Hurricanes are natural events that can impose a major perturbation to estuarine ecosystems. Some effects of previous hurricanes on Chesapeake Bay (e.g., Agnes in 1972) had lasting impacts on submerged aquatic vegetation (drastic decrease) and on fisheries (e.g. soft clam and oyster decline after Agnes). This SGER (Small Grant for Exploratory Reserch) project will examine the effects of Hurricane Isabel on the hydrographic and food-web structure of Chesapeake 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 storm surge, 6.12 ft at the Bay mouth took 18 hours to move up the Bay to Baltimore where maximum water level was 7.36 ft above mean high water. This significant intrusion of shelf water redistributed salt, plankton and fish within Chesapeake Bay. The 2003 Water Year (WY), which includes rainfall associated with Isabel (Oct . Sept) represented the highest WY freshwater input to Chesapeake Bay since 1937. The passage of Isabel during the unusually wet 2003 provides a unique opportunity to evaluate effects of a major 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 same sampling procedures are followed that were designated during the six TIES years (1995- 2000) and two BITMAX years (2001-2002) thus providing an essential contrast to conditions that observed in the wake of Hurricane Isabel. Investigators will intensively measure the hydrographic and ecosystem structure of the main stem of Chesapeake Bay. On leg 1 (3 days) they will conduct continuous mapping using a towed undulating recorder and surface mapping system which measures temperature, salt, oxygen, chlorophyll and zooplankton (Optical Plankton Counter) along a 350-km axial transect down the main stem of Chesapeake Bay and with up to 24 cross-Bay transects spaced 10 km apart. The vertical and horizontal resolution of these measurements will be approximately 1 m and 200 m, respectively. Maps of physical and biological properties will provide an essential background for the hydrographic, plankton and fish surveys that will follow. On the second leg (4 days) they will conduct hydrographic stations (CTDs) and measurements of nutrients, phytoplankton biomass and production, zooplankton pump and acoustic measurements, and fish abundance/distributions (Tucker trawl and midwater trawl) on 26 Bay-transects. CBOS moorings, including the damaged stations, will be maintained through the interval.
