Dynamics of an intense diatom bloom in the Northern Antarctic Peninsula, February 2016
Dynamics of an intense diatom bloom in the Northern Antarctic Peninsula, February 2016
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DOI：
10.1002/lno.11437
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发表时间：
2020-03-18
影响因子：
4.5
通讯作者：
Secchi, Eduardo Resende
中科院分区：
文献类型：
--
作者：
Costa, Raul Rodrigo;Mendes, Carlos Rafael Borges;Secchi, Eduardo Resende
硅藻被认为是南大洋食物网的主要基础，因为它们负责85%以上的年度初级生产，并在南极营养结构和地球化学循环中发挥关键作用。在此背景下，在2016年2月的夏末研究期间，在北方南极半岛（NAP）记录了叶绿素a> 45 mg m（-3）的强烈硅藻水华。鉴于营养盐浓度和放牧活动没有确定在这里作为限制因素的水华发展，本研究的目的是评估的水柱结构（稳定性和上层混合层深度）的浮游植物生物量和组成的NAP的效果。硅藻水华主要由大型中心型微花齿藻（Odontella weissfloptera）（大多数长度> 70 μ m）组成，与局部海洋二氧化碳吸收量相关，其值大于-60 mmol m（-2）d（-1）。我们假设，一个垂直的大水柱稳定性障碍的存在下，密度跃层，是主要的驱动程序，允许强烈的硅藻水华的发展，特别是在Gerlache海峡。首先，观察到从硅藻到甲藻（主要是< 20 μ m的裸藻目）的转变与高度稳定的薄层条件有关。结果表明，这种激烈的硅藻水华的大部分是在快速下沉过程中，与低放牧压力，显示了至关重要的作用，硅藻的生物碳泵在该地区的效率。
Diatoms are considered the main base of the Southern Ocean food web as they are responsible for more than 85% of its annual primary production and play a crucial role in the Antarctic trophic structure and in the biogeochemical cycles. Within this context, an intense diatom bloom reaching > 45 mg m(-3) of chlorophyll a was registered in the Northern Antarctic Peninsula (NAP) during a late summer study in February 2016. Given that nutrient concentrations and grazing activities were not identified here as limiting factors on the bloom development, the aim of this study was to evaluate the effect of water column structure (stability and upper mixed layer depth) on the phytoplankton biomass and composition in the NAP. The diatom bloom, mainly composed by the large centric Odontella weissflogii (mostly > 70 mu m in length), was associated with a local ocean carbon dioxide uptake that reached values greater than -60 mmol m(-2) d(-1). We hypothesize that the presence of a vertically large water column stability barrier, just below the pycnocline, was the main driver allowing for the development of the intense diatom bloom, particularly in the Gerlache Strait. Contrarily, a shift from diatoms to dinoflagellates (mainly Gymnodiniales < 20 mu m) was observed associated with conditions of a highly stable thin layer. The results suggest that a large fraction of this intense diatom bloom is in fast sinking process, associated with low grazing pressure, showing a crucial role of diatoms for the efficiency of the biological carbon pump in this region.