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Marine pollution, ecotoxicology and sustainability
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Trophic role of hermit crabs in the coastal mudflats: implications for fish production.
P-E1-10
Hong Wooi Teoh* , Xiamen University Malaysia
Ving Ching Chong, University of Malaya
Presenter Email: hongwooi.teoh@xmu.edu.my |
| Coastal mudflats fueled by a variety of primary producers such as the mangroves, seagrass, benthic microalgae and phytoplankton, support a great diversity of fauna. High Tidal current brings in phytoplankton from nearshore area while the regular exposure of the mudflat during low tide allow benthic microalgae to proliferate. The soft sediments of the mudflat trap high amount of organic matter that originated from these primary producers, forming an important biota that include a variety of inhabiting primary consumers. The diversity of marine fauna on the Matang coastal mudflats may suggest trophic energy inputs from autochthnous (e.g. benthic microalgae and phytoplankton) and allochthnous (mangrove detritus) sources fueling their abundance on seemingly wastelands that are devoid of vegetation. Among the least conspicuous fauna are the small diogenid hermit crabs that often occur in large numbers on the mudflats. We hypothesize that these hermit crabs serve as intermediary consumer-prey organisms. The study objective is to trace the flow of trophic energy from the potential basal sources to fish predators via the diogenid hermit crabs. Two methods were used; stomach content and stable C and N isotope analyses of both fish predators and the hermit crabs. Results from stomach content analysis reveal that the abundant and commercially important sciaenid fish (particularly Johnius belangerii) fed extensively on the hermit crabs offshore. The stomach contents of hermit crabs comprised of brown amorphous phyto-matter, diatoms and faunal remnants which suggests deposit feeding. Stable isotope analysis provides evidence of the transfer of energy from the sediment-trapped carbon sources. The benthic microalgae are the main contributor of the carbon assimilated by the hermit crabs, followed by phytoplankton and mangrove. The predation on hermit crabs in turn transfers trophic energy to the higher consumers, mainly fish predators. The present finding adds diogenid hermit crabs to the few, but growing versatile marine herbivorous organisms capable assimilating mangrove carbon. However, the dependency of hermit crabs on the mangrove-derived carbon decreased from estuary to offshore, reflecting the substantial carbon contribution of mangrove-fringed mudflat to the coastal food web and the role of the inhabiting primary consumers in mediating the transfer of energy for fish production. |
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