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Research about Maryland

Source-linked reports with geographic coverage including Maryland.

At least 307 records · Page 17Linked to original sources
USGS1986

Mortality of captive whooping cranes caused by eastern equine encephalitis virus

Of 39 captive whooping cranes (Grus americana), 7 died during a 7-week period (Sept 17 through Nov 4, 1984) at the Patuxent Wildlife Research Center, Laurel, Md. Before their deaths, 4 cranes did not develop clinical signs, whereas the other 3 cranes were lethargic and ataxic, with high aspartate transaminase, gamma-glutamyl transferase, and lactic acid dehydrogenase activities, and high uric acid concentrations. Necropsies indicated that the birds had ascites, intestinal mucosal discoloration, fat depletion, hepatomegaly, splenomegaly, and visceral gout. Microscopically, extensive necrosis and inflammation were seen in many visceral organs; the CNS was not affected. Eastern equine encephalitis (EEE) virus was isolated from specimens of the livers, kidneys, lungs, brains, and intestines of 4 of the 7 birds that died, and EEE virus-neutralizing antibody was detected in 14 (44%) of the 32 surviving birds. Other infectious or toxic agents were not found. Morbidity or mortality was not detected in 240 sandhill cranes (Grus canadensis) interspersed among the whooping cranes; however, 13 of the 32 sandhill cranes evaluated had EEE virus-neutralizing antibody. Of the 41 wild birds evaluated in the area, 3 (4%) had EEE virus-neutralizing antibody. Immature Culiseta melanura (the most probable mosquito vector) were found in scattered foci 5 km from the research center.

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USGS1985

The effects of grazers and light penetration on the survival of transplants of Vallisneria americana Michs in the tidal Potomac River, Maryland

Poor light penetration and grazing are among the factors potentially responsible for the lack of submersed aquatic macrophytes in the tidal Potomac River. Between 1980 and 1983, plugs, springs and tubers of Vallisneria americana Michx were transplanted from the oligohaline Potomac Estuary to six sites in the freshwater tidal Potomac River. Transplants made in 1980 and 1981 were generally successful only when protected by full exclosures which prevented grazing. Grazing resulted in the removal of whole plants or clipping off of plant leaves in unprotected plots. Plants protected in the first year were permanently established, despite the occurrence of grazing in subsequent years, at Elodea Cove and Rosier Bluff, where light penetration was high (average 1% light level was 1.6–1.7 m). Plants were not permanent;y established at Goose Island, where light penetration was lower (average 1% light level was 1.4 m) and grazing occurred, or Neabsco Bay where light penetration was very low (average 1% light level was 1.0 m) and grazing may not have occurred. In 1983, Secchi depth transparencies in the upper tidal river were improved significantly compared to 1978–1981. Both protected and unprotected transplants thrived in 1983.

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USGS1985

Authigenic potassium feldspar in Cambrian carbonates: Evidence of Alleghanian brine migration

The shallow-water limestones and dolostones of the Conococheague Limestone (Upper Cambrian) of western Maryland contain large amounts of authigenic potassium feldspar. The presence of halite daughter crystals in breached fluid inclusions, low whole-rock ratios of chlorine to bromine, and thermochemical data suggest that the potassium feldspar formed at low temperature by the reaction of connate brines with intercalated siliciclastic debris. Analyses of argon age spectra indicate that the authigenic feldspar probably formed during Late Pennsylvanian to Early Permian time. These results may indicate mobilization and migration of connate brines brought about by Alleghanian folding. The widespread occurrence of authigenic potassium feldspar in Cambrian and Ordovician carbonate rocks throughout the Appalachians suggests that this may have occurred throughout the entire basin.

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USGS1985

Toxic materials, fishing, and environmental variation: Simulated effects on striped bass population trends

Decreased survival of larval striped bass Morone saxatilis resulting from toxic chemicals in the environment and decreased survival of adults caused by fishing both are suspected as agents contributing to the decline in the Chesapeake Bay stock since the mid‐1970s. The relative power of each type of mortality to cause population declines was evaluated with simulation techniques. Equivalent levels of added mortality induced qualitatively identical and quantitatively similar trends in population simulations for all conditions examined except if strong density‐dependent mortality preceded the contaminant toxicity. In this case the contaminant effect caused a greater reduction in yield, but the population did not tend toward extinction. The results indicate that the observed downward trend in the Chesapeake Bay population can be halted or reversed by a reduction in fishing mortality, even if contaminant toxicity is the proximate cause for the decline.

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USGS1985

Maryland striped bass: Recruitment declining below replacement

A mathematical technique was developed to examine interrelationships among first‐year survival rates, adult fecundity, and adult survival of striped bass Morone saxatilis based on indices of year‐class strength. Application of this technique to striped bass in Maryland waters of the Chesapeake Bay provided evidence for reduced survival in the life cycle. If adult fecundity and survival have remained constant, first‐year survival declined significantly from 1969 to 1983, and averaged less than that needed for replacement for the last 10 years. Treatment of the individual spawning grounds separately indicated that the downward trend in survival for the pooled data was the result of declines in the upper bay and, to a lesser extent, in the Choptank River. Alternatively, if first‐year survival and adult fecundity were assumed to have remained constant, an annual decline of about 1.9% in adult survival would have been required to produce the observed trend in the pooled year‐class data. This would be consistent with increased fishing mortality and implies declining recruitment because of declining stock size. Continuing declines in first‐year or adult survival would eliminate the Maryland striped bass stock and the fishery it supports. Conversely, an increase in adult survival could offset the effect of the unknown factor or factors responsible for the apparent decline in first‐year survival.

