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The seasonal and spatial variation in the phytoplankton community structure and the environmental variables were investigated in December (the dry season) 2016 and July (the rainy season) 2017 in the Jinjiang River Estuary, China. We identified a total of 138 species of phytoplankton, which were mainly Chlorophyta, Bacillariophyta, and Cryptophyta in the dry season; however, in the rainy season, only Bacillariophyta were found. In the Jinjiang River Estuary, the species evenness and the biodiversity index were higher in the rainy season and that the species diversity was higher in the dry season. Redundancy analysis (RDA) revealed that the dominant species were statistically related to many of the environmental variables, including the water temperature (WT), pH, salinity (Sal), dissolved oxygen (DO), total phosphorus (TP), and total nitrogen (TN). Among the variables, the Sal, DO, TP, and TN had a significant influence on the dominant species distribution, and the WT and pH also affected the dominant species distribution to some extent., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background, Aim, and Scope: Fujian reservoirs in southeast China are important water resources for economic and social sustainable development, although few have been studied previously. In recent years, growing population and increasing demands for water shifted the focus of many reservoirs from flood control and irrigation water to drinking water. However, most of them showed a rapid increase in the level of eutrophication, which is one of the most serious and challenging environmental problems. In this study, we investigated the algae community characteristics, trophic state, and eutrophication control strategies for typical subtropical reservoirs in southeast Fujian., Materials and Methods: Surface water samples were collected using polyvinyl chloride (PVC) plastic bottles from 11 Fujian reservoirs in summer 2010. Planktonic algae were investigated by optical microscopy. Water properties were determined according to the national standard methods., Results and Discussion: Shallow reservoirs generally have higher values of trophic state index (TSI) and appear to be more susceptible to anthropogenic disturbance than deeper reservoirs. A total of 129 taxa belonging to eight phyla (i.e., Bacillariophyta, Chlorophyta, Chrysophyta, Cryptophyta, Cyanophyta, Euglenophyta, Pyrrophyta, Xanthophyta) were observed and the most diverse groups were Chlorophyta (52 taxa), Cyanophyta (20 taxa), Euglenophyta (17 taxa), Chrysophyta (14 taxa). The dominant groups were Chlorophyta (40.58%), Cyanophyta (22.91%), Bacillariophyta (21.61%), Chrysophyta (6.91%). The species richness, abundance, diversity, and evenness of algae varied significantly between reservoirs. TSI results indicated that all 11 reservoirs were eutrophic, three of them were hypereutrophic, six were middle eutrophic, and two were light eutrophic. There was a strong positive correlation between algal diversity and TSI at P < 0.05. Our canonical correspondence analysis (CCA) results illustrated that temperature, transparency, conductivity, DO, TC, NH(4)-N, NO(x)-N, TP, and chlorophyll a were significant environmental variables affecting the distribution of algae communities. The transparency and chlorophyll a were the strongest environmental factors in explaining the community data. Furthermore, the degradation of water quality associated with excess levels of nitrogen and phosphorus in Fujian reservoirs may be impacted by interactions among agriculture and urban factors. A watershed-based management strategy, especially phosphorus control, should be developed for drinking water source protection and sustainable reservoirs in the future., Conclusion and Recommendations: All investigated reservoirs were eutrophicated based on the comprehensive TSI values; thus, our results provided an early warning of water degradation in Fujian reservoirs. Furthermore, the trophic state plays an important role in shaping community structure and in determining species diversity of algae. Therefore, long-term and regular monitoring of Euglenophyta, Cyanophyta, TN, TP and chlorophyll a in reservoirs is urgently needed to further understand the future trend of eutrophication and to develop a watershed-based strategy to manage the Cyanophyta bloom hazards.

The estuarine phytoplankton composition, spatial and temporal distribution, primary productivity, and their influencing factors were reviewed, and the significance of estuarine phytoplankton in monitoring aquatic environment, biodiversity of estuarine phytoplankton, and edge effect were discussed. Generally, the dominant phytoplankton populations were diatoms and dinoflagellates in estuaries. Microphytoplankton and picophytoplankton played important roles in estuarine ecosystems. Spatial and temporal changes in estuarine phytoplankton species composition and primary productivity were apparent. Several factors including light, temperature, nutrients, herbivory and river flow could influence estuarine phytoplankton production.

The seasonal and spatial variation in the phytoplankton community structure and the environmental variables were investigated in December (the dry season) 2016 and July (the rainy season) 2017 in the Jinjiang River Estuary, China. We identified a total of 138 species of phytoplankton, which were mainly Chlorophyta, Bacillariophyta, and Cryptophyta in the dry season; however, in the rainy season, only Bacillariophyta were found. In the Jinjiang River Estuary, the species evenness and the biodiversity index were higher in the rainy season and that the species diversity was higher in the dry season. Redundancy analysis (RDA) revealed that the dominant species were statistically related to many of the environmental variables, including the water temperature (WT), pH, salinity (Sal), dissolved oxygen (DO), total phosphorus (TP), and total nitrogen (TN). Among the variables, the Sal, DO, TP, and TN had a significant influence on the dominant species distribution, and the WT and pH also affected the dominant species distribution to some extent. [ABSTRACT FROM AUTHOR]

• The effect of microplastics on the chlorophyll a content of algae was studied. • The changes of photosynthetic activity were determined. • High concentrations of microplastics inhibited photosynthesis of algae. • Toxicity of polyvinyl chloride (PVC) is greater than that of polypropylene (PP). Microplastics are widely distributed in freshwater environments. At present, most of the studies on the toxicity of microplastics are concentrated on aquatic feeding animals, but relatively few have addressed freshwater algae. This study investigated the effect of microplastics (polypropylene (PP) and polyvinyl chloride (PVC)) exposure on the photosynthetic system of freshwater algae over the logarithmic growth period. The results showed that both PVC and PP had a negative effect on chlorophyll a concentrations of Chlorella (C.) pyrenoidosa and Microcystis (M.) flos-aquae ; among them, when the concentration of PVC exceeded 250 mg/L, compared with the control group, the chlorophyll a content of C. pyrenoidosa was reduced by 55.23%. For photosynthetic activity, higher concentrations of PVC and PP can induce lower values of F v /F m , F v /F 0 , and F v '/F m ', suggesting a larger impact in algae. However, algae were able to adjust, with increased values of F v /F m , F v /F 0 , and F v '/F m '. This dose-negative effect phenomenon also exists in the study of the rapid light-response curves. In addition, comparing the two microplastics, we could see that PVC greatly inhibits the photosynthesis system of freshwater algae. Our study confirmed that microplastics can affect algae growth under certain concentrations, which provides evidence for understanding the risks of microplastics. [ABSTRACT FROM AUTHOR]