Toxic cyanobacteria in relation to sulfate, molybdenum, nitrogen and phosphorus in Alberta's shallow prairie lakes
Date
2018-10-19
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Abstract
Cyanobacteria are characteristic of poor global water quality. They create a public health concern and threaten biodiversity, particularly when they produce toxins such as microcystins. It is poorly understood why cyanobacteria produce microcystins, or how cyanobacteria in shallow prairie lakes will respond to increased salinity under changing climate. To study the effects of variable sulfate concentrations on cyanobacteria and to elucidate environmental patterns of microcystin production, I sampled 25 shallow lakes over four months for total nitrogen (TN), dissolved inorganic nitrogen (DIN), total phosphorus (TP), soluble reactive phosphorus (SRP), sulfate, molybdenum, microcystins, and the cyanobacteria-specific pigments canthaxanthin, myxoxanthophyll and echinenone. There was a negative relationship between cyanobacteria pigment and sulfate, and a positive relationship between cyanobacteria pigment and molybdenum and total nitrogen. Microcystins positively correlated with cyanobacteria pigment and turbidity. When microcystin samples above 10 µg·L-1 were removed, microcystins correlated with TN:TP in June and July. My results suggest that increasing sulfate leads to less cyanobacteria pigment. With the prairies expected to get hotter and dryer in the future, shallow prairie lakes are likely to see less cyanobacteria as they increase in salinity. My results also indicate that higher cyanobacteria pigments correlate with higher microcystins. Although low TN:TP can lead to high microcystins, low TN:TP is not enough to differentiate between high and low microcystins. No thresholds were found in either analysis, meaning there was no evidence for a tipping point where sulfate limits cyanobacteria nor the existence of environmental triggers associated with microcystin production over the season.
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Keywords
cyanobacteria, blue-green algae, shallow lakes, microcystins, sulfate, molybdenum
Citation
Anderson, S. M. (2018). Toxic cyanobacteria in relation to sulfate, molybdenum, nitrogen and phosphorus in Alberta's shallow prairie lakes (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/33226