Kwang-Guk An

An evaluation of a river health using the index of biological integrity along with relations to chemical and habitat conditions

We evaluated the health condition of a temperate river during June-November 1999 through applications of the index of biological integrity (IBI) using fish assemblages and qualitative habitat evaluation index (QHEI) as well as chemical analyses. Overall IBI values ranged from 13 to 37 and averaged 23 (n = 25, standard error = 1.16), indicating a poor or very poor condition according to the criteria of modified Karr [Fisheries 6 (1981) 21]. The values of mean IBI declined at a rate of 0.22 km(-1) (R2 = 0.91, p < 0.05) along the longitudinal distance from the headwaters to the downstream sites. Reduced IBI values at downstream sites reflected low forest cover, high population density and high nutrient enrichments. Ecotoxicity tests using the river water also showed that toxic impacts were evident in the downriver sites. These factors resulted in decreases of riffle benthic species and insectivores and increases of tolerant species, anormalies and exotic species in the river. Spatial pattern in IBI agreed with QHEI values, which showed a linear relation (R2 = 0.998, p < 0.001) with species richness. Field measurements of conductivity and pH, an indicators for variation of conservative ions, showed that the river water was diluted by 40% fold by summer monsoon rain and surface run-off from the watershed, resulting in a physical and chemical instability during the monsoon. For these reasons, average IBI values during the monsoon and postmonsoon decreased >20% compared to the premonsoon, indicating that IBI values were also affected by flow regime. Based on the overall physico-chemical data and IBI values, the river health is rapidly degrading due to the combined effect of chemical contaminations and habitat modifications.

Indirect influence of the summer monsoon on chlorophyll–total phosphorus models in reservoirs: a case study

Abstract This study examines how the Asian monsoon influences relationships between chlorophyll-a (Chl) and total phosphorus (TP), by means of a case study on Taechung Reservoir, Korea. A log–log regression model of Chl vs. TP was found to be quadratic relations, with Chl approaching an asymptote above 50 μg l−1 TP. This is similar to the pattern previously reported for temperate lakes in Europe and North America. However, viewing the data by season, a highly significant linear model was obtained during the pre- and post-monsoon periods (R2≥0.83), but not during the summer monsoon (R2=0.004). In the monsoon period, samples >50 μg l−1 TP (23% of the total observations) had fourfold lower Chl yields per unit TP (average=0.17) compared to samples from the same TP range in the other seasons (average=0.76) and were strongly correlated (r=0.97, n=17) to non-volatile suspended solids (NVSS). Yield of Chl per unit TP also increased significantly (P

Influence of seasonal monsoon on the trophic state deviation in an Asian reservoir

Trophic parameters including total nitrogen (TN), total phosphorus (TP), Secchi depth (SD), and chlorophyll-a (CHL) were analyzed to evaluate how the Asian monsoon influences the trophicstate of the Taechung Reservoir, Korea. By using conventional criteria, the trophic state of this system ranged from mesotrophic to hypertrophic with spatial and seasonal variationsdepending on landuse pattern and flow regime. Based on TP, CHL, and transparency, the overall trophic state declined from the headwaters to the dam. However, based on TN, the entire reservoir was hypereutrophic thoughout the year. Comparing nutrients and CHL as trophic parameters, large disparities of the trophic state have been observed in the headwaters during intensive monsoon. The trophic state was much greater when assessments were based on nutrients instead of CHL, indicating apotential trophic deviation. Using Carlsons (1990) twodimensional approach, deviations of the Trophic State Index(TSI), based on the relation between TSI (CHL) minus TSI(TP), and TSI (CHL) minus TSI (SD) during the intensivemonsoon indicated that factors other than phosphorus limitedalgal growth, and that non-algal particles affect lightattenuation. These findings were supported by high non-volatilesuspended solids (NVSS), short water residence time, and low CHL:TP ratios during monsoon. Such deviations, however, did not occur during weak monsoon. The trophic disparity during theintensive monsoon was considered to be a result of the shortwater retention time and reduced light availability throughdominance of inorganic suspended solids. Under these circumstances, trophic state assessments based only on nutrientloading may not be a useful indicator for water management.

