Non-monotonic Responses of Phytoplankton Biomass Accumulation to Hydrologic Variability: A Comparison of Two Coastal Plain North Carolina Estuaries
Non-monotonic Responses of Phytoplankton Biomass Accumulation to Hydrologic Variability: A Comparison of Two Coastal Plain North Carolina Estuaries
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DOI：
10.1007/s12237-012-9547-2
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发表时间：
2012-11-01
影响因子：
2.7
通讯作者：
Paerl, Hans W.
中科院分区：
文献类型：
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作者：
Peierls, Benjamin L.;Hall, Nathan S.;Paerl, Hans W.
淡水输入通常比氮(N)输入对河口浮游植物生物量（叶绿素a）积累起更直接的作用，因为排放同时控制着浮游植物的停留时间和N负荷。考虑到气候和人类活动的潜在变化可能影响排放和流域氮供应，了解这种联系至关重要。在相同的气候条件和事件影响下，对两个相邻的浅水（< 5 m）微潮河口（New和Neuse River河口，NC， USA）的3年时间序列进行了叶绿素a （chla）与水文变率的关系研究。在干旱和洪涝条件下，两个河口的N浓度和盐度分别对流量表现出直接的正响应和负响应。chla对排放的响应更为复杂，但可以通过将排放转换为淡水冲洗时间来解释，这是对运输时间尺度的估计。chla与冲刷时间的非线性拟合显示出非单调、单峰的关系，反映了各河口的内在增长与损失随时间和沿轴线的变化平衡。两个系统的最大生物量发生在大约10天的冲洗时间。对拟合数据的残差分析显示，chla与温度之间存在正相关关系，表明温度越高，生长速度越快。氮负荷与全系统体积加权chla呈正相关，且每氮负荷的生物量产量大于其他海洋系统。这些关于浮游植物生物量水文控制的结果与有关损失过程的信息相结合，将有助于制定预测生态系统对未来气候和人为变化的反应所必需的机制模型。
Freshwater inputs often play a more direct role in estuarine phytoplankton biomass (chlorophyll a) accumulation than nitrogen (N) inputs, since discharge simultaneously controls both phytoplankton residence time and N loading. Understanding this link is critical, given potential changes in climate and human activities that may affect discharge and watershed N supply. Chlorophyll a (chla) relationships with hydrologic variability were examined in 3-year time series from two neighboring, shallow (< 5 m), microtidal estuaries (New and Neuse River estuaries, NC, USA) influenced by the same climatic conditions and events. Under conditions ranging from drought to floods, N concentration and salinity showed direct positive and negative responses, respectively, to discharge for both estuaries. The response of chla to discharge was more complex, but was elucidated through conversion of discharge to freshwater flushing time, an estimate of transport time scale. Non-linear fits of chla to flushing time revealed non-monotonic, unimodal relationships that reflected the changing balance between intrinsic growth and losses through time and along the axis of each estuary. Maximum biomass occurred at approximately 10-day flushing times for both systems. Residual analysis of the fitted data revealed positive relationships between chla and temperature, suggesting enhanced growth rates at higher temperatures. N loading and system-wide, volume-weighted chla were positively correlated, and biomass yields per N load were greater than other marine systems. When combined with information on loss processes, these results on the hydrologic control of phytoplankton biomass will help formulate mechanistic models necessary to predict ecosystem responses to future climate and anthropogenic changes.