Kuroshio Biological Research Foundation 560 Nishidomari, Otsuki, Kochi, 788-0333, Japan.
Ecol Evol. 2012 Nov;2(11):2854-65. doi: 10.1002/ece3.391. Epub 2012 Oct 12.
To assess distributional shifts of species in response to recent warming, historical distribution records are the most requisite information. The surface seawater temperature (SST) of Kochi Prefecture, southwestern Japan on the western North Pacific, has significantly risen, being warmed by the Kuroshio Current. Past distributional records of subtidal canopy-forming seaweeds (Laminariales and Fucales) exist at about 10-year intervals from the 1970s, along with detailed SST datasets at several sites along Kochi's >700 km coastline. In order to provide a clear picture of distributional shifts of coastal marine organisms in response to warming SST, we observed the present distribution of seaweeds and analyzed the SST datasets to estimate spatiotemporal SST trends in this coastal region. We present a large increase of 0.3°C/decade in the annual mean SST of this area over the past 40 years. Furthermore, a comparison of the previous and present distributions clearly showed the contraction of temperate species' distributional ranges and expansion of tropical species' distributional ranges in the seaweeds. Although the main temperate kelp Ecklonia (Laminariales) had expanded their distribution during periods of cooler SST, they subsequently declined as the SST warmed. Notably, the warmest SST of the 1997-98 El Niño Southern Oscillation event was the most likely cause of a widespread destruction of the kelp populations; no recovery was found even in the present survey at the formerly habitable sites where warm SSTs have been maintained. Temperate Sargassum spp. (Fucales) that dominated widely in the 1970s also declined in accordance with recent warming SSTs. In contrast, the tropical species, S. ilicifolium, has gradually expanded its distribution to become the most conspicuously dominant among the present observations. Thermal gradients, mainly driven by the warming Kuroshio Current, are presented as an explanation for the successive changes in both temperate and tropical species' distributions.
为了评估物种对近期变暖的分布变化响应，历史分布记录是最必要的信息。日本西南部的高知县位于西北太平洋的黑潮上，其表层海水温度（SST）显著升高。过去，在该县 700 多公里长的海岸线上，每隔 10 年左右就会有关于潮下带冠层海藻（Laminariales 和 Fucales）的详细分布记录，同时还有几个地点的详细 SST 数据集。为了清晰地了解沿海海洋生物对变暖的 SST 的分布变化，我们观察了海藻的当前分布，并分析了 SST 数据集，以估计该沿海地区的时空 SST 趋势。我们发现，在过去的 40 年里，该地区的年平均 SST 以每十年 0.3°C 的速度上升。此外，将之前和现在的分布进行比较，清楚地表明了温带物种的分布范围缩小，热带物种的分布范围扩大。虽然主要的温带大型褐藻（Laminariales）在 SST 较冷的时期扩大了其分布范围，但随着 SST 的变暖，它们的分布范围随后又缩小了。值得注意的是，1997-98 年厄尔尼诺南方涛动事件中最暖的 SST 极有可能是大规模破坏大型褐藻种群的原因；即使在目前的调查中，在曾经适宜的温暖 SST 保持的地方也没有发现恢复。在 20 世纪 70 年代广泛占主导地位的温带马尾藻（Fucales）也随着最近变暖的 SST 而减少。相比之下，热带物种 S. ilicifolium 的分布逐渐扩大，成为目前观察到的最显著的优势种。主要由变暖的黑潮驱动的温度梯度被认为是温带和热带物种分布变化的原因。
