Climate change tweaks Arctic marine ecosystems

doi:10.1126/science.abd1231

GSTDTAP > 气候变化

DOI	10.1126/science.abd1231
	Climate change tweaks Arctic marine ecosystems
	Marcel Babin
	2020-07-10
发表期刊	Science
出版年	2020
英文摘要	Icepack reduction enhances exposure of the fairly dark Arctic Ocean (AO) to sunlight, thus promoting microalgae biomass buildup and productivity of the marine ecosystem. This seemingly reasonable assertion is a matter of lively debate centered on the function and fate of the Arctic marine ecosystem under climate change pressure. A second paradigm postulates that additional inputs of nitrogen, which is chronically low over large stretches of the AO, would be required to enable the algae to take full advantage of greater availability of light. On page 198 of this issue, Lewis et al. ([ 1 ][1]) confirm the latter notion with observations of recent biomass buildup at the AO surface that is likely driven by hydrodynamical processes that replenish essential nitrogen fuel. The AO hosts a rich community of living organisms. From microbes to mammals, nearly all depend directly or indirectly on primary production (PP) of plant biomass by microscopic marine algae (phytoplankton). In this most polar of oceans, phytoplankton must cope with two extraordinary constraints: a roller coaster–like seasonal light cycle and a water column vertically organized into a “mille-feuille” structure. The underwater light regimen is controlled by the polar night and midnight Sun alternation as well as by sea ice, which acts as a blind on top of the AO before abruptly vanishing over most of the AO each summer. The AO vertical structure is characterized by a density gradient formed from massive inputs of lightweight fresh water from rivers and ice melts at the surface. The resulting stratification limits vertical exchanges of solutes and thus the replenishment, in the surface layer, of inorganic nutrients necessary to the growth of microalgae. This phenomenon ultimately constrains the production of biomass at all levels of the food chain. On the basis of a prior analysis of historical data, a recent study hypothesized that the annually cumulated PP in seasonally ice-free regions is determined primarily by the input of nutrients (essentially nitrate) brought to the surface through vertical mixing ([ 2 ][2]). Despite the increase in underwater light from shrinking sea ice, growing freshwater inputs more strongly stratify the AO. This likely will lower the nutrient supply and thus PP, unless other physical changes reverse this trend ([ 3 ][3]). Ocean color can be detected from space and analyzed to estimate the concentration of chlorophyll a at the sea surface (a proxy for phytoplankton biomass) and the rate at which solar energy hits the AO surface. When the atmosphere is cloud free, these first-order determinants of PP, together with sea surface temperature, are monitored daily by several satellites over the entire world ocean. Such ocean color data have been available uninterruptedly since 1998. From the late 2000s on, several studies based on ocean color data have reported a substantial increase in the annual PP of seasonally ice-free Arctic waters ([ 4 ][4], [ 5 ][5]). Ecologists have ascribed this increase primarily to a decrease in the icepack during summer and early fall, combined with the lengthening of the ice-free season. As sea ice decreases, open waters are exposed to much more sunlight, which promotes photosynthesis and phytoplankton biomass production. It is unclear, however, how much of this increase results from new production that can be transferred to the food chain versus “useless” recycled production. Lewis et al. used satellite observations of AO color to determine the response of annual PP to climate change during the past two decades, the longest Arctic PP time series available. The authors observed a progressive increase in PP that over time reached 57%, which far exceeds previous estimates. These findings confirmed the role of sea ice shrinking as a driver of PP, but only during the 1998 to 2008 period. Lewis et al. then showed that the increase in PP between 2009 and 2018 was driven primarily by an increase in chlorophyll a concentration, although the authors documented substantially different regional trends. The standing stock of phytoplankton depends on the balance between gains from growth and losses from grazing by small animals. However, the stock also generally correlates with nutrient concentrations. A key conclusion that can be drawn from Lewis et al. 's study is that the budget of inorganic nutrients might be increasing rather than diminishing in specific AO sectors over the time periods studied. Nutrient input might intensify at the Pacific and Atlantic boundaries, whereas the reduction in sea ice cover might expose the AO to stronger atmospheric forcings that promote more vertical mixing. Lewis et al. also found that PP did not change in several areas. Therefore, it remains unknown whether overall AO-wide PP will continue to increase if the amount of sea ice keeps shrinking. The rest of this story will stem from longer time series and a better grasp of the physical phenomena that control nutrient concentrations. Although satellite observations provide relatively long time series and a means for exploring the AO at a large scale, information from AO satellite images comes with limitations—for example, restriction to surface