Characteristics of Phosphate Flux at the Sediment-water Interface in Gamak Bay during the Hypoxic Water Mass

Abstract

The environmental changes related to hypoxic water mass were investigated at Gamak bay in summer times, June, July and August 2006. The hypoxic water mass was found, in first, at the northern area of Gamak bay on 27 June. This water mass has been sustained until the end of August and disappear on 13 September. In Gamak bay, the hypoxic water mass was closely related to geography. During the formation of oxygen deficiency, changes in dissolved nutrients was studied and found that on surface layer and lower layer, DIN were 0.80 μM~19.8 μM(6.03 μM) and 1.13 μM～60.83 μM(10.66 μM), and DIP were 0.01 μM～0.92 μM(0.24 μM), and 0.01 μM～3.57 μM(0.49 μM), respectively, far higher distribution on lower layer of the water where hypoxic water mass was occurred. The configuration of phosphorus was analyzed to figure out the possibility of release of phosphorus from sediments. It was found that the Labile-Phosphorus, which is capable of easy move to water layer by following environmental change was found more than 70%. Therefore, in Gamak bay, it was found that the possibility of large amount of release of soluble P into the water, while hypoxic water mass was occurred in deep layer was higher. It is suggested that DIP in the northern sea of Gamak bay mainly sourced from the soluble P from lower layer of the waters where hypoxic water mass was created more than that from basin. However, existence form of phosphorus in sediments during normal times, not during creation of hypoxic water mass, needs further study.

C, N, and P Mass Balances in the Bottom Seawater–Surface Sediment Interface in the Reducing Environment due to Anoxic Water of Gamak Bay, Korea

“…This study found high concentrations of H 2 S, DIN, DIP, and DSi in the bottom water collected from GA4, consistent with previous studies [12,66]. The OEI was 16.5, indicative of severe eutrophication.…”

“…Although the DIN elution flux (2.1 mmol/m 2 /d) in this study was lower than those in other dense fishery farms [32,[62][63][64], the DIP elution (1.5 mmol/m 2 /d) was considerably higher than those in the farms [32,[62][63][64]. This reflects that the labile-P contents in the surface sediments were significantly high in Gamak Bay relative to the adjacent bays [66].…”

“…The case of nitrogen was consistent with this study, while this study observed a considerably high fraction of DIP elution flux under the reducing condition. Phosphorous in the surface sediments at Gamak Bay comprised 64% of NAI-P (non-apatite inorganic P), 25% of residual-P associated with organic matter, 8% of P absorbed to particles, and 4% of apatite P [66]. A high portion of labile P (NAI-P + absorbed-P), vulnerable to hypoxia/anoxia, pH, and ORP, is expected to induce the high fraction of DIP elution flux.…”

Impacts of hypoxia on the mesozooplankton community structure in a semi-enclosed bay

“…A large amount of phytoplankton is produced under the thermocline in summer due to an abundance of nutrients and sufficient solar radiation, both of which are required for photosynthesis. Although this study did not provide information on CTD and nutrient profiles according to water depth, Kim et al (2006) and Kim et al (2011) observed that the thermocline was mainly formed at depths of 3-5 m and 2-5 m. In turn, the organic matter that sinks to the bottom is decomposed and oxygen consumption rates increase. Additionally, the oxygen consumption rate of sediments increases, which further exacerbates hypoxia (Kim et al, 2006).…”