Abstract
The Hai River Basin (HRB) is one of the most polluted river basins in China. The basin suffers from various types of pollutants including heavy metals and nutrients due to a high population density and rapid economic development in this area. We assessed the relationship between heavy metal accumulation by periphyton playing an important role in fluvial food webs and eutrophication in the HRB. The concentrations of the unicellular diatoms (type A), filamentous algae with diatoms (type B), and filamentous algae (type C) varied along the river, with type A dominating upstream, and types B then C increasing in concentration further downstream, and this was consistent with changes in the trophic status of the river. The mean heavy metal concentrations in the type A, B and C organisms were Cr: 18, 18 and 24 mg/kg, respectively, Ni: 9.2, 10 and 12 mg/kg, respectively, Cu: 8.4, 19 and 29 mg/kg, respectively, and Pb: 11, 9.8 and 7.1 mg/kg respectively. The bioconcentration factors showed that the abilities of the organisms to accumulate Cr, Ni and Pb decreased in the order type A, type B, then type C, but their abilities to accumulate Cu increased in that order. The Ni concentration was a good predictor of Cr, Cu and Pb accumulation by all three periphyton types. Our study shows that heavy metal accumulation by periphyton is associated with eutrophication in the rivers in the HRB.
Highlights
Heavy metal pollution in aquatic ecosystems has been a serious global environmental problem for a long time [1,2,3]
The total N (TN) and total P (TP) concentrations clearly increased moving from the upstream part of the study area to the downstream part
Defining the trophic state is more difficult in rivers than in lakes [26], but the US Environmental Protection Agency has suggested boundaries for the trophic classification of rivers [27], and these are that the oligotrophic–mesotrophic boundary is at TN = 0.70 mg/L and TP = 25 mg/L and that the mesotrophic–eutrophic boundary is at TN = 1.5 mg/L and TP = 75 mg/L
Summary
Heavy metal pollution in aquatic ecosystems has been a serious global environmental problem for a long time [1,2,3]. Heavy metals are persistent in aquatic environments because of their resistance to decomposition under natural conditions [4,5]. One of the greatest problems associated with the persistence of heavy metals is the potential for them to bioaccumulate and biomagnify, potentially resulting in long-term implications for human and aquatic ecosystem health [6,7,8,9]. Periphyton is an important aquatic resource and is a significant component in river ecosystems [10,11], it plays an important role in fluvial food webs [12,13]. Heavy metal accumulation by periphyton has a strong effect on river ecosystems because of these factors
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