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Phytoplankton growth and grazing mortality through the oligotrophic subtropical North Pacific
Journal of Oceanography ( IF 1.3 ) Pub Date : 2021-01-01 , DOI: 10.1007/s10872-020-00580-4
Siyu Jiang , Fuminori Hashihama , Hiroaki Saito

The subtropical North Pacific has been historically considered as a stable and homogenous oligotrophic marine ecosystem. The consistently low phytoplankton biomass has been attributed to a close balance between phytoplankton growth and grazing mortality. However, phytoplankton summer blooms were frequently observed in the central North Pacific near the Hawaiian Islands. To determine whether this is a result of unbalanced phytoplankton growth and microzooplankton grazing, we conducted a trans-Pacific cruise through the subtropical North Pacific. The growth and microzooplankton grazing mortality rates of the phytoplankton community and specific groups in the surface layer (10 m), were examined by dilution experiments. Positive phytoplankton net growth rates (0.34 ± 0.29 day −1 ) were observed under the depletion of dissolved inorganic nitrogen (DIN, < 40 nM) throughout the study area. However, considering the grazing of micro- and mesozooplankton collectively, the phytoplankton growth was largely consumed (net growth rate of 0.08 ± 0.15 day −1 ), except in the central North Pacific (net growth rate of 0.42 ± 0.11 day −1 ). Phytoplankton biomass accumulation in this area was also demonstrated by the satellite-observed Chl a , although this was just sustained for a few days. The high phytoplankton growth rate in the central North Pacific (0.84 ± 0.26 day −1 ) was a result of the dominant Prochlorococcus , which contributed 88% of the community Chl a . The weak response of Prochlorococcus growth to ammonium addition indicates their growth (1.14 ± 0.55 day −1 ) was not limited by the ambient DIN and was likely a result of their advantage of utilizing various dissolved organic nitrogen.

中文翻译:

贫营养亚热带北太平洋浮游植物生长和放牧死亡率

亚热带北太平洋在历史上一直被认为是一个稳定且同质的贫营养海洋生态系统。持续低的浮游植物生物量归因于浮游植物生长和放牧死亡率之间的密切平衡。然而,在夏威夷群岛附近的北太平洋中部经常观察到浮游植物夏季大量繁殖。为了确定这是否是浮游植物生长和微型浮游动物放牧不平衡的结果,我们进行了一次穿越亚热带北太平洋的跨太平洋巡航。通过稀释实验检查浮游植物群落和表层(10 m)特定群体的生长和微型浮游动物放牧死亡率。在溶解无机氮(DIN,< 40 nM) 在整个研究区域。然而,考虑到集体放牧微型和中型浮游动物,除了在北太平洋中部(净增长率为 0.42 ± 0.11 天 -1 )外,浮游植物的生长被大量消耗(净增长率为 0.08 ± 0.15 天 -1 )。卫星观测到的 Chl a 也证明了该地区浮游植物生物量的积累,尽管这只是持续了几天。北太平洋中部浮游植物的高增长率(0.84 ± 0.26 天 -1 )是占优势的原绿球藻的结果,占群落 Chl a 的 88%。原绿球藻生长对铵添加的微弱响应表明它们的生长(1.14 ± 0.55 天 -1 )不受环境 DIN 的限制,并且可能是由于它们利用各种溶解的有机氮的优势。40 nM) 在整个研究区域。然而,考虑到集体放牧微型和中型浮游动物,除了在北太平洋中部(净增长率为 0.42 ± 0.11 天 -1 )外,浮游植物的生长被大量消耗(净增长率为 0.08 ± 0.15 天 -1 )。卫星观测到的 Chl a 也证明了该地区浮游植物生物量的积累,尽管这只是持续了几天。北太平洋中部浮游植物的高增长率(0.84 ± 0.26 天 -1 )是占优势的原绿球藻的结果,占群落 Chl a 的 88%。原绿球藻生长对铵添加的微弱响应表明它们的生长(1.14 ± 0.55 天 -1 )不受环境 DIN 的限制,并且可能是由于它们利用各种溶解的有机氮的优势。40 nM) 在整个研究区域。然而,考虑到集体放牧微型和中型浮游动物,除了在北太平洋中部(净增长率为 0.42 ± 0.11 天 -1 )外,浮游植物的生长被大量消耗(净增长率为 0.08 ± 0.15 天 -1 )。卫星观测到的 Chl a 也证明了该地区浮游植物生物量的积累,尽管这只是持续了几天。北太平洋中部浮游植物的高增长率(0.84 ± 0.26 天 -1 )是占优势的原绿球藻的结果,占群落 Chl a 的 88%。原绿球藻生长对铵添加的微弱响应表明它们的生长(1.14 ± 0.55 天 -1 )不受环境 DIN 的限制,并且可能是它们利用各种溶解有机氮的优势的结果。
更新日期:2021-01-01
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