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Physicochemical water quality characteristics in relation to land use pattern and point sources in the basin of the Dongjin River and the ecological health assessments using a fish multi-metric model
© The Author(s) 2016
Received: 2 February 2016
Accepted: 1 July 2016
Published: 24 October 2016
Little is known about how chemical water quality is associated with ecological stream health in relation to landuse patterns in a watershed. We evaluated spatial characteristics of water quality characteristics and the ecological health of Dongjin-River basin, Korea in relation to regional landuse pattern. The ecological health was assessed by the multi-metric model of Index of Biological Integrity (IBI), and the water chemistry data were compared with values obtained from the health model.
Nutrient and organic matter pollution in Dongjin-River basin, Korea was influenced by land use pattern and the major point sources, so nutrients of TN and TP increased abruptly in Site 4 (Jeongeup Stream), which is directly influenced by wastewater treatment plants along with values of electric conductivity (EC), bacterial number, and sestonic chlorophyll-a. Similar results are shown in the downstream (S7) of Dongjin River. The degradation of chemical water quality in the downstream resulted in greater impairment of the ecological health, and these were also closely associated with the landuse pattern. Forest region had low nutrients (N, P), organic matter, and ionic content (as the EC), whereas urban and agricultural regions had opposite in the parameters. Linear regression analysis of the landuse (arable land; AL) on chemicals indicated that values of AL had positive linear relations with TP (R 2 = 0.643, p < 0.01), TN (R 2 = 0.502, p < 0.05), BOD (R 2 = 0.739, p < 0.01), and suspended solids (SS; (R 2 = 0.866, p < 0.01), and a negative relation with TDN:TDP ratios (R 2 = 0.719, p < 0.01).
Chemical factors were closely associated with land use pattern in the watershed, and these factors influenced the ecological health, based on the multimetric fish IBI model. Overall, the impairments of water chemistry and the ecological health in Dongjin-River basin were mainly attributes to point-sources and land-use patterns.
The basin of the Dongjin River is made of one Dongjin River and two streams of Gobu and Jeongeup. The source of water is from Mt. Naejang, Jeonbuk Province, and the stream has a basin area of 1129 km2 and 52.4 km of total river length. The basin is located in the agricultural area located in the plain of rice paddy in Kimjae, Buahn, and Shintaein regions. The stream water is largely used by drinking water and agricultural irrigation along with partial use of industrial water. For these reasons, previous studies pointed out that water quality is degradated in the downstream regions, which are directly influenced by the wastewater treatment plants or agricultural crop-cultivation in the wide ranges of rice paddy (Seo et al. 2001; Jung et al. 2009; Seong and Park 2012). For these reasons, basin management is important for maintaining chemical water quality and the aquatic ecosystem.
Researches in the basin of the Dongjin River showed that intensive agricultural activities and constructions increased high nitrogen phosphorus in the streams and suspended solids (Uhm et al. 2000, Son et al. 2012). Also, runoff in small residential or urban area increased inputs of hazard chemicals, nutrients, and organic matter (Ko et al. 2001, Won et al. 2002, Lee et al. 2005) along with the sediments from the watershed (Yun et al. 2002, Lee et al. 2004). These activities increased sediment transport or deposition in the downstreams, and this forced to stream dredging, resulting in physical degradation of streams throughout the habitat modifications (Barbour et al. 1999, Morley and Karr 2002). Such factors changed nutrient ratios and nutrient regime (Lee and Shin 2013) and thus led to changes in the compositions of the biotic community inhabiting the stream and decreases in the biodiversity (Yeom et al. 2000). Under these circumstances, the key symptoms showing alterations of ecological structures and functions were decreases of fish species diversity (Kim et al. 2009), dominance of tolerant species (Kim and Lee 2001, Desirree et al. 2006, Walton et al. 2007), increased proportion of omnivore species, decreased number of sensitive species (Barbour et al. 1999), and increased abnormalities of fish (Yeom et al. 2000). The alterations of the ecological function resulted in massive impairment of overall ecological stream health (Karr 1981, Karr et al. 1986, US EPA 1993, An and Kim 2005, An et al. 2006). Karr et al. (1986) pointed out that development of stream assessment methodology throughout measuring not only chemical conditions but also indicator species characteristics is urgent for the diagnosis of the ecological health or the multilateral restoration of streams and rivers. For these reasons, assessments of ecological stream health, based on the index of biological integrity model (Karr 1981), were widely applied to numerous countries in relation to water chemistry or land use pattern.