properties and low spatial and time resolution, especially for optical sensors in thick cloud cover. Furthermore, scales relevant to PP span millimeters to the ocean basin (spatial) and seconds to decades (time). Satellites provide no observation under sea ice, where much occurs that is equally important to PP. Indeed, massive phytoplankton blooms were recently observed under sea ice and are thought to be more common than previously anticipated ([ 6 ][6]). The ongoing thinning of sea ice and increasing occurrence of melt ponds, which act as skylights at the ocean's surface in spring, might make blooms even more prevalent ([ 7 ][7]). Emerging approaches for capturing the various scales important to PP include autonomous sampling platforms with sensors for exploring the medium to large scales in ice-free and ice-covered waters. Much remains to be discovered about the small scales, such as those relevant to microalgae living in the inner interstices of sea ice. To address current and future changes of PP in the AO and their effects on the marine trophic network, researchers require new devices to explore tiny components and an integrated observation system to capture and connect all relevant scales. 1. [↵][8]1. K. M. Lewis, 2. G. L. van Dijken, 3. K. R. Arrigo , Science 369, 198 (2020). [OpenUrl][9][Abstract/FREE Full Text][10] 2. [↵][11]1. J. E. Tremblay et al ., Prog. Oceanogr. 139, 171 (2015). [OpenUrl][12] 3. [↵][13]1. W. K. W. Li, 2. F. A. McLaughlin, 3. C. Lovejoy, 4. E. C. Carmack , Science 326, 539 (2009). [OpenUrl][14][Abstract/FREE Full Text][15] 4. [↵][16]1. K. R. Arrigo, 2. G. L. van Dijken , Prog. Oceanogr. 136, 60 (2015). [OpenUrl][17][CrossRef][18] 5. [↵][19]1. S. Bélanger, 2. M. Babin, 3. J.-É. Tremblay , Biogeosciences 10, 4087 (2013). [OpenUrl][20][CrossRef][21] 6. [↵][22]1. K. R. Arrigo et al ., Science 336, 1408 (2012). [OpenUrl][23][Abstract/FREE Full Text][24] 7. [↵][25]1. K. E. Lowry, 2. G. L. van Dijken, 3. K. R. Arrigo , Deep Sea Res. Part II Top. Stud. Oceanogr. 105, 105 (2014). [OpenUrl][26] Acknowledgments: M.B. thanks M. Lizotte, A. Randelhoff, J.-E. Tremblay, and M.-H. Forget for valuable editing and scientific comments. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5 [6]: #ref-6 [7]: #ref-7 [8]: #xref-ref-1-1 "View reference 1 in text" [9]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DLewis%26rft.auinit1%253DK.%2BM.%26rft.volume%253D369%26rft.issue%253D6500%26rft.spage%253D198%26rft.epage%253D202%26rft.atitle%253DChanges%2Bin%2Bphytoplankton%2Bconcentration%2Bnow%2Bdrive%2Bincreased%2BArctic%2BOcean%2Bprimary%2Bproduction%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.aay8380%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [10]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIzNjkvNjUwMC8xOTgiO3M6NDoiYXRvbSI7czoyMjoiL3NjaS8zNjkvNjUwMC8xMzcuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [11]: #xref-ref-2-1 "View reference 2 in text" [12]: {openurl}?query=rft.jtitle%253DProg.%2BOceanogr.%26rft.volume%253D139%26rft.spage%253D171%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [13]: #xref-ref-3-1 "View reference 3 in text" [14]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DLi%26rft.auinit1%253DW.%2BK.%2BW.%26rft.volume%253D326%26rft.issue%253D5952%26rft.spage%253D539%26rft.epage%253D539%26rft.atitle%253DSmallest%2BAlgae%2BThrive%2BAs%2Bthe%2BArctic%2BOcean%2BFreshens%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.1179798%26rft_id%253Dinfo%253Apmid%252F19900890%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [15]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIzMjYvNTk1Mi81MzkiO3M6NDoiYXRvbSI7czoyMjoiL3NjaS8zNjkvNjUwMC8xMzcuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [16]: #xref-ref-4-1 "View reference 4 in text" [17]: {openurl}?query=rft.jtitle%253DProg.%2BOceanogr.%26rft.volume%253D136%26rft.spage%253D60%26rft_id%253Dinfo%253Adoi%252F10.1016%252Fj.pocean.2015.05.002%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [18]: /lookup/external-ref?access_num=10.1016/j.pocean.2015.05.002&link_type=DOI [19]: #xref-ref-5-1 "View reference 5 in text" [20]: {openurl}?query=rft.jtitle%253DBiogeosciences%26rft.volume%253D10%26rft.spage%253D4087%26rft_id%253Dinfo%253Adoi%252F10.5194%252Fbg-10-4087-2013%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [21]: /lookup/external-ref?access_num=10.5194/bg-10-4087-2013&link_type=DOI [22]: #xref-ref-6-1 "View reference 6 in text" [23]: {openurl}?query=rft.jtitle%253DScience%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.1215065%26rft_id%253Dinfo%253Apmid%252F22678359%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [24]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEzOiIzMzYvNjA4Ny8xNDA4IjtzOjQ6ImF0b20iO3M6MjI6Ii9zY2kvMzY5LzY1MDAvMTM3LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ== [25]: #xref-ref-7-1 "View reference 7 in text" [26]: {openurl}?query=rft.jtitle%253DDeep%2BSea%2BRes.%2BPart%2BII%2BTop.%2BStud.%2BOceanogr.%26rft.volume%253D105%26rft.spage%253D105%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx
领域	气候变化 ; 资源环境
URL	查看原文
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/283377
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Marcel Babin. Climate change tweaks Arctic marine ecosystems[J]. Science,2020.
APA	Marcel Babin.(2020).Climate change tweaks Arctic marine ecosystems.Science.
MLA	Marcel Babin."Climate change tweaks Arctic marine ecosystems".Science (2020).