Long-term empirical evidence of ocean warming leading to tropicalization of fish communities, increased herbivory, and loss of kelp
Long-term empirical evidence of ocean warming leading to tropicalization of fish communities, increased herbivory, and loss of kelp
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DOI：
10.1073/pnas.1610725113
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发表时间：
2016-11
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通讯作者：
A. Vergés;C. Doropoulos;H. Malcolm;Mathew Skye;Marina Garcia-Pizá;E. Marzinelli;A. Campbell;E. Ballesteros;A. Hoey;A. Vila‐Concejo;Y. Bozec;P. Steinberg
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作者：
A. Vergés;C. Doropoulos;H. Malcolm;Mathew Skye;Marina Garcia-Pizá;E. Marzinelli;A. Campbell;E. Ballesteros;A. Hoey;A. Vila‐Concejo;Y. Bozec;P. Steinberg
大多数关于全球变暖影响的研究都集中在气候变化的直接生理影响上。然而，全球变暖正在改变许多物种的分布，并导致以前分离的物种之间的新的相互作用，有可能改变整个生态群落。这项研究表明，随着海洋变暖，暖水物种比例的增加（“热带化”）正在增加海带森林中的鱼类食草性，导致其减少，随后持续处于交替的“无海带”状态。这些热带和亚热带食草动物正在越来越多地影响全球温带藻类群落，对这些标志性生态系统的长期稳定性及其提供的宝贵服务构成重大威胁。气候变化对生态群落的一些最深刻的影响是由于物种相互作用的改变，而不是环境条件变化的直接生理影响。然而，受气候影响的社区内物种相互作用的历史变化的经验证据是罕见的，很难获得。在这里，我们证明了最近消失的关键栖息地形成海带森林从澳大利亚东部的热带-温带过渡带变暖。使用包含0.6 °C变暖期的10年视频数据集，我们展示了随着海带逐渐减少然后消失，食草动物是如何增加的。与此同时，海藻原本丰富但随后消失的地方的鱼类群落越来越多地被热带食草动物所统治。饲养试验确定了两个关键的热带/亚热带食草动物，在这些网站的几个小时内消耗移植海带。也有一个明显的增加，在丰富的鱼类消费石生藻类，高得多的叮咬率，这组在网站上没有海带，这表明这些鱼类在保持珊瑚礁在无海带的状态，通过去除海带新兵的关键作用。海带丰度的变化与十年来的海水温度没有直接关系，也与其他测量的非生物因素（营养物质和风暴）无关。我们的研究结果表明，变暖介导的鱼类食草性增加对澳大利亚以海带为主的生态系统构成了重大威胁，并可能对全球造成威胁。
Significance Most studies of the impact of global warming focus on the direct physiological impacts of climate change. However, global warming is shifting the distribution of many species and leading to novel interactions between previously separated species that have the potential to transform entire ecological communities. This study shows that an increase in the proportion of warmwater species (“tropicalization”) as oceans warm is increasing fish herbivory in kelp forests, contributing to their decline and subsequent persistence in alternate “kelp-free” states. These tropical and subtropical herbivores are increasingly impacting temperate algal communities worldwide, posing a significant threat to the long-term stability of these iconic ecosystems and the valuable services they provide. Some of the most profound effects of climate change on ecological communities are due to alterations in species interactions rather than direct physiological effects of changing environmental conditions. Empirical evidence of historical changes in species interactions within climate-impacted communities is, however, rare and difficult to obtain. Here, we demonstrate the recent disappearance of key habitat-forming kelp forests from a warming tropical–temperate transition zone in eastern Australia. Using a 10-y video dataset encompassing a 0.6 °C warming period, we show how herbivory increased as kelp gradually declined and then disappeared. Concurrently, fish communities from sites where kelp was originally abundant but subsequently disappeared became increasingly dominated by tropical herbivores. Feeding assays identified two key tropical/subtropical herbivores that consumed transplanted kelp within hours at these sites. There was also a distinct increase in the abundance of fishes that consume epilithic algae, and much higher bite rates by this group at sites without kelp, suggesting a key role for these fishes in maintaining reefs in kelp-free states by removing kelp recruits. Changes in kelp abundance showed no direct relationship to seawater temperatures over the decade and were also unrelated to other measured abiotic factors (nutrients and storms). Our results show that warming-mediated increases in fish herbivory pose a significant threat to kelp-dominated ecosystems in Australia and, potentially, globally.