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Research activities

by Marcel Dijkstra last modified Feb 20, 2019 12:56 PM

Marcel is highly motivated and organized. He is bright, technically adept, and well-organized. I have been particularly impressed by the thoroughness of his research. He thinks deeply about technical questions and exhibits an ability to break down difficult concepts in a critical and creative fashion. His ability to mine and analyse the literature in a thorough and creative fashion is exemplary. All these characteristics will serve him well as a scholar.

Steven C. Chapra, Ph.D., F.ASCE, F.AEESP

Current research projects by the WDNR certified Environmental Research and Assessment Lab:

Determination of the impact of zebra mussels on nutrient cycling in Lake Winnebago.

Lake Winnebago zebra mussel banks

Nathan Nozzi and Tyler Befus running field experiments

Lake Winnebago field sampling

 Jacob Hernandez doing field sampling in Lake Winnebago

Excessive phosphorous loading to Green Bay causes eutrophication and subsequent harmful algal blooms. These blooms lead to use impairment limiting recreational use and damaging the ecosystem. Approximately half of the phosphorous enters Green Bay through the Fox River. The main source of phosphorus in the Fox River, in turn, stems from agricultural runoff and waste water treatment plant discharge. 

In 1978 the Great Lakes Water Quality agreement was enacted to reduce phosphorous loading to the Great Lakes by targeting these sources. As a result loadings decreased and eutrophication issues diminished. Loadings from the early 1980’s onward, however, remained more or less constant.  In the mid 1990’s eutrophication increased again possibly driven by a change in the ratio of bioavailable to unavailable phosphorus. The first stimulating algal growth and the later not. 

In current efforts to reach water quality goals in Green Bay, no distinction between phosphorus species is made which may result in suboptimal (and very costly) management interventions.  In this research we use a Dual Culture Diffusion Apparatus to determine the fraction of bioavailable phosphorus in the Fox River and its temporal variability. 

DCDA at UW osh


Dual Culture Diffusion Apparatus used to fractionate phosphorus in bioavailable and unavailable pools.

Lake Decatur, IL

Study of phosphorus dynamics



Lake Decatur bioP

Average concentrations of bioavailable P in each basin of Lake Decatur from 6 June 

The elevated bio P level in basin 5 is likely due to the dredging operations. Sediment dredged from the lake is pumped to a settling pond east of the reservoir. The supernatant surface water from that settling pond drains back to basin 5. 

Elevated levels in basin 1 seem to originate from an influx of flow from several creeks (draining a primarily agricultural landscape) carrying P with a highly bioavailable character. The  high levels of bio P in Basin 1 and 5 may lead to nuisance algal blooms and subsequent water quality degradation. Nutrients in basins 2–6, however, are also at levels indicative of eutrophic conditions and could foster algal blooms as well.

Lake Shelbyville, IL and Carlyle Lake, IL


Study of Nutrient Dynamics

Sediment core Carlyle lake and Lake Shelbyville

Example of nutrient concentration (Carbon, Nitrogen and Phosphorus shown in panel 1, 2 and 3, respectively) in sediment cores taken at Lake Shelbyville, IL indicating trend shifts in phosphorus loading to the system.

Past projects and involvement

Field sampling efforts in support of ecosystem model development and model confirmation.

View of Lake Superior and the back deck of the R/V Agassiz

 Lake Superior


Water sampling in Lake Superior using a 20L Niskin bottle on board the R/V Agassiz Research Vessel.


MD core agassiz

Lake Superior sediment-core taken in waters >200 meters deep

Dr. N. Auer

Dr. N. Auer showing a sample of Mysis.


Watkins and Rutstram

Dr. J. Watkins and Dr. L. Rutstram (Cornell field station) deploying acoustic sampler

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by Marcel Dijkstra last modified Feb 20, 2019 12:56 PM