Temporal variation in diversity, abundance and size class structure of planktonic copepods from a tropical estuary

A study on the community structure of planktonic copepods was carried out in the down stretch of Ashtamudi estuary (AE) for a period of two years (2018 to 2019). The copepod community composed of a total of 53 species under 31 genera belonging to 20 Families during the study period. Thirty Nine species of Calanoids, 9 species of Cyclopoids and 6 species of Harpacticoids were recorded from the AE. Of the total 20 families recorded during the study, 17 were noticed during pre-monsoon (PrM), 16 during post-monsoon (PsM), and 13 during monsoon (Mn) periods. Family Paracalanidae constitute > 50% irrespective of seasons followed by Acartiidae (18%), Oithonidae (9%), and Pseudodiaptomidae (4%). Family Pontellidae (11) and Acartiidae (9) represented the maximum number of species followed by Centropagidae (4), Pseudodiaptomidae (3), and Paracalanidae (3). The species Bestiolina similis belonging to the family Paracalanidae dominated throughout the study (~ 75%). The species such as Acartia plumosa, Acartia bowmani, Pseudodiaptomus serricaudatus, Paracalanus aculeutus, Dioithona rigida, and Oithona brevicornis were also recorded with higher abundance from the estuary. Copepods were grouped into 200–300 µm (smallest), 300–500 µm (Small), 500–1000 µm (Medium), and > 1000 µm (Large) size classes. Significant seasonal variation ( p