Decade-long meteorological and water quality dynamics of northern Lake Dianchi and recommendations on algal bloom mitigation via key influencing factors identification

Abstract Worldwide extension of hazardous algal blooms (HABs) in lakes has threatened animal and human health, drinking water supply, and aquatic ecosystems. Although both climatic and water quality changes can give rise to HABs, specific contribution of each factor is often lake region dependent. In this study, data from intensive local sampling sites were introduced to identify the key influencing factors of HABs in northern Lake Dianchi, where the bloom is severer than the rest of the lake. Decade-long meteorological and water quality dynamics including HABs community changes at various sites were revealed. Both dry weight of the bloom biomass (DW) and Chlorophyll a concentration (Chl. a) were adopted as indicators to HABs. Spearman correlation analysis and multiple stepwise linear regression were respectively used to identify the individual and joint influencing factors of HABs. Efficiency of a condensed bloom biomass pumping strategy was evaluated on HABs mitigation, and the impact of changing nutrients measurement protocols was also analyzed. Results indicated that Chl. a rather than DW could better represent the extent of HABs among various sampling sites. Although both meteorological and water quality factors are responsible for HABs in northern Lake Dianchi when individually considered, it was water quality and particularly TN and TP that were the “game changer” in HABs mitigation when joint influencing factors were concerned. The “pumping strategy” can only be adopted as an emergency method, and recommendations on nutrients reduction should be based on the conventional measuring protocol that includes particulate nutrients as well.