The application of Trophic State Index (TSI) in the classification and assessment of ecosystem health of Three Rivers in southern Nigeria
The application of Trophic State Index (TSI) in the classification of three rivers in the Niger Delta region of southern Nigeria was carried out between January and June 2017 on monthly basis across wet and dry seasons. The purpose of this investigation was to ascertain the nutrient status of the three rivers which have hitherto been plagued with a lot of anthropogenic activities over the years. The findings from this study reveal that all the rivers are eutrophic, with the calculated Calson’s Trophic State Index CTSI) going over 70 for each of the rivers. The eutrophic state of the rivers was consistent throughout the study and was not affected by season but more of anthropogenic activities. Igbokoda River recorded the highest phytoplankton abundance of 558 with 22 phytoplankton species, followed by Ethiope River with abundance of 554 with 47 species and Warri River with abundance of 249 and 54 species. Bacillariophyta was the dominant group in all the rivers investigated. The high phytoplankton abundance recorded is not unconnected with the high phosphorus content recorded in the study. Pollution indicator species like Closterium, Nitzchia, Phormidium, Oscillatoria, were observed in all the rivers.
Keywords: trophic, eutrophic, phytoplankton, pollution, rivers