Phytoplankton Community Structure, Species Diversity, and Environmental Interactions in the Anyanui Creek.

Abstract

This study aimed to assess the structure and distribution of phytoplankton communities in the Anyanui Creek, focusing on species composition, diversity, and the relationships between environmental factors and phytoplankton populations. The Anyanui Creek was zoned into three Zones A (upstream), Zone B (midstream), and Zone C (downstream) based on salinity levels from a preliminary study. Phytoplankton samples were collected between April 2023 and March 2024. A total of 34 phytoplankton species were identified, which were dominated by diatoms, comprising 92.92% of the population. The most abundant species, Chaetoceros sp. (36.85%), thrives in silica-rich environments, facilitating bloom formation and affecting the ecosystem dynamics. The presence of bloom-forming species raises concerns regarding eutrophication risks, whereas toxin-producing species pose potential threats to ecological and human health. The diversity of phytoplankton was assessed using the Shannon-Wiener diversity index (H′), with values ranging from 1.38 to 3.04, indicating low pollution levels. The high Pielou's evenness of species distribution (0.995-0.999) suggests a stable phytoplankton community structure across zones. Cluster analysis based on phytoplankton species compositions across the sampling zones isolated upstream, likely due to its higher salinity and absence of cyanobacteria, whereas midstream and downstream exhibited high similarity. Cluster analysis based on phytoplankton species compositions across the sampling period indicated seasonal influences, with March 2024 and April 2023 forming a distinct group due to variations in environmental conditions. Correlation analysis highlighted the relationship between the physicochemical parameters and species abundance. Salinity and dissolved oxygen were negatively correlated (r = -0.689, p < 0.01). Chaetoceros daniscus preferred oxygen-rich waters, whereas Nitzschia sp. preferred ammonium rich waters, low-oxygen conditions. This study provides insights into the factors shaping the phytoplankton community structure in the Anyanui Creek, which can inform future management and conservation strategies to preserve the creek’s ecological health.