Ecological assessment of water quality in freshwater wetlands based on the effect of environmental heterogeneity on phytoplankton communities in Northeast China.

Phytoplankton community characterized by strong vitality response to environmental change in freshwater ecosystems. This study aims to evaluate the effectiveness of using phytoplankton diversity as a water quality indicator in wetlands, and find out the main environmental variables affecting the distribution of phytoplankton. From 2020 to 2021, we examined phytoplankton assemblages and water environmental variables in spring, summer, and autumn at eight sampling sites from Hulanhe Wetland, Northeast (NE) China. The results showed that Bacillariophyta was the dominant species. Phytoplankton composition and abundance differed among sampling sites in each season; the abundance in summer (613.71 × 104 ind. L-1) was higher than that in autumn and spring. The water quality assessment of the trophic state index (TSI) based on the four physicochemical indicators was compared with phytoplankton diversity indices, which indicated that the phytoplankton community was stable, and these two indices were significantly lower in summer than in spring and autumn. According to redundancy analysis (RDA), total phosphorus (TP) and nitrogen (TN) were the main environmental variables affecting the distribution of phytoplankton. Temperature and dissolved oxygen (DO) changes also played a role, and their impact on the community was discussed. This work can provide relevant scientific references on the usefulness of phytoplankton diversity structure in assessing water quality in cold regions, in which the succession can be significantly affected by nutrients and temperatures.

Distribution and ecological risk assessment of organochlorine pesticides in sediments from four lakes of Heilongjiang Province, China.

There is growing concern for the lake environment because polluted sediments may cause ecotoxicological effects. In the current study, persistent organochlorine compounds (OCPs), including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and cyclodienes, were analyzed in core sediments taken from Huoshaohei Lake, Xihulu Lake, Wanghua Lake and Keqin Lake, Heilongjiang Province, China. The total OCPs concentrations ranged from 0.92 to 7.09, 0.15 to 9.95, 0.19 to 1.84 and 0.06 to 3.52 ng/g, respectively. The most dominant pollutants were the HCHs, high proportions of γ-HCH isomer indicating the recent input of lindane. The ratios of α-HCH/γ-HCH of four lakes are all lower than that in technical HCH mixtures indicating that there was input of lindane in the past several years, and the mean ratios of (DDE+DDD)/DDTs are all <0.5, suggesting recent release of DDT compounds. Compared with the corresponding ecological environmental quality guidelines from Ingersoll and base on the model of risk based corrective action environmental health risk assessment, the sediments from the four lakes poses a lower potential hazard to human health and the environment but still should be taken into account.