A paleolimnological assessment of factors affecting metal deposition and productivity in upland hydroelectric reservoirs, Nova Scotia, Canada


A 200-year paleolimnological study of two upland hydroelectric reservoirs in Nova Scotia provided insights into metal deposition and lake productivity associated with water level change. Black River Lake (BRL) and Gaspereau Lake (GL) were modified by dam installation beginning in the 1920’s and are influenced by similar hydrological and ecological conditions but are morphometrically distinct. Flooding resulted in increased metals (Pb As Zn Sr Ti) which peaked around 1970 in BRL. GL records increases in most metals until present, however, Sr and other grain size dependent elements decreased with flooding. Chlorophyll-a data indicates an increase in productivity during flooding though productivity in BRL increased much earlier than GL. These data suggest that the morphometry of the flooded surface strongly influences the timing of erosion, water column productivity and the composition and concentration of the metal load. The GL Sr record may also reflect the impact of damming on the transfer of nutrients and metals from marine environments to GL by alewife (Alosa pseudoharengus), an anadromous fish. Continuing research focuses on investigating the lake sediment isotopic record (13C 15N) to better resolve the mechanisms controlling metal flux and productivity into these two upland reservoirs.

Canadian Conference For Fisheries Research-Society of Canadian Limnologists Joint Meeting