Chesapeake Bay Tributaries Research Articles

Sensitivity of Early Life Stages of Blueback Herring to Moderate Acidity and Aluminum in Soft Freshwater

The sensitivity of the blueback herringAlosa aestivalis to acidity and aluminum (AI) in reconstituted, soft freshwater (23–25 mg I−1 hardness as CaCO3) was investigated in a continuous exposure laboratory study. Mature (20–24 h postfertilization) embryos were more tolerant than 1- to 5-day-old yolk-sac larvae. Significant mortality of embryos occurred only when pH was 5.0 and the total Al concentration was 0.42 mg I−1 (predicted MIBK-extracted total monomeric AI=0.34 mgI−1). Moderate acidity dramatically decreased the survival of yolksac larvae. Mean mortality was 99% in pH 5.0 and 89% in pH 5.7 compared to 38% in pH 6.5 and 16% in pH 7.8 without AI. The toxicity of AI to yolk-sac larvae was pH- and dose-dependent. Total AI concentrations up to 0.34 mg l−1 (predicted total monomeric AI up to 0.21 mg l−1) were not toxic at pH 6.5 and 7.8. At pH 5.0 and 5.7, AI increased the rate at which yolk-sac larvae died during a 96-h exposure (i.e., time to 50% mortality decreased with increasing AI). Continuous exposure to a predicted total monomeric AI level of only 0.03 mg I−1 at pH 5.0 killed all yolk-sac larvae in <24 hours. The mechanisms of acid and AI toxicity were apparently physiological and not associated with extensive cellular damage. Acidification events measured in Chesapeake Bay tributaries may reduce survival of blueback herring yolk-sac larvae and embryos exposed to those events.

Eustrongylides (Nematoda) Infection in Mummichogs and Other Fishes of the Chesapeake Bay Region

Abstract A survey of mummichogs Fundulus heteroclitus for Eustrongylides sp. (Nematoda) infection was conducted at 20 Chesapeake Bay tributary stations in 1983. Factors that might influence the prevalence of infection, including both station characteristics (salinity of the water and density of oligochaete intermediate hosts) and mummichog characteristics (length and sex), were also investigated. The prevalence of infection (percentage of fish parasitized) ranged from 0 to 41.3% among stations, was positively correlated with fish length, and was independent of fish sex. Prevalence was negatively correlated with salinity and was highest at stations near sewage treatment plants and near a heron rookery. The observed among-station variation in parasite prevalence appeared to reflect differences in density of an oligochaete intermediate host. Over 2,000 fish of 19 species other than mummichogs were also examined for Eustrongylides infection, but only other species of Fundulus were found to be infected.

Relative copper binding capacities of dissolved organic compounds in a coastal-plain estuary

Naturally occurring organics in samples taken from the mesohaline portion of a Chesapeake Bay tributary were separated into four nominal molecular weight fractions and analyzed for their ability to bind copper by using an algal bioassay. The organics exhibited a relatively high capacity for copper, with the binding capacity directly proportional to dissolved organic carbon (DOC) concentrations. The relationship between binding capacity and DOC is similar in the Chesapeake Bay and in other estuaries and marine ecosystems. Such correlation is not found in freshwater ecosystems. The strong relationship between DOC concentrations and binding capacities in marine ecosystems may be due to the autochthonous origin of marine organics. 44 references, 3 figures, 2 tables.

Mortality of Striped Bass Larvae in Relation to Contaminants and Water Quality in a Chesapeake Bay Tributary

Numerous factors have been implicated in the decline of striped bass Morone saxatilis along the east coast of the United States. This study was designed to evaluate the effects of contaminants and water quality on survival of striped bass larvae in a natural spawning habitat (Nanticoke River, Maryland). Larvae were tested in chambers submerged in the river. Organic and inorganic contaminants and water quality variables were monitored to correlate survival of larvae with habitat quality. In two 96-h experiments at three river stations, 90–99% of larvae died whereas control mortality was only 15–25%; the differences were significant. None of the 69 organic contaminants specifically analyzed were detected in river water and can be eliminated as causes of larval mortality. Of the eight metals analyzed, seven never exceeded 50 μg/L in river water, but total aluminum concentrations were 480–4,100 μg/L (39–181 μg/L filtered sample). Factors suspected as contributors to mortality were low pH (6.0–6.8), high aluminum concentrations, and the softness of the fresh river water (23–136 mg/L total hardness).

Preferred Wavelengths of Visible Light for Juvenile Atlantic Menhaden

Juvenile Atlantic menhaden (Brevoortia tyrannus) from Chesapeake Bay tributaries were tested for preferred wavelengths of visible light. Fish were subjected to test gradients from 460 to 660 nm at 20 nm intervals in a test trough, and light-and dark-acclimated fish were tested at three light intensities (0.1, 0.2, and 0.4 μEm −2 s −1). These fish exhibited a preference (P ≲ 0.05) for 460-540 nm wavelengths in all tests, and a concentration in the 460-500 nm wavelengths at the higher light intensities (0.2 and 0.4 μEm −2 s −1). Knowledge of these preferred light wavelengths can be helpful for increasing commercial fishery catches and lowering the industrial impingement rates in water intake systems.

