Meteorological and Nutrient Conditions Influence Microcystin Congeners in Freshwaters

Abstract

Cyanobacterial blooms increasingly impair inland waters, with the potential for a concurrent increase in cyanotoxins that have been linked to animal and human mortalities. Microcystins (MCs) are among the most commonly detected cyanotoxins, but little is known about the distribution of different MC congeners despite large differences in their biomagnification, persistence, and toxicity. Using raw-water intake data from sites around the Great Lakes basin, we applied multivariate canonical analyses and regression tree analyses to identify how different congeners (MC-LA, -LR, -RR, and -YR) varied with changes in meteorological and nutrient conditions over time (10 years) and space (longitude range: 77°2′60 to 94°29′23 W). We found that MC-LR was associated with strong winds, warm temperatures, and nutrient-rich conditions, whereas the equally toxic yet less commonly studied MC-LA tended to dominate under intermediate winds, wetter, and nutrient-poor conditions. A global synthesis of lake data in the peer-reviewed literature showed that the composition of MC congeners differs among regions, with MC-LA more commonly reported in North America than Europe. Global patterns of MC congeners tended to vary with lake nutrient conditions and lake morphometry. Ultimately, knowledge of the environmental factors leading to the formation of different MC congeners in freshwaters is necessary to assess the duration and degree of toxin exposure under future global change.

Cyanotoxins accumulate in Lake St. Clair fish yet their fillets are safe to eat

“…Total phosphorus (28.7 and 13.4 μg L -1 ), chlorophyll a (9.7 and 4.6 μg L -1 ) and total microcystins (0.2 and 1.0 μg L -1 ) were highest in 2018. Microcystin concentrations in the present study are similar to previous measurements from Lake St. Clair (Davis et al, 2014; Taranu et al, 2019).…”

The genetic and ecophysiological diversity of Microcystis

“…Indeed, Microcystis strains are often referred to as ‘toxic’ and ‘non‐toxic’ based on their ability to produce microcystins. In fact, this simplified classification scheme hides the fact that collectively, Microcystis produces a large array of secondary metabolites with possible toxic properties including over 200 (Puddick et al ., 2014; Taranu et al ., 2019) different microcystin variants (congeners), which range in their toxicity (Rinehart et al ., 1994; Chernoff et al ., 2020). These toxin congener profiles differ between strains (Puddick et al ., 2014) and environmental conditions (Amé and Wunderlin, 2005; Taranu et al ., 2019).…”

“…In fact, this simplified classification scheme hides the fact that collectively, Microcystis produces a large array of secondary metabolites with possible toxic properties including over 200 (Puddick et al ., 2014; Taranu et al ., 2019) different microcystin variants (congeners), which range in their toxicity (Rinehart et al ., 1994; Chernoff et al ., 2020). These toxin congener profiles differ between strains (Puddick et al ., 2014) and environmental conditions (Amé and Wunderlin, 2005; Taranu et al ., 2019). Understanding and modelling the ecology and physiology of these strains will be critical to inform forecasts and management of toxic blooms (Hellweger et al ., 2019).…”

Seasonal Occurrence of Cyanobacteria and First Detection of Microcystin-LR in Water Column of Foum-Gleita Reservoir, Mauritania

“…Although 279 microcystin congeners have been characterized (Bouaïcha et al 2019), only one microcystin variant most common and most toxic, microcystin-LR (MC-LR), has been detected for the rst time in freshwater ecosystems of Mauritania, in particular, in water of Foum-Gleita reservoir, with a peak (5.638 µg/L) exceeding 5 times the guideline value recommended by the World Health Organization for drinking water which is 1 µg/L (Taranu et al 2019). Indeed, microcystin-LR (MC-LR) has generally been detected as the main variant of cyanobacterial blooms, particularly in Africa and Europe, but it is frequently produced with one or more than 10 other minor variants (Ndlela et al 2016;Puddick et al 2016).…”