Hoppe C J M, Schuback N, Semeniuk D, Giesbrecht K, Mol J, Thomas H, Maldonado M T, Rost B, Varela D E, Tortell P D
1Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC Canada.
2Marine Biogeosciences, Alfred Wegener Institute - Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
Polar Biol. 2018;41(3):399-413. doi: 10.1007/s00300-017-2186-0. Epub 2017 Aug 9.
The Arctic Ocean is a region particularly prone to ongoing ocean acidification (OA) and climate-driven changes. The influence of these changes on Arctic phytoplankton assemblages, however, remains poorly understood. In order to understand how OA and enhanced irradiances (e.g., resulting from sea-ice retreat) will alter the species composition, primary production, and eco-physiology of Arctic phytoplankton, we conducted an incubation experiment with an assemblage from Baffin Bay (71°N, 68°W) under different carbonate chemistry and irradiance regimes. Seawater was collected from just below the deep Chl maximum, and the resident phytoplankton were exposed to 380 and 1000 µatm pCO at both 15 and 35% incident irradiance. On-deck incubations, in which temperatures were 6 °C above in situ conditions, were monitored for phytoplankton growth, biomass stoichiometry, net primary production, photo-physiology, and taxonomic composition. During the 8-day experiment, taxonomic diversity decreased and the diatom became increasingly dominant irrespective of light or CO levels. We found no statistically significant effects from either higher CO or light on physiological properties of phytoplankton during the experiment. We did, however, observe an initial 2-day stress response in all treatments, and slight photo-physiological responses to higher CO and light during the first five days of the incubation. Our results thus indicate high resistance of Arctic phytoplankton to OA and enhanced irradiance levels, challenging the commonly predicted stimulatory effects of enhanced CO and light availability for primary production.
北冰洋是一个特别容易受到持续海洋酸化（OA）和气候驱动变化影响的区域。然而，这些变化对北极浮游植物群落的影响仍知之甚少。为了了解海洋酸化和增强的辐照度（例如，由海冰退缩导致）将如何改变北极浮游植物的物种组成、初级生产力和生态生理学，我们在不同的碳酸盐化学和辐照度条件下，对来自巴芬湾（北纬71°，西经68°）的一组浮游植物进行了培养实验。海水是从深层叶绿素最大值以下采集的，当地的浮游植物在15%和35%的入射辐照度下分别暴露于380和1000微大气压的pCO₂环境中。在甲板上进行培养，培养温度比原位条件高6°C，监测浮游植物的生长、生物量化学计量、净初级生产力、光生理学和分类组成。在为期8天的实验中，无论光照或二氧化碳水平如何，分类多样性都有所下降，硅藻变得越来越占主导地位。在实验过程中，我们发现较高的二氧化碳或光照对浮游植物的生理特性没有统计学上的显著影响。然而，我们确实在所有处理中观察到了最初为期2天的应激反应，以及在培养的前五天对较高二氧化碳和光照的轻微光生理反应。因此，我们的结果表明北极浮游植物对海洋酸化和增强的辐照度具有很高的抗性，这对通常预测的二氧化碳增加和光照增加对初级生产的刺激作用提出了挑战。
