Experiments examining mercury (Hg) toxicity in Daphnia are usually conducted in highly standardized conditions that prevent the formation of biofilm. Although such standardization has many advantages, extrapolation of results to natural conditions and inference of ecological effects is challenging. This is especially true since biofilms can accumulate metals/metalloids and play a key role in their transfer to higher trophic level organisms. In this study, we experimentally tested the effects of spontaneously appearing biofilm in Daphnia cultures on accumulation of Hg and its natural antagonist selenium (Se) in Daphnia magna. We added Hg (in the form of mercury (II) chloride) at two concentrations (0.2 µg/L and 2 µg/L) to experimental microcosms and measured the uptake of Hg and Se by D. magna in the presence and absence of biofilm. To test for consistent and replicable results, we ran two identical experimental sets one week apart. Biofilm presence significantly reduced the accumulation of Hg, while increasing the tissue Se content in D. magna, and these findings were reproducible across experimental sets. These findings indicate that highly standardized tests may not be adequate to predict the bioaccumulation and potential toxicity of metals/metalloids under natural conditions.

中文翻译：

---

水生生物膜中生长的生物膜影响水蚤中汞和硒的积累。

检查水蚤中汞（Hg）毒性的实验通常在高度标准化的条件下进行，以防止形成生物膜。尽管这种标准化具有许多优点，但是将结果外推到自然条件和推断生态效应是具有挑战性的。这是特别正确的，因为生物膜可以积累金属/类金属，并在其转移到更高营养级别的生物中起关键作用。在这项研究中，我们实验性地测试了水蚤文化中自发出现的生物膜对水蚤中汞及其天然拮抗硒（Se）积累的影响。我们将两种浓度（0.2 µg / L和2 µg / L）的Hg（以氯化汞（II）的形式）添加到实验微观世界中，并在存在和不存在生物膜的情况下测量了D. magna对Hg和Se的吸收。 。为了测试一致且可复制的结果，我们每星期进行两次相同的实验。生物膜的存在显着减少了汞的积累，同时增加了大果线虫中的组织硒含量，并且这些发现在实验组之间是可重复的。这些发现表明，高度标准化的测试可能不足以预测金属/类金属在自然条件下的生物蓄积性和潜在毒性。