IMPACTS OF CLIMATE CHANGE ON PHYTOPLANKTON COMPOSITION AND VARIABILITY IN IKO RIVER, COASTAL WATER OF EASTERN OBOLO, NIGERIA

This study investigated the effects of climate change on phytoplankton composition and diversity in Iko River, coastal water of Eastern Obolo, Akwa Ibom State, South Eastern Nigeria. The study area was greatly influenced by tidal flush from the Atlantic Ocean. Phytoplankton samples were collected monthly from October 2021 to March 2022 at high tide and low tide from 3 stations. Phytoplankton was identified and diversity was calculated using standard indices. Dissolved oxygen (3.3–6.0 mg/L) was above WHO guidelines of <5.0mg/L and BOD (2.40-5.30 mg/L) in this study was above the (4.0 mg/L) limit recommended as suitable for aquatic life by the National Environmental Standards and Regulation Enforcement Agency (NESREA), which could pose a threat to aquatic life. A total number of 65 species of phytoplankton were identified in the study area. Bacillariophyta was the dominant group (69%) throughout the study in species number, occurrence and abundance. The increasing order of dominance values was; Bacillariophyta > Cyanophyta > Chlorophyta > Dinophyta > Euglenophyta . Diversity indices (Margalef, Shanon, Dominance, Simpson Evenness and Equitability) showed spatial variations significant at (P>0.05). Pollution-indicator species such as; Tabellaria fenestrata, Nitzschia. paradoxa, N. filiformis, N. longissima, Cymbella cuspidata, Melosira distans and Anabaena constrica were recorded at either high tide, low tide or at both tides. Concerted efforts have been recommended to Government agencies and individuals to help reduce natural and anthropogenic pollution of the coastal water bodies.