Can patchiness explain habitat variability in planktonic foraminifera?

浮游有孔虫壳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。锁定在壳中的微量元素和同位素特征可以用来重建过去上层海洋的关键参数。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。对分层浮游生物拖带的观察和沉积物中贝壳的地球化学分析表明，生物和钙化深度在物种之间和物种内部都有所不同。控制这种变异性的因素很难确定，并且由于涉及栖息地深度随昼夜周期到生殖周期的变化而变化的假设，使理解进一步复杂化。所有这些概念都依赖于所研究物种的分布在空间上是均匀的假设。在存在斑块的情况下，许多观测到的格局和生境变异性可以用不可预测的空间异质性来解释。在此，我们建议使用在RV METEOR探险队M140中以独特和前所未有的采样设计收集的分层浮游生物样本来确定浮游有孔虫斑块的存在和程度。通过将组合计数与复制样本中新的高分辨率3D自动图像分割技术相结合，我们将确定物种中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种群结构的程度，允许在模型和代理中更真实地表示它们的栖息地，并促进对全球碳预算估算中通过点采样获得的观测数据的正确解释。

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.