The objectives of this study were to analyze the physicochemical water quality and fish compositions in the basin of the Dongjin River and elucidate their relations to land use pattern and key point sources such as wastewater treatment plants near the streams. In addition, a multi-metric model of the index of biological integrity (IBI), based on fish assemblages, was applied in the three major streams of the basin for the diagnosis of current ecological health conditions.
Descriptions of study sites
Nine sampling sites belong to three streams in the basin; four sites of site 1–site 4 belong to the Jeongeup Stream, three sites of S5–S7 belong to the Dongjin River, and the remaining two sites of site 8 and site 9 belong to the Gobu Stream. Especially, site 4 is directly influenced by effluents of sewage disposal plants (Wp-1, Wp-2), and this water influences S7 in the downstream region. Morphological alterations of the stream bed are kept to a minimum in the headwater reach (S1–S3, S5), while habitat structure is more and more degraded due to agricultural activities or sewage disposal plants in the downstream reaches (S7, S4, S9).
Water quality parameters and analysis
Chemical dataset, based on monthly-based measurement, at nine sites (S1–S9) were obtained from the National Water Quality Monitoring Program (NWQMP) of the Ministry of Environment, Korea (MEK) during January 2009–December 2012. The parameters analyzed were dissolved oxygen (DO), pH, water temperature, bacterial most probable number (MPN), electric conductivity (EC), suspended solids (SS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD). Also, nutrients such as total nitrogen (TN), total phosphorus (TP), nitrate-nitrogen (NO3-N), and ammonia-nitrogen (NH4-N) were included in the analysis along with ratios of TDN to TDP (total dissolved nitrogen to total dissolved phosphate) and chlorophyll-a (CHL-a) as a measure of primary productivity. We analyzed the spatial patterns from upstream to downstream sites of the parameters using the data.
Data analysis of land use pattern
Land use pattern in the basin of the Dongjin River was analyzed using a land-coverage dataset of Geological Information System (GIS) in 2010. According to the original GIS data of land cover, the land use was categorized as a residential (urban) area, arable (agricultural) area, forest area, grassland area, wetland area, no-grass area, and the water-covered area. The basin was mainly composed of arable (agricultural) area and forest area with little amount of others. The land use pattern in this study, thus, was expressed as a pick cell of percent arable (agricultural) area and forest area, respectively.
Fish sampling and ecological analysis of fish compositions
Nine sites were selected from the 2012 data file of the basin of the Dongjin River. Fish sampling was followed by the wading method of An et al. (2002). In each sampling site, all habitat types including riffle, run, and pool were sampled in an upstream direction for a distance of 200 m during 50 min. At each site, we used sampling gears of hand net (5 × 5 mm) and casting net (5 × 5 mm) to collect fishes. All fishes were identified and released at the sampling locations, but some ambiguous specimens to identify were preserved in 10 % formalin. Guild analyses of sensitive and tolerant species were based on the previous regional studies of the MEK (An et al. 2006).
Ecological health assessments using a multi-metric model (IBI)
A multi-metric model of the IBI was applied to the basin of the Dongjin River for stream health assessments of the Jeongeup Stream, Dongjin River, and Gobu Stream. The IBI model was modified from a 10-metric to an 8-metric model (An et al. 2002), and the original metric was based on Karr (1981) and Barbour et al. (1999) in North America. The metrics (M) were composed of three major groups such as species richness and composition, trophic composition, and fish abundance and health condition. Metric scores of 1, 3, or 5 were assigned to each of the raw metric values after the approach of US EPA (Barbour et al. 1999). These scores were then summed to obtain a site-specific model value that ranged from 10 to 40, and five classes (excellent, 38–40; good, 32–34; fair, 26–29; poor, 18–22; and very poor, <14) were used for the evaluation.
