Abstract
The expansion of the aquaculture industry has resulted in accumulation of phosphorus (P)-rich organic matter via uneaten fish feed. To elucidate the impact of fish farming on P dynamics, P speciation, and benthic P release along with partitioning of organic carbon (Corg) mineralization coupled to sulfate reduction (SR) and iron reduction (FeR) were investigated in the sediments from Jinju Bay, off the southern coast of South Korea, in July 2013. SR in the farm sediment was 6.9-fold higher than the control sediment, and depth-integrated (0–10 cm) concentrations of NH4+, PO43–, and H2S in pore water of the farm sediment were 2.2-, 3.3-, and 7.4-fold higher than that in control sediment, respectively. High biogenic-P that comprised 28% of total P directly reflected the impact of P-rich fish feed, which ultimately enhanced the bioavailability (58% of total P) of P in the surface sediment of the farm site. In the farm sediment where SR dominated Corg mineralization, H2S oxidation coupled to the reduction of FeOOH stimulated release of P bound to iron oxide, which resulted in high regeneration efficiency (85%) of P in farm sediments. Enhanced P desorption from FeOOH was responsible for the increase in authigenic-P and benthic P flux. Authigenic-P comprised 33% of total P, and benthic P flux to the overlying water column accounted for approximately 800% of the P required for primary production. Consequently, excessive benthic P release resulting directly from oversupply of P-rich fish feed was a significant internal source of P for the water column, and may induce undesirable eutrophication and harmful algal blooms in shallow coastal ecosystems.
Highlights
Phosphorus (P) is a key nutrient, regulating primary production as a limiting nutrient in aquatic ecosystems, and inducing eutrophication that can stimulate undesirable algal blooms in coastal ecosystems (Tyrrell, 1999; Diaz and Rosenberg, 2008; Middelburg and Levin, 2009; Lomnitz et al, 2016)
total organic carbon (TOC), total nitrogen (TN), and Chl a concentrations in the surface sediment were greater in the farm sediment than in the control sediment (Table 3)
APP data were taken from National Institute of Fisheries Science (NIFS) (2013). bN and P demands for PP were calculated using Redfield’s ratio of C:N:P = 106:16:1. cDIN was calculated from the sum of NH4+ and NOx release rate, and dissolved inorganic phosphorus (DIP) was calculated from PO43− release rates (Figure 4). (Figure 5 and Supplementary Table 3), and (2) Aut-P and BioP were the dominant fractions of P forms (Figure 6)
Summary
Phosphorus (P) is a key nutrient, regulating primary production as a limiting nutrient in aquatic ecosystems, and inducing eutrophication that can stimulate undesirable algal blooms in coastal ecosystems (Tyrrell, 1999; Diaz and Rosenberg, 2008; Middelburg and Levin, 2009; Lomnitz et al, 2016). Phosphorus Dynamics in Aquaculture Sediment and release) or a sink (i.e., adsorption and precipitation) of P for the water column (Slomp, 2011; Kraal et al, 2015; An et al, 2019). P dynamics in coastal sediments are tightly coupled to the rate and partitioning of Corg mineralization and the resulting interaction between iron and sulfur (Rozan et al, 2002; Canfield et al, 2005; Kraal et al, 2013; Slomp et al, 2013; AndrieuxLoyer et al, 2014; An et al, 2019). Because the interaction of P with Fe and S has a profound impact on P dynamics in anoxic sediment (Rozan et al, 2002; An et al, 2019), quantification of the relative significance of SR and FeR, which regulate the availability of Fe to react with the P, is important to better understand the P dynamics in coastal sediments
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
