Regional variability in the abundance, type and activity of large particles in the Mesopelagic ("Twilight") Zone of the North Atlantic and its link to epipelagic biogeochemical provinces (M60/5)

从上层混合层以下到约1500米深的中上层（暮光）带是水柱中勘探最少的区域之一。大量的呼吸作用、再包装和再矿化作用表明，一个活跃的生物群落负责利用从上层海洋到深海沉积的80%以上的有机物质。间接证据表明，过渡带再矿化效率的区域差异与地表出口产量呈正相关，这使得该地区成为生物泵净出口的重要地区。在M60/5流星考察队期间，对北大西洋热带和亚热带不同生产力和营养状况区域以下中上层的颗粒进行了调查。此外，船上其他人对丝状和单细胞蓝藻多样性和分布的区域差异进行的研究，为研究下沉颗粒中重氮营养体的直接出口提供了独特的机会。部署海洋捕雪器和收集中上层颗粒的主要目的是确定颗粒丰度、类型和活动的区域变化，并将这些变化与中上层输出系统的差异联系起来，以及调查沉积聚集体中固氮蓝藻的输出。

The Mesopelagic ( Twilight ) zone, ranging from below the upper mixed layer to ca. 1500 m depth, is one of the least explored regions of the water column. Considerable respiration, repackaging and remineralisation point to the role of an active biological community that is responsible for utilising over 80% of the organic material sedimenting from the epipelagic zone to the deep sea. Circumstantial evidence suggests that regional variations in the efficiency of remineralisation in the twilight zone is positively correlated with surface export production, which makes this an important region for net export by the biological pump. During the Meteor expedition M60/5, to the tropical and subtropical North Atlantic investigations of particles in the mesopelagic layers below regions of varying productivity and trophic status. Additionally, studies on regional differences in the diversity and distribution of filamentous and unicellular cyanobacteria, conducted by others on the cruise offer the unique opportunity to investigate direct export of diazotrophs in sinking particles. Deployments of a marine snow catcher and collection of mesopelagic particles was done with the major aims of determining regional variability in particle abundance, type and activity and relating these to differences in pelagic export systems as well as investigating the export of nitrogen fixing cyanobacteria in sedimenting aggregates.