Sørensen Heidi Louise, Thamdrup Bo, Jeppesen Erik, Rysgaard Søren, Glud Ronnie Nøhr
1Department of Biology, Nordic Centre for Earth Evolution (NordCEE), University of Southern Denmark (SDU), Campusvej 55, 5230 Odense, Denmark.
2Greenland Climate Research Centre (GCRC), Greenland Institute of Natural Resources, Kivioq 2, 3900 Nuuk, Greenland.
Polar Biol. 2017;40(8):1593-1606. doi: 10.1007/s00300-017-2082-7. Epub 2017 Mar 1.
Every spring and summer melt ponds form at the surface of polar sea ice and become habitats where biological production may take place. Previous studies report a large variability in the productivity, but the causes are unknown. We investigated if nutrients limit the productivity in these first-year ice melt ponds by adding nutrients to three enclosures ([1] PO , [2] NO , and [3] PO and NO ) and one natural melt pond (PO and NO ), while one enclosure and one natural melt pond acted as controls. After 7-13 days, Chl concentrations and cumulative primary production were between two- and tenfold higher in the enclosures and natural melt ponds with nutrient addition compared with their respective controls, with the largest increase occurring in the enclosures. Separate additions of PO and NO in the enclosures led to intermediate increases in productivity, suggesting co-limitation of nutrients. Bacterial production and the biovolume of ciliates, which were the dominant grazers, were positively correlated with primary production, showing a tight coupling between primary production and both microbial activity and ciliate grazing. To our knowledge, this study is the first to ascertain nutrient limitation in melt ponds. We also document that the addition of nutrients, although at relative high concentrations, can stimulate biological productivity at several trophic levels. Given the projected increase in first-year ice, increased melt pond coverage during the Arctic spring and potential additional nutrient supply from, e.g. terrestrial sources imply that biological activity of melt ponds may become increasingly important for the sympagic carbon cycling in the future Arctic.
每年春夏时节，极地海冰表面会形成融池，成为可能进行生物生产的栖息地。此前的研究报告称生产力存在很大差异，但原因不明。我们通过向三个围栏（[1] 磷酸根，[2] 硝酸根，以及 [3] 磷酸根和硝酸根）和一个天然融池（磷酸根和硝酸根）添加营养物质，同时设置一个围栏和一个天然融池作为对照，来研究营养物质是否限制这些一年生冰融池的生产力。7 - 13天后，与各自的对照相比，添加营养物质的围栏和天然融池中叶绿素浓度和累计初级生产力高出两到十倍，围栏中的增幅最大。在围栏中分别添加磷酸根和硝酸根导致生产力有中等程度的增加，表明营养物质存在共同限制。细菌生产力以及作为主要食草动物的纤毛虫生物量与初级生产力呈正相关，表明初级生产力与微生物活动和纤毛虫食草作用之间存在紧密耦合。据我们所知，本研究首次确定了融池中营养物质的限制情况。我们还记录到，尽管添加的营养物质浓度相对较高，但仍能刺激多个营养级的生物生产力。鉴于预计一年生冰会增加，北极春季融池覆盖范围扩大以及例如陆地来源可能带来的额外营养物质供应，这意味着融池的生物活动在未来北极的共生碳循环中可能会变得越来越重要。
