Saraf Spencer R, Frenkel Amy, Harke Matthew J, Jankowiak Jennifer G, Gobler Christopher J, McElroy Anne E
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000 United States.
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000 United States; Dartmouth College, Hanover, NH 03755, United States.
Aquat Toxicol. 2018 Jan;194:18-26. doi: 10.1016/j.aquatox.2017.10.026. Epub 2017 Nov 2.
Freshwater cyanobacterial harmful algal blooms (CyanoHABs) caused by algae in the genus Microcystis have been increasing in frequency and severity in recent decades. Microcystis blooms threaten aquatic organisms through effects associated with the rapid increase of biomass and the production of the hepatotoxin microcystin (MC) by toxic strains. Among fish, effects of blooms are likely to be more severe for early life stages, and physiological impacts on this life stage could significantly impact recruitment and fish populations. This study explores the effects of Microcystis blooms on the development of fish using the model organism, the Japanese medaka (Oryzias latipes), under realistic exposure conditions. Medaka embryos were exposed to natural blooms collected from New York City (USA) lakes, lab cultures of Microcystis, and MC-LR solutions. Field collected samples were more toxic than lab cultures (even when compared at the same algal density or MC concentration), causing decreased survival, premature time to hatch, reduced body length, yolk sac edema, and decreased heart rate, while lab culture exposures only resulted in bradycardia. Heart rate was the most sensitive endpoint measured, being depressed in embryos exposed to both lab cultures and field collected blooms. Generalized linear model analysis indicated bradycardia was statistically associated with both cell densities of blooms and MC concentrations, while single factor analysis indicated that MC concentrations had a stronger correlation compared to cell densities. However, MC exposure could not fully explain the effects observed, as exposures to MC-LR solutions alone were not able to reduce heart rate as severely as algal exposures. Collectively, these experiments indicate that factors beyond exposure to MC or even isolated Microcystis strains influence heart rate of fish exposed to Microcystis blooms. Enhanced mortality, depressed heart rate, and abnormal development observed in response to environmentally realistic exposures of Microcystis blooms could affect success of fish at both individual or population levels.
近几十年来，由微囊藻属藻类引起的淡水蓝藻有害藻华（CyanoHABs）在发生频率和严重程度上都呈上升趋势。微囊藻藻华通过与生物量快速增加以及有毒菌株产生肝毒素微囊藻毒素（MC）相关的影响，对水生生物构成威胁。在鱼类中，藻华对早期生命阶段的影响可能更为严重，而对这一生命阶段的生理影响可能会显著影响补充量和鱼类种群。本研究利用模式生物日本青鳉（Oryzias latipes），在实际暴露条件下探究了微囊藻藻华对鱼类发育的影响。将青鳉胚胎暴露于从美国纽约市湖泊采集的天然藻华、微囊藻的实验室培养物以及MC-LR溶液中。实地采集的样本比实验室培养物毒性更强（即使在相同藻类密度或MC浓度下进行比较），导致存活率降低、孵化时间提前、体长缩短、卵黄囊水肿以及心率下降，而实验室培养物暴露仅导致心动过缓。心率是所测量的最敏感指标，在暴露于实验室培养物和实地采集的藻华的胚胎中均出现下降。广义线性模型分析表明，心动过缓在统计学上与藻华的细胞密度和MC浓度均相关，而单因素分析表明，与细胞密度相比，MC浓度具有更强的相关性。然而，MC暴露并不能完全解释所观察到的影响，因为单独暴露于MC-LR溶液并不能像藻类暴露那样严重降低心率。总体而言，这些实验表明，除了暴露于MC甚至分离的微囊藻菌株之外的因素，也会影响暴露于微囊藻藻华的鱼类的心率。在对微囊藻藻华进行符合环境实际情况的暴露时观察到的死亡率增加、心率降低和发育异常，可能会在个体或种群水平上影响鱼类的生存。
