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Biomedical subjects

S R Carpenter

Publications and source records attributed to S R Carpenter.

4 recordsLinked to original sources
PubMed2006

Rising variance: a leading indicator of ecological transition.

Regime shifts are substantial, long-lasting reorganizations of complex systems, such as ecosystems. Large ecosystem changes such as eutrophication, shifts among vegetation types, degradation of coral reefs and regional climate change often come as surprises because we lack leading indicators for regime shifts. Increases in variability of ecosystems have been suggested to foreshadow ecological regime shifts. However, it may be difficult to discern variability due to impending regime shift from that of exogenous drivers that affect the ecosystem. We addressed this problem using a model of lake eutrophication. Lakes are subject to fluctuations in recycling associated with regime shifts, as well as fluctuating nutrient inputs. Despite the complications of noisy inputs, increasing variability of lake-water phosphorus was discernible prior to the shift to eutrophic conditions. Simulations show that rising standard deviation (SD) could signal impending shifts about a decade in advance. The rising SD was detected by studying variability around predictions of a simple time-series model, and did not depend on detailed knowledge of the actual ecosystem dynamics.

Ecosystem↗
PubMed2001

Ecological forecasts: an emerging imperative.

Planning and decision-making can be improved by access to reliable forecasts of ecosystem state, ecosystem services, and natural capital. Availability of new data sets, together with progress in computation and statistics, will increase our ability to forecast ecosystem change. An agenda that would lead toward a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services requires a process that engages scientists and decision-makers. Interdisciplinary linkages are necessary because of the climate and societal controls on ecosystems, the feedbacks involving social change, and the decision-making relevance of forecasts.

Agriculture↗
PubMed2001

PCB congeners in Lake Michigan coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tshawytscha) salmon.

We determined PCB congener concentrations in coho and chinook salmon collected in two Lake Michigan tributaries during the fall of 1996. Chinook salmon were larger than coho salmon and contained higher concentrations of the 78 PCB congeners we detected. There were no differences between male and female chinook or coho salmon in size or their PCB concentrations. Among individual fish, we found little evidence for a relationship between congener concentrations and percent lipid; however, congener concentrations did show a generally positive relationship with salmon size. Fish and macroinvertebrate congener concentrations are clearly related, and PCB congeners biomagnify approximately 20-30-fold as they flow from macroinvertebrates, two trophic levels below salmon, to the salmon. Slopes of regressions of salmonid congener concentrations on macroinvertebrate congener concentrations within homologs indicated that the degree of biomagnification generally increased with the degree of congener chlorination, although this pattern was much stronger for Mysis than for Diporeia. Log Kow and categorical variables for coplanar and "toxic" PCBs were not significant additional model terms, indicating that bioaccumulation of PCB congeners was not statistically related to these physicochemical attributes of the PCBs. The distribution of homologue PCBs shifts from a distinct predominance of hexachlorobiphenyls in macroinvertebrates to pentachlorobiphenyls and hexachlorobiphenyls in the salmon.

Animals↗