Effect of habitat fragmentation on abundance and diversity of seagrass-associated crustacean assemblage at Hurghada, Red Sea

Seagrass beds in Red Sea are increasingly subject to both natural and anthropogenic disturbance and fragmentation, resulting in an increase in the edge habitats. Consequently, the present study was designed to study the effect of habitat fragmentation of seagrass on the diversity and abundance of epiphytic crustaceans inhabiting seagrass canopies. For this purpose, two sites, containing different seagrass patch sizes, were selected for seasonal sampling during the period from mid-April 2015 to mid-January 2016 around Hurghada, Red Sea. Evaluations of the differences in crustacean assemblage structure, abundance and diversity between fragmented and continuous seagrass beds as well as the edge and center of the same seagrass patches were figured out. Overall, 33 crustacean species belong to 30 genera, 25 families, and 7 orders were recorded, from all different seagrass patches with a comparable temporal and spatial distribution; whereas all recorded crustacean species belong to class Malacostraca. Results indicated that large seagrass patches harbor higher crustacean’s densities than medium and small seagrass patches, which promote the assumption of the negative effect of seagrass fragmentation. The abundance of crustacean groups are also markedly increase in the large patches except decapods in one site. Reduction of habitat size led to reducing the number of crustacean species in both sites. However, Evenness values (J') showed that habitat fragmentation had no effect on diversity. THE Total crustaceans abundance is relatively increase toward the patch edge with a percentage of increase up to 18 %. However, crustacean species richness was insensitive to differences in patch edge-center microhabitat. Relation between seagrass shoot density/biomass and the total crustacean abundance also figured out in this study.