04/07/2004 Council Packet - Laserfiche WebLink

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• • Rice Creek Watershed March 1, 2002 Dear Sir or Madam: Peltier Lake is a hypereutrophic lake located in the headwater region of Rice Creek. This lake has two different distinct water quality areas. The area to the south of the island is largely shallow water (mean depth 7 feet) with very few rooted aquatic macrophytes. This portion of the lake is very high in nutrients and experiences excessive growth of phytoplankton (algae). The growth of algae limits light penetration into the water column, therefore limiting the available habitat for rooted macrophyte growth. Large algal growths can also contribute to low periods of dissolved oxygen during low light conditions. This is caused by plant respiration or decomposition of the algal material. The area north of the island has a different water quality characteristic. This area of the lake is generally 3 to 5 feet deep and has extensive rooted aquatic macrophyte coverage (mainly coontail). The density of rooted macrophytes helps consolidate the lake bottom sediments and also consumes available nutrients, therefore leaving less available nutrients for algal uptake. The water clarity in the northern portion of Peltier Lake is generally much clearer than in the southern portion. During much of the growing season (May through September) the rooted macrophytes would consume nutrients from both the water column and also have some nutrient uptake through the root systems. Removal of aquatic macrophytes would have some impact on the water quality of the north basin. Some possible impacts would be redistribution of bottom sediments, and introduction of additional nutrients to the water column. Without adequate plant material to buffer wave action caused by boating and wind, bottom sediments would suspend and be transported either into the south basin or into the water column of the north basin. This action could increase the nutrient load to the water column, decrease water clarity, cause stress on resident fish populations, and potentially give algae the competitive edge to expand their range and have even more severe blooms. Rooted aquatic macrophytes benefit the water quality of lakes. There is evidence that healthy aquatic macrophytes do not excrete large quantities of nutrients into the water column during active growing periods (Barko and Smart, 1980). They do tend to concentrate sediment - supplied nutrients in their tissue. These nutrients are partially