Cyanotoxin occurrence in large rivers of the United States

Abstract

Cyanotoxins occur in rivers worldwide but are understudied in lotic ecosystems relative to lakes and reservoirs. We sampled 11 large river sites located throughout the United States during June-September 2017 to determine the occurrence of cyanobacteria with known cyanotoxinproducing strains, cyanotoxin synthetase genes, and cyanotoxins. Chlorophyll a concentrations ranged from oligotrophic to eutrophic (0.5-64.4 µg L − 1 ). Cyanobacteria were present in the algal communities of all rivers (82% of samples, n = 50) but rarely dominated the phytoplankton (0-52% of total abundance; mean = 8.8%). Pseudanabaena and Planktothrix occurred most often, and many (64%) of the cyanobacterial genera identified (n = 25) have known cyanotoxinproducing strains. Cyanotoxin synthetase genes occurred in all but one river. The mcyE and sxtA genes were most common, present in 73% of rivers and 44% and 40% of samples, respectively. The cyrA gene was less common (22% of samples) but occurred in 64% of rivers. The anaC gene was detected in one river (4% of samples). Anatoxin-a and microcystins were detected at low levels (0.10-0.38 µg L − 1 ) in 2 midcontinent rivers. Cylindrospermopsins and saxitoxins were not detected. Cyanobacteria, cyanotoxin synthetase genes, and cyanotoxins were present at low concentrations throughout this subset of US rivers. Eutrophic rivers located in the midcontinent region of the United States had the highest algal biomass, abundance of cyanotoxin synthetase genes, and cyanotoxin occurrence.

Recent Advancements in the Removal of Cyanotoxins from Water Using Conventional and Modified Adsorbents—A Contemporary Review

“…While existing data show cyanotoxins present in water sources in the US and worldwide [20,[123][124][125], treatment plants and private water sources may not be affected uniformly. Surface water accounts for nearly three-quarters of annual water withdrawals in the US but about 50% of the public water supply that reaches about 141 million people or 43.5% of the US population [126].…”

“…Finally, negative human health impacts are illustrated by Figure 1. Unites States Geological 2017 Survey (USGS) of 11 major coastal and inland rivers of the US for the detection of four cyanotoxins and their genes: mcyE (microcystins), anaC (anatoxins), sxtA (saxitoxins), and cyrA (cylindrospermopsin) [20].…”

Species-Richness Responses to Water-Withdrawal Scenarios and Minimum Flow Levels: Evaluating Presumptive Standards in the Tennessee and Cumberland River Basins

“…Intensification of low-flow conditions can impact fish species and communities at local and regional scales through increased mortality and disruption of reproduction, recruitment, and dispersal [2,7,60]. Nuisance and/or harmful algal blooms (HABs) and associated decreases in dissolved oxygen often occur during low flows, and cyanobacteria HABs and toxicity in lotic ecosystems are an increasing management concern in some regions [61,62]. Use of percentage-of-flow and presumptive standards are increasingly popular among water-management agencies within the US and elsewhere [30,57,63,64].…”

Fluvial seeding of cyanobacterial blooms in oligotrophic Lake Superior

“…The lack of research on this topic may be due to the greater likelihood of observing cyanobacterial blooms in lentic environments than in their lotic counterparts or because riverine conditions (including high turbulence, low light, short residence times, and cooler temperatures) are not typically associated with high algal growth rates (Paerl and Otten, 2013). Nevertheless, a recent study of 11 major rivers in the US showed that cyanobacteria was present in all rivers and comprised up to 52% of the community composition (Graham et al, 2020). The present study shows that rivers may play a critical role in the promotion of newly occurring cyanobacterial blooms in Lake Superior.…”