Current Research in the Stream Ecology Laboratory

My research interests are centered in aquatic ecology, especially stream and river ecology, and emphasize (i) interactions among aquatic ecosystems, such as ecological subsidies and the exchange of biological and chemical substances between ecosystems, (ii) the ecology of benthic organisms, particularly periphyton and macroinvertebrates, as they interact with other food web components, and (iii) responses of stream communities and ecosystem processes to environmental stressors, including land-use change and chemical toxicants. Current areas of investigation in my laboratory include the ecology of invasive aquatic organisms, the restoration of degraded aquatic ecosystems, the influence of nutrient subsidies on stream structure and function, and the ecology of natural and human-induced disturbance on aquatic ecosystems. Several funded research projects that are ongoing in my laboratory, along with my Notre Dame collaborators, are presented below:

1) Influence of Marine Nutrients from Salmon on Stream Ecosystems. (Funded by USDA – National Research Initiative 2006-2009; collaborative with Dr. J. Tank at UND and others). We have been studying salmon streams in southeast Alaska for the past 10 years. Salmon migrations into nutrient-poor streams of the Pacific Northwest are thought to contribute essential nutrients to streams after salmon die and carcasses decompose in the stream. All levels of stream food webs (periphyton, macroinvertebrates, and fish) may respond to this enrichment. We further hypothesize that riparian systems benefit from salmon runs via scavenging by terrestrial vertebrates and possible enrichment of riparian soils and plants with salmon nutrients. This project will attempt to determine if stream and riparian structure and function are linked to enrichment by marine-derive nutrients released by anadromous salmon. The project is centered in the marvelous Tongass National Forest of southeast Alaska, where natural runs of salmon are still near historical levels. In collaboration with USFS scientists in southeast Alaska, and researchers at Michigan State University, we will begin field research on this new project in summer 2006. In Year 1, we will use structural and functional measures to quantify the importance of salmon nutrients in watersheds with different forest management (old-growth, second-growth, and clear-cut). In Year 2, we will conduct manipulative experiments to enrich riparian soils plots and streams with salmon tissue and nutrients. Our goal is to determine if salmon nutrients constitute essential subsidies for entire watersheds, and how forest management affects this linkage.
Click here for pictures
Click here for publications

2) Role of Large Woody Debris in Maintaining Stream Ecosystem Function in Managed U.S. Forests. (Funded by USDA – National Research Initiative 2002-2006; collaborative with Dr. J. Tank). The U.S.D.A. Forest Service manages forests for multiple uses, including timber, water, wildlife/fisheries, and recreation. In the upper Midwestern U.S. (and in many other parts of the country), the legacy of past forest harvest has left streams and rivers nearly devoid of natural quantities of large woody debris (LWD).  Previous research has shown that LWD is an important component of stream ecosystems; it promotes channel stability, retains organic matter, increases substrate diversity, and provides habitat for invertebrates and fish. Some forests are now being managed for recovery of LWD both on the forest floor and in streams.  While it is generally recognized that LWD plays an important structural role in streams, the functional role of LWD in forested streams is virtually unknown.  There remains a paucity of information on how wood alters stream ecosystem processes such as stream productivity and metabolism, nutrient cycling, and material (energy) flow through food webs. For example, although LWD may be a local “magnet” for fish, it remains unknown whether stream productivity has been enhanced at the stream reach scale. Because wood alters geomorphology, provides a carbon source, and stores organic matter, we expect that it should impact benthic metabolism and nutrient cycling but this has not been experimentally tested in streams. To guide management of our national forests and streams, we need to know how LWD influences nutrient retention, organic matter processing, and productivity of stream ecosystems.  As an example, conversion of forests from conifer to hardwood species can greatly impact watershed nutrient release.  LWD may be crucial in retaining those added nutrients to improve downstream water quality. To address these questions, we will conduct truly replicated LWD additions (that mimic historical wood loading) in 3 streams in the Ottawa National Forest (ONF) in the Upper Peninsula of Michigan, and then determine functional responses to the wood addition over a span of 3 years. In each stream, an upstream control (no LWD) reach will be paired with a downstream treatment (LWD added) reach. Our response variables will include whole-stream measures of nutrient uptake and metabolism, organic matter retention and decomposition, as well as invertebrate and fish community structure to document “bottom-up” food web effects. Most studies of LWD in streams have focused on high gradient systems of the mountainous west. Our study takes the unique perspective of looking at LWD in low-gradient streams where the effects have not been previously studied.

3) Ecological Forecasting and Risk Analysis of Nonindigenous Species:Strategic Optimization Using a Bio-economic Approach. (Funded by NSF-IRCEB 2002-2007; collaborative with Dr. D. Lodge). Numbers of nonindigenous species – species introduced from elsewhere – are increasing rapidly worldwide. They are a major cause of biodiversity loss and environmental change, and are estimated to cost the US $137 billion/yr. The 2001 National Invasive Species Management Plan highlighted the urgent need for more rigorous and comprehensive risk analysis frameworks for nonindigenous species so that prevention and control strategies can be targeted appropriately. The central public policy consideration is how much of society’s resources should be expended in response to nonindigenous species, and how, for example, should it be allocated between prevention and control? These considerations, though, include a nexus of interacting ecological and economic factors that require interdisciplinary effort. Species invasions are caused by economic activities, and in turn affect economic activities. This ecological and economic linkage and feedback means that the assessment of risk interacts with the management of risk, which contradicts the common notion that risk assessment and risk management are independent. Social welfare and risk assessment are both determined jointly by ecological and economic processes.

4) IGERT: Global Linkages of Biology, Environment, and Society (GLOBES). (Funded by NSF 2005-2010). This new graduate training grant was recently funded by the National Science Foundation and will support up to 20 Ph.D. students at its completion. GLOBES will bring together the complementary skills of biologists, environmental and social scientists, public policy experts, lawyers, and religious and community leaders to seek innovative and interdisciplinary solutions to a wide range of interrelated problems in environmental and human health. The problems plaguing the environment are multifaceted in origin: from global issues such as climate change and infectious diseases, to "backyard" problems like invasive plants and animals. Because these problems have interrelated causes and feedbacks that are both biological and social in nature, resolving them demands biological, cultural, economic, legal, and ethical considerations. The University of Notre Dame's GLOBES program takes an interdisciplinary approach to human and environmental health studies. Teams of GLOBES student scholars, faculty, and researchers from throughout the University’s Colleges of Science, Arts and Letters, and Law School work together to find solutions to complex issues that threaten the well-being of humanity and the planet. Through GLOBES, students will engage in field studies in North America, Africa and China; gain hands-on experience using a range of analytical tools from genomic to economic to policy analysis; and train with scientists and other professionals both on campus and in Washington, D.C., to hone teaching, communication, and leadership skills. More information on this IGERT is available at http://globes.nd.edu/ and I urge to indicate on your formal application an interest in this program so that you will be considered for admission to the IGERT.