Hydrodynamic forcing of Alexandrium population biology

有毒甲藻亚历山大藻的水华是每年春季和夏季缅因湾反复出现的现象。由真菌产生的毒素在滤食性贝类的组织中积累，如贻贝和文蛤。人类摄入这些受污染的贝类可能会导致麻风性贝类中毒(PSP)，这是一种潜在的致命疾病。因此，了解决定真菌分布和丰度的因素具有相当大的经济和公共卫生利益。现有的数据和模型表明，风信子种群和缅因湾沿岸洋流系统之间存在很强的相互联系。事实上，人口的物理-生物耦合模型 动力学和水动力输运能够模拟观察到的真菌分布的一些一般特征。然而，这类模型对输入参数(如生长率、游泳速度、发芽率等)的选择很敏感。奇怪的是，模型匹配观测值的能力出现在这个参数空间的范围内，相对于实验室和现场测量定义的合理值的包络来说，这个范围相对较窄。这种明显不一致的一个可能解释是自然种群中的遗传异质性。我们假设，真菌的聚集分布是由一组遗传上不同的亚群组成的，每个亚群对环境条件有不同的生理和/或行为反应。该项目的目标是了解对这些种群的水动力和生物控制、它们的毒素产生，以及这些因素最终如何决定贝类毒性的波动。

Blooms of the toxic dinoflagellate Alexandrium fundyense are annually recurrent phenomena in the Gulf of Maine during the spring and summer months. Toxins produced by A. fundyense accumulate in the tissues of filter-feeding shellfish such as mussels and clams. Human ingestion of these contaminated shellfish can lead to Paralytic Shellfsh Poisoning (PSP), a potentially fatal illness. Understanding the factors that determine the distribution and abundance of A. fundyense is therefore of considerable economic and public health interest. Existing data and models demonstrate strong interconnections between A. fundyense populations and the Gulf of Maine coastal current system. Indeed, coupled physical-biological models of population dynamics and hydrodynamic transport are able to simulate some of the general features of the observed A. fundyense distribution. However, such models are sensitive to the choices of the input parameters (e.g. growth rate, swimming speed, germination rate, etc). Curiously, the ability of the models to match the observations occurs in a range of this parameter space that is relatively narrow with respect to the envelope of reasonable values defined by laboratory and field measurements. One possible explanation for this apparent inconsistency is genetic heterogeneity in the natural populations. We hypothesize that the aggregate distribution of A. fundyense is composed of a mosaic of genetically distinct subpopulations, each with different physiological and/or behavioral responses to environmental conditions. The goal of this project is to understand the hydrodynamic and biological controls on these populations, their toxin production, and how these factors ultimately determine fluctuations in shellfish toxicity.