In both 2005 and 2006, Cayelan Carey placed “traps” to catch the Gloeo migrating from the sediment into the water column. Twice a week she emptied the traps and counted the Gloeo colonies in the traps and from scoops of the lake surface water in a plankton net. This allowed her to monitor the increase/decrease in colonies entering the water column, and the density of Gloeo near the surface. She also analyzed the amount of phosphorus present in the sediment at each of the sites.
Carey conducted several lab experiments at the same time, growing Gloeo for insight into its life cycle, the timing of different phases, and its response to inputs of phosphorus.
In 2005, Carey placed traps all around the lake and found that the timing of pulses in phosphorus and Gloeo appearance were the same lake wide. In 2006, Carey placed her experiments only in Herrick Cove, as that area had had the most Gloeo in 2005. There were two sites there that she monitored throughout both seasons and a third Herrick Cove site she added in 2006.
Effect of Phosphorus Pulses
In 2006, Carey also conducted a separate experiment to definitively test the effect of phosphorus pulses on the migration of Gloeo from the lake sediment. She placed small tiles enriched with phosphorus on the surface of the sediment, with traps right by the tiles and also a meter distant. In both cases, the amount of Gloeo entering the water column increased significantly, but it took four days longer to occur in the more distant traps – precisely, as expected, the amount of time it took the phosphorus to diffuse one meter in the sediment.
Toxicity
Carey’s 2005 work included an analysis of the toxicity of the Gloeo in Lake Sunapee. (See the Beacon September, 2005.) She found that, though the Gloeo does contain toxins that can trigger digestive upsets and skin irritation, and that are toxic for the liver, the amounts of toxins in the Sunapee Gloeo are at present well below a level of concern.
Regional Survey
In 2006, Carey also visited and sampled 14 oligotrophic lakes in New England that have had Gloeo blooms. Although it was a one-shot view, not necessarily reflecting peak blooms, Carey found that Sunapee was at the high end for the amount of surface Gloeo, and in the lower third for the amount of phosphorus in the sediment.
Future Studies
Carey’s work involved many long hours in a wetsuit underwater, and even more hours in the laboratory growing and counting Gloeo colonies. Her dedication yielded significant scientific insight that is being submitted to scientific journals. Her work continues as a Fulbright fellow at Uppsala University in Sweden, where most of the world’s research on Gloeo has been done.
In the meanwhile, LSPA and Dartmouth students will continue Carey’s work in Herrick Cove, adding to the two years of data Carey amassed. We will continue to monitor the levels of toxins, sediment phosphorus, and Gloeo in the water and on the surface.
Date published on web site:
12-01-2006
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