Temperature and residence time controls on an estuarine harmful algal bloom: Modeling hydrodynamics and Alexandrium fundyense in Nauset estuary.
Temperature and residence time controls on an estuarine harmful algal bloom: Modeling hydrodynamics and Alexandrium fundyense in Nauset estuary.
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DOI：
10.1007/s12237-015-9949-z
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发表时间：
2015-11-01
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影响因子：
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通讯作者：
Anderson DM
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文献类型：
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作者：
Ralston DK;Brosnahan ML;Fox SE;Lee K;Anderson DM
建立了一个高分辨率的三维水动力学模型，研究了河口湾内反复发生的有害藻华的物理和生物控制。位于科德角（美国马萨诸塞州）的瑙赛特河口由三个盐塘组成，通过浅水沼泽和潮汐通道网络与海洋相连。利用定量技术指标对三次春华期间的物理和生物条件进行了评估。A. fundyense模型是基于先前在附近缅因湾的模型应用，但为了与Nauset的观测结果一致，进行了显著的修改。控制naseet水华的主要因素是调节生物生长速度的水温，以及由于水深限制、分层和细胞行为（diel垂直迁移）而导致的细胞有效保留。交换中的春季小潮变化改变了停留时间，但要使细胞保留时间大大超过细胞倍增时间，就需要积极的垂直迁移和分层，从而抑制风和潮汐流将细胞混合到表层。与缅因湾不同，模型结果对囊肿分布或发芽率相对不敏感。相反，在Nauset中，保留种群的营养细胞分裂率很高，这决定了开花的发育。与缅因湾相比，该地区的囊肿萌发时间较早，这表明恶心囊肿对萌发时间有不同的控制。模型结果对营养物浓度相对不敏感，这是由于受严重影响的河口富营养化条件或营养物采样的时空分辨率的限制。据推测，细胞损失率在开花生长阶段极低，但在最后阶段由于过程仍然不确定而迅速增加。经过验证的模型可以定量评估导致反复出现有害藻华的因素，并为评估受到类似影响的沿海系统提供框架。
A highly resolved, 3-d model of hydrodynamics and Alexandrium fundyense in an estuarine embayment has been developed to investigate the physical and biological controls on a recurrent harmful algal bloom. Nauset estuary on Cape Cod (MA, USA) consists of three salt ponds connected to the ocean through a shallow marsh and network of tidal channels. The model is evaluated using quantitative skill metrics against observations of physical and biological conditions during three spring blooms. The A. fundyense model is based on prior model applications for the nearby Gulf of Maine, but notable modifications were made to be consistent with the Nauset observations. The dominant factors controlling the A. fundyense bloom in Nauset were the water temperature, which regulates organism growth rates, and the efficient retention of cells due to bathymetric constraints, stratification, and cell behavior (diel vertical migration). Spring-neap variability in exchange altered residence times, but for cell retention to be substantially longer than the cell doubling time required both active vertical migration and stratification that inhibits mixing of cells into the surface layer by wind and tidal currents. Unlike in the Gulf of Maine, the model results were relatively insensitive to cyst distributions or germination rates. Instead, in Nauset, high apparent rates of vegetative cell division by retained populations dictated bloom development. Cyst germination occurred earlier in the year than in the Gulf of Maine, suggesting that Nauset cysts have different controls on germination timing. The model results were relatively insensitive to nutrient concentrations, due to eutrophic conditions in the highly impacted estuary or due to limitations in the spatial and temporal resolution of nutrient sampling. Cell loss rates were inferred to be extremely low during the growth phase of the bloom, but increased rapidly during the final phase due to processes that remain uncertain. The validated model allows a quantitative assessment of the factors that contribute to the development of a recurrent harmful algal bloom and provides a framework for assessing similarly impacted coastal systems.