Diatom communities in the riparian systems associated with Lagos Lagoon, Nigeria I. Seasonal and anthropogenic patterns in Majidun Creek
Adesalu, Taofikat Abosede; Kunrunmi, Olakunbi Anike
In this report, we describe the investigation of water samples from Majidun Creek, a riparian system emptying into Lagos Lagoon, over a period of twelve months (February 2010– January 2011). Samples were obtained using a 55 μ m plankton net towed at low speed for 10mins. Various physico-chemical parameters were monitored; surface water temperature, PO4 -P, transparency, NO3 -N, SO4 2- and silicate concentrations. All measured chemical parameters were lower in the rainy season while surface water pH ranged from acidic to alkaline (6.2–8.4), chlorophyll 'a' showed its highest value in the dry season. There was a remarkable change in seasonal salinity values while conductivity values ranged between 0.01 and 13.15 (mS/cm) in raining and dry seasons, respectively. Fifteen different orders of diatoms were recorded. The Naviculales dominated the diatom spectrum followed by Cymbellales, Fragillariales, Thalassiophysales, Nitzschiales and Eunotiales. Changes in diatom communities appear to be driven by two factors. The first, and dominant factor, is seasonality based on differences between the rainy and dry seasons which is correlating with peak biodiversity and peak biomass in diatom community structures. Anthropogenic impacts appear to be the second force influencing diatom community structure with areas of high population density, showing alterations in community composition when compared to regions with less human activity. Since most of the monographs used by Nigerian algologists are not indigenous, this paper may assist in solving a part of the diatom identification problems.