Potential influence of overwintering benthic algae on water quality

Overwintering benthic algae not only directly impact drinking water safety, but also affect the algae recruitment in warm spring seasons. Thus, understanding the characteristics of overwintering benthic algae can provide scientific references for formulating preventative strategies of reasonable water resource. However, they have received less attention. In this study, the spatiotemporal variation of benthic algae and their harmful secondary metabolites were studied from autumn to summer in Qingcaosha Reservoir. Benthic algae (picophytobenthos accounting for 55.42%) had a high biomass during overwintering, and the groups of overwintering benthic algae included pico-Cyanobacteria, pico-Cryptomonas, pico-Chlorophyta, pico-Diatoms, Cyanobacteria, Chlorophyta, Cryptomonas and Diatoms, which were consistent with the planktonic algae species in warm seasons. In oligotrophic or mesotrophic water bodies, micronutrients of iron and manganese were key nutrient factors influencing the biomass of benthic algae. Furthermore, pico-phytobenthos were important potential contributors of harmful secondary metabolites. The content of microcystins, anatoxin-a, geosmin and 2-methylisoborneol in sediment were 15.75 mu g/kg.FW, 48.16 mu g/kg.FW, 3.91 ng/kg.FW, and 11.76 ng/kg.FW during winter, which had potential to be released into water bodies to impact water quality. These findings indicate that water quality monitoring programs need to consider sediment in winter as a potential source of toxins and preventative measures to prevent excessive proliferation of algae should be implemented in winter. (C) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

The overwintering benthic algae have direct impacts on drinking water safety and influence the recruitment of algae in warm seasons. Understanding the characteristics of overwintering benthic algae is crucial for formulating effective strategies to prevent water resource contamination. This study found that picophytobenthos accounted for a large portion of benthic algae biomass in winter, and the species composition of overwintering benthic algae was similar to planktonic algae in warm seasons. Micronutrients, such as iron and manganese, played a key role in influencing the biomass of benthic algae in oligotrophic or mesotrophic water bodies. Additionally, the study highlighted the importance of monitoring harmful secondary metabolites released by pico-phytobenthos in sediment, as they have the potential to impact water quality.