Learn what it is like to be freshwater researcher focusing on the links between environmental processes and human health in this interview with Dr. Sandra McLellan, Professor and Senior Scientist at the School of Freshwater Sciences, University of Wisconsin-Milwaukee. Dr. McLellan is the principal investigator of the Water Center supported project Urban pollution footprints on the Great Lakes.
Please describe your current freshwater research and area(s) of expertise.
My laboratory is interested in understanding the impact of urban areas on nearshore coastal environments, particularly in terms of pathogens (disease causing organisms) entering waterways. We focus on tracking sources of fecal pollution, which can come from sewage leaking from failing infrastructure or from animal waste that runs off the land. Historically, fecal pollution is detected by culturing easy to grow organisms like E. coli that are present in the gut of almost all mammals. However, just detecting E. coli does not tell us where it is coming from. In the urban area, sewage is the main source of pathogens, so we are interested in determining if sewage is present when we see high levels of E. coli. We are using new sequencing technologies to gain a more complete picture of all the different types of organisms in the gut of humans and animals, as well as some extra ones in sewage (some that grow in the pipes). We can design assays for these organisms and now specifically detect the source of fecal pollution for many different applications, such as understanding why beaches are closed or for tracking down unrecognized sewage inputs in our stormwater systems.
How have you engaged end users in your freshwater research and how has this improved your work?
Over the past 15 years, many of our study sites have included beaches and we have been very involved in work groups that address beach closing issues. We have also worked with municipalities investigating high E. coli levels in stormwater systems. This has allowed us to get to know the beach managers, community groups, and water resource professionals in municipalities. We also spend a lot of time working with our wastewater agency, the Milwaukee Metropolitan Sewerage District on stormwater sampling. Now when we are embarking upon a study, we know who to call to find out more about a study site, or get the scoop on some of the dynamics they obverse. The wastewater agency and municipal engineers have a wealth of information. In turn, when they have questions, they call upon us. Overall, it is great to have long-term relationships with these groups because we feel we are several steps ahead in all of our research because of their participation.
What challenges and opportunities have you encountered in freshwater research and how have you approached them?
The biggest challenge has been learning how to breakdown some of the big, long-term problems into a series of small, answerable questions. Most research projects and funding are on a 2-3 year basis, but the problems and big questions we are tackling cannot be answered in that time frame, so we design our studies to be complementary and stepwise. This way we get a little more information each year and the bigger picture starts to fill in. One of the important things we have found is that our research data, while being used to illustrate a bigger dynamic, are usually of interest for other purposes to beach managers and municipal engineers. For example, we might use six study sites to learn something about urban beaches in general, but the data for each beach can be used by the beach manager to make some immediate decisions about what type of remediation strategies they might employ.
What are the critical components for impactful freshwater research?
Synergy between different disciplines and access and sampling capabilities at study sites. A great example of this is our collaboration with Steve Corsi and his colleagues at the U.S. Geological Survey. Their hydrology expertise and high level sampling capabilities are allowing us to actually quantify the amount of sewage from leaking infrastructure that enters Lake Michigan during rainfall from a whole urban area. We have documented that there is sewage seeping into rivers and then the lake, but it is very difficult to understand how big this problem is in relation to other problems, like sewage overflows that are large in magnitude but might only happen once per year. A grab sample, or even a series of them would not allow us to make these estimates but, over a three year time span, our two research groups have been able to design an approach to sample continuously from a watershed over a period of days, essentially sampling the runoff from an entire urban area during storm events, and then analyze these samples for the organisms that are specifically found in sewage. These measurements are a big component of the grant from the Water Center.
What do you see as the future of freshwater research—both in your area(s) of expertise and beyond?
Our capabilities for sequencing microbial communities is advancing so rapidly that now the limiting factor is analysis of the data. In my area, microbiologists are becoming well versed in bioinformatics just to keep up with maximizing the data. For example, a water sample might yield a profile of more than a million sequence reads for a microbial community, and the community might be very diverse with abundant, common organisms and rare organisms. In our lab, we are working with bioinformatic collaborators to come up with computational approaches to pull out a signature of different fecal pollution sources, like sewage, cows, or even a signal made up of a mixture of urban wildlife like birds, squirrels, and rabbits. Eventually, the most effective way to determine what is causing high E. coli levels, which tells us fecal pollution is there, will be to just sequence the microbial community. Ten years ago, I did not imagine we would have these capabilities so this is very exciting.