Influence of Nutrients on Seagrass Distribution in Malindi, Kenya

Abstract

Seagrass are marine flowering plants that occupy both tidal and subtidal marine environments. They are highly productive ecosystems that are useful indicators of environmental health due to their sensitivity to changes in the quality of the marine environment. Nutrients enrichment is known to be a leading cause in the declining of seagrass meadows worldwide. The changes of seagrass and the effects of nutrients fluctuations on their distribution pattern in Malindi have not been documented widely. The aim of the study was to determine the influence of nutrients on the distribution of seagrass in Malindi. Malindi Marine Park (MMP) sites were selected; one at the, the Malindi Marine Reserve (MMR), and the Malindi Marine Buffer (MMB) zone. At each site 30m transects were laid perpendicularly to the shore and samples collected in triplicate at intervals of 10m. Water and sediment samples were collected using plastic bottles and corers, respectively. Nutrients (nitrates, nitrites, ammonia and phosphates) in both water and sediments were analysed colorimetrically. Five species, viz Thalassia hemprichii, Enhalus acoroides, Syringodium isoetifolium, Cymodocea serrulata and Thalassodendron ciliatum were identified throughout the sites. Nutrients in sediment were generally higher than in water. Total biomass was predominantly influenced by nitrates (r=-0.141) and nitrites (r=+0.488) in sediments and ammonia (r=-0.364) and nitrites (r=+0.50) in water. The Malindi marine environment could still be oligotrophic but further studies across greater timescales and space are required to unravel seagrass variations due to tourism, urbanization and watershed changes, it was recommended that such be integrated in the monthly monitoring effort of the Kenya Wildlife Service (KWS) and Environmental Impact Assessment (EIA) efforts of the National Environment Management Authority (NEMA).