Volume 1 2014

Sea Grant Research

Green Bay Report Outlines Progress, Identifies Problems

After several years of work, Wisconsin Sea Grant has finalized “State of the Bay: The Condition of the Bay of Green Bay/Lake Michigan 2013.” This third edition of the report, written by Theresa Qualls, Bud Harris and Victoria Harris, and published 20 years after the previous edition, presents new data on water quality, as well as data on fish and wildlife populations, aquatic invasive species, beach conditions and the status of contaminants in the region. The authors point out the advantage of having data over such a long period of time is that it allows scientists and citizens to identify trends.

Areas of Progress

Progress has been made from the 1970s and 1980s in the Lower Green Bay and Fox River area of concern on levels of ammonia and dissolved oxygen found in the water. The report attributes the decrease in ammonia to improved wastewater treatment. Dissolved oxygen levels are also generally good in large portions of the bay. Nevertheless, hypoxic areas (“dead zones”) develop in isolated bottom waters during late summer.

Good news can be found for fish populations. Green Bay supports a walleye trophy fishery, which remains unchanged. Spotted muskies are also faring well due to stocking efforts and hatchery production. Northern pike are holding their own and currently receiving considerable attention with spawning habitat restoration.

Beach closings due to bacterial contamination are at a fair level and seem to be decreasing at most sites as a monitoring program progresses and communities work at identifying and controlling sources of the bacteria.

Coastal wetlands are currently in fair condition but remain endangered due to development pressures and an increase in sediment in the water, which limits the amount of light available for plants.

Areas Needing Work

Phosphorus concentrations are known to be tied to harmful algal blooms. Until levels can be reduced, algal blooms are expected to persist.

Nitrate and nitrite concentrations in the river have been increasing, likely a reflection of increased fertilizer use in the watershed.

The amount of “gunk” in the water in the form of suspended solids (things like algae, soil, decaying plant matter and wastewater particles) equal many dump-truck load equivalents every day in some parts of the bay and are considered excessive. Better land-use practices and other measures are needed for this factor to improve.

Levels of a crucial plant pigment called chlorophyll a are found in too great a quantity in water samples. This means there is excess growth of algae, including the potentially toxic blue-green kind, which can reduce water quality and cause human health problems for people in contact with the water.

The water clarity in Green Bay averages half a meter. To meet ecosystem health targets, it needs to be twice that.

Levels of toxic chemicals in the bay, such as PCBs, dioxins, DDT, arsenic and mercury continue at unacceptable levels. These chemicals pollute fish and bay sediments and pose health risks for wildlife and humans. They come from many sources and require coordinated, long-term cleanup efforts.

Although restoration projects and public outreach and education efforts have helped limit the spread of aquatic invasive species, they continue to take a toll on the health of the bay.

Bottom-dwelling animals, called benthic macroinvertebrates, are important food sources for fish and waterfowl and play a crucial role in keeping bay ecosystems healthy. Population levels of these bottom-dwellers are too low due to contaminated sediment and other pollution.

For more information, read the full report online at seagrant.wisc.edu/sotb.

Status and Trend Assessments of Green Bay Indicators

Indicator Status Trend
Total Phosphorus Poor Unchanging
Ammonia Good Unchanging
Nitrate Fair to Good Deteriorating
Total Suspended Solids Poor Unchanging
Chlorophyll a Poor Unchanging
Water Clarity (Secchi) Poor Unchanging
Dissolved Oxygen (DO) Fair Improving
Toxic Contaminants Poor Undetermined
Water Levels Below Average Declining
Beach Health Fair Undetermined
Aquatic Invasive Species Poor Deteriorating
Benthic Macroinvertebrates Poor Undetermined
Coastal Wetlands Fair Deteriorating
Walleye Good Unchanging
Yellow Perch Mixed Improving
Spotted Musky Fair Improving
Northern Pike Fair Unchanging
Lake Sturgeon Recovering Population Improving
Colonial Nesting Birds Mixed Improving to Deteriorating

The "State of the Bay" reports data collected over 20 years, allowing scientists and citizens to identify trends. Status and trend category details available at seagrant.wisc.edu/sotb.

The Aquatic Sciences Center is the administrative home of the
University of Wisconsin Sea Grant Institute & University of Wisconsin Water Resources Institute.

©2011 University of Wisconsin Board of Regents