Mineral ballasting enhances carbon export from the surface to the deep ocean; however, little is known about the role of this process in the ice-covered Arctic Ocean. Here, we propose gypsum ballasting as a new mechanism that likely facilitated enhanced vertical carbon export from an under-ice phytoplankton bloom dominated by the haptophyte Phaeocystis. In the spring 2015 abundant gypsum crystals embedded in Phaeocystis aggregates were collected throughout the water column and on the sea floor at a depth below 2 km. Model predictions supported by isotopic signatures indicate that 2.7 g m−2 gypsum crystals were formed in sea ice at temperatures below −6.5 °C and released into the water column during sea ice melting. Our finding indicates that sea ice derived (cryogenic) gypsum is stable enough to survive export to the deep ocean and serves as an effective ballast mineral. Our findings also suggest a potentially important and previously unknown role of Phaeocystis in deep carbon export due to cryogenic gypsum ballasting. The rapidly changing Arctic sea ice regime might favour this gypsum gravity chute with potential consequences for carbon export and food partitioning between pelagic and benthic ecosystems.
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机译:矿物压载增加了碳从地表到深海的出口;然而,对于这一过程在冰雪覆盖的北冰洋中的作用知之甚少。在这里,我们提出石膏压载作为一种新的机制,可能促进了由触藻类植物囊藻支配的冰下浮游植物水华增加的垂直碳出口。在2015年春季,在整个水柱和海床以下2千米以下的深度收集到了嵌入囊藻聚集体中的大量石膏晶体。同位素特征支持的模型预测表明,在低于-6.5°C的温度下,海冰中形成2.7 g m -2 sup>石膏晶体,并在海冰融化期间释放到水柱中。我们的发现表明,源自海冰的(低温)石膏足够稳定,可以出口到深海,并且可以作为有效的压载矿物。我们的发现还表明,由于低温石膏的压载作用,Phaeocystis在深层碳输出中可能具有潜在的重要作用,而以前却未知。迅速变化的北极海冰制度可能会偏爱这种石膏重力溜槽,这会对碳出口以及中上层和底栖生态系统之间的食物分配产生潜在影响。
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