An impact of tropical cyclone on meiobenthic fauna of Chennai coast, Tamil Nadu, India: A case study of cyclone Mandous

The meiofaunal diversity is used as an indicator to assess the complex and diverse impacts on the coastal environment during the natural calamities. The present study evaluates the effects of Mandous cyclone on ecologically two different stations, Pattinampakkam beach and Adyar estuary, which are located on Chennai coast, Tamil Nadu, India. The impact of the Mandous cyclone on physico-chemical parameters and meiobenthic faunal composition was investigated during, prior to, and after the cyclone. Thirty-nine species of meiofauna belonging to 15 taxa were recorded in both the stations. Nematoda, Oligochaeta and Harpacticoida taxa occurred with higher diversity and abundance than other meiofaunal taxa. Among these taxa, Polygastrophora sp. of Nematoda, Grania pusilla of Oligochaeta, and Arenosetella indica of Harpacticoida were the predominant species recorded during the study period. There was a prominent decline in the population density of meiofauna due to the Mandous cyclone, and thereafter, it took three weeks for recolonization and restoration to normalcy. Statistically, significant impact of the Mandous cyclone on the diversity, density, and evenness of the meiofaunal community with abiotic factors were observed through the Ecological indices and Canonical Correspondence Analysis. The Mandous cyclone assessment with special emphasis on meiofaunal communities allowed to fill the gap with knowledge regarding the diversity, abundance, composition, and distribution of meiofauna between pre- and post-Mandous cyclone, which helped in understanding the physico-chemical changes and response of meiofauna in a sandy beach and estuary.

Effect of multiple stressors on the functional traits of sub-tidal macrobenthic fauna: A case study of the southeast coast of India

The use of functional information of taxa is a promising approach to uncover the underlying mechanism of ecosystem functioning. We used biological trait analysis (BTA) to assess the functional response of subtidal macrobenthos with multiple stressors. Seventeen environmental variables from 42 stations of five coastal districts were assessed along the southeast coast of India. Dominant fauna was assigned into 20 categories belonging to six functional traits. Additionally, we used five ecological groups (EG) of AMBI as a covariable trait to validate functional traits and EG relationship. The trait composition in the communities showed significant variation between undisturbed and disturbed areas. RLQ/Fourth corner combined approach illustrated the effects of stressors and isolated the corresponding species associated with different stressors. Smaller, short-lived, deposit-feeding, and discretely motile fauna occurred at the disturbed areas, whereas, larger, long-lived, and highly motile at the undisturbed area. Dissolved oxygen, organic enrichment, and metals concentration were the main environmental descriptors influencing the trait composition. The results highlight the importance of the BTA approach to uncover the response of the macrobenthic community to anthropogenic disturbances-driven impacts in multi-stressed near-shore coastal ecosystems.

Assessment of biogrowth assemblages with depth in a seawater intake system of a coastal power station

Marine biogrowth infestation of a seawater intake system was investigated. A digital camera fixed onto a skid was used to record the biogrowth at intervals of 5 m up to a depth of 55 m. Divers inspected the intake shaft and collected the biogrowth samples for biomass estimation. A biomass density of 7.5 kg m^-2 and 28.2 kg m^-2 was recorded at 5 and 30 m depths respectively. Inspection by the divers revealed that hard-shelled organisms such as oysters and brown and green mussels were observed in plenty up to a thickness of 15 cm and bryozoans grew as epibionts. At lower depths (<40 m), hydroids grew on the shells of green mussels along with silt accumulation. The biofouling community was composed of 46 organisms, exhibiting variation in distribution and abundance. The study explains the extent and type of marine biogrowth phenomena with depth and describes biofouling preventive methods.Supplemental data for this article is available online at https://doi.org/10.1080/08927014.2021.1933457 .