Patrones de diversidad de poliquetos en hábitats intermareales tropicales selectos

Few studies have quantitatively compared benthic macrofaunal assemblages between different tropical intertidal habitats over differing spatial scales. The present study uses spatially nested material from vegetated (seagrass) and non-vegetated (mudflat) habitats in SW Thailand to address this issue. Polychaetes were the numerically dominant component of benthic assemblages throughout the region, comprising over 74% of the total macrofauna. Despite great within-site and sample variation, based on species diversity, polychaete assemblages were mostly site-specific. Not so visibly obvious were the evident differences in polychaete assemblages between habitats. The spatial pattern of polychaete diversity is explored.Pocos estudios han comparado cuantitativamente el macrozoobentos entre diferentes hábitats intermareales tropicales a diferentes escalas espaciales. Para remediar esta situación, esta investigación utiliza y compara material colectado en praderas marinas y zonas sin vegetación en la costa suroeste de Tailandia a diferentes escalas espaciales. Los poliquetos formaron la mayor parte del zoobentos, constituyendo el 74% del total. Pese al alto nivel de variación entre muestras, basado en la diversidad de especies, los conjuntos de poliquetos mostraron mayor afinidad a su lugar de colecta. Diferencias entre cada hábitat, aunque difíciles de apreciar a simple vista, son corroboradas estadísticamente. Se exploran cambios en la diversidad asociados con cambios en la escala espacial. &nbsp

Patterns of polychaete communities in tropical sedimentary habitats: a case study in south-western Thailand

ABSTRACT. – Few studies have compared macrofaunal assemblages (organisms retained on a 0.5 mm sieve) between different tropical sedimentary habitats. The present study aims to address this issue, investigating vegetated (seagrass), non-vegetated organic mud and exposed beach habitats. Polychaetes were the dominant taxonomic group at all sampling sites, followed by crustaceans and molluscs. Thirty-six polychaete families were recorded, 31 % of which were present in all three habitats. All families were represented in non-vegetated habitats. Polychaete family and functional group assemblages did not differ greatly between vegetated and non-vegetated habitats despite varying densities. Differences in polychaete assemblage structure were most pronounced between exposed beach and non-vegetated habitats. Polychaete assemblages were also negatively affected by the onset of the wet monsoon season. Overall, macrofaunal density (29- 2,629 ind. m-2) fell within the range of that reported by other authors in the region. Small-scale physical and environmental factors are thought to be responsible for the large variation in polychaete assemblage structure within habitats. Identification of polychaetes to species, together with further analysis of small-scale physical data should provide a deeper understanding of the spatial and temporal changes reported in this study. A call is made for the standardisation of future sampling efforts and techniques to allow meaningful comparisons amongst sedimentary habitats across large spatial scales. KEY WORDS. – seagrass, polychaete, macrofaunal density, inter-habitat

Post-Tsunami Recovery of Shallow Water Biota and Habitats on Thailand’s Andaman Coast

There have been very few quantitative studies of the intertidal and shallow water biota of the Andaman Coast of Thailand and thus it was very difficult to provide precise estimates of the impact of the tsunami on coastal resources. Some quantitative data from Laem Son National Park existed, having been collected by the present authors, and these indicated that the most severe impacts were on the intertidal sand beach fauna, on rocky shore assemblages and on the seaward edge of mangrove forests. Inside the forests there was heavy deposition of coarse sediment on the forest floor and this led to changes in the species composition of the infauna. Most, but not all, sea grass beds escaped serious damage. By 2008 intertidal sediment assemblages contained a similar number of individuals to that recorded before the tsunami. Pre-tsunami data indicate that open coast, estuarine and seagrasses assemblages are naturally highly variable and thus were well adapted to recovering from the tsunami disturbance. Offshore sediments lack pre-tsunami information, but they too appear to be normal. Size frequency analysis of a population of the heart urchin Brissopsis luzonicus indicate that some individuals survived the tsunami but that there is heavy domination by the first post-tsunami cohort suggesting heavy colonization of disturbed seafloor. The trees in the seaward fringe of the most exposed mangrove forests still have to recover from tsunami damage, although the benthic fauna within the forest has returned.<br/