SGER: Examining the Effects of Hurricane Ivan in Coastal Alabama and Northwestern Florida: A Positive Impact on Shallow Coastal Lagoons?

沿海泻湖是陆地-海洋边缘生态系统的关键组成部分，因为它们无处不在，发挥着重要的生态作用，如为许多生物提供食物和住所、过滤陆源营养物质和防止海岸线侵蚀。2004年9月16日，3级飓风伊万登陆彭萨科拉湾附近的佛罗里达半岛西北部。这场风暴造成了重大破坏，包括生命损失和房屋、道路以及供水和电力设施的大量破坏。在过去四年，督察一直广泛研究受飓风影响最严重地区的三个沿岸泻湖的生态情况。因此，飓风通过PIS研究地点，结合为这些地点编制的飓风前广泛日期，建立了一项史无前例的自然实验，以检查飓风对这些重要沿海环境的生态影响。事实上，与现有的几项飓风对珊瑚礁、河口、沼泽或红树林社区影响的研究相比，人们对飓风可能如何影响沿海泻湖及其为生态系统提供的重要服务知之甚少。PIS还预计，飓风伊万将对沿海泻湖的生态属性产生相当积极的影响，这将抵消已报告的对河口、珊瑚礁和沼泽/红树林社区的往往负面影响。预计对沿海泻湖产生积极影响的两个理由如下。首先，沿海泻湖由于其复杂和受保护的形态，往往有一个有限的引水区域(即开放水域，风可以通过该区域在底部形成切变)。因此，飓风对泻湖底栖植物(海草和大型藻类)施加的剪切强度将固有地受到泻湖形态的限制，并可能通过修剪旧部分和组织并使植物恢复活力而产生积极的影响。其次，由于没有河流输入(例如，在河口)，沿海泻湖一般有较低到中等的冲刷率，而且沿海水域存在相当有限的开口。因此，随着风暴引发的洪水消退，从周围陆地输入到沿海泻湖的营养物质将在泻湖中保留足够长的时间，以便被底栖植物有效地吸收。沿海泻湖底栖植物的生长往往受到营养可获得性的限制，因此，营养负荷的增加加上充足的吸收机会将是飓风伊万对这些植物的另一个积极影响。由于底栖植物是沿海泻湖的主要生产者和这些环境生态中的关键角色，我们假设飓风伊万通过刺激底栖植物的生长和健康，也将促进沿海泻湖的生态属性。特别是，PIS假设，在飓风伊万过后，所研究的沿海泻湖将增加初级生产力，为生物提供更高和更高水平的避难所(因此，底栖草甸中的大型动物数量更高)，并过滤和储存更多陆生营养物质。过去四年所研究的三个泻湖的广泛基线数据使PIS能够通过简单地将飓风前基线与飓风后获得的相应测量进行比较来明确地检验其假设。该研究将为两名研究生提供培训机会。密西西比-阿拉巴马州海洋赠款联盟和美国环保局建立的阿拉巴马州河口研究中心也支持这一项目。

Coastal lagoons are key components of land-ocean fringe ecosystems in view of their ubiquity and the important ecological roles they play, such as the provision of food and shelter for many organisms, the filtration of land-derived nutrients and the prevention of shoreline erosion. On September 16th 2004, Hurricane Ivan, a category 3 storm, landed on the NorthWestern Floridian Peninsula around Pensacola Bay. The storm generated substantial damage, including the loss of human lives and much destruction of houses, roads and water and electrical facilities. Over the past four years, the PIs have been studying extensively the ecology of three coastal lagoons located in the area most affected by the Hurricane. Hence, the passage of the Hurricane through the PIs study sites, in conjunction with the pre-hurricane extensive date set compiled for the sites, sets up an unprecedented natural experiment to examine the impacts of hurricanes on the ecology of these important coastal environments. Indeed, little is known as to how hurricanes may affect coastal lagoons and the important services they offer to the ecosystem, in contrast with the several existing studies of hurricane impacts on coral reefs, estuaries and marsh or mangrove communities.The focus on coastal lagoons is not the only novel aspect of this proposal. The PIs also expect that Hurricane Ivan will have a rather positive effect on the ecological attributes of coastal lagoons, which would counter the often negative effects that have been reported for estuaries, coral reefs and marsh/mangrove communities. The two arguments invoked to expect positive effects on coastal lagoons are as follows. First, coastal lagoons, in view of their convoluted and protected morphology, frequently have a restricted fetch (i.e. area of open water through which the wind can build up shear on the bottom). Hence, the intensity of shear imposed by the Hurricane on the benthic plants (seagrasses and macroalgae) of a lagoon would be inherently limited by the lagoon morphology and, likely, rather entail a positive effect by pruning old parts and tissues and rejuvenating the plants. Second, coastal lagoons have generally low to moderate flushing rates due to the absence of riverine inputs (as it happens, for instance, in estuaries) and the presence of a rather constrained opening into coastal waters. Thus, the nutrients imported into coastal lagoons from surrounding land as storm-driven flooding recedes would remain in the lagoons long enough for efficient uptake by benthic vegetation. The growth of benthic plants in coastal lagoons is often limited by nutrient availability and, thus, increased nutrient loading in combination with ample opportunity for uptake would represent another positive effect of Hurricane Ivan on those plants. Since benthic plants are the dominant producers in coastal lagoons and key players in the ecology of those environments, we hypothesize that Hurricane Ivan, through stimulating the growth and health of benthic plants, will also promote the ecological attributes of coastal lagoons. In particular the PIs hypothesize that, after the passage of Hurricane Ivan, the coastal lagoons studied will have increased primary production, offer higher and enhanced levels of shelter to organisms (and thus have higher levels of macrofauna in the benthic meadows) and filter and store larger quantities of land-derived nutrients.The extensive baseline of data obtained for the three lagoons studied over the past four years allows the PIs to unequivocally test their hypotheses by simply comparing the pre-hurricane baseline with corresponding measurements obtained after the Hurricane. The research will provide training opportunities for two graduate students. The Mississippi-Alabama Sea Grant Consortium and the EPA-founded Alabama Center for Estuarine Studies are also supporting this project.