Seasonal and Long-Term Connections between Trophic Status, Sestonic Chlorophyll, Nutrients, Organic Matter, and Monsoon Rainfall in a Multipurpose Reservoir

Abstract

Due to rapid eutrophication, sustainable water quality management and supply are essential in drinking water sources and aquatic biota in large reservoirs. We evaluated the potentially crucial factors influencing the algal chlorophyll (CHL-a), nutrients, and the links between the rainfall and other vital elements in a large multipurpose reservoir (Yongdam Reservoir) during 2013–2019. We developed the empirical models on algal CHL-a, total phosphorus (TP), total nitrogen (TN), and TN:TP’s ambient ratios considering the maneuvering influence of Asian monsoons. The intensive rainfall during the monsoon months strongly impacted the nutrient regime and other vital factors. The seasonal patterns of algal CHL-a varied in response to the nutrient contents (TN, TP), suspended solids, and ambient N:P ratios along the longitudinal gradient. The conditional plot analysis, empirical modeling, and observations supported an overall P-limitation scenario, as was evident from the magnitude of N:P ratios (R2 = 0.36, F = 24.9, p < 0.001). Furthermore, the reservoir’s trophic status alluded to the larger particles and blue-green algae during the monsoon and postmonsoon months. The correlation analysis, Mann–Kendall trend test, and principal component analysis illustrated compelling links between CHL-a, TP, and rainfall regime. The outcomes suggested the reservoir was primarily controlled by phosphorus limitation, with an increasing CHL-a tendency along with nitrogen dilution. However, a slight decline in phosphorus was also detected. The Yongdam Reservoir is under the threat of recurrent eutrophication events that could jeopardize this vital drinking water facility due to increasing agricultural and anthropic activities.

Long-Term Water Quality Patterns in an Estuarine Reservoir and the Functional Changes in Relations of Trophic State Variables Depending on the Construction of Serial Weirs in Upstream Reaches

“…The monthly decrease in TN was connected with the increase in monthly precipitation ( Figure 2 and Figure 3 ). The outcomes support the influence of ionic dilution on the nitrogen contents in connection with large amounts of rainfall [ 7 , 48 , 49 , 50 , 58 ]. The seasonal patterns of phosphorus contents (TP, TDP, PO 4 -P) in each zone showed no statistically significant differences.…”

“…This is because the EC is sensitive to variations in dissolved solids, mainly mineral salts [ 10 ]. However, in non-estuarine reservoirs of Korea, an increasing trend of EC from Lz to Tz and to Rz was generally observed, as EC is more correlated with anthropogenic pollutants [ 45 , 48 , 49 , 50 ].…”

“…In addition, it suggests that the large seasonal increase in TSS, Kna, and FCB strongly regulated water clarity as well as algal biomass. The PREC regulated moderately the seasonal variation of parameters with large and small loadings in this component, in agreement with increasing processes such as ionic dilution, anthropogenic effluents, and turbidity [7,15,38,50]. Secondly, the multivariate statistical approach was used to obtain more interpretations about the influence of the selected factors on water clarity and algal biomass.…”

Changes in Algal Plankton Composition and Physico-Chemical Variables in a Shallow Oxbow Lake

“…In the spring, the algal abundances indicated oligo-mesotrophic conditions; however, by summer, the trophic level of the water had increased significantly, and characteristic species showed eutrophic relations. Jargal et al [69] found that large macrovegetation coverage, water level fluctuation and nutrient enrichment are the most common water quality issues. With the arrival of fall, the trophic conditions decreased once again to a mesotrophic level.…”

Seasonal Water Quality and Algal Responses to Monsoon-Mediated Nutrient Enrichment, Flow Regime, Drought, and Flood in a Drinking Water Reservoir

“…Therefore, it is essential to control the high TP inflows and further investigate the phytoplankton species and their functional groups. This can be done by regulating the usage of P-yielding fertilizers and controlling industrial effluents to restrict nutrient inputs [25,80]. It is, therefore, crucial to locate the hotspots of high TP concentrations in the reservoir watershed and implement effluent standards based on individual points.…”