Iron and grazing constraints on primary production in the central equatorial Pacific: An EqPac synthesis
Iron and grazing constraints on primary production in the central equatorial Pacific: An EqPac synthesis
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DOI：
10.4319/lo.1997.42.3.0405
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发表时间：
1997-05-01
影响因子：
4.5
通讯作者：
White, JR
中科院分区：
文献类型：
--
作者：
Landry, MR;Barber, RT;White, JR
最近在赤道太平洋中部的研究允许在一个高营养，低叶绿素（HNLC）的生态系统浮游植物调节的全面评估。元素铁主要通过上涌进入真光层，并且存在于浓度（小于或等于30 pM）低于估计的半饱和常数（120 pM）的大细胞中，所述大细胞以铁富集而开花。此外，光合作用的量子产率的负向趋势表明，即使是占主导地位的小型浮游植物也因缺铁而低于其生理潜力。微型浮游动物的放牧占主导地位的浮游植物损失，几乎所有的测量浮游植物生产在厄尔尼诺条件下，类似于66%，在正常的上升流条件下，与中型浮游动物放牧和横向平流关闭平衡。硝酸盐的吸收与硅藻的色素生物量密切相关，硅藻在正常的上升流条件下相对丰度增加。尽管如此，f比在所有条件下都保持较低（0.07-0.12）。铁的预算是一致的概念，新的生产是由新的铁输入到系统的速度，而总产量取决于有效的铁回收草食动物。虽然限制基板不同，在HNLC地区的资源限制和放牧的相互作用在概念上是类似的寡营养亚热带地区的普遍接受的观点。在这两个系统中，小的优势浮游植物生长迅速，但通常低于生理最大，率;他们被裁剪到低稳定丰度的微型浮游动物;和他们的持续高增长率依赖于放牧的副产品。
Recent studies in the central equatorial Pacific allow a comprehensive assessment of phytoplankton regulation in a high-nutrient, low-chlorophyll (HNLC) ecosystem. Elemental iron enters the euphotic zone principally via upwelling and is present at concentrations (less than or equal to 30 pM) wen below the estimated half-saturation constant (120 pM) for the large cells that bloom with iron enrichment. In addition, the meridional trend in quantum yield of photosynthesis suggests that even the dominant small phytoplankton are held below their physiological potential by iron deficiency. Grazing by microzooplankton dominates phytoplankton losses, accounting for virtually all of the measured phytoplankton production during El Nino conditions and similar to 66% during normal upwelling conditions, with mesozooplankton grazing and lateral advection closing the balance. Nitrate uptake is strongly correlated with the pigment biomass of diatoms, which increase in relative abundance during normal upwelling conditions. Nonetheless, the f-ratio remains low (0.07-0.12) under all conditions. Iron budgets are consistent with the notions that new production is determined by the rate of new iron input to the system while total production depends on efficient iron recycling by grazers. Although the limiting substrates differ, the interactions of resource limitation and grazing in HNLC regions are conceptually similar to the generally accepted view for oligotrophic subtropical regions. In both systems, small dominant phytoplankton grow at rapid, but usually less than physiologically maximal, rates; they are cropped to low stable abundances by microzooplankton; and their sustained high rates of growth depend on the remineralized by-products of grazing.