Influence of sea squirt (Halocynthia roretzi) aquaculture on benthic–pelagic coupling in coastal waters: A study of the South Sea in Korea

The influence of sea squirt aquaculture on benthic–pelagic coupling was evaluated in semi-enclosed Korean coastal waters with an in situ benthic chamber and results show for the first time that suspended sea squirt cultures play an important role in benthic–pelagic coupling in the coastal zone. Measurements of primary production, vertical particulate fluxes, and benthic fluxes were made at two stations, a sea squirt (Halocynthia roretzi) farm (SSF) and an area of organic-matter-enriched sediment in Jinhae Bay. The vertical material fluxes of organic carbon, nitrogen, and biogenic silicate (BSi) were significantly higher at SSF than in Jinhae Bay, indicating massive biodeposits in the surface sediments at SSF. The organic carbon oxidation rates (Cox) were estimated after correction for CaCO3 dissolution. The average Cox at SSF (204 mmol C m−2 d−1) was significantly higher than that in the organic-enriched Jinhae Bay sediment (77 mmol C m−2 d−1). The organic carbon burial fluxes were determined using vertical profiles of organic carbon of up to 30 cm and the sedimentation rate calculated from the excess 210Pb distribution. At both stations, ∼95% of the settled organic carbon was oxidized and only ∼5% was buried in the deep sediment layer. The benthic fluxes of dissolved inorganic nitrogen and phosphate at SSF were 2–12 times higher than in Jinhae Bay, corresponding to 85%, and 270%, respectively, of the requirements for primary production.