Limnological Conditions in Five Small Oligotrophic Lakes in Terra Nova National Park, Newfoundland

Abstract

Five oligotrophic lakes in Terra Nova National Park, Newfoundland, varying in mean depth (1.06–9.22 m), in water renewal rate (0.2–20.7 times per annum), in salinity (18.2–42.6 mg/liter), in total phosphorus (0.1–0.6 mg-at P/m3), and in chlorophyll a concentration (0.5–3.2 mg/m3), were investigated for 17 mo in 1969 and 1970. Hypolimnetic oxygen deficits ranged between 111 and 217 mg O2 per m2/day. Low levels of nutrients, reduced solar radiation, and low underwater light penetration, owing to excessive cloudiness and high water color, seriously limited planktonic primary production. The relation between primary production at optimum light, and water renewal per annum, appeared to be curvilinear when the rate of primary production began to decline above an optimum water renewal rate. The seasonal and annual variations in water color and salinity were dependent on the rate of water renewal, but other lakes on the catchment areas modified that relation. Winter road salting operations within the catchment area caused a considerable increase in salinity, total phosphorus concentration, and primary production in one lake. A new morphometric index which reflects the littoral effect on basin volume was proposed.