Trophic State, Seasonal Patterns and Empirical Models in South Korean Reservoirs

ABSTRACT Data from 59 reservoirs in South Korea, sampled monthly during 1993–2000, showed that about one-third were mesotrophic, nearly one-half were eutrophic and the remainder were hypereutrophic based on conventional criteria for total phosphorus (TP), chlorophyll (Chi) and Secchi depth. Most reservoirs had >1 mg L−1 total nitrogen (TN) resulting in high mass ratios of TN:TP (range 23 to 243, median 76) relative to many temperate lakes. To compensate, conventional TN criteria were provisionally adjusted upward by about 2.5-times to classify Korean reservoirs uniformly across all trophicstate metrics. During die summer monsoon, TP and TN typically peaked in mesotrophic reservoirs and declined in the hypereutrophic group. The inference is that monsoon inflow produces these patterns by increasing non-point external inputs mat dominate the nutrient budgets of mesotrophic reservoirs while diluting point-source inputs important in hypereutrophic impoundments. Eutrophic reservoirs showed both response patterns, so that taken in aggregate a seasonal response was not apparent. The log relation between Chl and TP was linear and showed an average yield of Chl per unit of TP on par with other temperate lakes. Seasonally, die Chl-TP relation was strongest during summer and weaker during fall-winter which is consistent with increased light-limitation during mixis in these monomictic impoundments. Seasonal development of Chl did not show strong evidence of a spring or fail bloom. About half of the time maximum Chl values were measured during the monsoon or post-monsoon (July-September). Maximum Chl was ~3 times the annual mean and during summer maximum Chl was ~ double the mean. The log relation between Chl and Secchi depth matched mat found in North American lakes and the seasonal phenology for Secchi depth was die opposite of Chl and suspended solids. The analysis confirms that die monsoon is a major source of variation within and among Korean reservoirs.

Heavy metal pollution in the soils of various land use types based on physicochemical characteristics

Abstract In this study, soil samples were collected at eight different regional types of Seoul City and analyzed for their physicochemical properties. In addition, the distribution of heavy metal concentrations was analyzed using samples representing both the surface and deep soil layer. The physicochemical properties analyzed for those samples included parameters such as pH, moisture content, apparent (and true) density, pore ratio, solid content, conductivity, ionic strength, total dissolved solid (TDS), total organic carbon (TOC), and total phosphorus (TP). The contents of heavy metal components contained in plant leaves were also analyzed and compared with those measured from different soil layers. Contents of Cu and Cd were highest in the DH area among eight locations investigated and Pb was higher in the surface soil samples of the GS region than any other locations. According to physicochemical properties of the surface and deep soils, acidity was higher in the surface than deep soils. Depending on the selection of treatment method between strong and weak acids, the metal concentrations were larger by 3–5 times in the strong acid than the weak acid treatments. In addition, metals were higher in the deep than in the surface soil and relative metal contents of leaf samples closely resembled those of soil samples. Results of this study suggest that the physicochemical properties of soils determined from different regional types of Seoul area exhibited a close relationship with the land use types and environmental conditions surrounding each region.

Removal of Nitrogen and Phosphorus Using Dominant Riparian Plants in a Hydroponic Culture System

Abstract The objective of the study was to evaluate potential nutrient removal capacities from eutrophic stream waters using two riparian plants, Phragmites japonica and Salix gracilistyla. The removal efficiencies, removal rates of nutrients (N, P), and their specific growth rate were estimated as a function of inflow loading rate and hydraulic retention time (HRT) in a hydroponic culture system. Weight specific growth rates (WSGR) of P. japonica increased by 0.015u2009d−1 in the ambient concentrations of NH4–N, NO3–N, and PO4–P and increased up to 9 times higher than the control (i.e., base concentration), whereas the WSGR decreased at the higher levels of nutrients. Under the same nutrient concentrations, the WSGR in the S. gracilistyla increased up to 9 times higher than the control, and then increased slowly. Nutrient removal efficiencies of both species were higher under lower N and P concentrations and longer HRT conditions. The removal rate of P. japonica had a positive functional relation with surface loading rates of nutrients and leveled off at 3.0u2009gu2009d−1 of NH4–N, 12.5u2009gu2009d−1 of NO3–N, and 3.0u2009gu2009d−1 of PO4–P, respectively. The removal rate of S. gracilistyla also enhanced at the surface loading of 5u2009gu2009d−1 of NH4–N, 23u2009gu2009d−1 of NO3–N, and 5u2009gu2009d−1 of PO4–P, respectively, but was lower than that of P. japonica. It is concluded that the nutrient removal approach using the riparian plants may be used for efficient water quality management in the eutrophic streams with long HRT.

