We investigated growth, Dermo disease, and survival for nine groups of oysters, Crassostrea virginica (Gmelin) cultivated in Chesapeake Bay (CB). Five regional strains (upper CB, North Carolina (NC), South Carolina (SC), Louisiana (LA) and LA triploids) and four additional hybrid strains (CB oysters mated with NC, SC, LA and Texas (TX) oysters) were held in floating rafts at three locations representative of lower CB: 'low' salinity (3-14 g L-1), 'moderate' salinity (5-20 g L-1) and 'high' salinity (14-24 g L-1). At each site, patterns of growth and incidence of infection with Perkinsus marinus (Levine), the causative agent of Dermo disease, were similar. However, mortality trends were markedly different at each site; the CB strain being notable for accelerated mortality following infection with P. marinus. In addition, hybrids between CB and all four of the regional strains exhibited similar accelerated mortality in response to infection. Mortality was strongly correlated with infection only at the high salinity site implicating interaction of differences in both oyster strain and virulence of Dermo between moderate and high salinity areas as factors in differential mortality across sites.

Growth, intensity of Perkinsus marinus (Levine) infection, and survival of synchronously spawned North Carolina (NC) and Chesapeake Bay-heritage (CB) oysters, Crassostrea virginica (Gmelin) were evaluated under standard tray culture conditions at several sites in both regions (Wye River, Maryland; Mobjack Bay, Virginia; Pamlico River, NC and Bogue Banks, NC). Infection prevalence reached 100% in oysters held at all high- and moderate-salinity sites, at which time the CB strain ceased to grow. Shortly after growth ceased, CB oysters exhibited mortality that rapidly progressed to 100%. Unlike the CB strain, growth continued in the NC strain despite high P. marinus prevalence.When mortality did occur in the NC strain, at a reduced rate of 37^40%, it was associated with higher intensity of P. marinus than the infection intensity correlated with death of CB oysters. At the low-salinity site in NC, P. marinus infection persisted at low weighted prevalence throughout the latter portion of the culture period but was not associated with mortality of either strain. These trends in growth and disease resistance for the two strains demonstrate that aquaculture performance is related to the level of disease resistance in oyster strains, salinity of water in growing areas and virulence of P. marinus.

Over $3.5 billion were spent toward nutrient controls in the Chesapeake Bay watershed between 1985 and 1996. These expenditures were based on cost-shares between federal, state, local, and private sources and should be considered conservative. A comparison of point and nonpoint nutrient control expenditures in the Bay basin showed that about 50% of the funds were directed toward agricultural best management practices and 45% were allocated for point source nutrient reductions and combined sewer overflows (20% and 25%, respectively). The remainder was spent on various other estuarine-targeted programs. Maryland was responsible for 79% of the total expenditures, 16% was expended by Virginia, and the remainder was attributable to the District of Columbia and Pennsylvania (4% and 1%, respectively). The most costly basin was the Patuxent (over $125 per kilogram of total nitrogen removed) and the least costly was the Eastern Shore of Virginia, where the cost was just under $21 per kilogram of nitrogen removed. For the control practices examined, the analysis found that nutrient management was the least costly. Animal waste control and low tillage were the second and third most economical nutrient management strategies. Significant reductions were achieved from point sources for both total nitrogen (16%) and total phosphorus (53%) by 1996. Virtually all of the large reduction in point source phosphorus was a result of the phosphorus detergent ban implemented basinwide in the late 1980s. Nonpoint source nutrient reductions were more modest. An approximate 12% reduction in phosphorus was accompanied by an 8% reduction in total nitrogen loadings. Despite these nutrient reductions, no significant improvements in bottom-dissolved oxygen levels were detected along the Bay mainstem during the warmer months, and the mouth of Chesapeake Bay showed marginally significant degradation during the 11-year period. It was determined that dissolved oxygen conditions were influenced more by nitrogen than phosphorus reductions and that nutrient controls aimed at the mid-Bay region had the greatest potential for improving low dissolved oxygen conditions in the Bay's bottom waters.

ABSTRACT Populations of the Eastern oyster, Crassostrea virginica, in Chesapeake Bay have been greatly reduced over the last decade by two protozoan parasites. One of these, Perkinsus marinus, has been especially harmful, sometimes killing 70-80% of harvestable oysters in a given area. However, while P. marinus has caused substantial mortalities in the Chesapeake, oysters in states farther south and along the Gulf coast have not experienced such intense effects. This may be due to differences in P. marinus abundance and virulence at various sites or to differences in the tolerance of C. virginica stocks or to a combination of these and other factors. During the period March 1992 to May 1993, growth, intensity of infection with P. marinus, and survival of native North Carolina oysters (NC) held under standard tray culture conditions at several sites in both regions (Wye River, Maryland; Mobjack Bay, Virginia; Pamlico River, North Carolina; and Bogue Banks, North Carolina) were evaluated. At the Chesapeake Bay sites (Wye River and Mobjack Bay) the performance of the NC strain to native Chesapeake Bay oysters (CB) spawned synchronously were compared. Both NC and CB oyster spat were introduced at average lengths of 20-22 mm in March 1992. P. marinus infection reached 100% in oysters held at all high and moderate salinity sites by July 1992, at which time the CB strain held in Chesapeake Bay ceased to grow. Shortly after growth ceased, CB oysters experienced an accelerated mortality that rapidly progressed to 100%. Meanwhile, the native NC strain held at high and moderate salinity sites in both regions also experienced mortality, but at a much reduced rate of only 20-30%. High levels of P. marinus infection were accompanied by continued growth of the NC strain. When mortality did occur in the NC strain, it was associated with a much higher intensity of P. marinus than the infection intensity correlated with death of CB oysters. At the low salinity site, P. marinus infection persisted at low intensity throughout the latter portion of the culture period but was not associated with mortality of either strain. The trends in growth and disease tolerance for the two strains suggest that performance of oysters is related to genetic makeup and to other factors such as acclimatization and virulence off! marinus.

