Geology topics

V.D. Engle

Publications and source records attributed to V.D. Engle.

4 recordsLinked to original sources

USGS2007

A classification of U.S. estuaries based on physical and hydrologic attributes

A classification of U.S. estuaries is presented based on estuarine characteristics that have been identified as important for quantifying stressor-response relationships in coastal systems. Estuaries within a class have similar physical and hydrologic characteristics and would be expected to demonstrate similar biological responses to stressor loads from the adjacent watersheds. Nine classes of estuaries were identified by applying cluster analysis to a database for 138 U.S. estuarine drainage areas. The database included physical measures of estuarine areas, depth and volume, as well as hydrologic parameters (i.e., tide height, tidal prism volume, freshwater inflow rates, salinity, and temperature). The ability of an estuary to dilute or flush pollutants can be estimated using physical and hydrologic properties such as volume, bathymetry, freshwater inflow and tidal exchange rates which influence residence time and affect pollutant loading rates. Thus, physical and hydrologic characteristics can be used to estimate the susceptibility of estuaries to pollutant effects. This classification of estuaries can be used by natural resource managers to describe and inventory coastal systems, understand stressor impacts, predict which systems are most sensitive to stressors, and manage and protect coastal resources. ?? Springer Science+Business Media B.V. 2007.

Environmental Monitoring and Assessment↗

USGS2001

Utility of splenic macrophage aggregates as an indicator of fish exposure to degraded environments

The utility of splenic macrophage aggregates (MAs) as an indicator of fish exposure to degraded environments was evaluated in several species of estuarine fishes as part of the Environmental Protection Agency's Environmental Monitoring and Assessment Program–Estuaries (EMAP-E). Using image analysis, we measured the number and mean size of MAs per square millimeter on tissue sections of spleen from 983 fishes representing seven species from 266 stations scattered across coastal estuaries of the Gulf of Mexico. At 16 stations, at least one fish exhibited a high density of MAs (>40 MAs/mm 2 ). Densities of MAs that exceeded 40/mm 2 correlated with exposure to either hypoxic conditions or sediment contamination. Fisher's exact test showed that the observed frequencies of joint occurrence between high numbers of MAs and both high sediment contaminants and low dissolved oxygen were significantly greater than the expected background frequencies. For all 16 sites where MAs were greater than 40/mm 2 , sediments displayed at least one contaminant at a concentration in the highest 5% of those observed for all Gulf of Mexico stations. Additionally, comparison of subjective visual analyses with the image analysis measurements showed a strong correlation, indicating that similar analyses can be performed without computer image analysis. This study demonstrates that splenic MAs are effective biotic indicators for discriminating between fish exposed to degraded and nondegraded environments.

Alabama, Florida, Louisiana, Mississippi, Texas↗

USGS1999

Dissolved oxygen conditions in northern Gulf of Mexico estuaries

Because deficient dissolved oxygen (DO) levels may have severe detrimental effects on estuarine and marine life, DO has been widely used as an indicator of ecological conditions by environmental monitoring programs. The U.S. EPA's Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) monitored DO conditions in the estuaries of the Gulf of Mexico from 1991 to 1994. DO was measured in two ways: 1)instantaneous profiles from the surface to the bottom were taken during the day, and 2) continuous measurements were taken near the bottom at 15 min intervals for at least 12 h. This information was summarized to assess the spatial distribution and severity of DO conditions in these estuaries. Depending on the criteria used to define hypoxia (DO concentrations usually < 2 mg L-1 or 15 mg L-1) and the method by which DO is measured, we estimate that between 5.2 and 29.3% of the total estuarine area in the Louisianian Province was affected by low DO conditions.

Environmental Monitoring and Assessment↗

USGS1999

Refinement, validation, and application of a benthic condition index for northern Gulf of Mexico estuaries

By applying discriminant analysis to benthic macroinvertebrate data, we have developed an indicator of benthic condition for northern Gulf of Mexico estuaries. The data used were collected by the United states Environmental Protection Agency’s Environmental Monitoring and Assessment Program (EMAP) in the Louisianian Province from 1991 to 1994. This benthic index represents a linear combination of the following weighted parameters: the proportion of expected species diversity, the mean abundance of tubificid oligochaetes, the percent of total abundance represented by capitellid polychaetes, the percent of total abundance represented by bivalve mollusks, and the percent of total abundance represented by amphipods. We successfully validated and retrospectively applied the benthic index to all of the benthic data collected by EMAP in the Louisianian Province. This benthic index was also calculated for independent data collected from Pensacola Bay, Florida, in order to demonstrate its flexibility and applicability to different estuarine systems within the same biogeographic region. The benthic index is a useful and valid indicator of estuarine condition that is intended to provide environmental managers with a simple tool for assessing the health of benthic macroinvertebrate communities.

Gulf of Mexico↗