Data_Sheet_1_Imprint of Climate Change on Pan-Arctic Marine Vegetation.PDF

The Arctic climate is changing rapidly. The warming and resultant longer open water periods suggest a potential for expansion of marine vegetation along the vast Arctic coastline. We compiled and reviewed the scattered time series on Arctic marine vegetation and explored trends for macroalgae and eelgrass (Zostera marina). We identified a total of 38 sites, distributed between Arctic coastal regions in Alaska, Canada, Greenland, Iceland, Norway/Svalbard, and Russia, having time series extending into the 21st Century. The majority of these exhibited increase in abundance, productivity or species richness, and/or expansion of geographical distribution limits, several time series showed no significant trend. Only four time series displayed a negative trend, largely due to urchin grazing or increased turbidity. Overall, the observations support with medium confidence (i.e., 5–8 in 10 chance of being correct, adopting the IPCC confidence scale) the prediction that macrophytes are expanding in the Arctic. Species distribution modeling was challenged by limited observations and lack of information on substrate, but suggested a current (2000–2017) potential pan-Arctic macroalgal distribution area of 820.000 km2 (145.000 km2 intertidal, 675.000 km2 subtidal), representing an increase of about 30% for subtidal- and 6% for intertidal macroalgae since 1940–1950, and associated polar migration rates averaging 18–23 km decade–1. Adjusting the potential macroalgal distribution area by the fraction of shores represented by cliffs halves the estimate (412,634 km2). Warming and reduced sea ice cover along the Arctic coastlines are expected to stimulate further expansion of marine vegetation from boreal latitudes. The changes likely affect the functioning of coastal Arctic ecosystems because of the vegetation’s roles as habitat, and for carbon and nutrient cycling and storage. We encourage a pan-Arctic science- and management agenda to incorporate marine vegetation into a coherent understanding of Arctic changes by quantifying distribution and status beyond the scattered studies now available to develop sustainable management strategies for these important ecosystems.

北极气候正经历快速变化。气候变暖及由此引发的无冰水域时长延长，预示着广袤的北极沿岸海域存在海洋植被扩张的潜在可能。我们整理并评估了零散分布的北极海洋植被时间序列数据，针对大型藻类（macroalgae）和鳗草（Zostera marina）的变化趋势展开了系统探究。本次研究共确认38处监测点位，分布于阿拉斯加、加拿大、格陵兰、冰岛、挪威/斯瓦尔巴群岛及俄罗斯的北极沿岸区域，相关时间序列数据的观测时长可延伸至21世纪。其中绝大多数点位的植被丰度、生产力或物种丰富度均有所提升，地理分布范围亦出现扩张；部分时间序列未呈现显著变化趋势，仅有4组序列表现出负向趋势，这主要归因于海胆啃食或水体浊度升高。总体而言，基于中等置信度（即采用政府间气候变化专门委员会（IPCC）的置信度标尺，正确概率为5~8成），现有观测数据支持“北极大型水生植物（macrophytes）正处于扩张态势”的预测。物种分布建模受限于观测数据不足与底质信息缺失，但模型估算出2000—2017年间北极全域大型藻类的潜在分布总面积为82.0万平方千米（其中潮间带14.5万平方千米，潮下带67.5万平方千米）；相较于1940—1950年，潮下带大型藻类的潜在分布面积增长约30%，潮间带则增长约6%，且相关极地迁移速率平均为每十年18~23千米。若将沿岸峭壁占比的系数纳入潜在大型藻类分布面积的校正计算，该估算值将减半至412634平方千米。北极沿岸的气候变暖和海冰覆盖减少，预计将进一步推动源自寒带纬度的海洋植被扩张。此类变化或对北极沿岸生态系统的功能产生显著影响，原因在于海洋植被兼具栖息地功能，同时参与碳循环、养分循环与碳储存过程。我们呼吁构建北极全域的科学研究与管理议程，通过量化当前零散研究覆盖范围之外的海洋植被分布与现状，将海洋植被纳入北极变化的统一认知框架，从而为这些重要生态系统制定可持续的管理策略。