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Geology topics

Research about Maryland

Source-linked reports with geographic coverage including Maryland.

At least 289 records · Page 16Linked to original sources
USGS1991

Stocking of hatchery-reared striped bass in the Patuxent River, Maryland: Survival, relative abundance, and cost‐effectiveness

Hatchery‐reared fingerlings of striped bass Morone saxatilis were tagged, stocked, and recovered in the Patuxent River, Maryland, to estimate their survival and abundance relative to wild young of the year and to compare the costs and benefits of stocking phase‐I (35–50 mm, total length) and phase‐II (150–200 mm) fish. About 100,000 phase‐I fingerlings were tagged and released each year during midsummer 1988 and 1989. Both tagged and untagged (wild) young of the year were recovered by alongshore seining in the river through 80 d poststocking. Mortality rates of wild and hatchery‐reared young of the year were not significantly different‐about 3%/d. Wild young of the year were more abundant in 1989 than in 1988. In 1988, phase‐I fingerlings composed 56% of all young‐of‐the‐year striped bass in the river. In 1989 wild young‐of‐the‐year striped bass outnumbered hatchery‐reared fingerlings by about 11 to 1. Whether phase‐I or phase‐II stocking was more cost‐effective depended on the relative magnitudes of fingerling survival and on hatchery production costs. The range of phase‐II survival (5–50%) observed among different hatcheries and years of production was too broad to support generalizations about cost‐effectiveness, given the fivefold difference in the unit costs of phase‐I and phase‐II production.

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USGS1991

Social foraging and feeding environment of the black-crowned night heron in an industrialized estuary

A nesting colony of more than 300 pairs of Black-crowned Night-Herons in the Patapsco River estuary, Baltimore Harber, Maryland was monitored from May to July 1988. The departure direction and departure time of each Heron was recorded during mornjng and evening observations at the colony. In addition, individual Herons were followed to landing sites in the estuary with small boats and aircraft. Herons appear to be quite social in foraging and may concentrate their feeding in some of the most industrialized parts of the estuary. Night-Herons may prosper in urban environments because some of their prey are attracted to intense shoreline illumination at night. New quantitative methods were developed to cope with the lack of statistical independence when dealing with social species.

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USGS1991

Geology-based method of assessing sensitivity of streams to acidic deposition in Charles and Anne Arundel Counties, Maryland

The report describes the results of a study to assess the sensitivity of streams to acidic deposition in Charles and Anne Arundel Counties, Maryland using a geology-based method. Water samples were collected from streams in July and August 1988 when streams were at base-flow conditions. Eighteen water samples collected from streams in Charles County, and 17 water samples from streams in Anne Arundel County were analyzed in the field for pH, specific conductance, and acid-neutralizing capacity (ANC); 8 water samples from streams in Charles County were analyzed in the laboratory for chloride and sulfate concentrations. The assessment revealed that streams in these counties are sensitive to acidification by acidic deposition.

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USGS1990

The difference between the potentiometric surfaces of the Magothy Aquifer of September 1986 and September 1988 in southern Maryland

A map was prepared that shows the net change in the potentiometric surface of the Magothy aquifer (in the Cretaceous Magothy Formation) in southern Maryland from the fall of 1986 to the fall of 1988. The map, based on water level measurements from 79 observation wells, shows that during the 2 year period the potentiometric surface declined less than 5 ft in most of the northern part of the study area and more than 10 ft in a 4-sq-mi area in northern Charles County. Net water-level rises of as much as 2 ft were measured in central Charles County. (USGS)

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USGS1989

Studies of contaminant and water quality effects on striped bass prolarvae and yearlings in the Potomac River and upper Chesapeake Bay in 1988

