• Ocean and Polar Research
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• v.45 no.3
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• pp.103-111
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• 2023

To evaluate the impact of effluents from land-based fish farms on the coastal ocean of Wando, Korea, we analyzed inorganic nutrients, particulate organic carbon (POC), dissolved organic carbon (DOC), and colored dissolved organic matter (CDOM) in the effluent and influent of land-based fish farms during the summer (July) of 2021. The average concentrations of nutrients (Dissolved inorganic nitrogen, phosphorus, and silicate; DIN, DIP, and DSi, respectively) in the effluents of this study area were 17±3.7 μM, 1.4±0.7 μM, and 14±1.6 μM, respectively. The average concentrations of POC and DOC were 37±22 μM and 81±13 μM, respectively, with POC accounting for about 30% for total organic carbon in effluents. The Reduced Dissolved Inorganic Nitrogen/Total Dissolved Inorganic Nitrogen ratio (0.7), potential short-period index, indicates that the discharge of nutrients excreted by the fish and unconsumed feed into coastal water results in such nutrients being deposited and accumulated in the sediment. Subsequently, this continuous accumulation triggers the release of ammonium ions during organic matter decomposition, and the ammonium-enriched waters that encroach on fish farms as influent seem to be due to the diffusion of high concentrations of ammonium from bottom sediment. Furthermore, we used fluorescence indices to examine the characteristics of organic matter sources, obtaining mean values of 1.54±0.19, 1.06±0.06, and 1.56±0.06 for the humification index, biological index, and fluorescence index, respectively, in the effluent. These results indicate that the organic matters had an autochthonous origin that resulted from microbial decomposition, and such organic matters were rapidly generated and removed by biological activity, likely supplied from the sediment. Our results suggest that the effluent from land-based fish farms could be a potential source of deoxygenation occurrence in coastal areas.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.90-103
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• 2014

Distribution characteristics of water masses, dissolved inorganic and organic nutrients were investigated in the southern part of the East Sea of Korea in September, 2011. On the basis of the vertical profiles of temperature, salinity and dissolved oxygen, water masses in the study area were divided into 4 major groups, such as WM (water mass)-I, WM-II, WM-III, WM-IV. Their characteristics were similar to Tsushima Surface Water (TSW), Tsushima Middle Water (TMW), North Korea Cold Water (NKCW) and East Sea Proper Water (ESPW), respectively. In the vertical profiles of dissolved nutrients, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) concentrations were highest in the WM-IV, followed by WM-III, WM-II, WM-I. On the contrary, distribution of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) were highest in the WM-I, followed by WM-II, WM-III, WM-IV. Although the DIN : DIP ratio in all of the water masses was similar to Redfield ratio(16), the DIN : DIP ratio in mixed layer was about 5.3, indicating that inorganic nitrogen is the limiting factor for the growth of phytoplankton. However, the DON proportion in dissolved total nitrogen (DTN) was about 70% in the mixed layer where inorganic nitrogen is limiting factor. Thus, enriched DON may play an important source of the nutrient for the growth of phytoplankon in the East Sea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.357-365
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• 2011

The variation of the dissolved inorganic nutrients were investigated four times per year in the costal area of Gunsan, Yellow Sea from 2001 to 2010. Water samples were collected at 10 stations and phsico-chemical parameters were analyzed including water temperature, salinity, suspended solids, dissolved oxygen, chemical oxygen demand, chlorophyll a and dissolved inorganic nutrients. The average of dissolved inorganic nitrogen(DIN) for ten years at Gunsan area showed similar concentration between surface and bottom. The average of DIN at surface was 0.421mg/L (0.198~0.846mg/L) and bottom was 0.344mg/L(0.148~0.717mg/L). The highest value of annual average of DIN at surface was 0.846mg/L in 2002 and the lowest value was 0.198mg/L in 2010. The percentage of ammonia, nitrite and nitrate for the average DIN of 10 years showed 27%, 3% and 70% which showed most of DIN was nitrate. Dissolved inorganic phosphate(DIP) for ten years at Gunsan area showed similar concentration between surface and bottom and DIP was decreasing from 2003 to 2010. The average of DIP of 10 years was 0.024mg/L and annual average 0.021mg/L in 2008, 0.007mg/L in 2009 and 0.008mg/L in 2010 which showed decreasing pattern from 2007 to 2010. The average of DIN/DIP ratio from 2002 to 2010 was 6.0(3.2~10.1) at surface and 4.6(2.6~7.0) at bottom. The average value of dissolved inorganic silicate from 2004 to 2010 showed 0.372mg/L at surface layer and 0.352mg/L at bottom layer and was on decreased from 2006 to 2010. The Spearman's correlation analysis was carried out to knowrelation among the salinity and dissolved inorganic nutrients at the surface and bottom layer. The correlation factor of DIN was -0.72, DIP was -0.46 and dissolved inorganic silicate was -0.63 at surface layer and DIN was -0.70, DIP was -0.44 and dissolved inorganic silicate was -0.57 at bottom layer. The dissolved inorganic nutrients at the nearshore of Gunsan was affected from the freshwater discharge of Geum river. Especially, a lot of DIN flowed into the nearshore of Gunsan from Guem river. The concentration of dissolved inorganic nutrients at Gunsan showed high at station 1, 2 and 3 and there was a little concentration differences according to the cruise time. The concentration of dissolved inorganic nutrients showed high value at the station 1, 2, 3 which exist nearshore of Gunsan city and it means these stations mainly affected by Geum river and Gunsan city. The annual average of dissolved inorganic nutrients showed gradually decreased from 2003 to 2010 and we need more research on this conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.42-51
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• 2016

