Bioturbation by sea cucumbers Apostichopus japonicus affects sediment phosphorus forms and sorption characteristics

Abstract

An 84 d experiment was carried out to investigate the impact of sea cucumber Apostichopus japonicus (Selenka) bioturbation on different phosphorus forms and phosphorus sorption characteristics in the sediment. Sea cucumbers were cultured in fiberglass tanks (30 × 40 × 50 cm) with 5 cm thick sediment, and were divided into 4 groups according to culture densities, i.e. 0, 4, 6, and 8 ind. tank-1. For each of these 4 densities, 4 replicates of sea cucumbers were cultured. Results showed that the increasing culture density significantly increased the content of NaOH-extractable P (NaOH-P) and decreased the content of organic phosphorus (OP) in sediment. Phosphorus maximum buffer capacity (MBC) and energy adsorption (Kf) values of sediment in the lower density groups (0 and 4 ind. tank-1) decreased significantly with time, while no temporal changes were observed in MBC and Kf values of sediment in the higher density groups (6 and 8 ind. tank-1). Sea cucumbers facilitated the decomposition of OP and the formation of NaOH-P in sediment, and improved the ability and capacity of phosphorus sorption of the sediment with increasing culture density. Our results suggest that the use of sea cucumbers may help to prevent eutrophication in integrated multitrophic aquaculture systems.