Microcystin production by Nostoc in Greenlandic lakes

Benthic primary producers are recognized for their important role in contributing to ecosystem productivity and nutrient cycling in lake and stream ecosystems, particularly in polar environments. In Arctic lakes, benthic producers often comprise mats or colonies of cyanobacteria capable of producing cyanotoxins. However, the extent to which benthic communities contribute cyanotoxins in polar regions remains poorly described. We evaluated the potential for benthic colonies of the cyanobacterium Nostoc pruniforme from lakes in Kangerlussuaq, Greenland, to contribute microcystins (MCs) to lake water using three approaches. First, we dissected field-collected Nostoc colonies and measured MCs within multiple layers of fresh colony tissue. Second, we conducted a laboratory experiment to evaluate the temporal dynamics of MC release by incubated, intact colonies. Finally, we quantified whether MC concentrations in water and sediment samples in the field were higher in and above dense bands of b...