We investigated the distribution of dissolved nutrients, phytoplankton community structure and utilization of nitrogen compounds by dominant species in the southwestern part of East Sea in September, 2014. Dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were lower in the surface layer, and concentrations were increased with depth. Dissolved organic nitrogen (DON) and dissolved organic phosphorus were the opposite of dissolved inorganic nutrients. Although DIN DIP ratio in all of the water masses was higher than Redfield ratio (16), DIN : DIP ratio in mixed layer was about 2, indicating that inorganic nitrogen is the limiting factor for the growth of phytoplankton. In particular, DON proportion in dissolved total nitrogen was about 88 % in the mixed layer where inorganic nitrogen is limiting factor. The dominant species Chaeotceros debilis and Prorocentrum minimum were able to grow using DIN as well as DON such as urea and amino acids. Therefore, DON utilization of phytoplankton may play a role as a survival strategy in the DIN-limited conditions of East Sea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.1
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• pp.16-28
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• 2015

In order to elucidate the spatiotemporal variations of marine environmental parameters, we collected seawater samples in the south-western region of the East Sea in May, August, and November 2012 and February 2013. The concentrations of dissolved inorganic nutrients (dissolved inorganic nitrogen, phosphorus, and silicate) in surface seawater during the summer season were lower than those during autumn and winter seasons, which the mixed layer is deeper. The low nutrient concentration in spring and summer seasons seems by consumption of dissolved inorganic nutrients by phytoplankon photosynthesis (high chlorophyll a concentration) and the limited supply of dissolved inorganic nutrients from subsurface layer having high nutrients. The low nutrient concentration during spring season seems to be related to the limited supply of dissolved inorganic nutrients from land and subsurface layer because the concentration of chlorophyll a was low. The DIN:DIP ratio was a wide range of average $15.6{\pm}13.6$ in the surface seawater compared to that of average $14.8{\pm}4.2$ in the bottom seawater during sampling periods. The dissolved inorganic nitrogen might act as a limiting factor of the growth of phytoplankton because the DIN:DIP ratio (on average $8.35{\pm}4.67$) was low during the spring season.

• Journal of Environmental Science International
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• v.12 no.7
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• pp.745-751
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• 2003

The three-dimensional eco-hydrodynamic model was applied to estimate the physical process in terms of nutrients and net uptake(or regeneration) rate of nutrients in Kamak Bay for scenario analysis to find proper management plan. The estimation results of the physical process in terms of nutrients shelved that transportation of nutrients is dominant in surface level while accumulation of nutrients is dominant in bottom level. In the case of dissolved inorganic nitrogen, the results showed that the net uptake rate was 0∼60 mg/㎡/day in surface level(0∼3m), and the net regeneration rate was 0.0∼10.0 mg/㎡/day in middle level(3∼6m) and above 10mg/㎡/day in bottom level(6m∼below). In the case of dissolved inorganic phosphorus, the net uptake rate was 0.0∼3.0 mg/㎡/day in surface level, and the net regeneration rate was 0.5∼1.5 mg/㎡/day in middle level and 1.0∼3.0 mg/㎡/day in bottom level. These results indicates that net uptake and transport of nutrients are occurred predominantly at the surface level and the net generation and accumulation are dominant at bottom level. Therefore, it is important to consider the re-supplement of nutrients due to regeneration of bottom water.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.630-638
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• 2021

