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降低会对多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普遍担心，这种变化正在对海洋生物和海洋生态系统的稳定性产生影响，并将越来越多地产生影响。对于对CaCO3有很高要求的物种尤其如此，以制造骨骼(皇家学会2005，IPCC 2007)。因此，有必要更好地了解海洋物种如何应对pH值下降，那些目前生活在不同pH值环境中的物种如何适应这些条件，以及这些物种过去在工业化以来和更深的地质时期如何应对不同的pH值。解决这类问题的最好方法是研究一个钙化程度很高、广泛分布在不同pH值的地点、具有长期且具有良好代表性的化石记录的海洋类群。在这方面，现存的关节腕足动物即使不是最好的候选群体，也肯定是最好的群体之一。从极地到热带，从深海到潮间带，它们栖息在世界上所有的海洋中。它们可能是地球上最依赖碳酸钙的。它们90%以上的干质量(在某些物种中超过97%)是由钙质骨骼构成的。它们还拥有最好的化石记录之一，在长时间的地质时期中，它们的代表性和丰度是任何海洋动物群体中最好的。这一群体有极好的博物馆藏品，包括过去150年来同一物种的重复样本，以及来自单一遗址的几个主要地质时期的家族层面的广泛收藏品。因此，它们是研究与环境酸碱度变化相关的问题的理想选择。我们将使用最新的扫描电子显微镜和离子探针技术来量化腕足类的关节骨骼特征(壳层厚度、主次层厚度、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，我们将通过对生活在不同pH的地点的关键物种的种群进行采样，来研究当前环境中不同pH的影响。海藻分布于地中海至斯瓦尔巴群岛，种群生活在海涂和pH值低于近海的港口。Calloria inconspicua生活在新西兰各地类似的地点。我们将对生活在不同pH值条件下的种群进行采样，并分析它们的外壳。我们还将监测采样地区至少一年的酸碱值。这将使我们能够识别骨骼对自然环境中pH降低的反应。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。我们的两个主要物种在过去50年里都有来自特定地点的很好的博物馆收藏品，而T.retusa的收藏品可以追溯到1870年的BM Nat Hist。南极UVA的收集也可以追溯到20世纪60年代的S。我们计划利用这些收集来确定最近过去随着海洋二氧化碳的上升而发生的骨骼变化。第三，我们将分析不同地质时期关节腕足类的贝壳特征，当时环境中的二氧化碳水平与今天明显不同。这将使进化规模的反应得以解决。最后，我们将在pH条件改变的培养系统中保存我们的关键物种，并评估骨骼成分和结构的变化。这些办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范围内对酸化作出反应。

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.