Use of spionid polychaetes genus Prionospio in bioremediation of organically enriched sediment under green mussel rafts

Spionids, Prionospio spp., in this study were proposed as the potential bioremediators of organically enriched sediment under green mussel rafts in Sriracha Bay, Chonburi Province. Key criteria as bioremediator in selecting the potential Prionospio species were focused. The distribution and abundance of spionid polychaetes in Sriracha Bay revealed that Prionospio (Prionospio) membranacea, dominated of 70% of the spionids found in the area, was widely distributed in the high organic content area in the mussel raft culture area and nearshore station. Prionospio (Minuspio) pulchra, the second most abundant species, also found distributed in high organic content area but in low density. Morphological adaptation of respiratory structure in spionid polychaetes were considered one of the key criteria for selecting potential polychaete species. The present study revealed the presence of intraspecies morphological differences in respiratory structures in spionids as related to different organic conditions. In the high organic content area, branchial pairs were significant longer than those in the area of low organic content. The pinnules were more numerous in the high organic area. In addition, branchial length and pinnule numbers showed the tendency to increase in relation to body size. These morphological differences of these spionids under different organic condition occurred earlier in their early benthic juvenile stage. Reproductive and development pattern in spionid polychaetes in organically enriched sediment is another key criteria for potential bioremediator. The characteristic of reproduction and larval development patterns of the two dominant spionids, P. membranacea and P. pulchra fit the life history of opportunistic species. Organic enriched sediment increased their reproductive potential in term of increase fecundity and decrease time to metamorphosis and settlement. Organic enriched sediment also increased the settlement success in the larvae of these polychaete species. From the bioremediation efficiency assessment, the two spionids, P. membranacea and P. pulchra were efficiently converted the organic waste into biomass and reduced the organic matter in the sediment. From the results of key criteria as bioremediator, P. membranacea was selected as the potential species for the treatment of organically enriched sediment under green mussel rafts in Sriracha Bay, Chonburi Province. The artificially mass culture of selected spionid was efficiently bioremediate the enriched sediment through the process of converting organic waste into biomass and reduced the organic matter and sulphide. High density of P. membranacea increased the bioremediation efficiency.