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Geology topics

M. Spalding

Publications and source records attributed to M. Spalding.

5 recordsLinked to original sources
USGS2004

The case for regime-based water quality standards

Conventional water quality standards have been successful in reducing the concentration of toxic substances in US waters. However, conventional standards are based on simple thresholds and are therefore poorly structured to address human-caused imbalances in dynamic, natural water quality parameters, such as nutrients, sediment, and temperature. A more applicable type of water quality standarda??a a??regime standarda??a??would describe desirable distributions of conditions over space and time within a stream network. By mandating the protection and restoration of the aquatic ecosystem dynamics that are required to support beneficial uses in streams, well-designed regime standards would facilitate more effective strategies for management of natural water quality parameters.

BioScience↗
USGS1997

Mercury concentrations in feathers of wading birds from Florida

Primary or tail feathers were collected from 92 wading birds in Florida from Lake Okeechobee and wetlands farther south, from 1987 to 1990. Mean concentrations detected in feathers of nestlings were 2.0 ppm Hg in roseate spoonbills (Ajaia ajaja), 3.5 ppm Hg in great blue herons (Ardea herodias), 4.7 ppm Hg in great white herons (Ardea herodias occidentalis), and 7.1 ppm Hg in great egrets (Casmerodius albus). Concentrations in feathers of great white herons increased with the age of the bird, from 4.7 ppm Hg in nestlings, to 6.7 ppm Hg in juveniles, and 8.2 ppm Hg in adults. Mercury concentrations were greatest in species consuming large fish. Feathers collected from wood storks (Mycteria americana) contained an average of 3.3 ppm Hg. Mercury concentrations in feathers of wading birds from southern Florida were greater than those reported in feathers of wading birds from Asia. Both liver and feather Hg concentrations were known for 25 wading birds. The regression of liver (wet weight) Hg concentrations (Y) on feather Hg concentrations (X) was: log(Y) = 1.52 log(X) - 0.722. The correlation coefficient was 0.84. If reproductive disorders are expected when concentrations in feathers of adult birds average 9 ppm Hg, as might be inferred from a published laboratory study on mallards (Anas platyrhynchos), then Hg in southern Florida may be high enough to reduce productivity of wading bird populations. However, additional controlled studies are needed before a minimum toxic concentration in feathers can be designated with confidence.

Ambio↗