Efficiency comparisons of fish sampling gears for a lentic ecosystem health assessments in Korea

AbstractThe key objective of this study was to analyze the sampling efficiency of various fish sampling gears for a lentic ecosystem health assessment. A fish survey for the lentic ecosystem health assessment model was sampled twice from 30 reservoirs during 2008–2012. During the study, fishes of 81 species comprising 53,792 individuals were sampled from 30 reservoirs. A comparison of sampling gears showed that casting nets were the best sampling gear with high species richness (69 species), whereas minnow traps were the worst gear with low richness (16 species). Fish sampling efficiency, based on the number of individual catch per unit effort, was best in fyke nets (28,028 individuals) and worst in minnow traps (352 individuals). When we compared trammel nets and kick nets versus fyke nets and casting nets, the former were useful in terms of the number of fish individuals but not in terms of the number of fish species

Ecological connectivity analysis based on the fish community in Jeongan Stream

This study focused on the longitudinal connectivity analysis, based on fish communities in the aspect of spatial variations of 34 sites from upstream to downstream. The Fish Assessment Index (FAI), based on ecological guilds and species composition, was applied to compare the ecological health among the sampling sites. The total number of 35 fish species, were sampled during the study period with dominant species of Zacco platypus (35.4%) and Zacco koreanus (11.8%). Cluster analysis showed that all sites were categorized as 4 distinct group communities (A, B, C, D). Non-metric multidimensional scaling analysis showed distinct difference between upstream (A, B) and downstream groups (C, D). Indicator Value Analysis (IndVal method), conducted to identify indicator species within each group, indicated that the species favoring upstream environments Rhynchocypris oxycephalus for the Group A and Iksookimia koreensis for the Group B. In contrast, the analysis indicated that the species with a preference for downstream habitats Pseudogobio esocinus for the Group C and Carassius auratus for the Group D. Ecological health, based on the FAI scores, showed a declining pattern toward the downstream, along with an increasing proportion of tolerant species and omnivores within the fish community. Overall these findings suggest the compositions of fish communities, as four groups, were modified by the weir structures and organic matter, nutrient pollutions

Major nutrients and chlorophyll dynamics in Korean agricultural reservoirs along with an analysis of trophic state index deviation

The main objectives of this study were to determine how Asian monsoon influences nutrient regime, suspended solids, and algal chlorophyll (CHL) in 182 agricultural reservoirs, and then to develop the empirical models of nutrients-chlorophyll. The intensity of summer monsoon directly determined the ambient concentrations of nitrogen (N) and phosphorus (P). Regression analysis of empirical model showed that CHL had a high linear relation (R2 = 0.716, p < 0.01) with total phosphorus but a weak relation (R2 = 0.041, p < 0.01) with total nitrogen. Seasonal empirical models of TP-CHL showed that the regression coefficients in premonsoon (R2 = 0.605) and postmonsoon (R2 = 0.554) were greater than that of the monsoon. Values of trophic state index (TSI) implied that phosphorus limitation was severe in the Korean agricultural reservoirs. Overall, our study of 182 reservoirs suggested that phosphorus was key nutrient regulating the phytoplankton growth. This phenomenon was supported by the analysis of trophic state index deviation relations of “TSI (CHL)−TSI (SD) < TSI (CHL) – TSI (TP)”

Stream Health Evaluation Using a Combined Approach of Multi-Metric Chemical Pollution and Biological Integrity Models

Bouchung Stream is a large tributary of the Geum River watershed that is simultaneously affected by wastewater treatment plant effluents and agricultural activities in the watershed area. The focal subject was to diagnose the chemical and biological health of the temperate stream by using a combined approach of the multi-metric water pollution index (WPI) and the index of biological integrity (IBIKR), using datasets from 2008&ndash;2014. Water chemistry analyses indicated seasonal and inter-annual variations mainly linked to the intensity of monsoon rainfall in the watershed, potentially causing the availability of agricultural runoff water. The main events of phosphorus inflow and nitrogen dilutions occurred during July&ndash;August. Temporal and spatial heterogeneities were observed and were largely recognizable due to nutrient enrichment and organic matter intensification. Chlorophyll showed weak linear relation to total phosphorus (R2 = 0.17) but no relation to total nitrogen (p &gt; 0.05). Fish compositions analyzed as trophic/tolerance guilds in relation to water chemistry showed visible decline and modifications. Average WPI site scores ranged from 33&ndash;23, indicating an excellent upstream to fair downstream water quality status. Correspondingly, IBIKR scores ranged between 38&ndash;28 approximating with WPI site classification, as well as both indices showed higher regression relation (R2 = 0.90). Fish guild analyses revealed tolerant and omnivore species dominating the downstream, while sensitive and insectivores depleting in approximation with changing water chemistry and was confirmed by the principal component analysis. In addition, the fish guilds meticulously responded to phosphorus inflows. In conclusion, overall stream health and water chemistry analyses indicated continuous chemical and biological degradation influencing the trophic and tolerance fish guilds. Moreover, the combined application approach of WPI and IBIKR could help in better understanding the chemical and biological mechanisms in rivers and streams