Results and discussion
Water chemistry in the basin
Fish composition analysis
Total number of fish species and total number of individuals was 33 and 348 in the basin of the Dongjin River, respectively (S2 was not included; Table 1). As shown in Table 1, tolerance guilds were categorized as tolerant, intermediate, and sensitive species and trophic guilds were categorized as omnivore, insectivore, and carnivore species. The most dominant species was Carassius auratus, which is composed of 34.2 % of the total and is a tolerant and omnivore species in the fish guilds (Table 1). These characteristics indicate ecological degradations or impairment of the basin as suggested in the ecological indicator analyses of Karr (1981) and Barbour et al. (1999). According to the analysis of tolerance guilds, there were the tendency of typical downstream decreases in the proportions of sensitive species and downstream increases in the proportions of tolerant species. Also, in trophic guilds, there were the tendency of typical downstream decreases in the proportions of insectivore species and downstream increases in the proportions of omnivore species. The ecological guild analysis was matched well with nutrients (N, P) and organic matter analysis in the basin. In other words, the pattern of fish composition, based on the ecological guilds, was directly influenced by water chemistry; thus, organic matter pollution or nutrient enrichments from the watershed resulted in decreases in the proportions of sensitive and insectivore species and increases in the tolerant and omnivore species (Barbour et al. 1999). In the meantime, bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and gold fish (Carassius cuvieri) occurred in the three sites S3 (12 individuals), S8 (1), and S9 (1; Table 1).
Land use pattern in the sampling sites
Relations of land use pattern to water quality
Biological integrity model for the diagnosis of stream ecosystem health
The model values of the IBI varied from 10 to 22 depending on the sampling site of the basin of the Dongjin River and the mean IBI was 15 (n = 8; Table 2). Thus, the stream health in the basin, based on the mean IBI, was judged as a “poor–very poor” condition according to the modified criteria of IBI (An et al. 2006). The values of IBI decreased from the upstream of S1 (20, poor condition) to downstream of S4 (14, very poor condition) in the Jeongeup Stream, and this pattern was similar to the IBI values of the Dongjin River with 22 (poor condition) in the upstream (S5) and 10 (very poor) in the downstream (S7; Table 2). Three water bodies of the Jeongeup Stream, Dongjin River, and Gobu Stream showed poor to very poor health conditions (Table 2). This indicates that ecological degradation is evident in the basin, and also this was supported by the dominance of the tolerant species and dominant omnivore species. The analysis of external DELT anomalies showed that one individual of C. auratus had skin lesion (LE) in the sampling site S7 (Dongjin River) where IBI value was minimum (10). The external anomaly and minimum IBI in the S7 indicate the impairment of the downstream site along with the site S4, even if the percent of the anomalies was not high like C. auratus (24 %) in the Ohio streams (Sanders et al. 1999). This study supports the finding that chemical degradation by sewage treatment plants and agricultural farms resulted in external anomaly and low IBI.
Relations of fish trophic compositions and tolerance to chemical water quality
Relations of ecological stream health fish to water chemistry and land use pattern
In this study, physicochemical water quality and fish compositions were analyzed along with a diagnosis of ecological health in relation to land use pattern or key point sources. Overall, this research suggests that nutrient regime, organic matters (BOD, COD), and total number of E. coli were directly influenced by point sources of sewage wastewater plants and then also determined by land use pattern, based on the proportion of arable land and forest cover. This chemical water quality determined the fish compositions of trophic guilds (omnivore vs. insectivore sp.) and tolerance guilds (tolerant vs. sensitive sp.) in the basin of the Dongjin River. Thus, ecological stream health at all sites in the Jeongeup Stream, Dongjin River, and Gobu Stream was judged as “poor” to “very poor” conditions by the criteria of An et al. (2002). Especially, the model values of IBI, based on fish assemblages, were lower in the downstreams, compared to the upstreams, indicating an influence of sewage wastewater plants and nutrient runoff from the arable lands. Thus, ecological health, based on a multi-metric fish IBI model, was a positive functional relation with percent forest cover and a negative functional relation with percent arable land. Also, nutrient enrichments (N, P) and organic matter pollution resulted in degradations of the ecological health (IBI). We believe that the impairments of stream health in the basin were mainly attributed to the runoff from the arable land, sewages from the residential sub-urban area, and effluents from the Jeongeup industrial complex. Efficient watershed managements, therefore, are required in the basin for continual maintaining of water quality and ecological stream health.
This research was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF, no. 2013R1A1A4A01012939), and the Daejeon Green Environment Center under the Research Development Program (year 2009); thus, the authors would like to acknowledge these institutions for their assistance.
KG got a project from CNU and designed the experiments. GS analyzed the data and wrote the paper with KG. Both authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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