Influence of a microhabitat on the structuring of the benthic macrofaunal community in a mangrove forest

Abstract

Habitat heterogeneity contributes to the maintenance of species diversity; however, little is known about the influence of microhabitat heterogeneity on the diversity of mangrove invertebrates. We tested the hypothesis that the structures of benthic faunal communities differ among microhabitats because each microhabitat function differs widely according to their physical properties. The descriptors of invertebrate assemblages were determined every March (dry season) and August (wet season) of 2005, 2006, and 2007 in three different mangrove microhabitats—tidal creek, deep forest, and canopy gap—of an intertidal mangrove forest around the Sikao Creek in the Trang Province of southern Thailand. The physical properties of the selected microhabitats were studied in 2005. The properties of each microhabitat varied, especially with respect to the light intensity and sediment moisture content: the tidal creeks were wet and well-exposed to sunlight, forest interiors were moist and dark, and the canopy gaps were dry and well-exposed to sunlight. Seasonal differences in the microhabitats were also noted. The numerical abundance and biomass of benthic macrofauna differed among the microhabitats; both values were the highest in canopy gaps, and these values increased in the wet season. Despite seasonal differences, species composition differed in the three microhabitats; the majority of animals were members of the epifauna; these were surface deposit feeders. Each microhabitat functioned differently because their physical properties were disparate. A diverse benthic faunal community is formed by a combination of different functional microhabitats in mangrove ecosystems, thereby indicating that microhabitat heterogeneity should be considered as an important factor influencing the structuring of a benthic community.