Ocean Acidification Impacts on Sea-Surface Biology, Biogeochemistry and Climate

化石燃料的燃烧正在向地球大气层释放大量额外的二氧化碳。其中大部分会留在大气中，提高二氧化碳水平，但也有很多会在一段时间后离开大气，要么被隔离在树木和植物中，要么被海洋吸收。二氧化碳留在大气中是一种温室气体，导致全球变暖；进入海洋的二氧化碳使其更加酸性，在收集时间序列数据的各个地点的观测记录中可以看到海水正在发生的酸化。人们大多对海洋酸化引起的海水化学变化了如指掌，不存在争议。鲜为人知的是，不断变化的化学物质将对海洋生物和生态系统、对海洋中的生物地球化学循环以及海洋如何与大气相互作用影响气候产生影响。我们将着眼于研究这些问题，即世界海洋的表层水域和海洋中的生命将如何应对海洋酸化。我们对生物影响的大多数了解，以及目前对对海洋生物影响的担忧的来源，都来自于实验研究，在这些实验中，单个生物(例如单一珊瑚)或单一特定种群(例如浮游生物培养)在实验室实验中受到了高二氧化碳(和相关的低pH值)的影响。这些实验室实验的优点是可以在可控的条件下进行，在这种条件下，除了二氧化碳的变化外，一切都可以保持不变。因此，如果观察到了反应，那么原因就很清楚了。然而，实验室研究也有局限性。例如，生物体没有时间进行进化适应，物种组成不可能从更敏感的形式转向更耐酸的形式，这在自然界中可能会发生。另一个缺点是在大多数实验中没有食物网的复杂性，因此没有竞争、捕食和其他决定生物在自然环境中生存能力的相互作用。我们寻求通过收集对自然发生的生态系统的更多观察来推进海洋酸化的研究，这些生态系统位于海水化学成分自然更酸性的地方，和/或海水自然含有更多碳的地方，以及不那么酸性和/或含有更多普通碳的地方。通过对比这两组观察，我们将更好地理解酸化如何影响生活在自然环境中的有机体，在组装重新排序和进化适应有时间发挥之后。计划中的大部分工作将分三次进行，前往海水碳和pH梯度较强的地方：北冰洋、不列颠群岛周围和南大洋。在进行观测的同时，我们还将进行大量的实验，在这些实验中，我们将把大量的天然海水从海洋表面带入船甲板上的容器中，以及其中包含的任何生命，并使它们承受更高的二氧化碳和其他应激因素。随着海水变得更加酸性，我们将监测这些自然浮游生物群落发生的变化(包括生物地球化学和与气候有关的过程)。这类研究的一个主要优势是纳入了实验室实验中难以或不可能捕捉到的自然环境的变异性和复杂性。因此，在自然群落的这些实验中测量的反应可能更准确地代表了未来表层海洋对海洋酸化的反应。为了执行这项实验/观测工作计划，我们在全英国范围内组建了一支强大的团队，他们在成功开展这类远洋科学研究项目方面有着广泛的记录。

The burning of fossil fuels is releasing vast quantities of extra carbon dioxide to the Earth's atmosphere. Much of this stays in the atmosphere, raising CO2 levels, but much also leaves the atmosphere after a time, either to become sequestered in trees and plants, or else to become absorbed in the oceans. CO2 staying in the atmosphere is a greenhouse gas, causing global warming; CO2 entering the sea makes it more acidic, and the ongoing acidification of seawater is seen in observational records at various sites where time-series data are collected. The changing chemistry of seawater due to ocean acidification is mostly well understood and not subject to debate. What is much less well known is the impact that the changing chemistry will have on marine organisms and ecosystems, on biogeochemical cycling in the sea, and on how the sea interacts with the atmosphere to influence climate. We will look to investigate these questions in terms of how the surface waters of the world's oceans, and the life within, will respond to ocean acidification. Most of what we know about biological impacts, and the source of the current concern about the impact on marine life, comes from experimental studies in which individual organisms (e.g. single corals) or mono-specific populations (e.g. plankton cultures) have been subjected to elevated CO2 (and the associated lower pH) in laboratory experiments. These laboratory experiments have the advantage of being performed under controlled conditions in which everything can be kept constant except for changes to CO2. So if a response is observed, then the cause is clear. However, there are also limitations to laboratory studies. For instance, organisms have no time to adapt evolutionarily, and there is no possibility of shifts in species composition away from more sensitive forms towards more acid-tolerant forms, as might be expected to occur in nature. Another shortcoming is the absence of food-web complexity in most experiments, and therefore the absence of competition, predation, and other interactions that determine the viability of organisms in the natural environment. We seek to advance the study of ocean acidification by collecting more observations of naturally-occurring ecosystems in places where the chemistry of seawater is naturally more acidic, and/or where it naturally holds more carbon,as well as locations which are not so acidic, and/or hold more usual amounts of carbon. By contrasting the two sets of observations, we will gain an improved understanding of how acidification affects organisms living in their natural environment, after assemblage reassortments and evolutionary adaptation have had time to play out. Most of the planned work will be carried out on 3 cruises to places with strong gradients in seawater carbon and pH: to the Arctic Ocean, around the British Isles, and to the Southern Ocean. As well a making observations we will also conduct a large number of experiments, in which we will bring volumes of natural seawater from the ocean surface into containers on the deck of the ship, together with whatever life is contained within, and there subject them to higher CO2 and other stressors. We will monitor the changes that take place to these natural plankton communities (including to biogeochemical and climate-related processes) as the seawater is made more acidic. A major strength of such studies is the inclusion of natural environmental variability and complexity that is difficult or impossible to capture in laboratory experiments. Thus, the responses measured during these experiments on the naturally-occurring community may represent more accurately the future response of the surface ocean to ocean acidification. In order to carry out this experimental/observational work programme we have assembled a strong UK-wide team with an extensive track record of successfully carrying out sea-going scientificresearch projects of this type.