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 cyanotoxin-producing 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 cyanotoxin-producing 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.

摘要

氰毒素存在于世界各地的河流中，但在相对于湖泊和水库的抽水生态系统中却未被充分研究。我们在2017年6月至9月期间对全美国的11个大河站点进行了采样，以确定已知的产生氰毒素的菌株，氰毒素合成酶基因和氰毒素的蓝细菌的发生率。叶绿素一个浓度范围为贫营养至富营养（0.5-64.4微克大号^{- 1}）。蓝藻存在于所有河流的藻类群落中（82％的样本，n  = 50），但很少占主导地位的浮游植物（占总丰度的0–52％；平均值= 8.8％）。假单胞菌和浮游生物蓝藻的发生最常见，并且鉴定出的许多蓝细菌属（n  = 25）中（64％）具有已知的产生蓝毒素的菌株。氰毒素合成酶基因出现在除一条河外的所有河流中。的mcyE和的sxtA基因是最常见的，存在于分别的河流73％和44％和样品的40％。所述cyrA基因是不常见的（样品的22％），但发生在河流的64％。所述ANAC在一个河流（样品的4％）中检测到的基因。检测到低水平的抗毒素-a和微囊藻毒素（0.10–0.38 µg L ^{− 1}）在2条中洲河流中。未检测到圆柱形精子蛋白酶和沙毒素。在整个美国河流中，蓝细菌，蓝藻毒素合成酶基因和蓝藻毒素的浓度较低。位于美国中部大陆的富营养化河流具有最高的藻类生物量，丰富的蓝藻毒素合成酶基因和蓝藻毒素的发生。