Quantifying plankto-environmental interactions in a tropical river Narmada, India: An alternative model-based approach.

Plankton is one of the key elements for biological monitoring of riverine ecosystem. It is of paramount importance to understand plankto-environmental interaction for river ecological assessment. This article has presented an alternative model-based analytical framework to quantify plankto-environmental interactions and prediction thereof for a tropical river system. Analysis of secondary data on the Narmada River in India has made it possible to accomplish this. Hierarchical cluster analysis, based on water quality similarity, has been applied for grouping of sites. The resulted clusters slightly deviate from subjective division of the river, but their formation have been coherently ordered downstream-wise. Generalized additive modeling (GAM) with Poisson error assumption of plankton abundance has been the key modeling approach. The GAM, which has explained 66% and 88% deviance of phytoplankton and zooplankton density, respectively, has identified four (transparency, nitrate, temperature, alkalinity) out of thirteen water quality attributes in order of their relative influence on the phytoplankton and zooplankton abundance. The study has established that, in riverine system, application of GAM model under Poisson error assumption has been very effective; and the model has provided reasonably accurate prediction of plankton abundance along hydrologic distance—with noise reduction due to water quality parameters. [ABSTRACT FROM AUTHOR]