Netherlands Institute of Ecology, Department of Aquatic Ecology, 6700 AB Wageningen, The Netherlands.
Aquat Toxicol. 2011 Aug;104(3-4):230-42. doi: 10.1016/j.aquatox.2011.05.001. Epub 2011 May 6.
Metastudies have found no consistent effects of the cyanobacterial toxin microcystin on Daphnia, and there are discrepancies between field observations and experiments. Confounding factors include absence or presence of alternative high quality food or the presence of bioactive compounds, other than microcystins in cyanobacteria. Of specific interest are lipopolysaccharides (LPS) on the outer cell wall. LPS may have a number of biological effects, including reduced detoxication of microcystins in plants and animals. When grazing seston in the field, filterfeeders take up heterotrophic bacteria attached to cyanobacteria, as well as free-living bacteria. The LPS produced by heterotrophic bacteria have been shown to be much more harmful than cyanobacterial LPS. We performed two experiments in which we tested for potential synergistic effects between bacterial LPS and microcystins. Full-factorial experiments separated the main effects and interactions between (i) food quantity as well as food quality (addition of the green alga Scenedesmus), (ii) presence or absence of strains that vary in amount and composition of microcystins (microcystin free strain NIVA-CYA43, moderate microcystin producing strain NIVA-CYA140 and high microcystin producing strain PCC7820), and (iii) presence or absence of bacterial LPS on different life history traits of Daphnia galeata. We measured juvenile growth rate, age and size at first reproduction, death before first reproduction and standard carbon content of Daphnia. From the experiments we conclude that microcystin-producing Microcystis had deleterious effects on the life history of D. galeata, but especially when the availability of high quality green algal food was limited in comparison to the supply of microcystin producing strain PCC7820. In the experiment in which PCC7820 was used as microcystin-producing strain, addition of LPS lowered SCC of Daphnia, but had no effects on other life history parameters. The interaction between Microcystis strain, Microcystis concentration and LPS was highly significant in case of PCC7820, but not in case of CYA-140, indicating that the effects of LPS and its interactions with microcystin on Daphnia life history were strongly context dependent.
荟萃研究并未发现微囊藻毒素对水蚤有一致的影响，而且现场观察和实验之间存在差异。混杂因素包括是否存在替代的高质量食物，或者是否存在除微囊藻毒素以外的生物活性化合物。特别值得关注的是细胞壁上的脂多糖 (LPS)。LPS 可能具有多种生物学效应，包括降低动植物中微囊藻毒素的解毒作用。当滤食者在野外摄食悬浮物时，它们会摄取附着在蓝藻上的异养细菌以及自由生活的细菌。已经证明，异养细菌产生的 LPS 比蓝藻 LPS 危害大得多。我们进行了两项实验，以测试细菌 LPS 和微囊藻毒素之间潜在的协同效应。完全析因实验将主要效应和相互作用分开，包括：(i) 食物数量以及食物质量（添加绿藻栅藻），(ii) 存在或不存在微囊藻毒素含量和组成不同的菌株（无微囊藻毒素的 NIVA-CYA43 菌株、中等微囊藻毒素产生的 NIVA-CYA140 菌株和高微囊藻毒素产生的 PCC7820 菌株），以及 (iii) 不同生活史特征的水蚤 galeata 上存在或不存在细菌 LPS。我们测量了幼体生长率、首次繁殖时的年龄和大小、首次繁殖前的死亡以及水蚤的标准碳含量。从实验中我们得出结论，产微囊藻的微囊藻对水蚤 galeata 的生活史有有害影响，但特别是当高质量绿藻食物的供应与产微囊藻的 PCC7820 菌株的供应相比受到限制时。在使用 PCC7820 作为产微囊藻毒素菌株的实验中，LPS 的添加降低了水蚤的 SCC，但对其他生活史参数没有影响。在 PCC7820 的情况下，微囊藻菌株、微囊藻浓度和 LPS 之间的相互作用高度显著，但在 CYA-140 的情况下则不显著，这表明 LPS 及其与微囊藻毒素对水蚤生活史的相互作用强烈依赖于背景。
