Analyzing Spatial-temporal Variation in Water Quality Parameters in South Coast Estuarine Ecosystem, Kenya
Kobingi Nyakeya *
Kenya Marine and Fisheries Research Institute, Baringo Station, P.O. Box 231, Marigat, Kenya and Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.
James Onchieku
Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.
Frank Masese
Department of Fisheries and Aquatic Science, University of Eldoret, P.O. Box 254, Eldoret, Kenya.
Zipporah Gichana
Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.
Albert Getabu
Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.
Jane Nyamora
Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya and Kenya Marine and Fisheries Research Institute, Mombasa Headquarters, P.O. Box 81651 – 80100, Mombasa, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Estuarine ecosystems are classified as among the most productive systems on the planet earth supporting an array of biodiversity. However, due to the ever increasing human population, they experience environmental degradation originating from intensive anthropogenic activities hence the need for regular assessment and monitoring to inform its management. The purpose of this study, therefore, was to analyze the spatio-temporal variation in water quality parameters in South Coast estuarine ecosystem, Kenya. Twelve sampling stations were identified based on different hydrological regimes, anthropogenic activities, and accessibility factors. Sampling was done for 12 months taking into account different seasons of the year. Such parameters as temperature, dissolved oxygen, pH, conductivity, salinity and TDS were collected in situ using YSI Multiparameter meter (Professional plus) whereas nutrients (nitrates, phosphates and ammonia) were analyzed in the laboratory using established methods. Two-way analysis of variance (ANOVA) was applied to discriminate any significant differences among stations and between seasons, and where there was a difference, Tukey post hoc test was applied to show which site differed from each other. Principal Component Analysis (PCA) was performed to correlate the environmental factors with sampling sites, and months. There was significant difference in water quality parameters among the sampling stations (P = .05) that was attributed mainly to anthropogenic activities, and both the point and non-point sources of pollution. Conversely, there was no significant difference in most of the water quality attributes in terms of seasons due to unpredictable weather patterns associated with climate change. There is need for long term monitoring strategies in order to generate sufficient data for sound management of South Coast estuary in Kenya. The study further recommends for community sensitization and implementation of relevant policies on the protection and management of riparian land.
Keywords: Estuarine systems, Kenyan coast, environmental factors, anthropogenic activities, water quality