Included in the August 21, 2025, biweekly update

This week’s articles by MSU faculty, specialists, and students making a difference feature cold-stored E. coli in lettuce, invasive carp behavior in Lake Erie, and groundwater reshaping stream chemistry.

Impact of physiological transitions during forward processing on Shiga-toxin producing E. coli risks in lettuce

Owade et al. (2025) test whether longer cold storage before lettuce is processed in a separate facility (“forward processing”) changes E. coli O157:H7 in ways that affect the risk of illness. They compared two types of products—field-bagged romaine hearts and shredded, washed lettuce—using lab experiments and a quantitative microbial risk assessment (QMRA).

In the lab, the researchers found that cold storage can put some bacteria into dormant states that are harder to detect, but these changes did not meaningfully raise the risk of illness in their model. Instead, sanitation effectiveness and prevention of cross-contamination had a much bigger impact on safety than storage time.

The researchers results suggest that forward processing is not inherently riskier than packing lettuce at the farm, as long as the cold chain is maintained and wash steps are effective. Owade et al. recommend focusing on temperature control, proper use of sanitation, and clean equipment to keep lettuce safe for consumers.

Owade, J. O., Bergholz, T. M., & Mitchell, J. (2025). “Impact of physiological transitions during forward processing on Shiga-toxin producing Escherichia coli risks in lettuce.” Food Microbiology, 104892. https://doi.org/10.1016/j.fm.2025.104892

Corresponding author: Jade Mitchell, jade@msu.edu.

Grass carp (Ctenopharyngodon idella) movement states and backwater use can inform removal efforts

Bonjour et al. (2025) studied the movements of invasive grass carp in Lake Erie and their use of calm shoreline areas such as sheltered bays, marshes, and channels. Using tracking data, the researchers examined how the fish’s locations changed over time to identify the best opportunities for targeted removal.

The study shows that grass carp return to these calmer, vegetated waters in predictable ways, with movement patterns that vary by season and location. These behaviors create windows when removal efforts could capture more individuals with less effort. By understanding how the fish alternate between active movement and staying in localized areas, managers can plan operations that align with carp behavior instead of relying on broad, untargeted methods.

The researchers conclude that incorporating movement behavior into control programs can make removal strategies more efficient, reduce costs, and improve efforts to decrease grass carp populations in the Great Lakes.

Bonjour, S. M., Hunter, R. D., Roberts, J. J., Brenden, T. O., Colborne, S. F., Faust, M. D., Mayer, C. M., Mapes, R., Kraus, R. T., Calfee, R. D., & Acre, M. R. (2025). “Grass carp (Ctenopharyngodon idella) movement states and backwater use can inform removal efforts.” Journal of Great Lakes Research, 102654. https://doi.org/10.1016/j.jglr.2025.102654

Corresponding author: Sophia M. Bonjour, sbonjour@usgs.gov.

Wetlands, Groundwater, and Seasonality Influence the Spatial Distribution of Stream Chemistry in a Low-Relief Catchment

Weidner et al. (2025) examine how dissolved substances in stream water, like organic carbon, nitrate, sulfate, and chloride, are influenced by groundwater, wetlands, and seasonal changes in a mostly flat landscape. Their study focused on the Augusta Creek sub-watershed in Michigan, an area with abundant wetlands and varying underground structures that affect how water and chemicals move through the system.

Over 32 months, the researchers collected water quality data from 28 stream sites, providing a detailed view of how solute concentrations shift over space and time. They expected wetlands to noticeably slow the flow of water, store certain chemicals, or change them through natural processes, but these effects were only seen in a few small areas of the watershed. In larger downstream areas, groundwater inputs, particularly those that changed with the seasons, had a stronger effect and often masked wetland influence.

Weidner et al. conclude that in flat, wetland-rich areas like Augusta Creek, groundwater can dominate stream chemistry patterns even when wetlands are present. They recommend that water quality models and monitoring programs account for both surface water and groundwater processes, and that sampling occur across multiple locations and seasons to capture the full picture.

Weidner, C. R., Zarnetske, J. P., Kendall, A. D., Martin, S. L., Nesheim, S., & Shogren, A. J. (2025). “Wetlands, Groundwater, and Seasonality Influence the Spatial Distribution of Stream Chemistry in a Low-Relief Catchment.” Journal of Geophysical Research: Biogeosciences, 130, e2025JG008989. https://doi.org/10.1029/2025JG008989

Corresponding author: Caroline R. Weidner, weidne68@msu.edu.