Auburn University, School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn, AL, 36849, USA.
Department of Environmental Science and Ecology, The College at Brockport - State University of New York, Brockport, New York, 14559, USA.
Environ Monit Assess. 2018 Mar 25;190(4):247. doi: 10.1007/s10661-018-6595-5.
Forty-one livestock drinking water ponds in Alabama beef cattle pastures during were surveyed during the late summer to generally understand water quality patterns in these important water resources. Since livestock drinking water ponds are prone to excess nutrients that typically lead to eutrophication, which can promote blooms of toxigenic phytoplankton such as cyanobacteria, we also assessed the threat of exposure to the hepatotoxin, microcystin. Eighty percent of the ponds studied contained measurable microcystin, while three of these ponds had concentrations above human drinking water thresholds set by the US Environmental Protection Agency (i.e., 0.3 μg/L). Water quality patterns in the livestock drinking water ponds contrasted sharply with patterns typically observed for temperate freshwater lakes and reservoirs. Namely, we found several non-linear relationships between phytoplankton abundance (measured as chlorophyll) and nutrients or total suspended solids. Livestock had direct access to all the study ponds. Consequently, the proportion of inorganic suspended solids (e.g., sediment) increased with higher concentrations of total suspended solids, which underlies these patterns. Unimodal relationships were also observed between microcystin and phytoplankton abundance or nutrients. Euglenoids were abundant in the four ponds with chlorophyll concentrations > 250 μg/L (and dominated three of these ponds), which could explain why ponds with high chlorophyll concentrations would have low microcystin concentrations. Based on observations made during sampling events and available water quality data, livestock-mediated bioturbation is causing elevated total suspended solids that lead to reduced phytoplankton abundance and microcystin despite high concentrations of nutrients, such as phosphorus and nitrogen. Thus, livestock could be used to manage algal blooms, including toxic secondary metabolites, in their drinking water ponds by allowing them to walk in the ponds to increase turbidity.
在阿拉巴马州的肉牛牧场，有 41 个牲畜饮用水池塘在夏末进行了调查，以大致了解这些重要水资源的水质模式。由于牲畜饮用水池塘容易受到过量营养物质的影响，这些营养物质通常会导致富营养化，从而促进产毒浮游植物（如蓝藻）的大量繁殖，因此我们还评估了暴露于肝毒素微囊藻毒素的威胁。研究的 80%池塘含有可测量的微囊藻毒素，其中 3 个池塘的浓度超过了美国环境保护署（即 0.3μg/L）设定的人类饮用水阈值。牲畜饮用水池塘的水质模式与温带淡水湖泊和水库的典型模式形成鲜明对比。具体而言，我们发现浮游植物丰度（以叶绿素表示）与营养物质或总悬浮固体之间存在几种非线性关系。牲畜可以直接进入所有研究池塘。因此，随着总悬浮固体浓度的升高，无机悬浮固体（例如沉积物）的比例增加，这就是造成这种模式的原因。在微囊藻毒素与浮游植物丰度或营养物质之间也观察到单峰关系。在叶绿素浓度大于 250μg/L 的四个池塘（其中三个池塘占主导地位）中，眼虫类生物很丰富，这可以解释为什么叶绿素浓度高的池塘微囊藻毒素浓度低的原因。根据采样期间的观察和可用的水质数据，牲畜介导的生物搅动导致总悬浮固体升高，从而导致浮游植物丰度和微囊藻毒素降低，尽管营养物质（如磷和氮）浓度很高。因此，通过允许牲畜在池塘中走动以增加浊度，可以利用牲畜来管理其饮用水池塘中的藻类水华，包括有毒的次生代谢物。
