Current Research: Scott Cooper

My research deals with the basic ecological question: What factors determine the distributions and abundances of organisms? My current research encompasses both basic projects dealing with biological interactions in streams and applied projects dealing with the impacts of anthropogenic perturbations on freshwater systems. The basic projects revolve around the effects of consumers on the mean levels and spatial heterogeneity of their resources at different scales of space and time and on the effects of resource patchiness on trophic interactions in streams. Subsidiary basic projects examine the effects of predators on prey behavior with repercussions for other components of stream systems, and with the synthesis of experimental data. The applied projects deal with the effects of climate and land use changes, oil pollutants, and acidic deposition on lake and stream systems, and with the restoration of vernal pools.

Basic research

After arriving at UCSB in 1979, I focussed on the effects of biological interactions and disturbance on the distributions, abundances, and behavior of organisms in streams in southern California. Much of this work used field experiments conducted in in situ or streamside microcosms, or in stream pools or sections, to examine biological interactions in streams. Of particular interest are recent experimental studies on the effects of consumers on spatial heterogeneity in their resources. Papers produced since 1990 dealing wholly or partially with work completed in coastal Californian streams include Cooper et al. (1990), Dudley et al. (1990), Wiseman et al. (1993), Sarnelle et al. (1993), Douglas et al. (1994), Cooper et al. (1997), and Peckarsky et al. (1997). Recently, one of my graduate students (Nicole Barbee) has extended these approaches to Neotropical (Costa Rican) streams to examine the effects of grazers (atyid shrimp, gobies) on levels of deposited sediment, algae, and macroinvertebrates.

From 1989 - 1991 I directed UC's Education Abroad Program in Nairobi, Kenya, and conducted research in streams and ponds in East Africa. In one set of studies my colleagues (S. Wiseman, Drs. K. Mavuti, R. Griffiths) and I examined the distributions of invertebrates in streams draining basins with different land use practices. In another set of studies we collected data on the physical, chemical, and biological characteristics of savanna ponds over an annual cycle, and manipulated fish densities in ponds to examine the effects of fish on lower trophic levels. Papers dealing with my work on East African ponds and streams include Cooper (1996), Cooper et al. (1998), and Sarnelle et al. (in press).

Most recently I have concentrated my research activities on the experimental stream facility at the Sierra Nevada Aquatic Research Laboratory (SNARL), a facility administered by UC's Natural Reserve System. The experimental stream facility includes 9 identical, large, meandering stream channels (each 1 m wide X 50 m long) as well as 4 large stream sections (each 1100 m²). With NSF funding, two graduate students (K. Kratz, S. Roll), two research associates (S. Wiseman, T. Jenkins), two postdoctoral associates (S. Diehl, G. Englund), and I have used this facility to examine the effects of various resource renewal (immigration, nutrient inputs) and loss (emigration, predation) processes on stream communities at various scales of space and time. In each of the summers of 1992 through 1995, we manipulated stonefly and/or trout predators and, in some cases, prey migration rates in experimental channels, then monitored the responses of invertebrate densities, algal biomass, and detrital mass to these manipulations. In some cases, manipulations were conducted in arenas representing a range of spatial scales (0.04 m² to 1100 m²), so that we could examine the scale-dependence of ecological responses to manipulations. By applying geostatistical methods to data obtained from transects of grazer density and algal biomass, we also examined the effects of predators on the spatial heterogeneity of lower trophic levels in 1994 and 1995. Reviews dealing with the measurement of spatial heterogeneity (Cooper et al. 1997), with extrapolations from individual behavior to community and population responses (Peckarsky et al. 1997), and with scaling issues in stream ecology (Cooper et al. 1998) have acted as a template for, and summarize some of this work, and some of the empirical results are beginning to appear (Jenkins et al. in press).

Subsidiary experiments examined the functional response of stonefly predators in heterogeneous environments, density-dependent emigration by mayfly prey in the presence and absence of stonefly predators (Kratz 1996), the effects of stonefly predators on prey assemblages in simple versus complex environments, the effects of fast versus slow-moving grazers on the spatial heterogeneity of algae (Eichholtz et al. in prep), the effects of nutrients and grazers on algal biomass (Roll, MA thesis), the effects of prey drift on predator impacts on prey (Even in prep.), and grazer responses to algal spatial heterogeneity. Our SNARL investigations have been guided by food chain models for open systems developed in collaboration with Dr. R. Nisbet, Dr. W. Wilson, and D. Donalson (Nisbet et al. 1997). The consequences of model assumptions have been examined by comparing the outputs of models based on ordinary differential equations, partial differential equations, and spatially-explicit cellular automata formulations. Many of our subsidiary experiments were conducted to parameterize terms in model equations, and models are being tested by our large-scale experiments.

