 1K04631T=JCM 34206T).

Biodiversity of coral reefs ecosystem in Sabu Raijua Waters

The waters of Sabu Raijua are included in World’s Coral Triangle Region, which has high-potential Coral Reefs Ecosystems that have not been widely revealed. The remote location and erratic wave weather conditions give challenges in surveying biodiversity coral reef ecosystems. The observation of the Coral Reef ecosystem has been carried out at 12 stations in Sabu Raijua using underwater photo transect to determine the coral cover percentage, line transect for benthos noncoral, belt transect for community structure of coral reefs, and visual census method for measuring reef fish community. The result of coral reef condition is categorized as moderate, where the average live hard coral cover percentage is 22%, dominated by coral massive and submassive. Hard coral that found as many as 47 genera dominated by Porites, Galaxea, and Favites. There are 111 species of coral reef fishes have been identified. Benthos noncoral found as many as 109 species.

Suitability Index of Snorkeling Tourism In Sepulu District, Bangkalan, Indonesia

Bangkalan is one of the districts in Madura with a coastal area that can be developed as a marine tourism location for snorkelling, and their northern coast facing the Java Sea has only been used for coastal tourism. This research aimed to assess the suitability index of snorkelling tourism in Sepulu waters, Bangkalan. The research was carried out during September–October 2021. Coral cover, fish diversity, water conditions, and an analysis of tourism suitability and the carrying capacity of snorkelling tourism were assessed. Hard coral cover in Sepulu waters ranges from 22-38%, while the per cent of coral cover (including soft corals) ranges from 34-55.5%. The number of coral growth forms found in Sepulu waters ranged from 6-8 forms. Reef fish found in Sepulu district water were between 7-12 species. The tourism suitability index of Sepulu Waters, Bangkalan, which ranges from 61.40 – 75.44%, is included in the category of quite suitable. The area’s carrying capacity for snorkelling tourism activities is 152-500 people daily. Sepulu waters, especially Tengket and Labuhan waters, have a high potential to be used as snorkelling tourism objects.

Biodiversity of hard coral (Scleractinia) and relation to environmental factors turbid waters in Spermonde Islands, South Sulawesi, Indonesia

Abstract. Parenden D, Jompa J, Rani C, Renema W, Tuhumena JR. 2023. Biodiversity of hard coral (Scleractinia) and relation to environmental factors turbid waters in Spermonde Island, South Sulawesi, Indonesia s. Biodiversitas 24: 4521-4529. Water turbidity has an impact on coral growth and the diversity of coral species in the waters. Calculation of coral cover, coral diversity and environmental parameters need to be done to determine the effect of environmental parameters on growth. This research was conducted in July 2020-February 2021 in the Spermonde Islands, South Sulawesi, Indonesia, which focused on the inner zone area with high turbidity levels. The research was conducted at four observation locations, namely Kayangan Island, Samalona Island, Gusung Tallang and Lae-Lae Island. Primary data in the form of coral cover using the Underwater Photo Transect method, diversity data using the quadrant transect method and environmental parameters measured in-situ and ex-situ. The results of this study showed (1) the percentage of coral cover at each research location was classified as poor because it was in the range of 3-15%, (2) coral diversity on Samalona Island was classified as high (H'=3.2) while on Kayangan Island, Laelae Island and Gusung Tallang was classified as medium with values ranging from 2.21-2.83; and (3) environmental parameters such as turbidity, Total Suspended Solid (TSS), Total Dissolved Solid (TDS), nitrate, and phosphate and based on the results of regression analysis has a negative effect on coral cover, while turbidity and Total Suspended Solid (TSS) parameters have a significant effect on coral cover (p<0.05). These results have the potential to determine the composition of hard corals (Acropora sp.) in turbid areas and potentially serve as transplant fragments to mitigate coral damage.

Reproductive characteristics and gametogenic cycle of the scleractinian coral Dendrophyllia ramea.

The present study marks a pioneering investigation into the reproductive cycle of the scleractinian coral Dendrophyllia ramea. This is one of the first reproduction studies conducted in the Mediterranean Sea for a colonial azooxanthellate coral. Coral samples were collected in 2017 (May and October) and 2018 (February and July) in the Alborán Sea (SW Mediterranean). This location was selected due to its rarity as one of the few sites where this species thrives at depths shallower than 40 m. These samples were used to study the sexual patterns, fertilization mechanisms and gametogenic cycles by means of histological techniques. To broaden the scope, Sea Surface Temperature (SST) and Chlorophyll-a (Chl-a) data from open access databases have been considered to explore the potential influence of these environmental factors as triggers for gamete development and spawning time. The findings cast D. ramea as a gonochoric species, since no hermaphroditic specimens were observed among the analysed samples. Additionally, the lack of larvae and embryos in any of the analysed polyps, suggest that this species is fertilised externally. Two oocyte cohorts have been detected simultaneously, hinting at a yearly reproductive cycle, characterised by a prolonged oocyte maturation and seasonal spawning period taking place between August and October. Nevertheless, D. ramea display a low fecundity compared to other scleractinians inhabiting deep waters. Lastly, the early stages of gametogenesis seem to be coupled with the highest Chl-a values (i.e., March and December), whereas spawning takes place throughout the warmest period of the year (August to October).