Data_Sheet_1_Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies.xlsx

Mesozooplankton (June 2015 and September 2017) and micronekton (September 2017) were sampled along the eastern coast of Australia. Depth stratified mesozooplankton and micronekton were collected using a Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) and an International Young Gadoid Pelagic Trawl (IYGPT) equipped with an opening/closing codend. Sampling was undertaken at the center and edge of a frontal cold-core eddy (F-CCE Center and Edge) in 2015, and at the center of a cold-core eddy (B-CCE) and two warm-core eddies (R-WCE and WCE) in 2017. We assess the diel vertical structure, biomass, and downward active carbon transport by mesozooplankton and micronekton in eddies. Total water column mesozooplankton and micronekton biomass did not vary substantially across water masses, while the extent and depth of diel vertical migration did. Using in situ measurements of temperature and measurements of mesozooplankton and micronekton abundance and biomass, we estimated the contribution of respiration, dissolved organic carbon (DOC) excretion, gut flux, and mortality to total downward active carbon transport in each water mass. Overall, active carbon transport by mesozooplankton and micronekton below the mixed layer varied substantially across water masses. We corrected estimates of micronekton migratory biomass and active carbon transport assuming 50% net efficiency. In the R-WCE mesozooplankton remained within the mixed layer during the day and night; only 50% of the total micronekton population migrated below the mixed layer contributing to carbon transport, equating to 2.89 mg C m–2 d–1. Mesozooplankton actively transported 16.1 and 8.0 mg C m–2 d–1 at the F-CCE Center and Edge, respectively. Mesozooplankton and micronekton active carbon transport in the B-CCE were 5.4 and 0.74 mg C m–2 d–1, and in the WCE 88 and 13.4 mg C m–2 d–1. Differences in carbon export were dependent on food availability, temperature, time spent migrating, and mixed layer depth. These findings suggest that under certain conditions mesoscale eddies can act as important carbon sinks.

在2015年6月及2017年9月，我们对澳大利亚东海岸的浮游桡足类（Mesozooplankton）及微浮游动物（micronekton）进行了采样。采用多开口/闭合网（Multiple Opening/Closing Net）和环境传感系统（Environmental Sensing System，简称MOCNESS）以及配备可开合囊网的国际年轻鳕鱼浮游拖网（International Young Gadoid Pelagic Trawl，简称IYGPT）收集了分层深度的浮游桡足类及微浮游动物。2015年在锋面冷核涡旋（锋面冷核涡旋中心及边缘，F-CCE Center and Edge）的中心和边缘进行采样，2017年在冷核涡旋中心（B-CCE）及两个暖核涡旋（R-WCE和WCE）的中心进行采样。我们评估了涡旋中浮游桡足类及微浮游动物的昼夜垂直结构、生物量及向下主动碳传输。总水柱中浮游桡足类及微浮游动物的生物量在各个水团中变化不大，而昼夜垂直迁移的范围和深度则有所差异。通过现场温度测量和浮游桡足类及微浮游动物的丰度和生物量测量，我们估计了呼吸、溶解有机碳（Dissolved Organic Carbon，简称DOC）排泄、肠道通量及死亡率对每个水团中总向下主动碳传输的贡献。总体而言，浮游桡足类及微浮游动物在混合层以下的主动碳传输在不同水团中存在显著差异。在假设50%净效率的情况下，我们校正了微浮游动物迁移生物量和主动碳传输的估计。在R-WCE中，浮游桡足类在白天和夜晚都保持在混合层内；仅有50%的总微浮游动物种群迁移至混合层以下，参与碳传输，相当于每天每平方米碳传输2.89毫克。在F-CCE中心及边缘，浮游桡足类的主动碳传输分别为每天每平方米16.1毫克和8.0毫克。在B-CCE中，浮游桡足类及微浮游动物的主动碳传输分别为每天每平方米5.4毫克和0.74毫克，在WCE中分别为每天每平方米88毫克和13.4毫克。碳输出的差异取决于食物可及性、温度、迁移时间及混合层深度。这些发现表明，在特定条件下，中尺度涡旋可以作为重要的碳汇。