Epixylic algae and physico-chemical parameters as indicators of aquatic pollution in Elechi Creek, Port Harcourt, Rivers State, Nigeria

Abstract

Elechi Creek of the Upper Bonny Estuary, Port Harcourt, Nigeria and its resources are economically significant. Still, the Creek is a sink receiving various anthropogenic effluents from its surroundings. The study determined the epixylon assemblage and some physico-chemical parameters [temperature,  pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD), phosphate, sulphate, and nitrate] of  the Creek. Surface water and epixylon sample collections from three stations followed standard methods between August and November 2021. Epixylon  samples were analyzed microscopically. A total number of 461 individuals, 30 genera and 37 species from 6 families, namely: Bacillariophyceae (18  species), Chlorophyceae (9 species), Cyanophyceae (5 species), Chrysophyceae (1 species), Dinophyceae (3 species), Euglenophyceae (1 species) of epixylic  algae were recorded. Pollution- indicator genera were Cyclotella, Nitzschia, Synedra, Cocconeis, Tabellaria, Melosira (Bacillariophycea)  Ankistrodesmus, Chlorella, Closterium (Chlorophyceae), Oscillatoria and Phormidium (Cyanophyceae). Spatially, sulphate (137.02±25.00 mg/L) exceeded  the NESREA standard (100 mg/L, respectively), while temperature (30.00±1.72 ℃), pH (6.70±0.79), TDS (2308.92±858.14 mg/L), DO (6.56±0.78), BOD  (1.78±0.71 mg/L), nitrate (0.92±0.18 mg/L) and phosphate (0.25±0.06 mg/L) were within NESREA standard (<40 ℃, 6-9, 2000 mg/L, 6.0 mg/L, 3.0 mg/L, 9.1 mg/L and 3.5 mg/L, respectively). EC (4959.50±1836.34 µs/cm) exceeded the WHO standard (900 µs/cm). The presence of dominant Bacillariophyceae,  some bioindicator species, and higher EC and sulphate denotes organic pollution in Elechi Creek. The study recommends thus periodic monitoring of  Elechi creek and environmental awareness programmes to mitigate pollution and safeguard the health of the residents around this Creek.