Table_1_Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies.DOCX

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.

2015年6月及2017年9月，对澳大利亚东部海岸的中型浮游动物（Mesozooplankton）和微型浮游动物（micronekton）进行了采样。采用多重开启/关闭网（Multiple Opening/Closing Net）和环境传感系统（Environmental Sensing System，简称MOCNESS）以及配备开启/关闭囊网的国际年轻鲭类围网（International Young Gadoid Pelagic Trawl，简称IYGPT）对分层深度进行的中型浮游动物和微型浮游动物进行了收集。2015年在锋面冷核涡旋（Frontal Cold-Core Eddy，简称F-CCE）的中心和边缘进行了采样，而在2017年则在冷核涡旋（Cold-Core Eddy，简称B-CCE）的中心以及两个暖核涡旋（Warm-Core Eddy，简称R-WCE和WCE）中进行了采样。本研究评估了涡旋中中型浮游动物和微型浮游动物的昼夜垂直结构、生物量及向下主动碳通量。总体而言，全水柱中型浮游动物和微型浮游动物的生物量在不同水团之间没有显著变化，而昼夜垂直迁移的广度和深度则有所不同。通过现场测量的温度以及中型浮游动物和微型浮游动物的数量和生物量，我们估计了呼吸、溶解有机碳（Dissolved Organic Carbon，简称DOC）的排泄、肠道通量和死亡率对每个水团中向下主动碳通量的贡献。总体而言，中层以下中型浮游动物和微型浮游动物的主动碳通量在不同水团之间存在显著差异。在假设50%净效率的情况下，我们纠正了对微型浮游动物迁徙生物量和主动碳通量的估计。在R-WCE中，中型浮游动物在昼夜均保持在混合层内；仅有50%的总微型浮游动物种群向下迁移并参与了碳通量，相当于2.89 mg C m–2 d–1。在F-CCE的中心和边缘，中型浮游动物分别以16.1和8.0 mg C m–2 d–1的速率进行主动碳通量。在B-CCE中，中型浮游动物和微型浮游动物的主动碳通量分别为5.4和0.74 mg C m–2 d–1，而在WCE中则为88和13.4 mg C m–2 d–1。碳输出差异取决于食物可及性、温度、迁徙时间以及混合层深度。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。