Can we detect changes in Arctic ecosystems?

生态系统是相互作用的生物群落，也与环境相互作用。它们通常被认为是食物网或食物链，它描述了不同生物之间的相互作用以及它们的相对等级，即营养地位。海洋生态系统提供关键服务，如营养、气候控制、营养循环支持，并对某些社区具有文化意义。因此，了解环境变化如何重塑生态系统以管理气候变化的影响是非常重要的。北冰洋已经受到气候变化的严重影响。它的变暖速度比其他任何海洋区域都要快，而且由于它吸收了化石燃料的排放物，它正在逐渐酸化。北极海冰正以每十年10%的速度减少。这影响了从浮游生物到哺乳动物等生物的海冰栖息地的可用性，并改变了海洋环境。最后，北极受到来自太平洋和大西洋的水运动的大小变化以及这些水的组成的影响。因此，北极生态系统正在受到多种同时发生的压力因素的影响，必须适应。为了了解北极生态系统将如何在多种压力因素的影响下进化，评估持续变化的影响至关重要。通常，这些问题都是通过研究一个地方的特定生态系统并记录食物链的各种组成部分来解决的。然而，北极是多样化的，有各种各样的环境，对独特的压力源有不同的反应。我们需要一种新的方法，能够在十年的时间尺度上从泛北极的角度提供北极生态系统的信息。为了有效地监测泛北极生态系统的变化，需要关注关键生态系统成分的示踪剂，并提供生态系统结构的定量信息，为生态系统服务的管理和保护提供信息。我们的目标是应对这一挑战。我们将同时关注由海洋浮游植物活动控制的食物链底部，以及北极主要食肉动物——格陵兰海豹和环斑海豹。海豹是监测食物网的最佳人选，因为它们的泛北极分布和觅食行为，这意味着它们暴露在不断变化的环境中。氮和碳稳定同位素通常用于检查生态系统，因为它们在食物链的营养转移过程中被修改。因此，他们可以量化海豹的营养地位和食物链长度，这是生态系统结构的关键决定因素。然而，在这种情况下至关重要的是食物网基础的同位素值，即所谓的同位素景观，它本身受到一系列环境特征的影响，并在空间和时间上波动。同样，由于迁移模式的改变，海豹本身可能以不同等尺度的相似猎物为食，这将影响稳定同位素对生态系统结构的解释。这些都是使用稳定同位素的主要挑战。我们将把稳定同位素与食物网的新型示踪剂联系起来，即生物标志物。当将这些示踪物与观测到的变化等温线和海豹觅食数据进行比较时，它们可以通过量化海豹的营养地位和整个食物链长度来监测北极生态系统。通过一系列观测平台，我们的新食物网示踪剂将与北极等高景观和海豹行为的空间和季节趋势机械地联系起来。然后，通过将北极盆地周围的历史观测与最先进的海洋和海豹种群模型相结合，我们可以量化北极生态系统过去和未来的变化。这将提供有关北极生态系统过去变化的信息，但也将建立一种可用于监测未来变化并有助于管理和保护生态系统服务的方法

Ecosystems are communities of organisms that interact with each other and their environment. They are often considered in terms of food webs or chains, which describe the interactions between different organisms and their relative hierarchies, known as trophic position. Ocean ecosystems provide key services, such as nutrition, control of climate, support of nutrient cycling and have cultural significance for certain communities. It is thus important that we understand how changes to the environment reshape ecosystems in order to manage climate change impacts.The Arctic Ocean is already being heavily impacted by climate change. It is warming faster than any other ocean region and as it absorbs fossil fuel emissions, it is gradually acidifying. Arctic sea ice is declining by 10% per decade. This affects the availability of sea ice habitats for organisms from plankton to mammals and modifies the ocean environment. Finally, the Arctic is affected by changes in the magnitude of water movement to and from the Pacific and Atlantic Oceans and composition of these waters. Thus Arctic ecosystems are being impacted by multiple concurrent stressors and must adapt. To understand how Arctic ecosystems will evolve in response to multiple stressors, it is crucial to evaluate the effects of on going change. Often these questions are tackled by studies that focus on a specific ecosystem in one location and document the various components of the food chain. However the Arctic is diverse, with a wide range of environments that are responding to unique stressors differently. We require a new approach that can provide information on Arctic ecosystems from a pan-Arctic perspective over decadal timescales. To effectively monitor changes to pan-Arctic ecosystems requires tracers that focus on key ecosystem components and provide quantitative information on ecosystem structure, providing information for management and conservation of ecosystem services. Our goal is to respond to this challenge. We will focus simultaneously on the base of the food chain, controlled by the activity of marine phytoplankton, and key Arctic predators, harp and ringed seals. Seals are excellent candidates to monitor the food web due to their pan-Arctic distribution and foraging behaviour, which means they are exposed to the changing environment. Nitrogen and carbon stable isotopes are often used to examine ecosystems as they are modified during trophic transfer up the food chain. Hence, they can quantify seal trophic position and food chain length, key determinants of ecosystem structure. Crucial in this context however is the isotope value of the base of the food web, known as the isoscape, which is itself affected by a range of environmental characteristics and fluctuates in space and time. Equally, by virtue of changing migration patterns, seals themselves may feed on similar prey in different isoscapes, which would affect the interpretation of ecosystem structure from stable isotopes. These are the major challenges in using stable isotopes.We will link stable isotopes to novel tracers of the food web, known as biomarkers. When these tracers are compared against observations of the shifting isoscape and data on seal foraging, they permit seals to be used to monitor the Arctic ecosystem by quantifying their trophic position and overall food chain length. Via a range of observational platforms, our new food web tracers will be mechanistically linked to the spatial and seasonal trends in the Arctic isoscape and seal behaviour. By then combining historical observations from around the Arctic basin with state of the art ocean and seal population modelling, we can quantify past and future changes in Arctic ecosystems. This will provide information on past changes to Arctic ecosystems, but also put in place an approach that can be used to monitor future changes and aid in the management and conservation of ecosystem services