Shell composition and microstructure variation with pH in time and space

在过去的200年里，人类活动使大气中的二氧化碳增加了约40%，其中约25%被海洋吸收。这使海洋酸度增加了约30%。许多研究表明，pH值降低对各种海洋动物和藻类的生物功能产生负面影响。科学家、政策制定者和自然资源保护者对这种变化正在对海洋生物和海洋生态系统的稳定产生的影响以及这种影响将越来越大表示关切。对于需要大量碳酸钙来制造骨骼的物种来说，情况尤其如此（皇家学会，2005年;政府间气候变化专门委员会，2007年）。因此，有必要更好地了解海洋物种如何应对pH值降低，目前生活在不同pH值环境中的物种如何适应这些条件，以及这些群体如何应对工业化以来和更深地质时代的pH值变化。解决这类问题的最佳方法是研究一个严重钙化的海洋生物群，它广泛分布在不同pH值的地点，并有着悠久而完整的化石记录。在这方面，活的关节腕足动物，如果不是最好的候选群体，那么肯定是最好的之一。它们栖息在世界上所有的海洋中，从两极到热带，从深海到潮间带。它们可能是地球上最依赖碳酸钙的物种。超过90%的干物质（在某些物种中超过97%）是由钙质骨骼构成的。它们也有一个最好的化石记录，在任何海洋动物群体的长期地质时期的代表性和丰富性方面。这个群体有很好的博物馆收藏品，包括过去150年来相同物种的重复样本，以及来自单一地点的几个主要地质时期的家庭层面的广泛收藏。因此，它们是研究与环境pH值变化相关问题的理想选择。我们将使用最新的SEM和离子探针技术来量化关节腕足动物骨骼特征（壳厚度，初级和次级层厚度，晶体形态，主要和次要元素组成），以解决四个主要领域的问题。首先，我们将调查不同的pH值在当前环境中的影响，通过采样种群的关键物种生活在不同的pH值的网站。Terebratulina retusa分布从地中海到斯瓦尔巴群岛，人口生活在sealochs和港口的pH值低于离岸。不显眼的Calloria inscarcua栖息在新西兰附近的类似地点。我们将对生活在不同pH条件下的种群进行采样，并分析它们的贝壳。我们还将对采样区域的pH值进行至少一年的监测。这将使我们能够确定骨骼对在自然环境中降低pH值的反应。其次，我们将量化自工业革命以来发生的骨骼变化，当时二氧化碳水平一直在上升。我们的两个关键物种都有很好的博物馆收藏，从给定的地方涵盖了过去的50年，和T。retusa收藏可以追溯到1870年在BM国家历史。南极L。UVA也可以追溯到20世纪60年代。我们计划利用这些收集来确定骨骼的变化，在最近的过去，海洋二氧化碳已经上升。第三，我们将分析不同地质时期的腕足动物的外壳特征，当时环境中的二氧化碳水平与今天有显着不同。这将使进化规模的反应得到解决。最后，我们将在改变pH值条件的培养系统中保持我们的关键物种，并评估骨骼组成和结构的变化。这些方法应能很好地了解海洋物种如何在尽可能广泛的时间和空间尺度上对酸化作出反应。

Over the last 200 years human activity has increased CO2 in the atmosphere by around 40%, roughly 25% of which has been absorbed by the oceans. This has increased oceanic acidity by around 30%. Many studies have shown negative effects of lowered pH on biological functions in a wide range of marine animals and algae. There is widespread concern from scientists, policymakers and conservationists over the effects this change is having, and will increasingly have, on marine life and on the stability of marine ecosystems. This is especially so for species with high requirements for CaCO3 to make skeletons (Royal Society 2005, IPCC 2007). There is thus a need to understand better how marine species can cope with lowered pH, how those currently living in environments of different pH are adapted to those conditions, and how these groups have coped with varying pH in the past both since industrialisation and in deeper geological time. The best way to address questions of this type is to study a marine group that is heavily calcified, has widespread distributions in sites of different pH and has a long and well represented fossil record. In this respect living articulated brachiopods are, if not the best candidate group, then certainly one of the best. They inhabit all of the world's oceans from the poles to the tropics, and from the deep sea to the intertidal. They are possibly the most calcium carbonate dependent on Earth. Over 90% of their dry mass (in some species over 97%) is accounted for by calcareous skeleton. They also have one of the best fossil records in terms of representation and abundance over long geological periods of any marine animal group. There are excellent museum collections for this group, including repeat samples of the same species over the last 150 years and extensive collections at the family level for several major geological periods from single sites. They are, therefore ideal for investigating questions associated with changing environmental pH. We will use up to date SEM and ion probe techniques to quantify articulated brachiopod skeletal characteristics (shell thickness, primary & secondary layer thickness, crystal morphology, major & minor elemental composition) to address questions in four main areas. Firstly we will investigate the effects of varying pH in current environments by sampling populations of key species living in sites of different pH. Terebratulina retusa is distributed from the Mediterranean to Svalbard, with populations living in sealochs and harbours where pH is lower than offshore. Calloria inconspicua inhabits a similar range of sites around New Zealand. We will sample populations living in different pH conditions and analyse their shells. We will also monitor pH in the areas sampled for at least a year. This will allow us to identify skeletal responses to being raised in reduced pH in the natural environment. Secondly we will quantify changes in skeletons that have occurred since the industrial revolution, when CO2 levels have been consistently rising. Both our key species have good museum collections from given localities covering the last 50 years, and T. retusa collections date back to 1870 in the BM Nat Hist. Collections of the Antarctic L. uva also date back to the 1960's. We plan to exploit these collections to identify skeletal changes over the recent past as oceanic CO2 has risen. Thirdly we will analyse shell characteristics in Articulated brachiopods from different geological periods when CO2 levels in the environment were markedly different from today. This will allow evolutionary scale responses to be addressed. Finally we will hold our key species in culture systems with altered pH conditions and assess changes in skeletal composition and structure. These approaches should provide a very good understanding of how marine species have and can respond to acidification over as wide a range of time and spatial scales as possible.