Green Lake’s wetlands are being restored, one lily pad at a time

AFTER MONITORING AQUATIC vegetation in the County Highway K Estuary, Green Lake School District students and Green Lake Sanitary District staff remove invasive carp from a fyke net located in the estuary. Fyke nets jointly allow for carp removal and provide the Lake Management Planning team with valuable information on game fish and carp movement within the estuary. submitted photo

by Alison Niescier

Isolated sections of the County Highway K Estuary are getting greener. That was the general assessment by Green Lake School District students last month as they helped monitor ongoing efforts to revegetate the degraded wetland.

This is good news, given that there were previously no measurable aquatic plants in the CTH K Estuary several years ago.

The root structures of plants “glue down” loose sediment, preventing it from transferring nutrients detrimental to water quality downstream to Big Green Lake.

Sago pondweed and white lily, two native species indicative of wetland and lake health, have taken root within several fenced-in areas of the estuary. True to their name, these “carp exclosures” prevent carp from disrupting protected areas and allow fragile plants to take root.

The algae-dominated wetland is currently a liability to Green Lake. In fact, 495 tons of sediment (30 percent of total sediment loading to Green Lake) and 2,850 pounds of phosphorus (17 percent of total phosphorus loading to Green Lake) come from this one estuary every single year.

The concentrated carp population is largely to blame for the estuary’s dilapidated state.

The U.S. Fish Commission intentionally stocked carp in Wisconsin lakes in the 1880s. Even then, anglers quickly identified the carp as a nuisance fish. In the County Highway K Estuary, their agitated movements uproot beneficial aquatic plants and shift nutrients downstream, where it fuels the lake’s weed and algae growth.

That is why the Green Lake Association (GLA), Green Lake Sanitary District (GLSD) and other members of the Lake Management Planning (LMP) team have developed a multi-year plan to restore the wetland to a healthy state.

For two consecutive years, the team has placed native plant rootstock into isolated sections of the estuary. These plants filter out nutrients before they reach the lake and hold phosphorus-rich sediment in place.

The team is hoping this work, in tandem with continued carp removal, will prove to be a winning combination for the wetland, as sprigs of sago and white-lily leaf pads triumphantly reach the surface.

In addition to monitoring steady plant growth in the estuary, students had the opportunity to increase the plants’ odds of survival by removing carp from a series of nets in the wetland. The fyke nets jointly allow for carp removal and provide the LMP team with valuable information on game fish and general carp movement within the estuary.

Commercial fishermen, along with GLSD and GLA staff, have removed 78,000 pounds of carp from the estuary in 2018.

When combined with removal efforts in the lake itself, more than 155,000 pounds of carp have been eradicated from Big Green Lake this year.

In the eyes of the LMP team, every carp and every lily pad counts.

Efforts like that of the Green Lake School District contribute to the team’s ultimate goal: to tip the scale in favor of a restored County Highway K Estuary that serves as a nutrient sponge for a cleaner Green Lake.

Alison Niescier is the Project Manager for the Green Lake Association, a local not-for-profit that works to improve water quality for Green Lake. The GLA is a guest columnist on behalf of the LMP team.