Simultaneous on‐site and in situ studies of survival of prolarval and yearling striped bass Morone saxatilis were conducted in the Potomac River during the 1988 spawning season. Various water quality and contaminant conditions were monitored during these experiments. In situ experiments on yearlings and monitoring of water quality and contaminants were also conducted in the Susquehanna, Elk, and Sassafras rivers of the upper Chesapeake Bay. Survival of striped bass prolarvae ranged from 1 to 20% in the Potomac River during three concurrent 96‐h on‐site and in situ experiments; survival of control fish was 78% or greater. Survival of striped bass yearlings was 15% or less during 28‐d in situ tests at two Potomac River field locations; survival of control fish was 100%. Mortality of prolarvae in the Potomac River was likely caused by a combination of cadmium, lead, chlordane, and sudden drops in temperature. Mortality of yearlings was possibly caused by a combination of cadmium, lead, zinc, chlordane, and ammonia. Survivals of striped bass yearlings tested in 28‐d tests in the Susquehanna, Elk, and Sassafras rivers were 57, 100, and 100%, respectively; survival of control fish was 100%. Mortality of striped bass in the Susquehanna River may have been partly caused by copper and lead concentrations; however, other nonidentified factors were likely more important. Water quality problems were not detected in the Elk or Sassafras rivers.

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USGS1988

Postfledging survival of European starlings exposed as nestlings to an organophosphorus insecticide

To test the hypothesis that exposure to organophosphorus (OP) insecticides reduces postfledging survival of altricial birds, 16—d—old European Starlings ( Sturnus vulgaris ) were weighed and orally dosed with corn oil containing 6.0 mg of dicrotophos per kilogram of body mass or an equivalent exposure of pure corn oil (controls). Two days later, each survivor was weighed again and patagially tagged for identification after fledging. Resightings of marked fledglings were made during weekly 2—d intensive observations yielding four estimates of postfledging survival. Before fledging, only OP—dosed birds died (18.5%), and OP—dosed survivors lost more mass (5.2%, P = .001) than controls (1.4%) but their masses on day 18 were only slightly lower (2% of control mean, P = .10). Brain cholinesterase activity, a sensitive indicator of OP exposure in birds, was depressed and average of 93% in OP—dosed nestlings that died compared to controls, and an average of 46% in OP—dosed nestlings alive on day 18. Age at fledging, postfledging survival, flocking behavior, and habitat use, however, did not differ between OP—dosed and control birds. The effects of the OP on the nestlings appeared to be rapid, to be reversible in survivors, and did not extend into the postfledging period. In addition, we found no relationship between body mass at fledging and postfledging survival.

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USGS1988

Phytoplankton dynamics of the fresh, tidal Potomac River, Maryland, for the summers of 1979 to 1981

The distribution and abundance of phytoplankton in the fresh, tidal Potomac River, Md., was different during 1979-81 from that observed in the 1960's and 1970's. Concentrations of phytoplankton in the 1960's and 1970's reached maximum attainable levels that were limited only by self-shading. A sag in phytoplankton abundance, apparent during the summers of 1980 and 1981 between Rosier Bluff and Marshall Hall, appears to have been caused by the Asiatic clam, Corbicula fluminea. Reduced abundance of phytoplankton throughout the entire fresh, tidal river during the summers of 1980 and 1981 may have been due to grazing by Corbicula, high discharge, and perhaps phosphorus limitation in late August at and downstream of Hallowing Point. Phytoplankton growth rates and chlorophyll-to-cell ratios were highest at Hatton Point and Marshall Hall (the sag reach). A model was constructed that predicted phytoplankton growth rates by varying only chlorophyll a concentration and light penetration. Nutrient concentrations were not required to make the model fit the data. Primary productivity was highest for the year during August 1980 and August 1981. Productivity-per-unit chlorophyll was highest at Hatton Point, where reduced concentrations of phytoplankton permitted the deepest light penetration in the fresh, tidal river.