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USGS1985

Relationship between reported commercial landings and abundance of young striped bass in Chesapeake Bay, Maryland

The ability to predict subsequent landings of striped bass Morone saxatilis from the indices of abundance of juveniles (young of the year) determined annually by the Maryland Department of Natural Resources was evaluated by multiple‐regression techniques. About 57% of the variation in reported landings could be accounted for by the juvenile indices 2, 3, 4, and 5 years prior to the year of the landings for the period 1959–1983. Elimination of the first 4 years of record (1959–1962) increased the R 2 to 0.83. The regressions of reported landings on the indices of ages 2–5 striped bass for the periods 1964–1973 and 1974–1983 indicated that mortality in the fishable stock increased between the two periods. These results support the use of the juvenile indices for monitoring recruitment into the population and as a basis for management decisions.

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USGS1985

Geochemical mass-balance relationships for selected ions in precipitation and stream water, Catoctin Mountains, Maryland

Results of a study of input/output mass balances for major ions based on the chemical composition of precipitation and stream-water, geochemical reactions with different loading rates of hydrogen ion, and watershed processes influencing the chemical character of stream-waters in two small watershed areas are reported with a view to predicting the effect of additions of acidic rain to the watershed systems. Geochemical weathering processes account for the observed changes in the chemistry of stream flow. Although present in bedrock in extremely small quantities, calcite plays an important role in neutralization of the total hydrogen-ion input.

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USGS1985

Hydrogeology and water quality of the Catoctin Mountain National Park Area, Frederick County, Maryland

The Catoctin Mountain National Park area, located in the Blue Ridge physiographic province of central Maryland, is characterized by high local relief, an average annual precipitation of 44 inches, and stony soils underlain by weathered and fractured metamorphic rocks. The park is mostly forested land and includes several camps and roads. The groundwater reservoir consists of regolith and underlying fractured bedrock and is recharged by precipitation. Discharge from the groundwater flow system is mainly to nearby streams adjacent to areas of recharge. Approximately 56% of annual streamflow is contributed by groundwater. Wells located at Camp Round Meadow and Staff Quarters No. 5 can sustain pumping rates of 45 to 60 gal/min for several hours, with drawdown of 40 to 50 ft. Water quality samples from wells, springs, and streams indicate that groundwater is slightly affected by septic waste and road salt. Groundwater in remote areas is not affected by either source. Concentrations of chloride from road salt and concentrations of nitrate plus nitrite (as N) were below U.S. EPA drinking water limits in all groundwater and surface water samples.

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USGS1985

Atlantic Flyway review: Region V: Patuxent Wildlife Research Center, Laurel, Prince Georges County, MD (390-0764)

This was my 4th year of banding in a powerline right-of-way that is specially managed to encourage growth of dense scrub. Nets were run for 2 to 3 hours each morning, because activity dropped off rapidly after the sun hit the nets. I banded on 79 days, from 1 August to 22 November. Frost continues to be a problem late in the season; the frostpocket effect of the stream valley and the lack of vegetative cover over the nets result in frozen nets on more mornings than would be expected. Warblers continued to dominate, with as many as 16 species in one day and a season total of 33 plus a Brewster's hybrid. Net-hours declined from 8506 to 7672 because I discontinued six of my least productive nets; this change accounted for much of the increase in birds per 100 net-hours (Table 1). Overall effort was comparable to that of 1982.

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USGS1985

Hydrogeology, digital solute-transport simulation, and geochemistry of the Lower Cretaceous aquifer system near Baltimore, Maryland

