NUTRIENT DYNAMICS OF NEQUASSET LAKE: EFFECTS OF ANADROMOUS ALEWIFE SUBSIDIES

This study aims to create a detailed budget for nitrogen and phosphorous in Nequasset Lake, Woolwich, ME. Nequasset supplies drinking water to Bath and Brunswick, and its nutrient inputs are subsidized every spring by an annual migration of the Alewife Alosa Pseudoharengus. These anadromous fish swim upriver from the Gulf of Maine to spawn in the lake, bringing with them biomass and nutrients from the marine system that will be incorporated into lake nutrient cycles via excretion, gamete release, and mortality. Young of the year fish will in turn export some of these nutrients with their fall emigration. Fish passage, however, is limited by a dilapidated fish ladder and commercial alewife harvest. Preliminary results of water nutrient concentration data and carbon and nitrogen stable isotope analysis indicate that these marine derived nutrients (MDNs) currently represent a very small proportion of total lake nutrient cycling. Current modeling efforts seek to quantify the effects of potential fish ladder restoration and increased Alewife migration strength on lake health. Results should help to strengthen the case for the habitat restoration of this ecologically and economically important species.