The effect of Tropical Storm Agnes on the benthic fauna of eelgrass, Zostera marina, in the lower Chesapeake Bay

Tropical Storm Agnes caused major changes in the macroinvertebrate assemblages of both epifauna and infauna in eelgrass, Zostera marina, beds. Species abundance and density of infauna declined by one-third to one-half of values found prior to Agnes. Typical members of the infaunal community such as the amphipods, Ampelisca spp. and Lysianassa alba, the polychaetes Sabella microphthalma and Exogone dispar, ostracods and gastropods were either absent or rare following Agnes. Epifaunal density was much higher than that recorded before Agnes but the number of species was reduced. This high density was attributed to several species, e.g. Molgula manhattensis, which appeared to occupy space left open by the absence of typical members of this community, e.g. Paracereceis caudata and Bittium varium. The abnormally low salinities following Agnes affected various species in different ways. Some species were totally eliminated, severely reduced in abundance or, in a few euryhaline species, not affected at all. In some populations it appeared that adults survived but juveniles suffered high mortalities. Recovery and reestablishment by many species will be complicated by the disappearance of eelgrass in some portions of the Bay.https://scholarworks.wm.edu/vimsbooks/1076/thumbnail.jp

USING CHOICE EXPERIMENTS TO ELICIT FARMERS PREFERENCES? FOR CROP AND HEALTH INSURANCE

A random utility discrete choice experiments is used to determine farmers' preferences for health insurance, crop insurance, and a product that switches some portion of crop insurance subsidy to health insurance premium subsidy with access to large-pool risk groups.Risk and Uncertainty,

Submerged Aquatic Vegetation in Delaware\u27s Inland Bays

Submerged aquatic vegetation (SAV) is an important living resource in many coastal areas throughout the world. These plant communities have been cited as some of the most biologically important in the world. ...https://scholarworks.wm.edu/vimsbooks/1127/thumbnail.jp

Remote sensing of submerged aquatic vegetation in the Lower Chesapeake Bay : final report to National Aeronautical and Space Administration Langley Research Center

Kodak\u27s experimental water penetration film and black and white near infrared film were used to study the distribution of submerged aquatic vegetation in the lower Chesapeake Bay. The water penetration film was very useful in this study compared to the black and white N1R. Optimal results from this film were obtained with the camera aperture closed 1/2 stop from suggested settings. Detailed description of the grass beds were obtained by flying at an altitude of 5,000 feet, at low tide when wind conditions were minimal. There was a 36% reduction in the amount of submerged aquatic vegetation in the lower Chesapeake Bay from 1971 to 1974. The greatest losses occurred in the York, Piankatank and Rappahannock rivers. Recovery of some grass beds occurred primarily through seedling recruitment and subsequent vegetative growth. Cownose rays were suspected as a main factor for the decimation of some of the grass beds.

Evidence of widespread destruction of submersed aquatic vegetation (SAV) from clam dredging in Chincoteague Bay, Virginia

Beds of submerged aquatic vegetation (SAV) are important natural resources which are critical habitats for life stages of many commercially and recreationally important species of fish, crabs and shellfish in Virginia. SAV is comprised of rooted flowering plants which have historically grown throughout the Chesapeake Bay and Eastern Shore coastal lagoons in subtidal areas where water depths are less than 6 feet (Orth and Moore 1983). The presence of SAV in an area is indicative of water quality conditions which are low in nutrient enrichment and turbidity (Dennison et al. 1993). Given this relationship between water quality and growth, SAV have been chosen as an indicator species with which improvements in water quality conditions in the Chesapeake Bay and coastal lagoon systems are assessed (Chesapeake Bay Executive Council, 1992). SAV nearly disappeared from Virginia\u27s coastal lagoons and lower Chesapeake Bay regions in the 1930\u27s attributable in part to an infestation of disease. Subsequent re-growth in the lower bay was reversed in the 1970\u27s as decades long deteriorations in water quality, combined with large inputs of sediments and nutrients from Tropical Storm Agnes reduced SAV to only 10% of their historic abundance (Orth and Moore 1984). In Virginia\u27s coastal lagoons only Chincoteague Bay has experienced any subsequent recovery. Figure 1 shows the recent regrowth of SAV in Chincoteague and other northern coastal bays over the past 11 years as determined from annual aerial surveys. Each year the distribution and abundance of SAV in the Chesapeake Bay and Virginia\u27s coastal lagoons are mapped by VIMS scientists from aerial photography which is flown specifically for that purpose (Orth et al. 1996). Although a principal objective is to monitor area wide changes in SAV abundance, the photography is of such a scale and quality that impacts to SAV from dredging operation or boat scars are readily apparent (see accompanying photographs). Beginning in 1995 a few circular dredge scars were observed in SAV beds in the Virginia portion of Chincoteague Bay. These scars appeared to increase in number and size in 1996 and 1997, prompting us to alert officials at VMRC as to the increasingly significant impacts to the only remaining SAV populations along Virginia\u27s Eastern Shore. The objective of this report is to provide a summary of the field and laboratory analyses of impacts of the dredge scars to SAV in Chincoteague Bay, Va. for the Commission

Distribution and Abundance of Submerged Aquatic Vegetation in Chesapeake Bay

The Chesapeake Bay, with its extensive littoral zone and broad salinity regime of Oto 25 ppt, supports many different species of submerged aquatic vegetation (SAV) (Anderson 1972, Stevenson and Confer 1978, Orth et al. 1979). Approximately ten species of submerged vascular plants are abundant in the Bay, with another ten species occurring less frequently. In many areas, more than one species is found in a particular bed of SAV because of the similarity in the physiological tolerances of some species. Between regions of the Bay, salinity appears to be the most important factor in controlling the species composition of an individual bed of SAV (Stevenson and Confer 1978), while sediment composition and light regime are important factors in controlling the distribution of SAV within regions of the Bay. All species, regardless of the salinity regime, are found in regions of the Bay\u27s littoral zone and are iocated in water less than two to three meters deep (mean low water - MLW), primarily because of low levels of light that occur below these depths (Wetzel et al. 1981).https://scholarworks.wm.edu/vimsbooks/1096/thumbnail.jp

Distribution and Abundance of Submerged Aquatic Vegetation in 1984 and 1985

Communities of submerged aquatic vegetation (SA V) are an integral part of the Chesapeake Bay ecosystem. They provide an important habitat for many species, either as a food source or as protection from predators, i.e., as a nursery. By reducing currents and baffling waves, they allow for deposition of suspended material. In addition, they bind sediments with their roots and rhizomes to prevent erosion of the underlying material. They are important in nutrient cycling through both the absorption and release of nitrogen and phosphorus.https://scholarworks.wm.edu/vimsbooks/1165/thumbnail.jp