In summary, our initial experimental investigations were aimed at quantifying the effects of predation, competition, and disturbance on aquatic invertebrate and algae assemblages. We have expanded these investigations to examine the effects of predators on the behavior, diet, and microdistributions of prey; to delineate the complex pathways of interaction in stream systems; and to quantify the contribution of various loss (predation, emigration) and gain (birth, immigration) processes to observed changes in prey populations. A particular focus of our recent research is determinations of the influence of prey exchange rates on the effects of predators on prey populations at different scales of space and time, and examinations of the effects of consumers on spatial heterogeneity in their resources. In an earlier paper (Cooper et al. 1990), I quantitatively synthesized literature results to examine relationships between prey exchange rates and the impact of predators on prey populations. That paper led to collaborations with Drs. C. Osenberg and O. Sarnelle on methods for quantitatively synthesizing the results of ecological experiments (Osenberg et al.1997). That paper, in turn, engendered a National Center for Ecological Analysis and Synthesis (NCEAS) working group, including theoreticians, statisticians, and field ecologists, dealing with meta-analysis, biological models, and the quantification of effect sizes. A series of papers resulting directly or indirectly from this working group are in review (Osenberg et al. in review, Englund et al. a. in review, Englund et al. b. in review). The central theme of my basic research, then, is to delineate the role of biological interactions in freshwater systems, and to examine factors which influence that role, such as disturbance, nutrient inputs, refuge space, turbidity, prey exchange rates, and spatial/temporal scale. I am addressing this theme through a combination of theoretical and empirical approaches and through the synthesis of literature data.

Applied research

Over the last decade my colleagues (Drs. J. Melack, R. Holmes, T. Jenkins, L. Barmuta, R. Knapp, D. Bradford, K. Kratz, R. Knapp) and I have conducted extensive investigations of the effects of acid deposition on High Sierra lakes and streams. These studies have been supported by the California Air Resouces Board (CARB) and consist of three basic components: (1) a long-term monitoring study of representative, sensitive systems, (2) surveys of the chemistry, invertebrates, and fish of High Sierra waters, and (3) experimental studies in large lake bags or stream channels examining the responses of invertebrates, algae, and early fish stages to acid inputs. The results of some of these investigations are included in several reports or papers published since 1990, including two technical reports (Jenkins et al. 1994, Bradford et al. 1994) and three papers (Barmuta et al. 1990, Kratz et al. 1994, Bradford et al. in press).

In regards to other pollution studies, my collaborators (Dr. K. Kratz, Dr. G. Forrester) and I have investigated the effects of runoff from asphaltic products on stream communities in California. As part of this study we have sampled fish and invertebrate communities, and chemical concentrations (PAHs, metals) in the water and in fish and invertebrate tissue, in areas upstream and downstream of asphalt-covered bridges or stream crossings (technical report, Kratz et al. 1996).

I have also conducted a series of investigations on the effects of land use changes on stream systems. While in Kenya, my colleagues (S. Wiseman, Drs. K. Mavuti, R. Griffiths), students (E. Githunguri, M. Gikungu), and I conducted studies of relationships between land use patterns and the structure of faunal assemblages in drainage streams. These investigations include comparisons of urbanized versus rural streams, and streams draining forested versus non-forested basins. With support from the Water Resources Center (WRC, 1983-85), Drs. T. Dudley, R. Knapp, and I examined relationships between the intensity of livestock grazing in Sierran catchments and the physical, chemical, and biological characteristics of drainage streams. One of my Master's students (D. Sarr) was associated with this project and recently completed his thesis on the effects of livestock grazing on riparian vegetation. In co-operation with the U.S. Forest Service and California Department of Fish and Game, I also supervised the research activities of two additional M.A. students (C. Carpanzano, P. Douglas) working on the ecology and restoration of steelhead and rainbow trout stocks in southern California. One of my doctoral students (A. Beaumord) currently is investigating the effects of dam construction and pollution on fish assemblages in rivers of southeastern Brazil.

A colleague (S. Wiseman), a graduate student (R. Bolser), and I have examined the effectiveness of creating vernal pools in southern California. Vernal pools in California are disappearing rapidly owing to urban and agricultural development, and mitigations for many construction projects require creating or enhancing vernal pools by digging depressions. At present, however, it is not known if created vernal pools biologically resemble natural vernal pools. With Wayne Ferren (Director, Museum of Ecology and Systematics, UCSB) we have been comparing floral and faunal assemblages in created versus natural vernal pools. A technical report and paper on this work have been published (Wiseman et al. 1997, Ferren et al. 1998).

I was also a member of a NCEAS working group dealing with the effects of climate and land use changes on global biodiversity. This working group, headed by Dr. F. S. Chapin (UC-Berkeley), consisted of experts on each of the world's major biomes, as well as climate and land use modellers. The modellers provided maps of scenarios of climate, vegetation, and land use changes resulting from projected human population growth and increases in carbon dioxide concentrations. The biologists, in turn, provided projections of the potential effects of these changes on species diversity in each of the major biomes. I was part of the working subgroup which provided projections of the responses of stream and river communities to projected land use and climate changes (Poff et al. in press).

Scott Cooper | Research | Publications | Curriculum Vitae

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