Schaller Jörg, Planer-Friedrich Britta
Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
Chemosphere. 2017 May;174:531-537. doi: 10.1016/j.chemosphere.2017.02.037. Epub 2017 Feb 7.
Organic sediments in aquatic ecosystems are well known sinks for nutrients, silicon, and metal(loid)s. Organic matter-consuming organisms like invertebrate shredders, grazers, and bioturbators significantly affect element fixation or remobilization by changing redox conditions or binding properties of organic sediments. Little is known about the effect of filter feeders, like the zebra mussel Dreissena polymorpha, an invasive organism in North American and European freshwater ecosystems. A laboratory batch experiment exposing D. polymorpha (∼1200 organisms per m) to organic sediment from a site contaminated with arsenic, copper, lead, and uranium revealed a significant uptake and accumulation of arsenic, copper, iron, and especially uranium both into the soft body tissues and the seashell. This is in line with previous observations of metal(loid) accumulation from biomonitoring studies. Regarding its environmental impact, D. polymorpha significantly contributed to mobilization of silicon, iron, phosphorus, arsenic, and copper and to immobilization of uranium (p < 0.001), probably driven by redox conditions, microbial activity within the gut system, or active control of element homeostasis. No net mobilization or immobilization was observed for zinc and lead, because of their low mobility at the prevailing pH of 7.5-8.5. The present results suggest that D. polymorpha can both ameliorate (nutrient mobilization, immobilization of toxicants mobile under oxic conditions) or aggravate negative effects (mobilization of toxicants mobile under reducing conditions) in ecosystems. Relating the results of the present study to observed population densities in natural freshwater ecosystems suggests a significant influence of D. polymorpha on element cycling and needs to be considered in future studies.
水生生态系统中的有机沉积物是众所周知的营养物质、硅和金属（类金属）的汇。像无脊椎动物碎食者、食草动物和生物扰动者等消耗有机物质的生物，通过改变氧化还原条件或有机沉积物的结合特性，显著影响元素的固定或再迁移。对于滤食性动物的影响，如斑马贻贝（Dreissena polymorpha），一种在北美和欧洲淡水生态系统中的入侵生物，人们了解甚少。一项实验室批量实验将斑马贻贝（每立方米约1200个个体）暴露于受砷、铜、铅和铀污染场地的有机沉积物中，结果显示砷、铜、铁，尤其是铀大量被吸收并积累到软体组织和贝壳中。这与之前生物监测研究中关于金属（类金属）积累的观察结果一致。关于其环境影响，斑马贻贝显著促进了硅、铁、磷、砷和铜的迁移，并使铀固定（p < 0.001），这可能是由氧化还原条件、肠道系统内的微生物活动或元素内稳态的主动控制驱动的。由于锌和铅在7.5 - 8.5的当前pH值下迁移率较低，未观察到它们的净迁移或固定。目前的结果表明，斑马贻贝在生态系统中既能改善（营养物质迁移、在有氧条件下可移动毒物的固定）也能加剧负面影响（在还原条件下可移动毒物的迁移）。将本研究结果与天然淡水生态系统中观察到的种群密度相关联，表明斑马贻贝对元素循环有显著影响，这在未来研究中需要加以考虑。
