DISSERTATION RESEARCH: Abundance, trophic transfer, and cross-ecosystem movement of multiple cyanotoxins in arctic lakes

Dartmouth College, Hanover NH

Investigators

Abstract

Freshwater lakes provide critical value human populations, from water supply for households, industry, and agriculture to opportunities for active and passive recreation. However, lake-dwelling cyanobacteria and their toxins, cyanotoxins, are of increasing concern, threatening the health of aquatic food webs and the safe uses of freshwaters. Most studies of cyanotoxins have focused on temperate and tropical systems with conspicuous surface blooms of planktonic cyanobacteria. However, not all toxin-producing cyanobacteria form surface blooms, both bottom-dwelling cyanobacteria and very small single cells in the water column, can produce toxins, and the abundance, impacts on organisms that consume the cyanobacteria, and the potential for toxins to move from lakes to the lands surrounding them is poorly understood, especially in polar regions. To date, very few studies have examined whether polar freshwater cyanobacteria produce cyanotoxins and the extent to which cyanotoxins move through polar aquatic food webs or into terrestrial ecosystems remains largely unknown. This project will expand our understanding of the types of ecosystems that support toxic cyanobacteria and contribute to the evaluation of which systems are currently at risk or may become at risk in the future. Studies of the cyanotoxins produced by both bottom-dwelling cyanobacteria and very small single cells in the water column will take place in lakes and ponds in Greenland. To complement ongoing studies of the most common class of cyanotoxin, the researchers will evaluate the production of four additional toxins and their transfer through aquatic food webs and into terrestrial ecosystems. As such, this project will expand the knowledge on the geographic and taxonomic range and ecological distribution of cyanotoxins relevant in both the scientific and public health communities. The research funded by this grant will use samples previously collected from 19 lakes and ponds in southwestern Greenland to (1) quantify the abundance of four additional classes of cyanotoxins (anatoxin-a, saxitoxins, cylindrospermosins, and BMAA) within the aquatic ecosystem and (2) estimate cyanotoxin transfer to terrestrial ecosystems in order to obtain a more complete picture of within- and across-ecosystem movement of biotoxins in Arctic lakes and nearby terrestrial habitats. Preliminary data suggest that hepatoxic microcystins are produced and released by benthic colonial cyanobacteria of the genus Nostoc and are also found in pelagic non-blooming phytoplankton. Moreover, microcystins are being transferred into zooplankton and invertebrate larvae. This research will extend these microcystin analyses into the terrestrial environment and investigate the presence of four additional cyanotoxins within the food web. The researchers will investigate toxin production, the transfer of cyanotoxins to other organisms in the lake, and several mechanisms (i.e., emerging insects, aerosols) that may influence the movement of toxins from the aquatic to terrestrial ecosystem. The already-documented presence and movement of cyanotoxins in these lakes demonstrate that high-latitude lakes can support toxigenic cyanobacteria, and that we may be underestimating the potential for these systems to develop high levels of toxicity in the future.