Geology topics

Research about Delaware, Maryland, Pennsylvania, Virginia

Source-linked reports with geographic coverage including Delaware, Maryland, Pennsylvania, Virginia.

2 recordsLinked to original sources

USGS2000

Quantitative polymerase chain reaction for transforming growth factor-β applied to a field study of fish health in Chesapeake Bay tributaries

Fish morbidity and mortality events in Chesapeake Bay tributaries have aroused concern over the health of this important aquatic ecosystem. We applied a recently described method for quantifying mRNA of an immunosuppressive cytokine, transforming growth factor-β (TGF-β), by reverse transcription quantitative-competitive polymerase chain reaction to a field study of fish health in the Chesapeake Basin, and compared the results to those of a traditional cellular immunoassay macrophage bactericidal activity. We selected the white perch ( Morone americana ) as the sentinel fish species because of its abundance at all of the collection sites. White perch were sampled from Chesapeake Bay tributaries in June, August, and October 1998. Splenic mononuclear cell TGF-β mRNA levels increased and anterior kidney macrophage bactericidal activity decreased, particularly in eastern shore tributaries, from June to August and October. The results of the two assays correlated inversely (Kendall's τ b = -0.600; p = 0.0102). The results indicated both temporal and spatial modulation of white perch immune systems in the Chesapeake Basin, and demonstrated the utility of quantitative PCR for TGF-β as a molecular biomarker for field assessment of teleost fish immune status.

Delaware, Maryland, Pennsylvania, Virginia↗

USGS1974

Interpretation of aeromagnetic anomalies bearing on the origin of upper Chesapeake Bay and river course changes in the Central Atlantic Seaboard Region: Speculations

On an aeromagnetic map of the Chesapeake Bay area, the northeastern part of the bay coincides well with a deep, “flat” magnetic low, and the upper part of the Delmarva Peninsula east of the bay coincides with detailed magnetic highs; the two areas are separated by a steep, straight gradient that matches the eastern shore of the bay. On the basis of magnetic and geologic evidence, we interpret the Chesapeake Bay magnetic low as a buried Baltimore Gneiss dome, bounded on the southeast by a normal or reverse fault marked by the steep, straight gradient; mafic and ultramafic plutonic rocks probably underlie the southeast side of the fault zone. The flatness of the Chesapeake Bay magnetic low, as opposed to the detail of the anomalies on either side, however, suggests that an abnormal thickness of nonmagnetic sedimentary rocks also coincides with the low. This could reflect a buried Triassic basin or, more probably, a thickened section of Coastal Plain sedimentary rocks deposited in the fault-bounded basin. The present course of the upper part of Chesapeake Bay is probably inherited from the pre-Pleistocene course of the Susquehanna River, but the river's course may have been determined by the fault zone. Thus, this zone and similar en echelon fault zones along strike may explain the sudden change in course of major rivers in the central Atlantic Seaboard region.

Delaware, Maryland, Pennsylvania, Virginia↗