Treating Lake Anita Louise
Lake Anita Louise drew considerable attention last winter with its almost overnight chameleon transformation from dark olive to auburn red. It was a surprising and seemingly unnatural sight. Few, if any in the community had ever seen such a display, certainly not at any of our lakes over the past 40 years. It turned out that the color change was nature at work. Assisting the HOA’ s Friends of the Lake, Hood College’ s Center for Coastal and Watershed Studies( Hood), and the Maryland Department of the Environment determined that the red pigment was due to the proliferation of a naturally occurring, toxin producing, cold water cyanobacteria, Planktothrix rubescens, found in alpine lakes( think Switzerland). Today, more than a year later, still nobody knows how or when the cyanobacteria took up residence in Lake Anita Louise. The cyanobacteria could have been dormant in the lake for some time or alternatively more recently transplanted.
The January 2016 blizzard and weeks of ice on the lake surface took its toll on Planktothrix. Subsequently, the summer’ s heat progressively forced the cyanobacteria into retreat and Lake Anita Louise’ s normal color returned. Even so, as late as October 2016, there were signs of Planktothrix in the deeper, cooler part of the lake. In November 2016 the lake was proactively treated with hydrogen peroxide( Figure 1) under state permit to reduce the chances of a reoccurrence over the cool winter months( Hood has documented the cyanobacteria treatment effort in a report available for LLA residents to review on the HOA’ s Membership Portal). Additionally, the lake was partially drained to:( a) limit the volume of water that might need to be treated again over the winter;( b) enable the lake to be isolated from Lake Linganore should the bacteria return; and( c) facilitate helpful warming of the sediments and water in the spring and early summer. Unless there is a reoccurrence, the lake will be refilled during the summer. So far, so good.
While it is uncertain how the Planktothrix took up residence in Lake Anita Louise, it is clear that the environmental conditions in the lake last winter were ideally suited for the Planktothrix in order for it to have dominated over all the other lake algae and bacteria. Certainly, we had the requisite cool, low light conditions last year. But these cyanobacteria also thrive when nutrients associated with human activity( nitrogen and phosphorus) are present in abundance. Subsequent testing confirmed abundant nutrients in the lake and its sediments but nothing particularly unusual was found in its tributaries. There had been some recent hydroseeding of several storm drainage swales in the neighborhood lake drainage area but when the tributary sampling was completed, no specific source of nutrients could be identified. What specifically produced the ideal conditions to trigger the Planktothrix bloom, therefore, remains unknown.
The phenomenon indicated a tip in the ecological balance with nutrient runoff into the lake a likely contributing to the tilt. Since the drainage area feeding Lake Anita Louise is nearly entirely within the Lake Linganore community, Hood experts have pointed out that nutrient runoff is an environmental factor that our community can influence. Reduced flow of nutrients into Lake Anita Louise may occur by being even more careful about what chemicals we use around our homes, yards, roads and common areas and decreasing run-off by limiting impervious surfaces and increasing infiltration with trees and vegetated buffers( e. g., not mowing up to the lake shore).
With a goal of identifying economical and effective means of reducing sediment and nutrient flow into Lake Anita Louise, Friends of the Lake Co-chair Erin Johnson surveyed the lake grounds with two forestry professionals in October 2016. Two steeply sloped grassed areas above Farm Pond and one sloped grass area above Lake Anita Louise were identified as likely contributing more runoff than necessary. Based on these observations, a conceptual plan was developed & budgeted to plant 200 new native Maryland tree seedlings in these areas this spring, pending final HOA approvals( Figure 2). The plan also calls for allowing the grass to grow longer in these new“ no mow” areas. While the natural wetlands in the northwest corner of Lake Anita Louise appears to be in good condition filtering runoff entering the lake, Friends of the Lake plans on minor improvements during the warmer months( trash pick-up, invasive plant removal and protection of desirable native fauna). Updating historical storm water systems feeding into the lake was deferred.
Reforestation of the steeply sloped grassed areas close to Lake Anita Louise and encouraging beneficial wetlands growth may help, but will not in and of itself likely solve the issue. Incremental improvements will also need to come from each of us in how we live and use the environment around our homes in the Lake Anita Louise watershed. There is reason for optimism given the increasing awareness & support of the community and HOA management for environmental stewardship and with high level of expertise coming to our assistance from Hood and other
Planned Reforestation Areas organizations. 20 LakeTalk March 2017
Lake Anita Louise
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