Implication of Heavy Metals Dynamics in Sediment Pore-Water Interface on Macro Benthic Invertebrate Assemblage in Makupa Creek, Mombasa.

Abstract

Coastal systems, particularly lagoons, creeks and estuaries worldwide are experiencing increased pollution from anthropogenic inputs including effluents discharged from urban, industrial, agricultural and atmospheric deposition. This has led to degradation of water and sediment quality leading to loss of biological diversity and problems in human health. Loss of biological diversity is significant for ecological integrity of a system and for aquatic food web it is the cause of poor energy transfer along the trophic levels. Heavy metals in sediments cause adverse lethal and sub-lethal effects on the dwelling community. Benthic macro-invertebrates integrate effects of contaminants over time and are useful indicators of aquatic environment health. The objective of this study was to determine the implication of Fe, Cu, Cd, Zn, Mn and Pb dynamics in pore-water sediment interface and sediments quality on spatial distribution of benthic macro invertebrates in Makupa Creek, Mombasa. The results suggested that sewage effluents from domestic and industrial activities, seepage from solid waste disposal and restricted hydrologic dynamics influences benthic macro-invertebrates and heavy metal distribution in both sediment and pore-water concentrations compared to a pristine coastal area. Analysis of similarity (ANOSIM) revealed no significant difference (ANOSIM Global R: = 0.018, -0.026, -0.196 at p>0.05) and was attributed to common species in Makupa Creek stations. SIMPER analysis revealed limnodriloides barnadi, unidentified nematode, Mesanthula Catenula, Heterodrilus jamiessoni, Olavius geniculatus, Oktedrilus monospermlectus, and unidentified polychaete and Lucifer chacei are the species that contributed highest dissimilarity. High values of metals partitioning coefficients Kd indicated a strong affinity of the metal with sediment and suggested restricted bioavailability of the metal to benthic invertebrates. Conservation of estuarine and coastal wetlands is important because they are areas rich in biodiversity that play a very important role in energy transfers in aquatic ecosystem.