Freshwater Ecology

Our long-term interest in freshwater ecology continues with examinations of food webs and the impacts of consumers on their resources. We focus especially on predator-prey and plant-herbivore interactions. A major overall question motivating this area of research is "how does community structure affect ecosystem function in lakes and streams?" Consumer species that we have studied in detail include algivorous snails, herbivorous waterfowl, predacious fishes, and omnivorous crayfishes.

Our experiments at the University of Notre Dame Environmental Research Center ( UNDERC ) have changed the tradition in limnology of separately studying the pelagic and benthic habitats in lakes. We have demonstrated that benthic algae often contribute substantially to whole-lake primary production, and partially compensate for increases in phytoplankton production when lakes become eutrophic. Other experiments demonstrate that macrophytes provide a predation refuge for Daphnia , allowing them to suppress phytoplankton and maintain clear water. Additional experiments suggest that when crayfish clear-cut the lake bottom, benthic productivity declines and lake-wide energy flows shift. In general, our studies demonstrate that consumer-resource interactions, especially between benthic and pelagic habitats, powerfully change freshwater community structure and ecosystem function.

More recently, we’ve been investigating alternate stable states in lakes. For example, why do invasive crayfish co-exist with native crayfish in some types of lakes and not in others? By investigating what makes some lakes “breakout” and not others, we hope to learn more about ecosystem function and invasion biology.

Relevant Pubs:

Whole-lake effects of invasive crayfish.pdf

Dispersal patterns and community change in a north temperate lake.pdf

Effects of light and nutrients on two macrophytes.pdf

Global Invasion Biology

Because invasive species are one of the most common causes of loss of native biodiversity and changes in ecosystem function, invasion biology has emerged in recent years as a central focus of conservation biology in our laboratory. These same species threaten human health, and cause enormous financial damage to crops, forests, and industrial infrastructure all over the world. Much of our work takes place in the Great Lakes region but  we currently have projects on-going in Zambia and developing in China.

Lodge lab researchers are exploring questions at all stages of the invasion process. How are species introduced into new environments and what pathways are important to these introductions? What are the important factors that allow some species to establish and not others? How are species spread? What impacts to do these species have? 

We are studying the pathways (of commerce and human behavior) by which nonindigenous species are being introduced, the interactions (e.g., competition, predation, hybridization) that nonindigenous species (e.g., zebra mussel, ruffe, rusty crayfish and, most recently, Nile tilapia in Zambia) have with native species, and how those interactions affect community and ecosystem function. We are also conducting extensive statistical analyses of nonindigenous and native species in the Great Lakes to discover characteristics that distinguish invasive from non-invasive species, and species that become nuisances from those that do not. We have several projects currently that are modeling spread of aquatic species in and around the Great Lakes region. These projects not only contribute to our overall knowledge of invasion biology but also advance our understanding of community ecology.

Relevant Pubs:

Global hotspots of biological invasion .pdf

Species invasions from commerce in live aquatic organisms.pdf

Ecological predictions and risk assessment for alien fishes in North America.pdf

Ecological Risk Analysis and Bioeconomics

Lodge researchers have developed several risk assessment tools for predicting where invaders may show up next and to identify which non-native species may have the highest risk of becoming invaders. For instance recent work has shown that fecundity can play a large role in predicting invasiveness for mussels. Currently we’re also working on an aquatic plant screening tool for Indiana. Our most recent work has acknowledged that these risk assessment tools are most effective when they are combined with risk management. Thus, we’ve been collaborating with with economists and mathematicians, to inform risk analyses of invasive species, to guide the development of management practices, and to guide allocation of resources to prevention or control to reduce the probability of future invasion disasters in the most cost-effective way possible.

Some recent groundbreaking work in this area includes the use of structured expert judgement to quantify impacts from invasive species.  This technique has been used in other areas of risk assessment before but its use to quantify impacts of non-native species is novel. Our project focuses on the introductions from trans-oceanic shipping in the Great Lakes and these results are being used by our economic collaborators to develop bioeconomic models  The results of these projects will be quite useful to managers and policy makers in determining how to allocate resources.

Relevant Pubs:

Risk assessment for invasive species produces net bioeconomic benefits .pdf

Bioeconomic analysis of invasive species Proc. B.pdf

Fecundity as a basis for risk assessment .pdf

Genetic Surveillance

Lodge lab researchers are applying new advancements in genomics to invasion biology.  Using genetic markers we can more fully understand how species are spread across the landscape. Currently, we’re studying  the spread of bythotrephes  in the Great Lakes region using this technique.

Most of the 180 introduced species in the Great Lakes have been introduced through transoceanic shipping.  Being able to identify ships that are most at risk for carrying these and future potentially harmful species is critical to effective management. In collaboration with engineers from the University of Notre Dame,we’re working to develop of a real-time portable genetic probe, which would be able to detect the DNA of various invasive species in a ballast water samples.

Relevant Pubs:

Importance of hybridization.pdf

Implications of hybridization.pdf

Policy and Management of Invasive Species

Much of our on-going research has direct application to natural resource management and policy. All of the research topics above need to be  put in the broader contexts of differential impacts on different people, management decisions, and investments of society's resources before scientific results can be applied.  Thus, in the last few years, we have been conducting research at both very specific levels of policy (how much should society invest in preventing the further spread of zebra mussel?).  We’ve partnered with on-the ground agencies such as The Nature Conservancy, the US Army Corps, the US Forest Service, and other federal agencies, state agencies and other NGOs to ensure that our science is relevant to the questions that society needs answered. We also work directly to communicate our results to policy-makers to help inform management and policy of invasive species.

Relevant Pubs:

Failure of the Lacey Act to protect.pdf

Evaluating an invasive species policy-ballast water exchange in the GL.pdf

ESA position paper Biological Invasions.pdf