Seasonal Dynamics of Algal Communities under Environmental and Anthropogenic Stressors in the Kopili River, Northeast India

Abstract

Aim: This study was aimed to document algal species diversity and evaluate the influence of environmental and anthropogenic factors on algal community structure in the Kopili River, addressing the existing lack of baseline ecological and bioindicator data for this river system. Algal samples and water quality parameters were monitored monthly across three ecologically distinct study sites from June 2023 to May 2024. Parameters such as pH, temperature, conductivity, and water current were measured on-site, while nutrient- and oxygen related parameters were analyzed in the laboratory using APHA (2012). Identification and diversity analyses were done following standard procedures. A total of 64 (sixty-four) algal species were recorded, with Bacillariophyceae being the most prevalent group, followed by Chlorophyceae, Cyanophyceae and Zygnematophyceae. Shannon diversity showed strong seasonal variation Seasonal variation with lowest values during monsoon due to high turbidity and highest during pre-monsoon and winter conditions. Seasonal hydrology combined with local anthropogenic stressors significantly shaped algal composition and abundance. The results confirm algae as effective bioindicators and provide essential baseline data for long-term ecological monitoring and watershed management for preserving the river ecosystem's health.