Dynamics of aquatic ecosystems and models under toxicant stress: State space analysis, covariance structure, and ecological risk

Technical Report · Wed Jun 01 00:00:00 EDT 1988

OSTI ID:6954664

Johnson, A R; Bartell, S M

The state of an ecosystem at any time t may be characterized by a multidimensional state vector x(t). Changes in state are represented by the trajectory traced out by x(t) over time. The effects of toxicant stress are summarized by the displacement of a perturbed state vector, x/sub p/(t), relative to an appropriate control, x/sub c/(t). Within a multivariate statistical framework, the response of an ecosystem to perturbation is conveniently quantified by the distance separating x/sub p/(t) from x/sub c/(t) as measured by a Mahalanobis metric. Use of the Mahalanobis metric requires that the covariance matrix associated with the control state vector be estimated. State space displacement analysis was applied to data on the response of aquatic microcosms and outdoor ponds to alkylphenols. Dose-response relationships were derived using calculated state space separations as integrated measures of the ecological effects of toxicant exposure. Inspection of the data also revealed that the covariance structure varied both with time and with toxicant exposure, suggesting that analysis of such changes might be a useful tool for probing control mechanisms underlying ecosystem dynamics. 90 refs., 53 figs., 9 tabs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6954664
• Report Number(s): ORNL/TM-10723; ON: DE88015333
• Resource Relation: Other Information: Thesis (Ph.D). Portions of this document are illegible in microfiche products. Thesis submitted by A.R. Johnson to The Univ. of Tennessee, Knoxville
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
AQUATIC ECOSYSTEMS
BIOLOGICAL STRESS
DOSE-RESPONSE RELATIONSHIPS
MATHEMATICAL MODELS
RISK ASSESSMENT
SPACE DEPENDENCE
TOXIC MATERIALS
ECOSYSTEMS
MATERIALS
520200* - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)
990230 - Mathematics & Mathematical Models- (1987-1989)