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The present report describes the first record of two brachyuran crabs, Drachiella morum Alcock, 1896 and Quadrella maculosa Alcock, 1898 along the coast of Tamil Nadu, India. The morphological characters of the specimens are described and discussed. Among the two crabs, Q. maculosa was previously recorded only in the Andaman & Nicobar Islands.

Tropical seagrasses experience considerable spatio-temporal changes with light and other biogeochemical conditions and adopt species-specific acclimatization strategies. Variation in photo-acclimatory responses of three tropical seagrass species (Cymodocea serrulata, Thalassia hemprichii, and Enhalus acoroides) was studied by measuring photosynthetic electron transport rates (ETR) using Pulse Amplitude Modulated (PAM) fluorometry. Quantitative values of ETR and rates of photosynthetic O2 evolution (net O2 exchange corrected for dark respiration) were compared to establish species-specific relationships in shallow water conditions. The apparent average molar ratio of O2 evolution to ETR for the studied species found lower than the theoretical value (0.25). The highest photosynthetic activity (ETRmax) varied significantly among the three studied species in the decreasing order as: E. acoroides (59.27); T. hemprichii (54.06), and C. serrulata (46.72). The effective quantum yield (Y) of PS II (Photosystem II), one of the most useful indicators of stress conditions for seagrass, was observed to be significantly higher for E. acoroides compared to the other two species. It appears that the variations in water temperature and pCO2 could significantly alter the photosynthetic characteristics of these shallow water seagrass species. This study is useful in predicting the photo-acclimation strategies to any change in light availability and subsequent biogeochemical changes at the sea bed by these tropical seagrass species.

This study reports an updated checklist of marine shrimps found along the Indian coast, including the Lakshadweep and the Andaman & Nicobar Islands. A total of 364 species classified under 128 genera belonging to the order Decapoda is reported, thus adding 27 species to the existing checklist of 337 species. Marine shrimps are classified under two suborders of the order Decapoda, viz., Dendrobranchiata and Pleocyemata, and the two suborders account for 155 (42.6 %) and 209 species (57.4 %) of these 364 species, respectively. Pleocyemata is represented by three infraorders, viz., Axiidea, Caridea and Stenopodidea, while Caridea has a maximum of 199 reported species. Among the 12 superfamilies, Penaeoidea contributed to 38.13% (135 species) followed by Paleaemonidea with 18.07% (64 species). All other superfamilies were found to contribute less than 12%. Superfamilies, Bresilloidea and Psalidopodoidea had only single species representatives (0.28% each). The final list was compiled after reviewing all existing literature including monographs, catalogues, checklists, websites and fishery reports. The scientific names were validated with the World Register of Marine Species (WoRMS) database. A total of 25 issues were identified from the previous checklist out of which 19 species have been updated with the correct, accepted names and six species have been removed from the previous list.

Our study documents the outbreak of a coral-killing sponge Terpios hoshinota in the coral reefs of Lakshadweep archipelago and highlights that it has further extended its territory into the isolated atolls of Arabian Sea and maybe a growing threat to the existing coral reefs in the region. [ABSTRACT FROM AUTHOR]

During late November and early December of 2015, Chennai city in the coastal state of Tamil Nadu experienced unprecedented rainfall that resulted in a flash flood. It was one of the worst affected coastal cities of southern India resulting in an alteration of the coastal environment. We was made an attempt to document the impact of the flood on coastal fauna following which a survey was conducted from the estuarine river mouths of Adyar to Cooum along the Marina beach. 177 marine species were identified, represented by 5 fishes, 15 crustaceans, 95 bivalves, and 57 gastropods. Other groups include echinoderm, coral, polychaete, anthozoan and bryozoan represented by a single individual. Presence of various freshwater species including various plastic components indicates that the heavy freshwater outflow from the rivers and canals have had a notable effect, calling for a long term assessment of the study area. [ABSTRACT FROM AUTHOR]

This study was conducted to assess the recruitment rate of coral spats and other invertebrates near to the coral reef ecosystem of Gulf of Mannar. The reef region examined was at Kurusadai Reef Complex (Gulf of Mannar) for this assessment. There were two sets of invertebrate settlement tripods deployed and exposed at a depth of 2m. Seventy two settlement tiles measuring 20x20 cm in two different angles were fixed in these tripods in the benthic reef ecosystem. In order to assess the impact of Sea surface temperature on the invertebrate settlement, Onset Hobo Pendant® Temperature logger was also attached with the tripods. The sediment traps in duplicate were also erected in the study site to assess the sedimentation rate of the reef ecosystem. About 80% of recruited coral spats were observed on the tiles which were exposed at 60° angle. Principal component analysis also supported that the most influencing species were coral spats followed by barnacles and bivalves in the 60° angle exposed settlement tiles. It was also observed that the most influencing place of coral spats' recruitment was on the inner tiles. The mean sedimentation rate observed was 14.6 ± 4.8 mg.cm−2.d−1. The lower density of coral spats observed on 90° and 60° angle exposed outer tiles might be due to the observed sedimentation rate and it is believed that coral spats preferred the shaded environment initially for further perpetuation in the environment. Moreover, Bray-Curtis cluster analysis supported that the coral spats found on the inner tiles having 80% similarity in this assessment. The coral spats found in this assessment were species from Pocilloporidae and Poritidae. [ABSTRACT FROM AUTHOR]

Seagrass meadows are among the most important coastal/ marine ecosystems for long-term carbon storage and conditioning of coastal waters. A combined air-water flux of CO2 and CH4 from the seagrass meadows was studied for the first time from Asia’s largest brackish–water lagoon, Chilika, India. Ecosystem-based comparisons were carried out during two hydrologically different conditions of dry and wet seasons in the seagrass dominated southern sector (SS); macrophyte-dominated northern sector (NS); the largely un-vegetated central sector (CS) and the tidally active outer channel (OC) of the lagoon. The mean fluxes of CO2 from SS, NS, CS and OC were 9.8, 146.6, 48.4 and 33.0mM m-2d-1, and that of CH4 were 0.12, 0.11, 0.05 and 0.07mM m-2d-1, respectively. The net emissions (in terms of CO2 equivalents), considering the global warming potential of CO2 (GWP: 1) and CH4 (GWP: 28) from seagrass meadows were over 14 times lower compared to the macrophyte-dominated sector of the lagoon. Contrasting emissivity characteristics of CO2 and CH4 were observed between macrophytes and seagrass, with the former being a persistent source of CO2. It is inferred that although seagrass meadows act as a weak source of CH4, they could be effective sinks of CO2 if land-based pollution sources are minimized. [ABSTRACT FROM AUTHOR]