Univ Rennes 1, CNRS, ECOBIO - UMR 6553, F-35000 Rennes, France.
Univ Rennes 1, CNRS, ECOBIO - UMR 6553, F-35000 Rennes, France.
Harmful Algae. 2020 Apr;94:101803. doi: 10.1016/j.hal.2020.101803. Epub 2020 Apr 25.
Due to eutrophication, freshwater ecosystems frequently experience cyanobacterial blooms, many of which produce bioactive metabolites that can affect vertebrates and invertebrates life traits. Zooplankton are able to develop tolerance as a physiological response to cyanobacteria and their bioactive compounds, however, this comes with energetic cost that in turn influence Daphnia life traits and may impair populations. Vice versa, it has been suggested that Daphnia are able to reduce cyanobacterial dominance until a certain cyanobacterial density; it remains unclear whether Daphnia metabolites alone influence the physiological state and bioactive metabolites production of cyanobacteria. Hence, this study investigates mutual physiological reactions of toxic Microcystis aeruginosa PCC7806 and Daphnia magna. We hypothesize that a) the presence of D. magna will negatively affect growth, increase stress response and metabolites production in M. aeruginosa PCC7806 and b) the presence of M. aeruginosa PCC7806 will negatively affect physiological responses and life traits in D. magna. In order to test these hypotheses experiments were conducted in a specially designed co-culture chamber that allows exchange of the metabolites without direct contact. A clear mutual impact was evidenced. Cyanobacterial metabolites reduced survival of D. magna and decreased oxidative stress enzyme activity. Simultaneously, presence of D. magna did not affect photosynthetic activity. However, ROS increase and tendencies in cell density decrease were observed on the same day, suggesting possible energy allocation towards anti-oxidative stress enzymes, or other protection mechanisms against Daphnia infochemicals, as the strain managed to recover. Elevated concentration of intracellular and overall extracellular microcystin MC-LR, as well as intracellular concentrations of aerucyclamide A and D in the presence of Daphnia, indicating a potential protective or anti-grazing function. However, more research is needed to confirm these findings.
由于富营养化，淡水生态系统经常发生蓝藻水华，其中许多产生生物活性代谢物，会影响脊椎动物和无脊椎动物的生命特征。浮游动物能够通过生理反应来耐受蓝藻及其生物活性化合物，然而，这会带来能量成本，从而影响水蚤的生命特征，并可能损害种群。相反，有人认为，水蚤能够降低蓝藻的优势，直到达到一定的蓝藻密度；目前尚不清楚水蚤的代谢物是否单独影响蓝藻的生理状态和生物活性代谢物的产生。因此，本研究调查了有毒微囊藻 PCC7806 和大型溞之间的相互生理反应。我们假设：a）大型溞的存在将对微囊藻 PCC7806 的生长产生负面影响，增加其应激反应和代谢物的产生；b）微囊藻 PCC7806 的存在将对大型溞的生理反应和生命特征产生负面影响。为了验证这些假设，在专门设计的共培养室中进行了实验，该共培养室允许代谢物的交换而无需直接接触。结果证明存在明显的相互影响。蓝藻的代谢物降低了大型溞的存活率，并降低了氧化应激酶的活性。同时，大型溞的存在并不影响光合作用活性。然而，在同一天观察到 ROS 增加和细胞密度下降的趋势，这表明可能将能量分配给抗氧化应激酶，或其他针对水蚤信息素的保护机制，因为该菌株设法恢复了。在存在大型溞的情况下，细胞内和总体细胞外微囊藻 MC-LR 以及细胞内aerucyclamide A 和 D 的浓度升高，表明可能具有保护或抗放牧功能。然而，需要进一步的研究来证实这些发现。
