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Morphometric estimation of copepod carbon biomass in coastal Antarctica: a case study in Prydz Bay


 Estimation of copepod carbon (C) biomass is essential in studies of secondary production and ecology in aquatic systems. The coastal Antarctic region belonging to the Indian Ocean sector of the Southern Ocean is a globally well-known sink for carbon and is extremely sensitive to climate change. During the austral summer, an attempt was made in Prydz Bay to measure copepod prosomal length and use regression equations to derive copepod C-biomass. The technique involved microscopic measurements, by means of a digital imaging device, of copepods collected at four intervals during a period of 48 hr, and the application of appropriate conversion factors to convert these values into C-biomass. Totals of 10.38 mgC m–3 and 25.55 mgC m–3 were recorded in the upper 200 m on day 1 and day 2, respectively. Out of the six copepod species present, Paraeuchaeta antarctica (Giesbrecht, 1902) (31.12 ± 11.10 µg m–3) and Oithona similis (Claus, 1866) (1.01 ± 0.42 µg m–3) represented the highest contributors to C-biomass amongst the calanoids and cyclopoids, respectively. Reports on copepod C-biomass estimates in general are extremely sparse. To our knowledge, this study is the first of its kind in the study area that provides species-specific estimates of C at every time point using a labor-saving and non-destructive method that allows preservation of the samples for further analyses. Based on the C estimates from our study, it can be said that copepod community is an extremely important component of the carbon cycle in coastal Antarctica.