An appraisal of nutrient status and productivity with emphasis on phytoplankton assemblage in Karamana River, Kerala, India

Abstract

Nutrient pollution of rivers is one of the prime threats facing the aquatic systems. In the present study, water samples (n = 20) were collected from the Karamana river (KR) during the pre-monsoon (PMN) and monsoon (MN) seasons of 2019 to analyze the seasonal variations. The water samples were analyzed for various physico-chemical parameters and to understand the nutrient status of the river. Furthermore, gross primary productivity (GPP), net primary productivity (NPP) and phytoplankton analysis were carried out to assess relationship among productivity variables and phytoplanktons. The study revealed that water quality is better during MN than PMN due to dilution. Among the two seasons, PMN showed relatively higher values for most of parameters like pH, EC, TDS, TA, Cl, NH4-N, NO3-N, NO2-N, Chl-a, GPP and NPP. The correlation among GPP, NPP, nutrients and other water quality parameters were done using SPSS. Phytoplankton of 23 genera belonging to three classes, namely Chlorophyceae (40%), Bacillariophyceae (40%) and Cyanophyceae (20%) have been identified in KR. The various phytoplankton diversity indices and statistical analyses were estimated and their relevance discussed in this paper. The nutrient enrichment in the downstream regions was affected the phytoplanktonic structure and diversity of the river. HIGHLIGHTS Water quality of Karamana river is better during monsoon.; Higher nutrient contents enhances productivity of Karamana river.; Higher values of nutrients and productivity variables noted at downstream stretches.; Phytoplankton analysis and diversity indices of Karamana river.; Palmer's index shows downstream stations are organically polluted.;

Keywords

• biodiversity index
• chlorophyll-a
• karamana river
• nutrients
• phytoplankton
• primary productivity