Study of copepod diversity from Gahirmatha coastal stretch: An ecological sensitive area, Northeast coast of India

A three-year study (February 2020-April 2023) of copepod community structure at 14 GPS fixed locations along an ecologically sensitive stretch of 42 km (Lat. 200 29ʹ 59.537” N; Long. 860 46ʹ 41.96” E to Lat. 200 26ʹ42.21” N; Long. 860 48ʹ 36.685ʺE) in the south to (Lat. 200 42ʹ 22.955” N; Long. 870 5ʹ3.32” E to Lat. 200 40ʹ 28.23” N; Long. 870 7ʹ 34.757”) towards north along the northeast coast of India revealed altogether 73 species of copepods. Among these, 50 species were calanoids, 16 were cyclopoids and 7 were harpacticoids. The most numerically abundant species included Paracalanus parvus (16.43%), Euterpina acutifrons (11.28%), Oithona rigida (10.40%), Coryceaus danae (9.6%), Acrocalanus gibber (7.24%), Coryceaus catus (6.26%), Temora turbinata (5.82%), Corycella gibbula (4.64%), Canthocalanus pauper (2.94%), Oithona brevicornis (2.41%), Oithona sp (1.4%), and Labidocera acuta (2.92%) which together constituted more than 80% of the population. Across stations, all measures of alpha diversity were higher along offshore compared to the near shore stations. Using multivariate analysis (hierarchical clustering performed in PRIMER) with abundance data, the 14 locations were categorized into 2 clusters: the estuarine coastal group (2.5 km from the coast) and the offshore group (5.0 km from the coast). BVSTEP (similarity analysis implemented in PRIMER) identified 13 influential species while Bio-Env revealed that 5 variables (salinity, turbidity, ortho-phosphate, chlorophyll-a and phytoplankton abundance) significantly impacted copepod distribution in the study area.