The impacts of climate change and extreme weather events on cyanobacteria blooms in lakes

"There has been an increased awareness in recent years of the problems associated with harmful cyanobacteria algal blooms (cyanoHABs) in freshwater systems. These can have devastating effects on aquatic biota, fisheries and human health via the contamination of drinking water supplies. The exact causes of cyanobacteria blooms are still not well understood, although nutrient enrichment driven by anthropogenic processes (e.g. agricultural intensification) and climate change are two major factors that can drive their proliferation (Benayache et al., 2019). As well as promoting algal growth via temperature change, climate change can affect rainfall patterns, leading to alternating periods of drought and intense storms. The latter can cause increased runoff of nutrients into waterbodies, leading to cyanoHAB formation. Re-suspension of surficial, nutrient-rich sediments during storms can have a similar effect, particularly in shallow lakes. There is a pressing need to better understand these and other controls on cyanoHAB formation in the light of future predicted climate change and increased storm intensity, and to consider how the combined effects of climatic stressors and nutrients will impact biotic communities in lakes and other sensitive water bodies.

This project will use a combination of palaeolimnological (geochemistry, pigments, microfossils) and instrumental water quality and climate data to examine the impacts of recent (last ca. 300 yr) climate change and extreme weather events on cyanoHAB development in two study regions: New Brunswick in eastern Canada and western Ireland, where cyanobacteria blooms are having a detrimental effect. Palaeolimnological approaches, which utilise the rich archive of environmental information preserved in sediment cores, have great potential for understanding the character and causes of harmful cyanobacteria blooms in lakes, and can greatly extend the inferences that can be drawn from water quality monitoring data alone. Sediment cores (<1m) will be collected from lakes with a known history of water-quality change and cynaoHAB proliferation following documented storms. The palaeolimnological work will be supplemented by statistical and GIS analysis of contemporary water quality monitoring data and select climate and landscape limnological variables in the study catchments (e.g. water depth, lake connectivity, fetch, ice-free season) to further elucidate the controls on cyanoHAB development."