Cyanotoxins have received considerable attention in eutrophic temperate systems where conspicuous blooms of planktonic taxa threatening its safe use for recreation and drinking water. Although cyanobacteria inhabit a diverse range of freshwater habitats across the globe, our current understanding of cyanotoxins derives almost entirely from studies of bloom-forming pelagic taxa in temperate and tropical regions. Consequentially, we know much less about cyanotoxins in Arctic regions, despite the ability of non-bloom forming taxa to thrive in these habitats. We tested for the presence and trophic transfer potential of the widespread cyanotoxin, microcystin (hereafter MC), in whole lake water and within Arctic lake food webs of southwestern Greenland. In addition to within-lake toxin transfer, we also investigated the potential for cyanotoxins to be transferred from lake to land via riparian vegetation and emerging insects. To investigate both within-lake and lake-to-land modes of transfer, we collected samples from 9 lakes in Kangerlussuaq in 2015, testing for the presence of the widespread MC from (1) within the aquatic food web, (2) plant material from riparian and upland zones surrounding each lake, (3) emerging insects (midges, mosquitoes), and (4) terrestrial invertebrates (caterpillars, spiders).
Results/Conclusions
We detected MC in all samples: whole lake water, in-lake organisms, and land-based organisms. In aquatic samples, median MC varied by two orders of magnitude across taxa, ranging from a high of 843.7 ng g-1 wet weight (ww) in phytoplankton, followed by benthic Nostoc, zooplankton, snails, dysticid larvae, and a low of 0.084 g-1 ww in chironomid larvae. In terrestrial samples, MC varied across plant types (shrub, sedge, moss) and across lakes, but the overall range in MC was low (range: 0.7 – 13 ng g-1 ww). We also detected MC in terrestrial invertebrates, with highest median concentrations in spiders (16.3 ng g-1 ww), followed by adult midges and mosquitos (2.7 and 2.8 ng g-1 ww, respectively), and caterpillars (0.5 ng g-1 ww). These findings demonstrate that microcystins can exist in multiple trophic levels within an Arctic aquatic food web, and are capable of being transferred into terrestrial food webs via multiple potential routes. Further, such cross-ecosystem fluxes of cyanotoxins may be widespread and a complete understanding of trophic toxin transfer, and its effects on food webs, requires quantification of these connections.