Consumers mediate the effects of experimental ocean acidification and warming on primary producers
Consumers mediate the effects of experimental ocean acidification and warming on primary producers
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DOI：
10.1073/pnas.1303797110
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发表时间：
2013-05-21
影响因子：
11.1
通讯作者：
Sundback, Kristina
中科院分区：
文献类型：
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作者：
Alsterberg, Christian;Eklof, Johan S.;Sundback, Kristina
众所周知，海洋酸化会对海洋生物产生深远的影响。然而，我们对海洋酸化的直接和间接影响知之甚少，也不知道这些影响如何与气候变暖和消费压力下降等环境变化的其他特征相互作用。在这项研究中，我们测试了消费者（无脊椎中食草动物）的存在是否影响海洋酸化和变暖对底栖微藻的交互作用。通过方差分析评估，酸化和变暖对底栖微藻生物量和产量的净影响相对较弱，与食草动物的存在无关。然而，使用结构方程模型将这些净效应划分为直接效应和间接效应，揭示了几种强烈的关系。在没有食草动物的情况下，底栖微藻受到与沉积物相关的微藻食草动物和大藻遮荫的负向和间接影响，但受到酸化和变暖的直接和正向影响。间接效应和直接效应相结合，没有产生净效应或净效应很弱。在有食草动物存在的情况下，几乎所有的直接和间接气候影响都不显著。我们的分析强调(1)气候变化的间接影响可能至少与直接影响一样强烈；(2)食草动物在调节这些影响方面至关重要；(3)海洋酸化的影响可能只有通过间接影响和与其他变量（如变暖）结合才能显现出来。这些发现突出了实验设计和统计分析的重要性，使我们能够分离和量化多种气候变量对自然群落的直接和间接影响。
It is well known that ocean acidification can have profound impacts on marine organisms. However, we know little about the direct and indirect effects of ocean acidification and also how these effects interact with other features of environmental change such as warming and declining consumer pressure. In this study, we tested whether the presence of consumers (invertebrate mesograzers) influenced the interactive effects of ocean acidification and warming on benthic microalgae in a seagrass community mesocosm experiment. Net effects of acidification and warming on benthic microalgal biomass and production, as assessed by analysis of variance, were relatively weak regardless of grazer presence. However, partitioning these net effects into direct and indirect effects using structural equation modeling revealed several strong relationships. In the absence of grazers, benthic microalgae were negatively and indirectly affected by sediment-associated microalgal grazers and macroalgal shading, but directly and positively affected by acidification and warming. Combining indirect and direct effects yielded no or weak net effects. In the presence of grazers, almost all direct and indirect climate effects were nonsignificant. Our analyses highlight that (i) indirect effects of climate change may be at least as strong as direct effects, (ii) grazers are crucial in mediating these effects, and (iii) effects of ocean acidification may be apparent only through indirect effects and in combination with other variables (e. g., warming). These findings highlight the importance of experimental designs and statistical analyses that allow us to separate and quantify the direct and indirect effects of multiple climate variables on natural communities.