Detritus is present in all aquatic ecosystems and yet there is still much debate about its importance in supporting the growth of large organisms, such as invertebrates and fish. For example, mangrove detritus may not be utilized directly by shrimp but it may support a rich microbial assemblage that ultimately supports shrimp growth. This study will test the hypothesis that the foodweb based on mangrove detritus is important in supporting the growth of post-larval penaeaid shrimp. The proposed research will be carried out in a Costa Rican estuary which has large shrimp fisheries and a biological station. Although early studies using stomach analysis emphasized the importance of mangrove detritus in supporting shrimp growth, more recent studies have challenged this. To help resolve this controversy, stomach contents and stable isotope (C, N and S) analysis and mesocosm experiments will be conducted to examine shrimp growth and possible food chain isotope fractionation. By combining tools in invertebrate biology, microbiology and geochemistry it may be possible to determine the ultimate source of primary production (mangroves, phytoplankton or benthic algae) supporting growth of postlarval shrimp. This research will also examine whether the microbial loop, here supported by mangrove detritus, is a source or sink for the biomass production of higher trophic levels.
