Chiang Mai Journal of Science

A study was conducted to determine the fractional contributions of seagrasses and other sources to the sediment and the diet of the sea cucumbers Holothuria scabra and H. atra-leucospilota in a tropical seagrass meadow. The contribution from each source was estimated using the MixSIAR mixing model wherein the trophic enrichment factors of communities were integrated in the model. The results of the study suggest that the seagrass contribution to the sediment was coupled with the sea cucumber diet. Seagrass species contributed 32.0 % of the organic matter in the sediment while the contributions from the land plants, mangroves, microphytobenthos, coastal particulate organic matter, river particulate organic matter were 15.0, 14.4, 14.3, 13.2, and11.0 %, respectively. Subsequent assimilation of these sources by the sea cucumbers H. scabra and H. atra-leucospilota revealed that 61-70 % of their diet was derived from the seagrasses. This finding suggests these two sea cucumbers shared similar diet sources in the meadow as reflected in the similarity of proportional contributions of sources to their diets. The implications of this study may help in the conservation of sea cucumbers due to the destruction of seagrass habitats in many parts of the Southeast Asian region.