Distribution and flux of microcystin congeners in lake sediments

Session: 37. - Harmful Algal Blooms (HABs) and their Toxicity: Remote Sensing and Modeling Approaches

Arthur Zastepa, Environment and Climate Change Canada, [email protected]
F. Pick, Department of Biology, University of Ottawa, [email protected]
Jules Blais, Department of Biology, University of Ottawa, [email protected]

Abstract

Sediment concentrations of microcystin congeners and exchange across sediment–water interface were determined in Lake of the Woods, a large water body between Canada and the United States experiencing cyanobacterial blooms. Dated sediment cores were used to examine historical occurrence of microcystins and showed levels below detection prior to the 2000s. More recent sediments were dominated by the MC-LA and –LR congeners with -RR, -YR, -7dmLR, -WR, -LF, -LY, and -LW also present. MC-LA and -LR were distributed in the pore waters whereas MC-RR and -YR were strongly adsorbed to sediment particles. Overall, burial rates were low across sites (2.6 to 298.1 ng/m2/d) when compared to diffusion of microcystins from sediments to overlying water (303.1 to 1078.0 ng/m2/d) suggesting that sediments can be a source of microcystins to the water column. However, the relatively high diffusive flux may be short term and the result of a temporal disconnect between water column productivity and sediment processes. The higher diffusion fluxes and lower burial rates of MC-LA compared to MC-LR point to differences in environmental fate. Given that microcystin congeners vary in their toxicity, these results highlight the need for congener-specific measurements of environmental fate and persistence.

1. Keyword
harmful algal blooms

2. Keyword
sediments

3. Keyword
water quality

4. Additional Keyword
Lake of the Woods

5. Additional Keyword
microcystins

6. Additional Keyword
environmental fate