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

化石燃料的燃烧向地球大气中释放了大量额外的二氧化碳。其中大部分留在大气中，提高了二氧化碳水平，但也有很多在一段时间后离开大气，要么被树木和植物隔离，要么被海洋吸收。停留在大气中的二氧化碳是一种温室气体，导致全球变暖；进入海洋的二氧化碳使海水变得更酸，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酸化。由于海洋酸化，海水的化学成分发生了变化，这在很大程度上是众所周知的，没有争议。但鲜为人知的是，化学变化将对海洋生物和生态系统、海洋生物地球化学循环以及海洋如何与大气相互作用从而影响气候产生的影响。我们将根据世界海洋的表层水以及其中的生命对海洋酸化的反应来研究这些问题。我们对生物影响的了解，以及目前对海洋生物影响的关注的来源，大多来自实验研究，在实验室实验中，个体生物（如单个珊瑚）或单一特定种群（如浮游生物培养）受到二氧化碳升高（以及相关的pH值降低）的影响。这些实验室实验的优点是在受控条件下进行，除了二氧化碳的变化外，一切都可以保持不变。因此，如果观察到反应，那么原因就很清楚了。然而，实验室研究也存在局限性。例如，生物没有时间进化适应，物种组成也不可能从更敏感的形式转变为更耐酸的形式，这可能会发生在自然界中。另一个缺点是在大多数实验中缺乏食物网的复杂性，因此缺乏竞争、捕食和其他决定生物在自然环境中生存能力的相互作用。我们试图通过收集更多的自然生态系统的观测数据来推进海洋酸化的研究，这些生态系统位于海水化学性质自然偏酸的地方，和/或自然含有更多碳的地方，以及酸性不那么强的地方，和/或含有更多碳的地方。通过对比这两组观察结果，我们将更好地了解在组合重组和进化适应有时间发挥作用之后，酸化如何影响生活在自然环境中的生物体。计划中的大部分工作将在三次巡航中进行，前往海水碳和pH值梯度较大的地方：北冰洋、不列颠群岛周围和南大洋。在进行观察的同时，我们还将进行大量的实验，在实验中，我们将从海洋表面抽取大量的天然海水，连同里面的任何生命一起放入甲板上的容器中，并在那里将它们置于更高的二氧化碳和其他压力下。我们将监测随着海水酸化，这些天然浮游生物群落发生的变化（包括生物地球化学和气候相关过程）。此类研究的一个主要优势是包含了在实验室实验中难以或不可能捕获的自然环境变异性和复杂性。因此，在这些实验中对自然发生的群落测量的响应可能更准确地代表未来表层海洋对海洋酸化的响应。为了开展这项实验/观测工作计划，我们组建了一支强大的全英国团队，他们在成功开展这类海上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.