Coldfish: potential benefits and risks of borealisation for fish stocks and ecosystems in a changing Arctic Ocean

北冰洋正在表现出异常的变暖和冰川融化，预计这将深刻改变共存的动物群的类型，以及动物之间和动物与人类之间相互作用的性质。特别是，非永久冰盖地区的冰盖范围一直在下降。夏季海冰的消失导致开放无冰水域的浮游生物数量增加，而冰下藻类也是北极物种的重要食物来源，随着冰盖的消退，浮游生物的数量减少了。潜在的海洋变暖也使得来自较温暖水域的物种有可能向北迁移。虽然这些外来物种一直在蓬勃发展，但一些北极本土物种的数量却在减少。其中几个物种，包括常驻北极鳕鱼和传入的大西洋鳕鱼，在渔业中很重要，这构成了社会从这些高纬度水域获得的最直接利益。北极物种具有对寒冷的适应能力，这可能在一定程度上有助于保护它们免受外来物种的侵袭，但到目前为止，我们对这些最近的变化将带来的长期生态后果知之甚少。ColdFish项目将把重点放在这些水域的鱼类上，探索它们的行为，特别是它们吃的食物的类型，如何在冰盖不同的广泛地点发生变化，以及外来物种存在的程度和其他环境方面的变化。我们将通过测量鱼类组织中碳、氮和硫的不同稳定同位素的比率来跟踪鱼类的饮食。通过比较生活在不同群落和不同物理条件下的鱼类种群中发现的不同同位素组成的范围，我们可以回答关于北极生态系统当前和未来状态的一系列重要问题。例如，生态系统对变化的敏感性取决于有多少不同的物种扮演着类似的生态角色，从而能够在某些物种丧失时进行补偿。我们将通过测量种群间同位素组成的重叠程度来确定鱼饲料中这种所谓的“冗余”的程度。我们将测量碳从地表水转移到海床的效率，以及在冰盖反差和鱼类群落不同的地区这一变化情况。我们还将研究外来物种在向北迁移到更冷的水域时有何反应，它们的摄食习性和新陈代谢是否因此发生变化，以及外来物种是否可能与北极本土物种直接竞争。ColdFish研究人员带来了北极生物地球化学、极地鱼类生物学、海洋生态学和稳定同位素生态学方面的专业知识，这种方法和途径的混合将有助于提供新的见解。我们的项目建立在北冰洋巴伦支海地区生态研究的基础上，并受益于与我们在挪威的项目合作伙伴协调的广泛生态调查的密切结合。

The Arctic Ocean is exhibiting exceptional levels of warming and ice loss, which are expected to profoundly change the types of animal communities that coexist and the nature of interactions between animals and between animals and humans. In particular, the extent of ice cover in regions that are not permanently ice covered has been declining. The loss of summer sea ice has led to an increase in plankton in open ice free waters, while under-ice algae which are also important food-sources to Arctic species have declined with the retreating ice cover. The underlying marine warming is also making it possible for species from warmer waters to move northward. While these incomers have been flourishing, some native Arctic species have declined in abundance. Several of these species including resident Arctic cod and the incoming Atlantic cod are important in fisheries, which constitute the most direct benefit that society derives from these high-latitude waters. The Arctic species have adaptations to cold that may help protect them from the incoming species to some extent, but to date we have very few ideas of what the long-term ecological outcomes of these recent changes will be. The Coldfish project will focus on the fish of these waters, exploring how their behaviour, specifically the types of food they eat, changes across a wide range of sites which vary in ice cover, the extent to which the incoming species are present and in other environmental respects. We will track fish diets by measuring the ratio of different stable isotopes of carbon, nitrogen and sulfur in their tissues. By comparing the range of different isotopic compositions found in populations of fishes living in different communities and under different physical conditions, we can answer a series of important questions about the current and future states of Arctic ecosystems.For instance, the sensitivity of an ecosystem to change depends on how many different species perform similar ecological roles and are therefore able to compensate if some species are lost. We will determine the extent of this so-called 'redundancy' in terms of fish diets by measuring the degree of overlap in isotopic compositions between populations. We will measure how effectively carbon is transferred from surface waters to the seabed, and how this varies in regions of contrasting ice cover and differing fish communities. We will also study how the incoming species are responding as they move northwards into colder waters, whether their feeding habits and metabolism are changing as a result, and whether the incoming species are likely to compete directly with those native to the Arctic. Coldfish investigators bring a mix of expertise in arctic biogeochemistry, polar fish biology, marine ecology and stable isotope ecology, and this blend of methods and approaches will help deliver new insights. Our project builds on ecological study in the Barents Sea sector of the Arctic Ocean, and benefits from close integration with extensive ecological surveys co-ordinated by our project partners in Norway.