Plankton dynamics and their relationship with environmental factors shape fish community structure in fluvial ecosystem: A case study

Phytoplankton and zooplankton serve as bioindicators and are critical components for the functioning of ecosystem and support a wide range of ecosystem services. To understand the interrelationship between plankton, fish and habitat parameters; aforementioned parameters were recorded seasonally from six sites, representing different habitat types along the stretches of Ib River, a tributary of Mahanadi River system in India. A total of 47 phytoplankton and 14 zooplankton species were recorded. Maximum density and diversity of phytoplankton and fish were observed at downstream sites while those of zooplankton were recorded in upstream sites. Maximum phytoplankton and zooplankton were recorded in summer season. A high correlation of species richness was observed with water and air temperature, dissolved oxygen (DO), pH, conductivity, turbidity, total dissolved solids (TDS) and total nitrogen. Plankton always had complex interactions with ecological abiotic factors and variations in the distribution of plankton affect the fish diversity of the region. Canonical correspondence analysis (CCA) was used to establish relationship between important fish species and environmental variables. Maximum plankton abundance in the winter months also coincided with maximum fish diversity corroborating an existing positive relationship between the plankton and fish. The study helps in better understanding the influence of plankton and habitat parameters in determining fish community structure and its importance to ecosystem services.