Interaction of Some Environmental Gradients with Bloom Forming Coscinodiscus Species (Kützing, 1844) in the Upper reaches of Bonny Estuary Rivers State, Niger Delta

This study was carried out from December 2021 to November 2022 to examine the interaction of environmental factors with bloom-forming Coscinodiscus species. Plankton samples were collected with a 20 µm mesh plankton net. The nutrients were analysed in the laboratory using the APHA 2012 Method, while physico-chemical characteristics were determined in situ. Three species were recovered C. concinnus, granni, and radiatus C. Concinnus recorded the highest mean density values in stations 1 and 2. C. granni recorded the lowest density values in stations 2 and 3, while C radiatus recorded the highest density value in station 2 and the lowest in station 1. The three species decreased across seasons (from dry to wet). Interaction between principal component analysis, environmental parameters, and Coscinodiscus spp. across stations indicates that temperature. and nitrate showed a strong positive correlation with C. granni species, while C. concinus showed a strong positive correlation with salinity. Conductivity, pH, and nitrate. Phosphate and nitrite showed a strong positive correlation with C. radiatus. These environmental parameters (temp.NO3, salinity, pH, TDS, and DO) greatly influence the distribution and abundance of the Coscinodiscus spp. and were the most used predictors in the forecast of Coscinodiscus spp., which were positively correlated. The regression coefficient, R2 = 0.878, in the model for Coscinodiscus concinus species accounted for 87% of the significant predictors and therefore confirmed the predictive power of this ARIMA model for predicting bloom forming C. concinus species, while the remaining species could not be accounted for. Human activities are having an increasing influence on the marine environment, especially the eutrophication of water. With an increase in the environmental gradients, there is a possibility of the species forming a bloom. There is the need for best management practices to address nutrient discharge in the Bonny Estuary.