Patterns of recent sediment accumulation in Chesapeake Bay (Virginia—Maryland, U.S.A.) tributaries

Sediment accumulation rates obtained from 39 cores in 10 tributaries of the western shore of Chesapeake Bay average 0.30 cm yr. −1 since European settlement, compared with pre-settlement rates in three tributaries of 0.14 cm yr. −1. Drainage areas of six of the tributaries extend from the Coastal Plain into the Piedmont and four are restricted to the Coastal Plain. Rates are highly variable, but higher in the upper parts of the tributaries and lower at the mouths. During the period of early agriculture, when <20% of the land was under cultivation, the average rate was 0.19 cm yr. −1. Later, when land under cultivation reached 40–50%, rates almost doubled averaging 0.34 cm yr. −1. There are no differences in post-settlement mass accumulation rates (g cm −2yr. −1 during periods of different land use or in different stretches of the tributaries. Pre-settlement rates are based on unpublished reports of 14C dates, ranging from 670 to 5330 yr. B.P., of peat layers from three western shore tributaries where sediment deposition is believed to have been continuous. Post-settlement rates are average rates calculated between a maximum of five pollen horizons. The pollen horizons represent historically documented changes in the regional vegetation and include initial land clearance (1634, 1650, 1720 and 1730, depending on the tributary), shift to intensive agriculture (1780 and 1840), beginning of the chestnut blight (1910), demise of chestnut (1930) and the beginning of large-scale urbanization (1960).

Osprey Reproductive Success along Choptank River, Maryland

Reproductive success was determined for 275 osprey nesting attempts along the Choptank River, Maryland in 1972–79. Young were fledged from 64% of the nests, and 1.25 young fledged per occupied nest. This level of reproductive success was above that found in the same area in 1968–71, better than that observed in other portions of the United States including most other Chesapeake Bay tributaries, and within the estimate necessary for population stability. Human disturbance and environmental pollution reduced reproductive success.

Brackish Water Hydromedusa Maeotias inexpectata in North America

THE Virginia Institute of Marine Science has recently been studying the biota of waters of low salinity in several Chesapeake Bay tributaries. During two successive cruises to the Pamunkey River in autumn 1968, hydromedusae of the family Olindiidae, never before found in Virginia, were collected in trawls. The specimens were identified as Maeotias inexpectata, a brackish water species originally described from the Don and Kuban estuaries, Sea of Azov1, and known elsewhere only from the Black Sea2. Ten specimens were collected on October 15, 1968, at station P–40 (37° 33′ N, 76° 53′ W, 4.2‰ salinity, 20.1° C water temperature) and one specimen was found on November 14, 1968, at station P–30 (37° 33′ N, 76° 50′ W, 10.7‰ salinity, 11.3° C water temperature. Hydrographic conditions at these two stations vary considerably at different tidal stages as well as seasonally, but salinities are mesohaline or lower at all times. Over a 13 year period, 1955–1967, the mean salinity and temperature during autumn were 9.0‰ and 12.5° C at station P–30, 1.2‰ and 12.2° C at station P–40 (W. A. Van Engel, personal communication).

Seasonal Movements of Striped Bass, Roccus saxatilis (Walbaum), Tagged and Released in the Potomac River, Maryland, 1959-61

During 1959–61, 8,793 striped, bass,Roccus saxatilis (Walbaum), were tagged and released in the Potomac River, Maryland. Of the 3,344 (37.3%) recaptured, 98.0% were taken in the Maryland part of Chesapeake Bay and its tributaries, 0.5% were recovered in the Virginia part of Chesapeake bay and its tributaries, and 1.5% were taken outside Chesapeake Bay along the Atlantic coast from Delaware to Nova Scotia. In the wintering season (November–March), the tagged fish were concentrated in the lower river and were very active, traveling several miles a day. In the spawning season (April–June), they mostly moved upstream to the spawning grounds where the tagged fish remained for most of the season, and then dispersed downstream to the lower river and into Chesapeake Bay. In the feeding season (July–October), tagged fish were scattered throughout Chesapeake Bay and tributaries. Some striped bass which overwintered in the Potomac were recaptured during the following spawning season in other Chesapeake Bay tributaries, and fish from the Potomac contributed materially to the stocks of striped bass along the northeast Atlantic coast. Spawning striped bass return to the same spawning grounds in successive years. Recaptures of tagged fish by date and location during the wintering, spawning, and feeding seasons, and the miles traveled and days at large by individuals, are tabulated.