03/03/09

Troubled Waters at Peltier Lake

What are those weeds in Peltier Lake? Why is the lake sometimes so green and rotten?

Read these words from Wikipedia about the former pristine condition of the watershed before settlement. It certainly isn't that way anymore!

"According to the Minnesota Historical Society, Rice Creek was named for Henry Mower Rice, one of the first pair of U.S. Senators sent to represent Minnesota upon its statehood, who acquired extensive lands near the lower course of the creek in 1849. Early surveys conducted by Joseph Nicollet record the name of Rice Creek as "Ottonwey River" or Atoonowe-ziibi in the Ojibwe language meaning "River for making Canoes." However, its Ojibwe language name has also been recorded as "Manominikan Sibi" or Manoominikaan-ziibi, meaning "river full of wild rice," which is known to have grown plentifully in the lakes of the watershed. Nicollet described the creek as: "At 2:45, as we left the islands behind, a rivulet about thirty feet wide entered the river from the left. Its shores are adorned with beautiful white lilies. Chagobay told me that it winds back to the vicinity of the Falls of the St. Croix River, being separated from the latter by only a short portage. Its course links several alkes, while irrigating a land abundant with wild rice where the Sioux gather their yearly provisions. The Sioux call it in their language Wild Rice River, and the Chippewa Manominikan Sibi, which means river where one reaps wild rice. "Manomin" (wild rice) was also the basis for the naming of the former Manomin County, which later was incorporated into Anoka County and ultimately became, in part, the city of Fridley, where the creek joins the Mississippi River."

"Archaeological evidence exists that suggests ancestors of the Sioux hunted and fished in the vicinity of Bald Eagle Lake (approximately present-day White Bear Township) in the Rice Creek watershed, and had a summer village in the present-day city of Centerville as early as 2000 B.C."

In keeping with the Clean Water Act, the Minnesota Pollution Control Agency (MPCA) has listed Peltier Lake on its impaired water list.

 The reasons for the impaired waters are numerous, but one cause is the effect of a non-native aquatic plant, curlyleaf pondweed. 

 The exotic curlyleaf pondweed grows earlier than most native species in the lake, so it becomes dominant in the water.

In late June when the waters become warmer, the curlyleaf dies, which then results in the plant releasing nutrients into the lake. But before dying, the plant produces millions of seeds, called turions, which will grow the following year.

 Algae in Peltier Lake thrives on the nutrients curlyleaf releases, which causes the algae to bloom in huge quantities creating scum and a strong smell. Sometimes blue-green algae blooms can be toxic, so caution on the part of people and pets is advised.

 Algae is generally related to the amount of phosphorus in the lake. With excessive phosphorus, there is excessive algae. In Peltier Lake, phosphorus is internal and external. Internal phosphorus is already in lake sediments, or in a cycle with non-native aquatic plants like the curlyleaf. External sources of phosphorus come from the watershed.

 The south part of Peltier Lake involves a vicious cycle in which curlyleaf and algae help each other create an environment that discourages anything else from taking hold. A lake should have beneficial aquatic plants to absorb nutrients and avoid algae blooms. In the spring, Peltier Lake can look quite good because the aquatic plants are healthy. But by midsummer, algae and its scum take over when the plants die and release nutrients — the algae blocks light and tends to knock back all submerged aquatic plants.

 Another player in the lake is eurasian watermilfoil. Other lakes have huge problems with eurasian watermilfoil as well, when it covers areas with thick surface mats of vegetation. This exotic first appeared in 2000 and has been expanding its presence in the lake ever since. Every year it seems to increase its density and range, until the algae in July knocks it back. But the milfoil hangs on until next year’s clear spring waters.

 In addition to Peltier Lake, Centerville, George Watch, Marshan, and Reshanau Lakes in the Rice Creek Chain of Lakes Regional Park Reserve have all been placed on the impaired water list.

 What might be done?

 On July 31, 2008, water resource experts Matt Kocian of the Rice Creek Watershed District (RCWD), Gary Oberts of Emmons & Oliver, Inc, and Joe Bischoff of Wenck Associates presented Total Maximum Daily Load (TMDL) information and strategies to improve the impaired waters. A TMDL study looks at lake loading of nutrients and makes recommendations to bring the lake into compliance with water quality standards. The study is now underway and the group is developing a restoration strategy for the lake.

 Remediation to consider includes water level changes, fish management, chemical treatment, macrophyte control, aeration/circulation, habitat restoration, sediment removal, wetland restoration, low impact development, bioretention, detention ponding, local/RCWD rules, buffers, and infiltration/filtration.

 Peltier lake is considered a shallow lake, and the group is trying to bring the state of the water from “turbid” to “clear”. Left turbid, the lake houses pike predator fish, lots of carp, minnows and pan fish, few invertebrates, way too much algae, almost no beneficial submerged plants, and sediments full of nutrients.

 The situation means the small number of predator fish allow too many minnows and pan fish, which in turn eat most of the invertebrates that would otherwise eat and help control algae. The carp stir up the lake bottom, releasing nutrients that hamper beneficial aquatic plant growth. The huge algae population blocks the light, further preventing beneficial aquatic plants which would help stabilize the sediments and absorb nutrients.

 In the clear-water state, a large population of predator fish reduce the minnow and pan fish population. That allows the invertebrates to flourish and eat the algae. Beneficial aquatic plants could then flourish, stabilize the sediments and absorb nutrients.

 Going from the clear-water state to a turbid-water state is easy. But Peltier Lake needs to go the other way, which is not so easy. One strategy under consideration is a lake drawdown. Keeping the lake level down over the winter might kill many of the non-native aquatic plants. Keeping it down over the summer months could reduce nutrients in the sediments. But first, external sources have to be addressed or phosphorus might just accumulate in the sediments again and little would be gained.

The public can help. Runoff into the lake adds to the nutrient loading. Consider the following: planting raingardens to reduce runoff; keeping lawn clippings and vegetation off the street so they won’t wash into the lake; not mowing next to wetlands; keeping high speed boat traffic far from shore and shallow water; respecting the no-wake zone by the island; establishing buffers and natural vegetation on shorelines to reduce nutrients going into the lake and not fertilizing by the lake. See www.BlueThumb.org for more information.

Also see the TMDL button for more detail.