Meiofauna and nematode community assemblage as sediment disturbance indicator in Mida Creek, Kenya

Abstract

Abstract. Wafula M, Muthumbi A, Wang’ondu V. 2019. Meiofauna and nematode community assemblage as sediment disturbance indicator in Mida Creek, Kenya. Ocean Life 3: 24-37. Meiofauna is a group of benthic fauna mostly found in the sediments’ upper centimeters (cm), including Copepoda, Polychaeta, and Nematoda. This study focused on determining nematodes’ potential as bio-indicators of sediment disturbance caused by bait harvesting. Furthermore, bait harvesting was common, albeit with different intensities, on the different beaches of Mida Creek, Kenya, on November 2013. Sediment samples were collected along two transects within the mud flat running from the mangrove forest edge to the edge of the subtidal zone. Along the transects, 1 m² was placed at 20 m intervals. A replicate of 2 sediments core (3.4 cm diameter, 10 cm deep) was taken from each quadrat. Next, samples were fixed using 5% formalin, stored in plastic bottles, and then transported to the laboratory for processing and identification. The nematodes were used because it could bring out a clear difference in their distribution, community assemblage, diversity, and abundance due to sediment disturbance compared to other meiofauna. Of the total meiofauna, 3,988 individual nematodes were identified to the genus level. In addition, Nematoda was the most abundant taxon of all other meiofauna taxa. The bait harvesting through digging was more pronounced in Mayonda due to its wider mud flat width. The result showed a clear difference in the distribution, diversity, and community assemblage of the nematodes seen in all the sites. A sum of 83 nematode genera was encountered in Mida Creek. Kirepwe had 58 genera, Dabaso had 46 and Mayonda had 35. Mayonda had the highest nematode diversity, then followed by Kirepwe and Dabaso. On the contrary, Dabaso had the highest nematode density, then followed by Mayonda and Kirepwe. The meiofauna had a high community similarity, while nematode community similarity was lower at different levels of sediment disturbances. That makes the nematodes better bio-indicators as compared to meiofauna as a group. Therefore, this study points out that digging out polychaetes causes sediment disturbance. The disturbance affects the benthic fauna distribution, community assemblage, diversity, and abundance. Moreover, Terschellingia and Spirinia were distributed across all sites, even though in disturbed quadrats the numbers reduced significantly. On the contrary in disturbed quadrats, Viscosia, Pontonema, Synochium, Haliplectus, and Pheronus increased in numbers. To measures such as educating the fishermen on the effects of digging polychaete should be emphasized to safeguard marine biodiversity and its ecosystem.