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USGS1987

Toxicity of paraquat in nestling birds: effects on plasma and tissue biochemistry in American kestrels

Beginning the day after hatching, American kestrel ( Falco sparverius ) nestlings were orally dosed daily for 10 days with 5 μL/g of distilled water (controls), 10 mg/kg, 25 mg/kg, or 60 mg/kg of paraquat dichloride (1,1′-dimethyl-4,4′-bipyridinium dichloride) in distilled water. Forty-four percent of the nestlings receiving 60 mg/kg died after 4 days. Plasma LDH activity and total protein concentration were elevated, and plasma alkaline phosphatase activity was lower in survivors of the 60 mg/kg group at 10 days. Lung total sulfhydryl (TSH) and protein-bound sulfhydryl (PBSH) concentrations were significantly higher in the 10 mg/kg, 25 mg/kg, or 60 mg/kg groups. Lung DNA, RNA, protein, and hydroxyproline (collagen) concentrations were not significantly affected by treatment. Liver NPSH was lower in the 60 mg/kg group while liver glycogen concentration was not affected by treatment. Kidney DNA, RNA, and RNA to protein concentration ratio were higher in the 25 mg/kg or 60 mg/kg groups. These findings in combination with recently reported effects on growth and histopathology suggest that altricial nestling kestrels are more sensitive to paraquat exposure than young or adult birds of precocial species. From a comparative viewpoint, lungs of nestling kestrels are less sensitive to paraquat than mammalian lungs.

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USGS1987

Difference between the potentiometric surfaces of the Magothy Aquifer in Fall of 1975 and Fall of 1986 in southern Maryland

The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Magothy aquifer; (2) the approximate location of the line of equal difference between the potentiometric surface in fall 1975 and fall 1986; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

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USGS1986

The relationship between body mass and survival of wintering canvasbacks

Mass and recapture histories of 6,000 Canvasbacks ( Aythya valisineria ) banded in upper Chesapeake Bay were used to test two hypotheses: (1) early-winter body mass is associated with the probability of surviving the winter, and (2) early-winter body mass is associated with annual survival probability. Data were analyzed by a binary regression method that treated mass as a continuous variable and estimated parameters to describe a general relationship between body mass and survival probability. Results for adult males, which provided our largest data sets, presented strong evidence that birds with high relative early-winter masses had both greater overwinter and annual survival probabilities. Results of overwinter analyses necessarily are qualified by the alternative explanation of mass-dependent emigration, i.e. the possibility that lighter birds move south in response to cold weather and leave only heavy birds for recapture. Such a phenomenon remains to be documented. Results concerning annual survival probabilities are not vulnerable to this alternative explanation because of the strong fidelity of Canvasbacks at the banding site. Because of small sample size, data were inadequate to permit mass/survival inferences for adult females. Sample sizes were adequate for young Canvasbacks, but the results were less consistent than for adult males. Although early-winter body mass was associated positively with overwinter as well as annual survival for young Canvasbacks in some years, we suspect that the lack of established wintering patterns among these birds may underlie the less consistent result.

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USGS1986

Reconnaissance of the ground-water, surface-water system in the Zekiah Swamp Run basin, Charles and Prince Georges Counties, Maryland

The water table in the alluvium of the Zekiah Swamp Run valley in southern Maryland is above stream level during most of the year and the alluvial aquifer contributes water to the stream. During the summer, however, high evapotranspiration sometimes lowers the water table below the stream level. Water then moves from the stream to the alluvium and, at times, reaches of the stream become dry. Pumping from the confined aquifers has caused water levels to decline several tens of ft, which has increased the downward gradient between the water-table aquifer and the underlying confined aquifers. Three synoptic surveys of base flow show areal and temporal variations in stream discharge, pH, specific conductance, dissolved oxygen, and temperature. April 1984 base flows were high (141 cu ft/sec, at the Route 6 gage) because of high precipitation during March. July 1983 base flows were low (2.35 cu ft/sec at the Route 6 gage) and showed significant loss of streamflow because of high antecedent evapotranspiration. Estimates of inflow and outflow of the Zekiah Swamp Run basin above Route 6 during the 1984 water year include: Precipitation, 50.21 in; stream outflow, 20.10 in; shallow groundwater underflow, 0.1 in; stream outflow, 20.10 in; shallow groundwater underflow, 0.1 in; and evapotranspiration, 33 in. A streamflow budget of a 5.1 mi area of the valley of Zekiah Swamp Run between Routes 5 and 6, during the April 1984 survey and a loss of almost 5 cu ft during the July 1983 survey.

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