A series of toxicity tests were conducted on liquid and suspended solid phase fractions of sediments from the Port of Hampton Roads, Virginia. The respiration and hyporegulatory capacity of grass shrimp proved to be sensitive indices of sublethal stress associated with exposure to contaminated sediments. On the other hand, hyper-regulatory capacity was not affected by any of the experimental conditions. Experiments involving sediments from Hampton Roads Harbor and most of the mainstem of the Elizabeth River showed no indications of stress. However, sediment elutriates from the most industrialized region of the Southern Branch of the Elizabeth River produced significant sublethal effects. The present study clearly defined the region of significant sediment contamination. The findings also indicated that most materials dredged during port deepening operations should be less contaminated than those routinely taken by maintenance dredging.

Abstract Data from a comprehensive series of toxicity bioassays and chemical surveys were analyzed by discriminant analysis to statistically classify sediment quality in the Port of Hampton Roads, Virginia. A consensus “map” indicating sediment quality was developed to classify stations into “clean” vs. “contaminated” groups. The “clean” group, which produced few biological effects, included stations with low levels of polynuclear aromatic hydrocarbons (PAHs), while significant biological effects were associated with “contaminated” sediments containing high levels of PAHs. The statistical analysis clearly indicated different characteristic patterns of PAHs in the various geographic regions. Both the toxicological and PAH data indicated a change in the sediment quality between dredging operations. The multivariate statistical approach to the classification of sediment quality has been shown to provide an effective, objective means of evaluating dredged materials being considered for ocean disposal.

Climate and sea level changes have been relatively stable for the last few centuries. The delicate balance between global and oceanic systems, however, may be altered due to the increased warming of the earth's average surface temperature. A few degrees increase could cause a 15-17 cm sea level rise by the year 2000, resulting in wide spread flooding of low lying areas. Recent studies indicate the...

: The coastal zone has long been a source of sustenance for the human community. Because of its aesthetic and economic value there has occurred a continual ingress to this dynamic, yet finite area. A vital component of the routine operations around most coastal harbors and embayments is the maintenance dredging of navigational channels. Associated with this particular operation is the need for adequate disposal site. Recently, questions have been raised concerning the potential impact of dredged material disposal on the aquatic resources, in particular the plankton community. Conclusion of report is that the Dam Neck Disposal Site (DNDS) does not appear to represent a major larval transport route for any but the most common and commercially insignificant species (e.g. sand shrimp, Bay anchovies, gastropods, and hermit crabs). The only possible exception would be the blue crab megalopae found in the neuston in the center of the study area. This population represents only a small portion of the recruitment stock in the Bay. Previous studies have documented equal or greater concentrations of megalopae offshore. Blue crab zoea were found in greatest numbers offshore of DNDS. Keywords: Commercial fisheries, Recreational fisheries.

: Peak abundance of blue crab larvae occurs in mid to late summer at the deeper channels of the Chesapeake Bay mouth and NDS stations. Although no vertical stratification was noticed for early stage larvae, a seaward migration is indicated. Larval development occurs offshore where megalopae concentrate in the neuston layer prior to re-invasion of the Bay. Larval rock crabs were collected throughout the colder winter months at the Bay mouth and NDS stations. Although peak abundances occurred in May offshore, larvae were also collected in early fall. The larvae tended to remain in the higher salinity and cooler bottom waters, as did the later stage megalopae. Oyster larvae tended to remain in the vicinity of the James and Elizabeth Rivers confluence and infrequently occurred seaward. Most larvae occurred in the plankton during July and August. In 1983, a bimodal distribution was observed with a second peak as late as September. Bivalve larvae were very abundant at the outer stations; however, declined sharply at the inner stations. Oysters comprised a significant proportion of the total bivalve larvae present at these inner stations. Keyword: Meroplankton.

Abstract : An open ocean disposal site designated the Norfolk Disposal Site (NDS) is being considered as an alternative for some of the Norfolk Harbor system dredged material. The Present on-going study involves the monitoring of baseline water quality characteristics at the NDS. This study was undertaken to characterize the magnitude of natural spatial-temporal variability of various ecological parameters and to develop a series of multi-variate statistical models to be used as an 'early warning system' in historic trend assessment studies. This report presents the results of the 1984 baseline water quality programs at the dam Neck and Norfolk Ocean disposal Sites. The report recommends that chlorophylls, dissolved oxygen and suspended solids loads be monitored to account for natural sources of variation (seasonal, depth, and geographic effects) and to allow the detection of any potential impacts associated with operations at DNDS before they become excessive.

: Contents: Biological: Benthic, Sea Grasses, Plankton, Nekton, Miscellaneous, Pollution, Ecology, Taxonomy; Chemical: Nutrients, Organics, Trace Elements, Water Quality, Synthesis Reports, Heavy Metals; Geological: Shore Erosion, Suspended Sediments, Remote Sensing, Sediment Distribution, Bathymetry and Sediment Transport, Dredging; Physical: Circulation, Temperature and Salinity, Tides and Currents, Models, Remote Sensing, Miscellaneous.