Concurrent Sessions D: Fish Passage Around the World-II - Massive Weir and Fishway Construction as a National River Restoration Project in Korean Government and the Fish Movement Evaluations Using Various Monitoring Methodologies

The major objective of the research was to evaluate integrative impacts of fish movements and migrations after the constructions of weirs and fishways as a part of the National River Restoration (NRR) Project in Korean government. In the presentation, we introduce some plans and scales of the National River Restoration Project in Korea, and discuss some ecological problems on fish passage along with chemical water quality. The specific targets of our research are summarized as follows. First, fish species distribution and compositions were evaluated in the tributaries and mainstream sites of Yeongsan-River watershed after the completion of the fishway and weir constructions in migrations and fish passage in fishways and weirs. Third, we traced the passage of migratory and non-migratory fishes using various fish tracking methodologies including Passive Integrated Transpondents (PITs) tags, ultrasonic telemetry, video recording, trap-setting, and ultra eco-sounder monitoring approaches, and evaluated some impacts of the weir/fishway constructions. Lastly, we are trying to establish a national protocol of fish monitoring methodology for the surveys of the weirs and fishways in Korea. Currently, this study is on-going project in 2013 and will be continued until 2014. Our outcomes are preliminary results now, but will contribute to the ecological conservation of national rivers in Korea after the completion of our research

Integrated Ecological River Health Assessments, Based on Water Chemistry, Physical Habitat Quality and Biological Integrity

This study evaluated integrative river ecosystem health using stressor-based models of physical habitat health, chemical water health, and biological health of fish and identified multiple-stressor indicators influencing the ecosystem health. Integrated health responses (IHRs), based on star-plot approach, were calculated from qualitative habitat evaluation index (QHEI), nutrient pollution index (NPI), and index of biological integrity (IBI) in four different longitudinal regions (Groups I–IV). For the calculations of IHRs values, multi-metric QHEI, NPI, and IBI models were developed and their criteria for the diagnosis of the health were determined. The longitudinal patterns of the river were analyzed by a self-organizing map (SOM) model and the key major stressors in the river were identified by principal component analysis (PCA). Our model scores of integrated health responses (IHRs) suggested that mid-stream and downstream regions were impaired, and the key stressors were closely associated with nutrient enrichment (N and P) and organic matter pollutions from domestic wastewater disposal plants and urban sewage. This modeling approach of IHRs may be used as an effective tool for evaluations of integrative ecological river health.

Roles of N:P Ratios on Trophic Structures and Ecological Stream Health in Lotic Ecosystems

Little is known about the functions of N:P ratios in determining trophic structures and ecological health in lotic ecosystems, even though N:P ratios have been frequently used as a stoichiometric determinant in ambient water for trophic allocation of low-level organisms such as phytoplankton or zooplankton. In this study, nutrients (N, P) and sestonic chlorophyll (CHL) from 40 different streams in the Geum-River watershed were measured from 2008 to 2011. Fish compositions and stream health were also assessed, based on the multi-metric modeling of an index of biological integrity. Land use patterns in these watersheds were a key factor regulating nutrient contents and N:P ratios in ambient water, and also influenced empirical relationships between N:P ratios (or nutrients) and sestonic CHL. Land use patterns in forested, urban and wastewater treatment plant regions were associated with significant differences in stream N:P ratios, and the ratios were mainly determined by phosphorus. Sestonic CHL was significantly correlated with nutrient level (N, P); the ratios had a positive linear relationship with the proportion of omnivores, and a negative relationship with the proportion of insectivores. A similar trend in the N:P ratios was observed in indicator fishes such as N. koreanus and Z. platypus. Overall, the N:P ratio may be a good surrogate variable of ambient concentrations of N or P in assessing trophic linkage and diagnosing the ecological stream health in aquatic ecosystems

Multiyear Links between Water Chemistry, Algal Chlorophyll, Drought-Flood Regime, and Nutrient Enrichment in a Morphologically Complex Reservoir

