Ecosystem Consequences of Alteration in Stream Community Composition: Interpreting Measures of Biological IntegrityEPA Grant Number: U915884
Title: Ecosystem Consequences of Alteration in Stream Community Composition: Interpreting Measures of Biological Integrity
Investigators: Simmons, Leonard M.
Institution: Utah State University
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2001 through January 1, 2004
Project Amount: $91,286
RFA: STAR Graduate Fellowships (2001) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems
Clean water and healthy aquatic ecosystems constitute a rapidly dwindling natural resource. As a consequence, the maintenance of healthy stream and river ecosystems and the restoration of degraded systems have become important management objectives worldwide, and the development of methods for assessing the biological integrity of these ecosystems has become a critical priority. These methods rely on detection of changes in stream biota as an indication of ecosystem degradation. Predictive models provide a powerful suite of such techniques, although they are only now beginning to be implemented in the United States for stream bioassessment. An implicit assumption of these models, as well as of other commonly used bioassessment methods, is that changes in species composition are indicators of systematic changes in ecosystem attributes, and hence, of a significant perturbation. However, this assumption has yet to be adequately tested. This issue reflects the larger question of how changes in biodiversity affect ecosystem function in general. The paradigm in conservation biology is that reductions in biodiversity adversely affect essential ecosystem processes; however, the available evidence is somewhat mixed, and is largely derived from studies of plant communities and simple microcosm experiments. We clearly need to extend the scope of investigation to include more complex communities. The objective of this research project is to investigate whether significant differences in stream community composition are correlated with measurable differences in the rates of representative stream ecosystem processes.
I hypothesize the following:
1. Streams with similar physiographic characteristics and species assemblages will be similar with respect to measures of ecosystem function. In other words, stream ecosystem process rates should be to some extent predictable, given an adequate classification scheme.
2. Streams that differ in terms of macroinvertebrate biodiversity, as measured either at the species level or at the functional group level, will differ with respect to measures of ecosystem function.
3. Streams with similar expected community compositions, as determined by multivariate predictive modeling, but different actual community compositions (as a result of anthropogenic disturbance) will differ with respect to measures of ecosystem function. A corollary of this hypothesis is that the magnitude of the change in ecosystem process rate will scale to the magnitude of the change in expected species composition.
Hypotheses 1 and 2 will be addressed by comparing rates of leaf litter decomposition among a large number (approximately 50) of reference quality streams in the intermountain West. A variety of biologically and physiographically based classification schemes will be compared to determine the extent to which ecosystem process rates can be predicted. If possible, rates of primary productivity and nutrient uptake also will be compared. Hypothesis 3 will be addressed by comparing those same rates in a set of 18 streams that vary in the degree to which they are impacted by anthropogenic disturbance (e.g., livestock grazing). The streams used in this research project will be selected from a group of several hundred streams that have been analyzed as part of a large-scale study to assess the biological integrity of streams throughout the western United States.