DISSERTATION RESEARCH: Abundance, trophic transfer, and cross-ecosystem movement of multiple cyanotoxins in arctic lakes

淡水湖提供了至关重要的人口价值，从家庭、工业和农业的供水到主动和被动娱乐的机会。然而，居住在湖中的蓝藻细菌及其毒素（cyanotoxins）日益受到关注，威胁着水生食物网的健康和淡水的安全利用。大多数关于蓝藻毒素的研究都集中在温带和热带系统中，这些系统表面浮游蓝藻大量繁殖。然而，并不是所有产生毒素的蓝藻都能形成表面的水华，无论是底部居住的蓝藻还是水柱中非常小的单细胞，都能产生毒素，而且对消耗蓝藻的生物的丰富影响，以及毒素从湖泊转移到周围土地的可能性知之甚少，特别是在极地地区。迄今为止，很少有研究调查了极地淡水蓝藻细菌是否产生蓝藻毒素，以及蓝藻毒素在多大程度上通过极地水生食物网或进入陆地生态系统仍然不得而知。该项目将扩大我们对支持有毒蓝藻的生态系统类型的理解，并有助于评估哪些系统目前处于危险之中或将来可能处于危险之中。对生活在海底的蓝藻细菌和水柱中非常小的单细胞产生的蓝藻毒素的研究将在格陵兰岛的湖泊和池塘中进行。为了补充正在进行的对最常见种类的蓝藻毒素的研究，研究人员将评估另外四种毒素的产生及其通过水生食物网和进入陆地生态系统的转移。因此，该项目将扩大在科学界和公共卫生界有关的蓝藻毒素的地理和分类范围以及生态分布方面的知识。这项由该基金资助的研究将使用先前从格陵兰岛西南部的19个湖泊和池塘收集的样本，以(1)量化水生生态系统中另外四类蓝藻毒素（anatoxin-a, saxitoxins， cydrospermosins和BMAA）的丰度；(2)估计蓝藻毒素向陆地生态系统的转移，以便更全面地了解北极湖泊和附近陆地栖息地生物毒素在生态系统内和跨生态系统的移动情况。初步数据表明，含肝毒素的微囊藻毒素是由底栖藻蓝藻产生和释放的，也存在于远洋未开花的浮游植物中。此外，微囊藻毒素正在转移到浮游动物和无脊椎动物的幼虫中。这项研究将把这些微囊藻毒素分析扩展到陆地环境，并调查食物网中另外四种蓝藻毒素的存在。研究人员将调查毒素的产生、蓝藻毒素向湖中其他生物的转移，以及可能影响毒素从水生生态系统向陆地生态系统移动的几种机制（即新出现的昆虫、气溶胶）。已经记录的蓝藻毒素在这些湖泊中的存在和运动表明，高纬度湖泊可以支持产毒蓝藻，我们可能低估了这些系统在未来发展高水平毒性的潜力。

Freshwater lakes provide critical value human populations, from water supply for households, industry, and agriculture to opportunities for active and passive recreation. However, lake-dwelling cyanobacteria and their toxins, cyanotoxins, are of increasing concern, threatening the health of aquatic food webs and the safe uses of freshwaters. Most studies of cyanotoxins have focused on temperate and tropical systems with conspicuous surface blooms of planktonic cyanobacteria. However, not all toxin-producing cyanobacteria form surface blooms, both bottom-dwelling cyanobacteria and very small single cells in the water column, can produce toxins, and the abundance, impacts on organisms that consume the cyanobacteria, and the potential for toxins to move from lakes to the lands surrounding them is poorly understood, especially in polar regions. To date, very few studies have examined whether polar freshwater cyanobacteria produce cyanotoxins and the extent to which cyanotoxins move through polar aquatic food webs or into terrestrial ecosystems remains largely unknown. This project will expand our understanding of the types of ecosystems that support toxic cyanobacteria and contribute to the evaluation of which systems are currently at risk or may become at risk in the future. Studies of the cyanotoxins produced by both bottom-dwelling cyanobacteria and very small single cells in the water column will take place in lakes and ponds in Greenland. To complement ongoing studies of the most common class of cyanotoxin, the researchers will evaluate the production of four additional toxins and their transfer through aquatic food webs and into terrestrial ecosystems. As such, this project will expand the knowledge on the geographic and taxonomic range and ecological distribution of cyanotoxins relevant in both the scientific and public health communities.The research funded by this grant will use samples previously collected from 19 lakes and ponds in southwestern Greenland to (1) quantify the abundance of four additional classes of cyanotoxins (anatoxin-a, saxitoxins, cylindrospermosins, and BMAA) within the aquatic ecosystem and (2) estimate cyanotoxin transfer to terrestrial ecosystems in order to obtain a more complete picture of within- and across-ecosystem movement of biotoxins in Arctic lakes and nearby terrestrial habitats. Preliminary data suggest that hepatoxic microcystins are produced and released by benthic colonial cyanobacteria of the genus Nostoc and are also found in pelagic non-blooming phytoplankton. Moreover, microcystins are being transferred into zooplankton and invertebrate larvae. This research will extend these microcystin analyses into the terrestrial environment and investigate the presence of four additional cyanotoxins within the food web. The researchers will investigate toxin production, the transfer of cyanotoxins to other organisms in the lake, and several mechanisms (i.e., emerging insects, aerosols) that may influence the movement of toxins from the aquatic to terrestrial ecosystem. The already-documented presence and movement of cyanotoxins in these lakes demonstrate that high-latitude lakes can support toxigenic cyanobacteria, and that we may be underestimating the potential for these systems to develop high levels of toxicity in the future.