Assessment of Sediment Characteristics and Impact on Macro invertebrate Distribution in Lamu County

Macroinvertebrates are soft bottom organisms that live in or on marine sediment substrates that pass through a 1 mm sieve and are retained on a 0.5 mm sieve. Owing to their small size, high abundance, easily available and high sensitivity to environmental disturbance, macrobenthos are good environmental indicators. In Lamu, there is still a paucity of information on macroinvertebrates distribution and diversity. Therefore, this current study aimed to assess the abundance and diversity of macroinvertebrates communities in the mangrove ecosystems of Lamu. Mangrove forests are one of the world’s most productive coastal wetlands found in the estuaries and intertidal zones in marine environments. They are important coastal resources for marine species and coastal communities’ livelihood and climate. They also provide permanent habitat for benthic organisms such as macroinverterbrates. The research study was conducted in Lamu County, which is located on Kenya's northern coast stretching stretches from the Kenya-Somalia border (north) to the Tana River (south). We sampled two study sites namely Kacha (Marine Protected Area) and Sagafi (a highly fishing ground). A stratified random sampling design was employed to conduct the study at 50 m intervals, 10 m X 10 m plots were laid perpendicular to the shoreline, with three line transects sampled per site. Replicates sediment cores for grain size and macroinvertebrate samples were collected within each plot using a Perspex hand corer (6.4 cm diameter) to a maximum depth of 10 cm. For macroinvertebrates analysis, macroinverterbrates abundance data was formalized to ind.m-2 before conducting univariate analysis. T-test was used to examine the significant differences between sites (p < 0.05). A total of 26 macroinvertebrates were recorded in both sites. Nematoda was the most abundant taxa in Kacha whereas in Sagafi Gastropoda was the most abundant taxa. For grain size, 200 mm sieve size retained the highest mass in both sites.