Increased risk of cyanobacterial blooms in northern high‐latitude lakes through climate warming and phosphorus enrichment

Abstract

Harmful cyanobacterial blooms are an increasing problem at many locations throughout the world but are rarely reported in aquatic habitats at high latitudes. Shallow lakes are a major feature of northern permafrost landscapes and are likely to experience large‐scale changes in their limnological properties in the future as a consequence of climate warming. In the present study, we addressed the question of what preconditions would be necessary to stimulate the growth and dominance of bloom‐forming cyanobacteria in northern fresh waters. We analysed the summer phytoplankton of 18 lakes on eroding permafrost (thaw lakes) and on glacier‐scoured rock (rock basin lakes) in subarctic Quebec, Canada, to determine their phytoplankton community structure and the biomass contribution of cyanobacteria. This survey was complemented with an incubation experiment to evaluate the direct warming and indirect phosphorus (P) enrichment effects of climate change on cyanobacterial bloom development. All lakes contained diverse phytoplankton communities, often dominated by chrysophytes, dinoflagellates and chlorophytes. Cyanobacteria were present in all waterbodies, but their contribution to the total community biovolume was highly variable (mean of 8.7%, range 0.1%–47%). Cyanobacterial community biovolumes correlated positively with surface water temperatures, and negatively with dissolved organic carbon, soluble reactive phosphorus, iron and manganese concentrations in the surface waters. Phosphorus enrichment of water from a thaw lake resulted in a fourfold increase of chlorophyll a (Chl‐a) and an increase in the cyanobacterial pigments echinenone and zeaxanthin. The phytoplankton counts showed that there was a sharp decrease in diversity (expressed as decline of the Shannon–Wiener index from 1.69 to 0.16), accompanied by a shift to cyanobacterial dominance, notably by the heterocystous, potentially toxic species Dolichospermum cf. planctonicum. Increased temperature led to an initial doubling of cyanobacterial biovolume, followed by the development of a chrysophyte bloom. Combined warming and P enrichment led to reduced phytoplankton biodiversity, with a community composed of cyanobacteria and chrysophytes. There was also a pronounced response by the picophytoplankton community; picocyanobacteria were strongly stimulated by P enrichment, while picoeukaryotes increased in response to warming. The current inoculum levels of cyanobacteria in subarctic lakes and their responsiveness to temperature and phosphorus indicate the potential for an abrupt increase in their abundance, accompanied by a decrease in phytoplankton diversity. Ongoing climate change will increase the risk of noxious cyanobacterial blooms in northern lakes and ponds, with potentially negative consequences for higher trophic levels.

From clear lakes to murky waters – tracing the functional response of high‐latitude lake communities to concurrent ‘greening’ and ‘browning’

“…Subarctic lakes provide opportunities for transport, drinking water and year-round subsistence fisheries to indigenous local communities (Sj€ olander 2011). Eutrophication caused by increasing water temperature and intensification of land use is threatening these ecosystem services, reducing water quality (Przytulska et al 2017), shifting fish fauna towards less nutritious and smaller-sized species , and reducing the growth and condition of resident cold water adapted salmonids (Guzzo et al 2017). Our results indicate an additional sensitivity, as a shift towards pelagic reliance represents a major ecological change in food webs that, in their original state, are reliant on benthic algae (Sierszen et al 2003).…”

“…Eutrophication caused by increasing water temperature and intensification of land use is threatening these ecosystem services, reducing water quality (Przytulska et al . ), shifting fish fauna towards less nutritious and smaller‐sized species (Hayden et al . ), and reducing the growth and condition of resident cold water adapted salmonids (Guzzo et al .…”

Effect of Environmental Conditions and Morphometric Parameters on Surface Water Temperature in Polish Lakes

“…In this context, it is important to identify factors differentiating the process. The importance of this knowledge is evidenced by the observed effects of current transformations in lakes [83][84][85][86][87]. According to numerous papers [88][89][90][91], further transformation of thermal conditions (and the accompanying processes) will take place in the future.…”

Atmospheric change as a driver of change in the Canadian boreal zone1

“…3. Effects of potentially more frequent and intensifying cyanobacterial blooms: future occurrences of toxic blooms are challenging to predict, given the poorly known bloomforming cyanobacterial presence in many northern boreal lakes, and the relationships between cyanotoxins (especially microcystins) and drivers of atmospheric change (e.g., Pick 2016;Przytulska et al 2017;Taranu et al 2017).…”