Zonation and structuring factors of meiofauna communities in a tropical seagrass bed (Gazi Bay, Kenya)

This study deals with the relation between tropical meiofauna and environme ntal variables by comparing the 'benthic' (i.e. in the bare sediment adjace nt to seagrass plants) and the 'epiphytic' (i.e. in samples including seagr ass plants) meiofauna associated with five seagrass species from the high i ntertidal to the high subtidal zone in Gazi Bay (Kenya). Ordination and var iance analysis revealed three distinct 'benthic' and two 'epiphytic' meiofa una assemblages. These assemblages corresponded entirely with those identif ied for the seagrass species: a high intertidal pioneer association (Haloph ila ovalis/Halodule wrightii), an intertidal climax assemblage (Thalassia h emprichii) and a high subtidal pioneer association (Halophila stipulaceal S yringodium isoetifolium). These data support the hypothesis that meiofaunal communities correspond to the characteristic zonation of the seagrass vege tation in Gazi Bay. In beds of the pioneer seagrass species, the close relationship between sed iment characteristics and both 'benthic' and 'epiphytic' meiofauna communit ies suggests that these pioneer communities were mainly driven by physical factors. The 'benthic' communities adjacent to the climax seagrass species T. hemprichii were more structured by biogenic factors, e.g. % TOM, chlorop hyll (a and c. fucoxanthin, habitat complexity and growth form of the seagr ass species. For its associated 'epiphytic' meiofauna the latter conclusion was even more striking. These data corroborate the importance of physical factors in disturbed environments (intertidal zone, near pioneer seagrasses ) and of biotic factors in more stable conditions (subtidal zone, near clim ax seagrasses). (C) 2001 Elsevier Science B.V. All rights reserved.