UTILIZATION OF BIOLOGICAL-ACTIVITIES OF C APITELLID POLYCHAETE FOR TREATMENT OF HEDORO (ORGANICALLY ENRICHED SEDIMENT) DEPOSITED ON THE MARINE BOTTOM BELOW FISH NET PEN CULTURE

We have attempted to promote the decomposition of organic matter depos ited on the marine bottom below fish net pen culture by the biological activities of a deposit feeding capitellid polychaete, Capitella sp. 1. The organically enriched sediment was reproduced in the tub in the laboratory by the addition of moist pellets for fish culture on the se diment. We compared the chemical characteristics of the sediments betw een the experiments with and without Capitella. In these experiments, the Capitella colonies increased rapidly, and the biological activitie s such as feeding, reworking etc. efficiently decomposed the organic m atter added on the sediment. The levels of organic matter of the sedim ent with Capitella fluctuated stably around the initial level througho ut the period of the experiments for 60 days, while the levels in the experiments without Capitella gradually increased. The promotion of or ganic decomposition of the sediment in the experiments with Capitella also prevented the development of reduced conditions in the sediment. If we can re-establish a dense Capitella population on the bottom belo w the fish net pen quickly in the environmental recovery process from autumn to winter by releasing artificially cultured colonies of the wo rms, the potential of organic decomposition on the bottom will be sign ificantly enhanced.