9. Analysis of potential impacts of lake-level management on outbreaks
of "swimmers itch" in Sebago Lake.
FOSL observations on Long Point at Sebago Lake suggest heavy outbreaks of
swimmers itch from time to time. Younger children who play in the near shore
waters and lake edge seem to the most vulnerable to these immature flatworms,
called Cercariae. The outbreaks appear to occur in years when the lake bottom
is coated with algae and periphyton.
FOSL believes the higher incidence of swimmer's itch may be a result of
several factors:
1. Shoreline erosion contributes to periphyton and aquatic plant growth.
This provides habitat and food for snails.
2. Maintaining higher water levels with a reduction in the range allows
algae and snails to live and grow in shallow zones from season to season.
3. Ducks are another host of the Cercariae and are attracted to areas where
lake bottom is richer in biomass.
Residents on Montana's Flathead Lake have noticed a correlation between
increased algae in the nourisher zone and increased incidence of swimmers
itch.
The June 1997 Flathead Lake Monitor stated: "Longtime residents commonly
report that swimmers itch is much more prevalent in Flathead Lake now than
in the past. Dr. Craig Spencer of Augustana College in South Dakota (and
formerly with the Flathead Lake Biological Station) studied swimmers itch
in the summer of 1992. Spencer suspects that the primary culprit of the
increased incidence of swimmers itch is increased algae growth around the
shoreline of the lake. Since attached algae appears to have increased significantly
in recent years, snails may now be more abundant, providing more potential
hosts for the parasite. Research conducted at the Flathead Lake Biological
Station indicates that increased growth of algae around the shoreline of
Flathead Lake has been stimulated by increased amounts of nutrients (phosphorus
and nitrogen) entering the lake."
Available at http://www.flatheadlakers.org/NEWS_LTR/june_97.htm
Swimmers itch can have a substantial impact on beach and lake use recreation
therefore FOSL requests the EIS analyze the relationship between lake regulation
and outbreaks of swimmers itch.
NEXT
BACK TO SHORE
BACK TO SCOPING COMMENTS TABLE OF CONTENTS