Assessment of Cyanotoxins and their Public Health Significance in West Michigan Lakes

Cyanobacteria blooms are increasing due to cultural eutrophication, climate change, and the introduction of exotic species.  These blooms can produce cyanotoxins which are harmful to human health.  Microcystins are among the most commonly occurring cyanotoxins found in freshwater systems and are hepatotoxic. They can be present as over 200 structural analogues with microcystin-LR (MC-LR) being the most common and the only cyanotoxin with a WHO guideline.  Anatoxin (neurotoxin) and cylindrospermopsin (cytotoxin and hepatotoxin) also can be found in lakes.  It has been estimated that 25 -75% of cyanobacterial blooms are toxic and toxin production is limited to strains within species.  The spatial and temporal variability of these cyanotoxins in seven west Michigan lakes was investigated using enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography with mass spectrometry (HPLC/MS) and protein phosphate inhibition assay (PPIA) and compared to WHO guidelines.  All three cyanotoxins can be measured by HPLC/MS while PPIA and ELISA only determine microcystins.  Anatoxin-a and cylindrospermopsin were measured by analyzed by HPLC/MS and were not detected at a concentration of 0.1 ug/l.  Cyanobacteria species know to produces these cyanotoxins were present in 6 of the lakes, indicating that Microcystins were present in 6 of the lakes and detected by PPIA, EISA, and HPLC/MS.  Cyanobacteria species composition, chlorophyll-a, and water quality parameters also were evaluated.  The diversity of cyanobacteria communities and analytical results suggests that no single analytical method can be used to assess cyanotoxin levels.  Our data suggests that a combination of HPLC/MS and a broad screening method such as PPIA may be necessary to accurately measure MC-LR concentrations and evaluate the total amount of cyanotoxins present.  Since PPIA and ELISA consistently over predict the level of MC-LR, these methods appear to be good conservative screening tools for the cost effective evaluation of large numbers of samples.