This investigation targeted the largest morphologically complex reservoir (Soyang) in South Korea during 1992&ndash;2013. It is a prominent source of domestic water supply, irrigation, flood control, and hydroelectric power generation. Therefore, this investigation focused on regional- to global-scale applications. We revealed the empirical links between chlorophyll (Chl-a) and total nitrogen (TN) and total phosphorus (TP), the impact of the monsoon regime on nutrients, and flood and drought regime. Further, we investigated the trophic status dynamics, tendencies of water chemistry factors, and valuation of zonal water chemistry by the application of a modified multimetric water pollution index (WPI). The physicochemical indicators illustrated significant disparities among the Lacustrine (Lz), Transition (Tz), and Riverine (Rz) zones. The solid contents (TSS) displayed a significant increase in the lake zones in the order of Lz (4.58 &plusmn; 13.7 mg/L), Tz (6.16 &plusmn; 16.2 mg/L), and Rz (7.38 &plusmn; 18.9 mg/L). However, TP and allied chemical species revealed an inverse relationship with the TN:TP ambient ratios. Nevertheless, Chl-a displayed sharp interzonal fluctuations from the Lz (2.90 &plusmn; 3.29 &micro;g/L) to Tz (4.61 &plusmn; 4.98 &micro;g/L). The seasonal deviations, however, exposed divergent heterogeneities among the TSS, TN, TP, and Chl-a. The regression plot between the observed and predicted Chl-a in the Soyang reservoir displayed a very strong relationship (R2 = 0.997). The seasonal and interannual variations of trophic status displayed a higher impact of precipitation, particularly in the case of TP and Chl-a. The flood years indicated phosphorus limitations, while drought years alluded to the non-algal light limitations (biogenic turbidity). Water temperature (WT), dissolved oxygen (DO), biological oxygen demand (BOD), TSS, TP, and Chl-a displayed decreasing trends in the ambient water. In contrast, pH, chemical oxygen demand (COD), electrical conductivity (EC), and TN displayed increasing tendencies by the application Mann&ndash;Kendall trend analysis. The WPI outcomes designated Lz with excellent water quality while Tz an Rz indicated good water quality. It also indicated impending sedimentation tendencies in the Rz. In conclusion, our findings indicated fluctuating rainfall patterns (drought and flood conditions) that significantly impacted the Soyang reservoir water quality, flood and drought severity, and trophic status of the reservoir. This study highlights the requirements of further studies to substantiate the drought and flood dynamics and their impacts on nutrients and overall water quality status

Assessment of Water Quality Based on Trophic Status and Nutrients-Chlorophyll Empirical Models of Different Elevation Reservoirs

Water quality degradation is one of the most pressing environmental challenges in reservoirs around the world and makes the trophic status assessment of reservoirs essential for their restoration and sustainable use. The main aims of this study were to determine the spatial variations in water quality and trophic state of 204 South Korean reservoirs at different altitude levels. The results demonstrated mean total phosphorus (TP), chlorophyll-a (CHL-a), total suspended solids (TSS), organic matter indicators (chemical oxygen demand: COD; total organic carbon: TOC), water temperature (WT), and electrical conductivity (EC) remain consistently higher in the very lowland reservoirs (VLLR) than those in other altitudes, due to sedimentary or alluvial watersheds. The average TP and CHL-a levels in VLLR crossed the limit of the eutrophic water, symptomizing a moderate risk of cyanobacterial blooms. Empirical models were developed to identify critical variables controlling algal biomass and water clarity in reservoirs. The empirical analyses of all reservoir categories illustrated TP as a better predictor of CHL-a (R2 = 0.44, p &lt; 0.01) than TN (R2 = 0.02, p &lt; 0.05) as well as showed strong P-limitation based on TN:TP ratios. The algal productivity of VLLR (R2 = 0.61, p &lt; 0.01) was limited by phosphorus, while highland reservoirs (HLR) were phosphorus (R2 = 0.23, p &lt; 0.03) and light-limited (R2 = 0.31, p &lt; 0.01). However, TSS showed a highly significant influence on water clarity compared to TP and algal CHL-a in all reservoirs. TP and TSS explained 47% and 34% of the variance in non-algal turbidity (NAT) in HLR. In contrast, the TP and TSS variances were 18% and 29% in midland reservoirs (MLR) and 32% and 20% in LLR. The trophic state index (TSI) of selected reservoirs varied between mesotrophic to eutrophic states as per TSI (TP), TSI (CHL-a), and TSI (SD). Mean TSI (CHL-a) indicated all reservoirs as eutrophic. Trophic state index deviation (TSID) assessment also complemented the phosphorus limitation characterized by the blue-green algae (BGA) domination in all reservoirs. Overall, reservoirs at varying altitudes reflect the multiplying impacts of anthropogenic factors on water quality, which can provide valuable insights into reservoir water quality management

Predicting Taste and Odor Compounds in a Shallow Reservoir Using a Three–Dimensional Hydrodynamic Ecological Model

The objective of this study was to establish a technique to predict the occurrence of algal bloom and the algal-derived taste and odor compounds 2-methylisoborneol (2-MIB) and geosmin using a three-dimensional (3D) model that could reflect the complex physical properties of a shallow reservoir. Water quality, phytoplankton, and taste and odor compounds monitoring was conducted at the Jinyang Reservoir in 2016. In June, there was a potential for a high concentration of 2-MIB (maximum 80 ng/L) to occur owing to the appearance of Pseudanabaena sp.; additionally, from July to August, there was potential for a high concentration of geosmin (maximum 108 ng/L) to occur, because of the presence of Anabaena sp. A 3D hydrodynamic model was coupled with an ecological model to predict cyanobacteria bloom and the presence of taste and odor compounds. Cyanobacteria producing either 2-MIB or geosmin were distinguished to enhance the accuracy of the modeled predictions. The results showed that the simulations of taste and odor compounds spatial distribution and occurrence time were realistic; however, the concentration of geosmin was overestimated when Microcystis sp. was blooming. The model can be used as a management tool to predict the occurrence of algal taste and odor compounds in reservoir systems and to inform decision-making processes concerning dam operation and water treatment