Beneficial co‐culture of jellyfish Rhopilema esculenta (Kishinouye) and sea cucumber Apostichopus japonicus (Selenka): implications for pelagic‐benthic coupling

This study investigated monthly changes of sedimentation and sediment properties in three different culture systems (ponds) – i.e. jellyfish Rhopilema esculenta monoculture ( J ), sea cucumber Apostichopus japonicus and jellyfish co‐culture ( SJ ) and sea cucumber monoculture ( S ) – to verify the feasibility of co‐culturing jellyfish and sea cucumbers. Results showed that jellyfish culture accelerated the settling velocity of total particulate matter ( TPM ). Average TPM settling velocities in the SJ (75.6 g m −2 day −1 ) and J (71.1 g m −2  day −1 ) ponds were significantly higher than that in the S pond (21.7 g m −2  day −1 ) from June to September during the jellyfish culture period. Average settling velocities of organic matter ( OM ), total organic carbon ( TOC ), total nitrogen ( TN ) and total phosphorus ( TP ) in the SJ pond increased significantly by 3.0, 2.9, 3.3 and 3.8 times, respectively, compared with those in the S pond. Sediment contents of OM , TOC , TN and TP in the SJ and J ponds were significantly higher than those in the S pond during the jellyfish culture season. The specific growth rate of sea cucumbers feeding on SJ sediment was significantly higher than that of those feeding on S sediment. Co‐culturing sea cucumbers with jellyfish may help alleviate benthic nutrient loading due to the jellyfish and provide a secondary cash crop.