Diversity rhythm in pontellid copepods (Pontellidae: Copepoda) from the Covelong coast pre- and post-COVID-19 lockdown, Bay of Bengal

Copepods act as indicators of the aquatic ecosystem since they rapidly respond to changes in nutrient content of the environment. Plankton samples were collected for two years from the Covelong coast, India (January to December 2019 and January to December 2021). The diversity patterns of pontellid copepods before and after the COVID-19 lockdown were analyzed. Physicochemical parameters like temperature, salinity, pH, dissolved oxygen, calcium, magnesium, nitrite, phosphate, and ammonia level for both years were measured to compare and contrast the coastal health before and after the lockdown. Six species of pontellid copepods were reported before the lockdown period and 10 species were reported after the lockdown. Physicochemical parameters like ammonia, nitrite, and phosphate levels were reduced after the lockdown. Temperature and nitrite showed a considerable negative correlation with pontellid copepods (-0.749 and -0.782), whereas dissolved oxygen showed a high positive correlation (0.732). Regression analysis was carried out to emphasize the relationship between pontellid copepods with the environment. The regression (R-2) coefficient with temperature, nitrite, and dissolved oxygen were 0.571, 0.682, and 0.636, respectively. However, high species diversity was observed in February during both pre- and postlockdown periods. Redundancy analysis was used to visualize the relationship between the pontellid copepods and physicochemical parameters. The density of pontellid copepods and the level of physicochemical parameters greatly fluctuated throughout the entire study period and showed variation in density and diversity.