This study was made to develop information on the hydrogeology and ground-water geochemistry of the Patuxent and Patapsco aquifers (Lower Cretaceous) near Baltimore, Maryland. This information is needed to evaluate the availability and chemical quality of water from these aquifers. The Patuxent aquifer unconformably overlies Lower Paleozoic and Precambrian basement rocks and consists primarily of medium- to coarse-grained quartz sand. Discontinuous lenses of gravel and silty clay are commonly interbedded with the sand-sized material. The Patuxent aquifer in this area attains a thickness of 250 feet and transmissivities range from 2,000 to 8,000 feet squared per day. The Patuxent is the most productive source of ground water in the Baltimore area. In 1982, approximately 11 million gallons of water per day was produced from this unit. Several cones of depression, ranging from 30 to 50 feet below sea level, have developed in response to this pumping stress. The Arundel Formation conformably overlies the Patuxent aquifer. The Arundel is composed predominantly of clay and ranges from 0 to 150 feet thick. The Arundel exhibits very low vertical hydraulic conductivities that are on the order of 10 -9 to 10 -11 feet per second. This unit acts as the upper confining bed of the Patuxent aquifer in much of the project area. The Patapsco aquifer unconformably overlies the Arundel Formation and is a medium- to fine-grained quartz sand. The Patapsco functions as a water-table aquifer in much of the project area. Although the Patapsco has been heavily pumped in the past, pumpage from that aquifer in Baltimore was negligible in 1982. Brackish-water contamination of the Patuxent and Patapsco aquifers has been a major water-quality problem since the early 1900's. The Patuxent aquifer presently (1982) contains a circular plume of brackish-water contamination about 5 miles in diameter. This plume is centered on the Harbor district and has enlarged measurably since 1945. The Patapsco aquifer has a smaller zone of brackish-water contamination that has decreased in size since 1945. Borehole data demonstrate that the Arundel Formation has been breached by Pleistocene river channels near the Harbor district. These erosional channels provide a conduit for brackish water to intrude into the Patuxent aquifer. A two-dimensional areal solute-transport model of the Patuxent aquifer was constructed. This model was designed to estimate the future movement of the brackish-water plume based on alternative scenarios of aquifer use. Model simulations suggest that the plume will remain relatively immobile if 1982 pumping patterns continue into the foreseeable future. However, increased pumpage in the Marley Neck peninsula could draw the plume to the southeast and increase contamination of the Fairfield area. The water quality of the Patuxent aquifer is extremely variable. Because of this variability, it is useful to divide the aquifer into three water-quality zones: Zone 1 -- This zone corresponds to the plume of brackish-water contamination. Zone 2 -- This zone exhibits evidence of urbanization-related contamination such as measurable concentrations of organic chemicals and elevated concentrations of trace elements and total organic carbon. Zone 3 -- Water composition in this zone is controlled exclusively by naturally occurring chemical processes. These processes are dominated by reactions involving dissolved iron. Near the outcrop area, oxidation of pyrite and lignite consumes dissolved oxygen and produces ledges of iron hydroxide-cemented sandstones and conglomerates. The predominant dissolved iron species in oxic water is Fe(OH) 2 + . Downgradient, the water becomes anoxic and sulfate reduction becomes an important process. The predominant dissolved iron species in anoxic water is Fe 2+ .

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USGS1985

Atlantic Flyway review: Region V: Laurel, Prince Georges County, MD (390-0765)

My being away nearly all of September and on half the October weekends cut deeply into this season's banding. Totals for permanent residents and winter residents were close to normal, but numbers of the transient species are not at all comparable with other years. The only species that seemed more common than usual was the Northern Cardinal, for which my total of 28 was the second highest in ten years. The Veery and Common Yellowthroat were missed for the first time. I had only 36 returns, of 9 species. The oldest was a 5-year-old White-throated Sparrow. A Yellow Warbler was the 113th species and the 31st species of warbler banded at this station.

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USGS1984

Analysis of potential yield per recruit for striped bass produced in Chesapeake Bay

The yield of striped bass ( Morone saxatilis ) in biomass and numbers was estimated for constant recruitment of young fish into the population on the basis of vital statistics of the Maryland stock. Separate computations were performed for males, females, and sexes combined. Yield in biomass per individual entering the population was highest when the minimum legal length was in the range of 80-90 cm fork length and no upper size limits were imposed. The yield would increase at these size limits in both the Bay and Coastal fisheries, although the Coastal fishery would gain a slight relative advantage because the escapement of immature females from the Bay would increase. The most significant negative effect associated with an increase in the size limits would be the elimination of the traditional fisheries that focus on panfish (male and immature female striped bass 28-40 cm long). Although the length limits recommended in an existing Interstate Fisheries Management Plan for Striped Bass will increase yield per recruit, more stringent regulations would further increase the yield.

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USGS1984

Preliminary map showing the potentiometric surface of the Aquia Aquifer in southern Maryland, September 1982

A map was prepared that shows the potentiometric surface of the Aquia aquifer in southern Maryland in September 1982. The map is based on measurements from a network of 78 observation wells. The highest measured level of the potentiometric surface, 34 ft above sea level, was near the outcrop of the aquifer in a topographically high area of Anne Arundel County. The potentiometric surface slopes downward to the extensive cone of depression--much of it more than 40 ft below sea level--has developed around the well fields in the vicinity of Lexington Park. The network of observation wells was developed as part of the cooperative program between the U.S. Geological Survey, the Maryland Geological Survey, and the Maryland Energy Administration.

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USGS1984

Preliminary map showing the difference between the potentiometric surfaces of the Aquia aquifer of April 1979 and September 1982 in southern Maryland

A map was prepared that shows the net change in the potentiometric surface of the Aquia aquifer in southern Maryland between April 1979 and September 1983. During this period, the potentiometric surface declined (1) at least a few feet throughout the entire southern Maryland area, and (2) more than 10 feet in the eastern Charles County area and in a few scattered localized areas. The network of observation wells was part of the cooperative program between the U.S. Geological Survey, the Maryland Geological Survey, and the Maryland Energy Administration.

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