Spatial and Temporal Variabilities of Nutrient Limitation Based on In Situ Experiments of Nutrient Enrichment Bioassay

Abstract In situ experiments of Nutrient Enrichment Bioassays (NEBs) were performed in a morphologically complex reservoir of a temperate region to identify primary limiting nutrient regulating phytoplankton productivity and determine a severeity of the nutrient limitation. Absolute nutrient contents and nutrient ratios of TN : TP and TDN : TDP in the ambient water indicated a potential limitation of phosphorus. This outcome agreed with the results of NEBs; Algal response in the P treatments, expressed as a ratio of CHL f : CHL i , showed significantly (p<0.05) greater algal response than P + NH4-N or P + NO3-N treatments. The magnitude of the limitation, however, showed large spatial and temporal variations. The response in treatments enriched with phosphorus (P, P + NH4-N, and P + NO3-N) was greatest in the downlake zone and least in the point-source zone, while the response was greater during summer monsoon than any other seasons. Algal growth rate experiments showed that the response in treatments enriched with NO3-N and P + NO3-N never exceeded >0.50 µg L−1 per day and was significantly (p<0.05) less than that in the three treatments with P (1P, 2P, and P + NH4-N), indicating a reduced response in the treatments enriched with NO3-N. The suppression of nitrate on algal growth seemed to be involved with inhibition effect of nitrogenase activity through low-nitrate uptake rate in the high nitrate-rich environment and large additions of potassium with phosphorus in spike. Regression analysis of log10-transformed CHL f : CHL i ratios against ambient nutrient contents showed that in situ algal response in the P treatments was inversely related (r = − 0.77; p<0.001) with ambient TP and positively correlated (r = 0.75; p<0.001) with TN : TP ratios. This result suggests that in situ response depends largely on external loading of limiting nutrients.

In situ experimental evidence of phosphorus limitation on algal growth in a lake ecosystem

ABSTRACT This paper presents the results of in situ Nutrient Stimulation Experiments (NSEs) demonstrating that phosphorus was the primary nutrient controlling algal growth in the Taechung Reservoir, Korea. Algal response in most treatments with only nitrogen added was less than or the same as in the controls, whereas the growth in treatments enriched with phosphorus increased by as much as fivefold. Phosphorus limitation was consistent over the experimental period when bioassay experiments were conducted, but the magnitude of growth response to phosphorus enrichments varied with the season. Algal yield in P-treatments was maximum when thermal stratification was strong and total dissolved phosphorus (TDP) was near the level of depletion. Regression analyses of NSEs showed that in situ algal response in P treatments, measured as log-transformed CHLf : CHLi ratios, declined (R 2 = 0.995, p < 0.001) with ambient concentrations of log-transformed TDP. Also, algal response in the P treatments showed a first-order linear fit (R 2 = 0.961, p<0.001) with log-transformed DIN (dissolved inorganic nitrogen) : TDP ratios. These outcomes indicate that the magnitude of in situ algal response increased with lower levels of P and higher dissolved N : P ratios in the ambient lake water. Our experimental approach employing NSEs suggests that abatement of phosphorus from the watershed seems to be an efficient management strategy to control the eutrophication of this system.

An assessment of aquatic ecosystem health in a temperate watershed using the index of biological integrity.

Abstract The health effect of an aquatic ecosystem on habitat modifications were evaluated in the Keum river watershed, Korea during 1977–1996 using the Index of Biological Integrity (IBI) based on fish assemblages. Values of IBI, based on overall sites, averaged 35 (range: 26–45, n = 38) before dam construction, indicating a “fair health condition” based on the modified criteria of Karr and Chu (Karr, J.R.; Chu, E.W. Restoring Life in Running Waters: Better Biological Monitoring; Inland Press: Washington, DC, 1999; 206pp.), while the values averaged 33 (range: 18–48, n = 15) after dam construction, indicating a similar ecosystem health condition in the IBI between the two periods. Marked modifications in the IBI, however, were partially observed along the longitudinal gradients from the headwaters to downstream along with variations of trophic compositions and habitat guilds. Annual mean of IBI showed significant decreases (p<0.001, t = 10.03) in the mid-reach of 100–240 km location after the construction along with >20% decreases of insectivores and >25% increases of omnivores. Comparisons of habitat guilds indicated that the proportion of riffle benthic species declined linearly from 1977 to 1996 and had inverse relations (r = −0.78, p<0.01) with that of water column species. Such variations were explained by serial discontinuity concept that was developed by Ward and Stanford (Ward, J.V.; Stanford, J.A. The serial discontinuity concept of lotic ecosystems Dynamics of Lotic Ecosystems; Fontaine, J.V., Bartell, S.M., Eds.; Ann Arbor Science: Ann Arbor, Michigan, USA, 1983; 29–42). Chemical data of long-term BOD5 and COD5 indicated that chemical impacts after the dam construction were minor compared to the condition before the construction. Overall variation of IBI was highly accounted (p < 0.001, R 2 = 0.91, n = 38) by the Qualitative Habitat Evaluation Index (QHEI), suggesting that the ecosystem health was mainly affected by the habitat modifications.