Abstract
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 2008–2014. 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–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 > 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 33–23, indicating an excellent upstream to fair downstream water quality status. Correspondingly, IBIKR scores ranged between 38–28 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.
Highlights
Stream health evaluation has been one of the hottest research areas over the recent decades in developed countries such as U.S.A. [1], Canada [2], France [3], Germany [4], and England [5].Human interaction with the environment was inevitable and resulted in processes leading to several ecological perturbations in lotic ecosystems
These results showed a starting point of chemical health deterioration in the downstream waters that was mainly due to agricultural runoff waters, especially during floods caused by summer monsoons
The anthropogenic effects became clearer downstream, which may be linked to wastewater treatment plant (WWTP), industrial unit effluents, as well as agricultural runoff
Summary
Stream health evaluation has been one of the hottest research areas over the recent decades in developed countries such as U.S.A. [1], Canada [2], France [3], Germany [4], and England [5]. The sites which are in headwater stream regions are considered as the reference sites, they can be used in comparison with downstream sites to conclude the assessment process [37,38] It is note-worthy that fish assemblages may vary along the stream gradient based on several biological aspects not limited to species diversity, tolerance to chemical stressors, habitat preference, feeding niches as well as origin of each species [35,39]. Variations among these aspects depict the severity and level of degradation in stream health.
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