SGER: Hurricane Isabel Impacts on Chesapeake Bay

飓风是会对河口生态系统造成重大干扰的自然事件。前几次飓风对切萨皮克湾的一些影响(例如1972年的Agnes)对水下水生植被(急剧减少)和渔业(例如Agnes之后的文蛤和牡蛎的减少)产生了持久的影响。这个SGER(探索性研究小额赠款)项目将研究飓风伊莎贝尔对切萨皮克湾水文和食物网结构的影响。2003年9月18日袭击切萨皮克湾的飓风伊莎贝尔为记录和评估一次重大干扰事件的影响提供了一个独特的机会。超过每小时70英里的大风猛烈地混合了海湾水域。海湾入海口6.12英尺的风暴潮花了18个小时才沿着海湾向上移动到巴尔的摩，那里的最高水位比平均高水位高7.36英尺。这种巨大的陆架水入侵在切萨皮克湾重新分配了盐、浮游生物和鱼类。2003年水年(WY)，其中包括与伊莎贝尔有关的降雨量(10月9月)是自1937年以来向切萨皮克湾输入淡水的最高值。在异常潮湿的2003年，伊萨贝尔的通过提供了一个独特的机会，来评估一次重大扰动对海湾生态系统已经增加的淡水输入的影响。该项目将于2003年11月初进行一次为期7天的巡航，按照在六个平局年(1995-2000年)和两个BITMAX年(2001-2002年)指定的抽样程序进行，从而与飓风伊莎贝尔之后观察到的情况形成了根本的对比。调查人员将对切萨皮克湾主干的水文和生态系统结构进行密集测量。在第一航段(3天)，他们将使用拖曳起伏记录器和表面测绘系统进行连续测绘，该测绘系统测量切萨皮克湾主干下350公里长的轴向横断面上的温度、盐分、氧气、叶绿素和浮游动物(光学浮游生物计数器)，以及相距10公里的多达24个跨湾横断面。这些测量的垂直和水平分辨率将分别约为1米和200米。物理和生物特性地图将为随后的水文、浮游生物和鱼类调查提供基本背景。在第二航段(4天)，他们将在26个海湾横断面上进行水文站和营养物质、浮游植物生物量和生产量、浮游动物泵和声学测量以及鱼类丰度/分布(Tucker拖网和水中拖网)的测量。CBOS系泊设施，包括受损的车站，将在间隔期间保持不变。

Hurricanes are natural events that can impose a major perturbation to estuarineecosystems. Some effects of previous hurricanes on Chesapeake Bay (e.g., Agnes in1972) had lasting impacts on submerged aquatic vegetation (drastic decrease) and onfisheries (e.g. soft clam and oyster decline after Agnes). This SGER (Small Grant for Exploratory Reserch) project will examinethe effects of Hurricane Isabel on the hydrographic and food-web structure ofChesapeake Bay. Hurricane Isabel, which struck Chesapeake Bay on September 18,2003, provides a unique opportunity to document and evaluate effects of a significant.disturbance event.. Winds in excess of 70 mph vigorously mixed Bay waters. A stormsurge, 6.12 ft at the Bay mouth took 18 hours to move up the Bay to Baltimore wheremaximum water level was 7.36 ft above mean high water. This significant intrusion ofshelf water redistributed salt, plankton and fish within Chesapeake Bay. The 2003 WaterYear (WY), which includes rainfall associated with Isabel (Oct . Sept) represented thehighest WY freshwater input to Chesapeake Bay since 1937. The passage of Isabelduring the unusually wet 2003 provides a unique opportunity to evaluate effects of amajor perturbation on already enhanced freshwater input to the Bay ecosystem. The project will involved a 7-day cruise in early November, 2003 in which the samesampling procedures are followed that were designated during the six TIES years (1995-2000) and two BITMAX years (2001-2002) thus providing an essential contrast toconditions that observed in the wake of Hurricane Isabel. Investigators will intensively measure the hydrographic and ecosystem structure of the main stem ofChesapeake Bay. On leg 1 (3 days) they will conduct continuous mapping using a towedundulating recorder and surface mapping system which measures temperature, salt,oxygen, chlorophyll and zooplankton (Optical Plankton Counter) along a 350-km axialtransect down the main stem of Chesapeake Bay and with up to 24 cross-Bay transectsspaced 10 km apart. The vertical and horizontal resolution of these measurements will beapproximately 1 m and 200 m, respectively. Maps of physical and biological propertieswill provide an essential background for the hydrographic, plankton and fish surveys thatwill follow. On the second leg (4 days) they will conduct hydrographic stations (CTDs)and measurements of nutrients, phytoplankton biomass and production, zooplanktonpump and acoustic measurements, and fish abundance/distributions (Tucker trawl andmidwater trawl) on 26 Bay-transects. CBOS moorings, including the damaged stations,will be maintained through the interval.