Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event
Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event
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DOI：
10.1016/j.pocean.2017.04.007
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发表时间：
2017-04
影响因子：
4.1
通讯作者：
N. Loick‐Wilde;Deniz Bombar;H. Doan;L. Nguyen;Anh Mai Nguyen-Thi;M. Voss;J. Dippner
中科院分区：
文献类型：
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作者：
N. Loick‐Wilde;Deniz Bombar;H. Doan;L. Nguyen;Anh Mai Nguyen-Thi;M. Voss;J. Dippner
调查不同气候条件下的微型浮游生物生物量和多样性是了解气候变化对养分循环和生物生产力的级联效应的关键。在这里，我们使用的数据收集在两个对比鲜明的夏季沿着越南海岸，以显示气候驱动的变化可以有一个显着的影响，通过其对水体中的营养物浓度的影响，对微型浮游生物群落及其生物量的分布。2003年7月的第一个夏季是在一次弱的厄尔尼诺南方涛动（ENSO）事件之后，其特征是弱的沿海上升流，在2004年7月的第二个夏季，上升流是正常的。2004年7月上升流的源水质量以非常低的硅酸盐（SiO 4）浓度和SiO 4：DIN比值为特征，动态SiO 4与溶解无机氮的比值（SiO 4：DIN）主要低于Redfield-Brzezinski比值，DIN与磷酸盐的比值（DIN：PO 43 −）低于Redfield比值是越南海域的一个共同特征。高得多的颗粒浓度和PSi/PC比值在正常的上升流揭示了夏季之间的微型浮游生物群落结构的重大变化。小型甲藻（10-20 µm）在上升流减少期间普遍存在。在正常上升流期间，硅藻根管藻。在富硅酸盐上升流沃茨中，Trichodesmium alumraeum占优势，在湄公河影响和营养盐枯竭的近海沃茨中，Trichodesmium alumraeum与R. soleniasp共存。这两个物种都直接与更高的初级生产力（PP）和N2固定率，在早期的研究中量化，以及更高的dilemma在这些近海网站。沿着海岸，Rsoleniasp.和PP速率不太清楚，影响龙须菜生物量的因素。在上升流沃茨中。上升流源水体中硅酸盐浓度很低，湄公河羽流离岸偏转，可能引发了与ENSO后条件相比，在正常上升流季节越南近海微型浮游生物群落中观察到的生态差异。
Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event and was characterized by weak coastal upwelling, in the second summer during July 2004, upwelling was normal.Very low silicate (SiO4) concentrations and SiO4:DIN ratios characterized the source water mass for upwelling in July 2004, and dynamic SiO4to dissolved inorganic nitrogen ratios (SiO4:DIN) mainly below the Redfield-Brzezinski ratio and DIN to phosphate ratios (DIN:PO43−) below the Redfield ratio were a common feature off Viet Nam. Much higher particle concentrations and PSi/PC ratios during normal upwelling revealed major changes in the microplankton community structure among summers. Small dinoflagellates (10–20 µm) prevailed ubiquitously during reduced upwelling. During normal upwelling, the diatomRhizosoleniasp. dominated the cell-carbon biomass in the silicate poor upwelling waters.Trichodesmium erythraeumdominated in the Mekong-influenced and nutrient depleted offshore waters, where it co-occurred withRhizosoleniasp. Both species were directly associated with the much higher primary production (PP) and N2fixation rates that were quantified in earlier studies, as well as with much higher diversities at these offshore sites. Along the coast, the correlation betweenRhizosoleniasp. and PP rates was less clear and the factors regulating the biomass ofRhizosoleniasp. in the upwelling waters are discussed. The very low silicate concentrations in the source water mass for upwelling and the offshore deflection of the Mekong river plume likely triggered the observed ecological differences in the microplankton communities off Viet Nam in the normal upwelling season compared to the post ENSO conditions.