Contango Strategies Limited , 15-410 Downey Road, Saskatoon, SK S7N 4N1, Canada.
Toxicology Center, University of Saskatchewan , 44 Campus Drive, Saskatoon, SK S7N 5B3, Canada.
Environ Sci Technol. 2017 Jul 5;51(13):7532-7541. doi: 10.1021/acs.est.7b01001. Epub 2017 Jun 14.
A major source of uncertainty in predicting selenium (Se) distribution in aquatic food webs lies in the enrichment factor (EF), the ratio of Se bioconcentration in primary producers and microorganisms relative to the concentration of Se in the surrounding water. It has been well demonstrated that EFs can vary dramatically among individual algal taxa, but data are lacking regarding the influence of periphyton community composition on EFs for a given geochemical form of Se. Therefore, the goals of this study were first to assess whether different periphyton communities could be established in aquaria with the same starting inoculum using different light and nutrient regimes, and second, to determine if the periphyton assemblage composition influences the uptake of waterborne Se (as selenite) and subsequent Se transfer to a model macroinvertebrate primary consumer. Periphyton biofilms were grown in aquaria containing filtered pond water (from Saskatoon, SK) spiked with approximately 20 μg Se/L (mean measured concentration 21.0 ± 1.2 μg Se/L), added as selenite. Five different light and nutrient regimes were applied to the aquaria (three replicates per treatment) to influence biofilm community development. After 6 weeks of biofilm maturation, 40 to 80 immature cultured snails (Stagnicola elodes) were added to each aquarium. The bacterial and algal members of the periphyton community were characterized by targeted metagenomic analyses before and after addition of snails to ensure the snails themselves did not significantly alter the biofilm community. Samples were collected for Se analysis of water, periphyton, and whole-body snail. The nutrient and light treatments resulted in substantially different compositions of the periphytic biofilms, with each being relatively consistent across replicates and throughout the study. Although the aqueous concentration of dissolved Se administered to treatments was constant, uptake by the different periphytic biofilms differed significantly. Both the low-light (61.8 ± 12.1 μg Se/g d.w.) and high-light (30.5 ± 4.7 μg Se/g d.w.) biofilms, which were found to have high proportions of cyanobacteria, contained statistically higher concentrations of Se relative to the other treatments. Furthermore, the concentration of Se in bulk periphyton was predictive of Se bioaccumulation in grazing snails but as an inverse relationship, opposite to expectations. The trophic transfer factor was inversely correlated with periphyton enrichment factor (r = -0.841). A number of different bacterial and algal taxa were correlated (either positively or negatively) with Se accumulation in periphyton biofilm and snails. Recent advancements in genetic methods make it possible to conduct detailed characterization of periphyton assemblages and begin to understand the influence that periphyton composition has on Se biodynamics in aquatic systems.
硒（Se）在水生食物网中分布的预测存在很大的不确定性，主要原因在于富化因子（EF），即初级生产者和微生物中硒的生物浓缩与周围水中硒浓度的比值。已经充分证明，EF 在单个藻类分类群之间可能有很大差异，但关于给定硒地球化学形态的底栖生物群落组成对 EF 的影响的数据却缺乏。因此，本研究的目标首先是评估是否可以使用不同的光照和营养条件在具有相同起始接种物的水族箱中建立不同的底栖生物群落，其次是确定底栖生物群落组成是否会影响水载硒（亚硒酸盐）的吸收以及随后向模型大型无脊椎初级消费者的硒转移。在含有过滤池塘水（来自萨斯卡通，SK）的水族箱中生长底栖生物生物膜，并用约 20μg Se/L（平均实测浓度 21.0 ± 1.2μg Se/L）添加亚硒酸盐。应用五种不同的光照和营养条件（每种处理三个重复）来影响生物膜群落的发展。在生物膜成熟 6 周后，将 40 到 80 只未成熟的养殖蜗牛（Stagnicola elodes）添加到每个水族箱中。在向水族箱中添加蜗牛之前和之后，通过靶向宏基因组分析来描述底栖生物群落的细菌和藻类成员，以确保蜗牛本身不会显著改变生物膜群落。收集水样、底栖生物和整只蜗牛进行硒分析。养分和光照处理导致底栖生物生物膜的组成有很大差异，每种处理在整个研究过程中在重复之间都相对一致。尽管施用到处理中的溶解态硒的水相浓度保持不变，但不同底栖生物生物膜的吸收却有很大差异。低光（61.8 ± 12.1μg Se/g d.w.）和高光（30.5 ± 4.7μg Se/g d.w.）生物膜的硒浓度均高于其他处理，这两种生物膜都发现含有相对较高比例的蓝细菌。此外，底栖生物中硒的浓度可以预测摄食蜗牛的硒生物累积，但呈反比关系，与预期相反。营养转移因子与底栖生物富化因子呈负相关（r = -0.841）。许多不同的细菌和藻类分类群与底栖生物生物膜和蜗牛中的硒积累呈正相关（或负相关）。遗传方法的最新进展使得对底栖生物群落进行详细特征描述并开始理解底栖生物组成对水生系统中硒生物动力学的影响成为可能。
