Thick coating of algaeic slime on boulders in littoral zone of Sebago Lake. Photo taken at Buoy 81 off Frye Island in August, 1997 by Sonny and Helen McAlpin, Underwater Photo & Video.
2. Analysis of impacts of lake-level management on the littoral zones of Sebago Lake.


Because most recreation occurs in the nearshore areas and the importance of the near shore to the food web of Sebago Lake, FOSL requests the EIS review the impacts of the present lake level regulation on the biota and water quality of the littoral zone of Sebago Lake.

Since 1987 a substantial change in the littoral zones of Sebago Lake has occurred. The littoral zone is the shallow area between the wave swash zone and the depth to which the lake bottom can support aquatic plants. Recent shoreline erosion has caused siltation of the bottom of Sebago Lake, a highly oligotrophic lake. Nutrients in the sediment have fueled a proliferation of aquatic macrophytes and periphyton. This is the case for undeveloped areas as well as developed areas. The littoral areas have become very algaeic with substantial accumulations of dead biomass on the lake floor.

The littoral zones have been altered from that of an oligotrophic to a mesotrophic littoral zone. Accelerated eutrophication has occurred because of the present lake level management plan. In view of the new high biomass levels on the lake bottom we are witnessing, FOSL suspects the oxygen levels at the sediment-water interface may be adversely impacted.

In the summer of 1997, at Buoy 81 in 17 feet of water, one quarter mile from the southwest shore of Fryes Island, a professional diver working with FOSL stirred the lake bottom with flipper action. At the surface, two FOSL observers noticed a strong smell of sulfurous "swamp" gases. The site of Buoy 81 is far from shore and in a zone under the impact of clay pluming from the eroding clay-silt bluffs on Fryes Island. Sulfurous gases are a strong indicator of anaerobic conditions. In anaerobic conditions phosphorus deposited in the bottom stratum can be recycled and enter the water column. FOSL has learned these clay plumes are very difficult to observe unless light and surface conditions are ideal. A polarized lens camera will often reveal a clay plume many times larger than can be seen with the naked eye.

FOSL requests that as a condition of the relicensing the licensee photographically monitor the littoral zones and scientifically monitor oxygen levels at the sediment water interface. The varial zone of Sebago Lake now has a very distinct algaeic film that covers all rocks and stratum not exposed to strong wave swash and sand abrasion. Many people have mentioned this at various lake meetings. Older residents who grew up on Sebago Lake recall a mostly pristine lake bottom.

Sixty years ago many farms existed in the Sebago Lake watershed and most roads were dirt. There was much new development around the lake. Safe phosphorus watershed prevention did not happen. However, like for the hundred years prior to the 1980s, lake level management caused no recorded harm to the resilience of the lake and its ability to safely handle phosphorus loading. In the 1860s the populations of the towns surrounding Sebago Lake were similar to the population in the 1960s. In the 1800s, 90 percent of the population was agriculturally based. Dairy and sheep farms covered the hillsides. Today, there are strict building codes and most farms have disappeared. The watershed is now mostly forested -- yet an unprecedented biomass growth has occurred in Sebago Lake since the late 1980s.

In the 1800s the Portland Water Company diverted water to Portland via an aqueduct located in the Sebago Lake Basin. Even with extensive agricultural use of the area, the owner of the Water Company boasted how sandy and free of algae the Basin was.

Montana's Flathead Lake has suffered similar damage due to changes in lake level management. Several studies of Flathead Lake have documented the adverse consequences of unnatural lake regulation. According to Stanford and Hauer (1992), Flathead Lake has developed a condition called 'ring around the lake':

"The 'ring around the lake' is a consequence of both eutrophication (lakewide nutrient pollution) and lake level regulation. Similar processes may be occurring in the mainstem Flathead River, where abundant biofilms occur within the varial zone. Just how the enhanced productivity of the lakeshore may be related to dynamics of the shoreline food web is unknown. But, two observations may be made: 1. enhanced productivity of shoreline biofilms, coupled with entrainment of fines in the substrata, which is itself a form of nutrient pollution (Ellis and Sanford, 1988a; 1988b), could have caused major changes in the shoreline ecology by clogging interstitial spaces and possibly reducing localized oxygen levels and thereby altering habitat quality (ie. for fish spawning) ; and 2) dewatering of the varial zone, coupled with changes in the fish and invertebrate populations in the lake, very likely has directly (ie. stranding, predation) or indirectly (ie. cascading food web effects) altered the zoobenthos and community structure of the shoreline."
NEXT
BACK TO SHORE
BACK TO SCOPING COMMENTS TABLE OF CONTENTS