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

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 (IBI KR ), 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 (R 2 = 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, IBI KR scores ranged between 38-28 approximating with WPI site classification, as well as both indices showed higher regression relation (R 2 = 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 IBI KR could help in better understanding the chemical and biological mechanisms in rivers and streams.

Biological Health Assessments of Lotic Waters by Biotic Integrity Indices and their Relations to Water Chemistry

“…nitrogen if the water-body is under P limitation circumstances. However, the non-significant relationship between TN:TP mass ratios and nitrogen could be attributed towards the low variant ambient N level in comparison to the phosphorus [2,5,25,55,58].…”

“…The majority of study sites displayed huge decline in the total number of native fish species in approximation to the decline of the total number of native individuals as well as the number of sensitive species (SS), which is an unambiguous indication of degrading biological health [35,41,50,59,60]. The proportion of omnivorous fish species showed an increase in the majority of sites and similar was the case with the proportion of individuals as native insectivores that yet again indicated the declining ecological health [2,5,17,35,59]. D = 09 3 12 03 01 01 01 05 04 01 5 07 01 01 01 03 04 05 13 Geum River Watershed Overall Health Status: A = 03; B = 21; C = 73; D = 52…”

“…Additionally, this concept strongly sustained by the previous conclusions by Downing and McCauley [57], who presented that TN:TP mass ratios are more reliant on the phosphorus, as compared to nitrogen if the water-body is under P limitation circumstances. However, the non-significant relationship between TN:TP mass ratios and nitrogen could be attributed towards the low variant ambient N level in comparison to the phosphorus [2,5,25,55,58]. nitrogen if the water-body is under P limitation circumstances.…”

“…The TP level during premonsoon months was very low in comparison to post-monsoon duration. It clearly indicated that the precipitation amount and pattern mainly influenced the watershed water chemistry, especially the nutrient contributing factors, i.e., TN, TP, their ambient ratios, and sestonic CHL-a [2,24,31]. The ambient ratios of TN and TP are widely used to estimate the limitation scenario of nutrient contributing factors in water-bodies [13,42].…”

“…The negative linear relationship between CHL-a and TP and positive linear relationships between CHL-a and TN again strongly indicated the water body was N and P-co-limited during the study duration. Therefore, the empirical modeling approach concluded that the primary nutrient contributing factor supporting the sestonic CHL-a productivity was P and both nutrient factors were originating from the agricultural activities and industrial effluents [2,13,31]. Previous studies have reported that in streams and rivers, limiting nutrients are also reinforced by the abiotic factors such as turbidity as well as geographical location of the water body, that indicate the water residence time and all these factors strongly influenced the light availability, which is a long-established catalyst for primary production [13,17,21,24,28].…”