The effect of industrial activities on the periphyton community at the upper reaches of New Calabar river, Niger delta, Nigeria

Periphyton diversity and biomass were studied for wet and dry seasons (between 1994 and 1995), selected stations at the upper New Calabar river. The periphyton species assemblage were dominated by diatoms species (45 species) except for areas with crude oil tainting on the substrates. The periphyton standing crop and biomass were higher in concentrations for the crude oil impacted environment (Stations 4 and 5). Also the values for the upper limits area (stations 1, 2 and 3) of the river were lower than that obtained for the lower limit area (station 7, 8, 9 and 10). In comparison using student t-test, there were no significant differences in values between seasons for the periphyton standing crop and biomass (P > 0.05). The assemblage structure for all the stations, showed that diatoms dominated the population and constituted over 70% of the entire periphyton community except for stations 4 and 5 where the Cyanophyta (blue greens) predominated the periphyton population. The species diversity for the stations were above 2.50 except for Stations 4 and 5 (impacted by crude oil), that had diversity values <2.0. Some of the physicochemical parameters such as pH and the nutrient parameters (NH4+ -N, NO3 -N, and PO4+3) showed strong co-linearity with periphyton standing crop and biomass. It is concluded that the activities of industries in the upper New Calabar river had impacted on the periphyton community, but such impact was localised and not on the entire stretch of the study area. (C) 1998 Elsevier Science Ltd. All rights reserved.