Variations in the phytoplankton community due to dust additions in eutrophication, LNLC and HNLC oceanic zones
Variations in the phytoplankton community due to dust additions in eutrophication, LNLC and HNLC oceanic zones
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由于富营养化、LNLC 和 HNLC 海洋区灰尘增加导致浮游植物群落的变化
DOI：
10.1016/j.scitotenv.2019.02.068
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Huiwang Gao
中科院分区：
文献类型：
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作者：
Chao Zhang;Xiaohong Yao;Ying Chen;Qiang Chu;Yang Yu;Jin-Hui Shi;Huiwang Gao
扬尘沉降可将营养物质和微量元素带入海洋上层，影响浮游植物的生长和群落结构。本文在东海（富营养区）、西北太平洋副热带环流（低营养低叶绿素区）和黑潮-漂潮过渡区（高营养低叶绿素区，HNLC）进行了不同尘量（0.2、1和2 mg L-1）修正的船上微观实验对比研究。相对于孵育实验收集的海水（基线），粉尘的添加提供了相当数量的氮(N)和微不足道的磷(P)，有助于叶绿素a随着粉尘添加量的增加而增加。各区域大细胞（微尺度：bbb20 μm和纳米尺度：2-20 μm）的净生长率与有效N（基线和添加N之和）呈显著的线性相关，表明浮游植物的大小结构随着粉尘添加量的增加而向大细胞转移。在LNLC和HNLC区域进行的实验中，微浮游植物（主要以硅藻为主）从粉尘添加中获益最多。然而，在富营养区进行的实验中，主要受益者是纳米级浮游植物（主要由鞭毛藻组成）。考虑硅藻相对于N:P比值的相对丰度（RAD，硅藻丰度除以硅藻和甲藻的总和）的时间滞后1天，我们发现随着N:P比值的增加，相对丰度大幅增加，直到接近Redfield比值（N:P = 16:1），然后随着N:P比值的增加，相对丰度逐渐下降。这是由于与硅藻相比，鞭毛藻对营养缺乏的敏感性较低。总体而言，我们的研究结果表明，沙尘沉降带来的氮相对于磷的压倒性输入可能通过改变不同营养海水的氮磷比而产生显著的生态影响。
Dust deposition can bring nutrients and trace elements to the upper ocean and affect phytoplankton growth and community structure. We conducted a comparative study using on-board microcosm experiments amended with varying amounts of dust (0.2, 1, and 2 mg L-1) in the East China Sea (eutrophic zone), the subtropical gyre (low-nutrient and low-chlorophyll zone, LNLC), and the Kuroshio-Oyashio transition region (high-nutrient and low-chlorophyll zone, HNLC) of the Northwest Pacific Ocean. The additions of dust supplied a considerable amount of nitrogen (N) and negligible phosphorus (P) relative to the seawater collected for incubation experiments (baseline), contributing to increases in Chlorophyll a with increasing dust additions. Significant linear correlations were observed between the net growth rates of larger cells (i.e., micro-size: >20 μm and nano-size: 2-20 μm) and available N (sum of baseline and added N) at each zone, demonstrating that phytoplankton size structure shifts towards larger cells with the increasing dust additions. In the experiments conducted in LNLC and HNLC zones, micro-sized phytoplankton (primarily consisting of diatoms) benefited most from dust additions. In the experiments conducted in eutrophic zone, however, the primary beneficiary was the nano-sized phytoplankton (primarily consisting of dinoflagellates). When a time lag of one day in relative abundance of diatoms (RAD, the abundance of diatoms divided by the sum of diatoms and dinoflagellates) relative to the N:P ratio was considered, we found the RAD increased substantially with increases in the N:P ratio until the ratio approached the Redfield ratio (N:P = 16:1), and then the RAD decreased gradually as the N:P ratio increased. This was ascribed to the lower sensitivity of dinoflagellates to nutrient shortage, relative to diatoms. Overall, our results suggested that the overwhelming input of N relative to P by dust deposition might cause significant ecological impacts by altering the N:P ratio of varying trophic seawaters.