In this study, we investigated the effects of dissolved inorganic and organic nutrient on the growth of dinoflagellate Alexandrium affine (LIMS-PS-2345). The maximum uptake rates (ρ_max) and half saturation constants (Ks) calculated from the uptake kinetics experiment were 77.0 pmol/cell/hr, 17.6 μM for nitrate and 15.5 pmol/cell/hr, 3.88 μM for phosphate, respectively. These results suggested that this species has high inorganic nutrient demand and a low affinity for inorganic nutrients. During the utilization of organic nutrients for A. affine, growth rates of experimental groups added by organic nitrogen (urea and glycine) and phosphorus (adenosine triphosphate and glycerol phosphate) were above 70 %, compared to the experimental groups added by inorganic nutrients. Thus, A. affine may need to utilize organic nutrients to understand the dominant strategy and advantageous position in the interspecific competition within low inorganic nutrient environments.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.4
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• pp.232-242
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• 2014

We investigated the interspecific competition between the harmful dinoflagellate Cochlodinium polykrikoides and diatom Skeletonema sp. based on the utilization and uptake of dissolved organic nutrients. C. polykrikoides and S. costatum were able to grow using dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) as well as dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP). This result indicates that the utilization of dissolved organic nutrients may play a role in surviving strategy in the DIN or DIP-limited environments. The half-saturation constants (Ks) of urea and glycerophosphate (glycero-P) calculated from uptake kinetics experiment of C. polykrikoides was lower than those of Skeletonema sp. This result indicates that Skeletonema sp. have higher affinity for dissolved organic nutrients, such as urea and glycero-P, than C. polykrikoides. Although Skeletonema sp. have higher affinity of dissolved organic nutrients, C. polykrikoides could effectively uptake for urea and glycero-P at sub-saturating nutrient concentrations (${\alpha}$ (${\rho}_{max}/Ks$) of C. polykrikoides was higher than Skeletonema sp.. Therefore, C. polykrikoides by utilization and effectively uptake of dissolved organic nutrients under monoculture may have an advantageous position in the interspecific competition with Skeletonema sp. in the low nutrient environments.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.164-176
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• 2003

During summer, the DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphate) observed in the Jindong Bay in the southern sea of Korea show much higher values in the inner area of the bay. In general, they have high values in the upper (0-1 m) and lower layers (8 m-bottom), but are relatively lower in the middle layer (1-8 m). These features in their distribution are examined using an ecosystem model with considering the wind, tidal current, horizontal gradient of water density and residual flow. The experiments were focused on how to influence nutrients associated with these conditions. In the experiment with tide-induced residual flow, the values of nutrients appeared lower than the observation, and were well corresponded to it when the effects of wind, tide-induced residual current and horizontal gradient of water density were additionally imposed. A statistical analysis identifies these results. This paper suggests that variation of nutrient in the Jindong Bay during summer should be seriously a(footed wind-driven current by the wind and density-driven current is induced by the horizontal gradient of water density as well as tidal current.

• Journal of Environmental Science International
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• v.12 no.9
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• pp.957-966
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• 2003

Gunsan coastal area is one of region increasing pollution problems. To improve water quality, the reduction of these nutrients loads should be indispensible. In this study, the three-dimensional numerical hydrodynamic and ecosystem model were applied to analyze the processes affecting the eutrophication. In field survey, the average concentrations of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus(DIP) at surface waters were found to be 0.43mg/$\ell$ and 0.03mg/$\ell$ respectively, which were exceeding second grade of water quality criteria. In hydrodynamic modelling, the comparison between the simulated and observed tidal ellipses showed fairly good agreement. The ecosystem model was calibrated with the observed data in study area. The simulated results of DIN were fairly good coincided with the observed values within relative error of 32.39%, correlation coefficient(r) of 0.99. In the case of DIP, the simulated results were fairly good coincided with the observed values within relative error of 24.26%, correlation coefficient(r) of 0.82. The simulations of DIN and DIP concentrations using ecosystem model were performed under the conditions of 20∼80% reductions for pollutant loading. At simulation results, concentration of DIN and DIP were reduced to 20∼80% and under 10% in case of the 80% reduction of pollutant loading, respectively.