Can patchiness explain habitat variability in planktonic foraminifera?

浮游有孔虫壳体的化学性质记录了其钙化过程中上层海洋的物理和化学条件。贝壳中的微量元素和同位素特征可以用来重建过去海洋上层的关键参数。为了释放这些信号的全部潜力，必须限制水柱中发生钙化的位置。从分层浮游生物拖曳物的观察和沉积物中贝壳的地球化学分析表明，物种之间以及物种内部的生活和钙化深度各不相同。控制这种变化的因素是很难确定和理解是进一步复杂的假设，涉及栖息地深度变化，通过生活的节奏与昼夜生殖周期。所有这些概念都依赖于这样一个假设，即所研究的物种在空间上的分布是均匀的。在斑块的存在下，许多观察到的模式和栖息地的变异性可以解释为不可预测的空间异质性。在这里，我们建议使用分层浮游生物样品收集在一个独特的和前所未有的采样设计在RV METEOR远征M140，以确定斑块的存在和程度的浮游有孔虫。通过将集合计数与重复样本中新的高分辨率3D自动图像分割技术相结合，我们将确定物种内不同大小的个体在水柱中的位置，并通过分析它们的同位素特征，我们将确定这些栖息地的暂时稳定性。这些结果将严格限制海洋微型浮游动物的种群结构的程度，允许更现实的代表性，其栖息地的模型和代理，并促进正确的解释点采样获得的观测数据，全球碳预算估计。

Chemical properties of planktonic foraminifera shells record physical and chemical conditions in the upper ocean during their calcification. Trace element and isotopic signatures locked in the shells can be used to reconstruct key parameters of the upper ocean in the past. To unlock the full potential of these signals, the position in the water column where calcification occurs has to be constrained. Observations from stratified plankton tows and geochemical analyses of shells from the sediment revealed that living and calcification depth varies among species as well as within species. The factors that control this variability are difficult to identify and the understanding is further complicated by hypotheses involving habitat depth changes through life in pace with diurnal to reproductive cycles. All of those concepts rely on the assumption that the distribution of the studied species is spatially uniform. In the presence of patchiness, many of the observed patterns and habitat variability could be explained by unpredictable spatial heterogeneity. Here we propose to use stratified plankton samples collected in a unique and unprecedented sampling design during RV METEOR expedition M140 to determine the existence and the extent of patchiness in planktonic foraminifera. By combining assemblage counts with a new highly resolved 3D automated image segmentation technique in replicate samples we will determine where in the water column individuals of different sizes within species live and by analyzing their isotopic signatures, we will determine how temporarily stable these habitats are. These results will critically constrain the extent of population structuring of marine microzooplankton, allowing a more realistic representation of their habitat in models and proxies, and facilitating correct interpretation of observational data obtained by point sampling for global carbon budget estimations.