Impact of finfish aquaculture on biogeochemical processes in coastal ecosystems and elemental sulfur as a relevant proxy for assessing farming condition

Phosphorus Dynamics Associated With Organic Carbon Mineralization by Reduction of Sulfate and Iron in Sediment Exposed to Fish Farming

“…The study area was located in semi-enclosed Jinju Bay near Sacheon and Namhae Island on the southern coast of South Korea (34 • 55 -34 • 57 N, 127 • 57 -127 • 59 E) (Figure 1). Fish farming activities have been ongoing for several years in which most fish were harvested in November (fall), and restocking of empty cages with fry took place in the following March to May (spring) (Choi et al, 2020). Sampling was conducted in July 2013 at a farm site (34 • 57 08 N, 127 • 59 07 E) where sea bass (Lateolabrax japonicus), gray mullet (Mugil cephalus), and black porgy (Acanthopagrus schlegelii) were intensively cultivated.…”

“…Annual fish production in the farming zone with an area of 1,323 m 2 was approximately 445 tons in 2013. Fish feed, consisting of a mix of trash fish and extruded pellets (EP), was continuously supplied in accordance with the growth stage of the fish (Choi et al, 2020). In July 2013, only EP was used, and the input of EP at the fish farm was approximately 1.2 kg m −2 d −1 .…”

“…Despite its economic importance, irresponsible aquaculture activities have led to massive accumulations of organic matter induced by uneaten fish feed and fecal production in coastal sediments (Hall et al, 1990;Holby and Hall, 1991;Holmer et al, 2002Holmer et al, , 2003Husa et al, 2014). This has generated various environmental issues including accumulation of chemically reactive and toxic H 2 S and regeneration of reduced inorganic nitrogen (NH 4 + ) and phosphate (PO 4 3− ) in the sediment (Holmer et al, 2005;Hyun et al, 2013;Choi et al, 2018Choi et al, , 2020. The release of inorganic nutrients into the water column may result in changes in composition and diversity of macroalgae, eutrophication, and (harmful) algal blooms in coastal ecosystems Price et al, 2015;Ferrera et al, 2016;Stigebrandt and Andersson, 2020).…”

“…Given the overall economic and environmental significance of the aquaculture industry, relevant proxies for assessing the condition of fish-farm sediment are required (Ministery of Oceans and Fisheries (MOF), 2016; Choi et al, 2020). P enrichment of sediment has been recognized as a useful indicator for assessing the environmental impact of fish farms that make use of large amounts of feed (Holmer and Frederiksen, 2007;David et al, 2009), as natural variation of P in sediment is small compared with that of C and N (Soto and Norambuena, 2004).…”

Aquaculture Farming Effect on Benthic Respiration and Nutrient Flux in Semi-Enclosed Coastal Waters of Korea

“…In an organic-rich aquaculture system, liberated ammonium and phosphate, byproducts during OM remineralization, are accumulated in the pore water and then released via the sediment-water interface (SWI) by diffusion and advection processes [21,22]. The benthic nitrogen and phosphate fluxes may enhance the eutrophication in the water column, resulting in supplying more than 50% of the nutrient required for phytoplankton production via benthic-pelagic coupling [23][24][25][26]. Unexpected high nutrient release from sediment occasionally leads to the occurrence of red tide in a coastal ecosystem [27,28].…”