| Summary: | 博士 === 國立中山大學 === 海洋科學系研究所 === 103 === Meiofauna is considered an ecological indicator for their composition as it might shift consistently with the ambient environment. The structural complexity of macrophytes provides various microhabitats, which increases the local infaunal abundance and diversity. Seagrass is regarded as an ecosystem engineer and alters the benthic environment, which enables several adapted meiofauna to thrive in the sediments. The differences in meiofaunal communities between seagrass beds and adjacent unvegetated areas have been reported, whereas most studies are based on a comparatively long distance of sampling distribution. This study was designed to test if the community structures of meiofauna and marine nematodes differ between seagrass beds and adjacent unvegetated sediments on a small scale, i.e. within several meters. A total of 21 meiofaunal taxa and 63 nematode genera were identified from a tropical seagrass bed of Thalassia hemprichii in Ludao, Taiwan. Although the compositions of higher meiofauna taxa are undistinguished, according to correspondence analysis, the assemblages of nematode genera differ substantially between seagrass beds and unvegetated sediments. The number of replicates for reasonable estimation of the local diversity index was calculated using the randomization technique. Regarding local seagrass beds, only a single core with 2-cm internal diameter is sufficient for reliably estimating meiofaunal diversity, but at least three cores or a sample size of 300 individuals are needed for nematode community. The effects of seagrass species in a mixed-species seagrass bed at Haikou, Taiwan were examined. Analyzing quantitative samples obtained from patches of T. hemprichii, Halodule uninervis, Halophila ovalis, and adjacent unvegetated sediments inspected the community structures of meiofauna and marine nematodes. The abundance and diversity of crustaceans and nematodes were substantially higher in habitats in which seagrass grew than in those comprising unvegetated sediments. Both the compositions of higher meiofaunal taxa and nematode species were distinct between seagrass habitats and unvegetated areas. Several nematode species existed exclusively in patches of individual seagrass species, whereas no nematode particularly occurred in unvegetated areas. Regarding the trophic types of nematodes, non-selective deposit feeders were prevalent in the present study, whereas selective deposit feeders and epistrate feeders were relatively dominant in seagrass habitats. Sediments underneath various patches of seagrass species harbor dissimilar nematode communities, even with similar sediment parameters and at a small-scale distance.
|
|---|
