The Trophic Status of Port John Lake, British Columbia
Port John Lake is situated on King Island on the central British Columbia coast. Area is about 0.35 square miles (910,000 sq. m.). The drainage basin is 3.6 square miles (9.3 sq. km.) with an igneous foundation supporting a coniferous forest. Annual precipitation is 116 inches (295.5 cm.). An oligotrophic lake, it has a volume development of 1.53 and a mean depth of 82.2 feet (25.1 m.). The thermal stratification is second order, temperate, of the Whipple classification. The summer heat income is approximately 11,000 gram-calories per sq. cm. The ratio of O2 in the hypolimnion to O2 in the epilimnion is 6.58. Total dissolved solids are 39 ppm. at the lake surface.Large amounts of organic matter are washed into the lake imposing a potential stress on its oligotrophy. However, dredge and net collections, which are dominated by chironomids and cladocerans, respectively, contained very few organisms. Plankton was most abundant in the surface water.Low production of organisms is partly the result of the heavy rainfall which dilutes the trophic stratum above the hypolimnion, and the small amount of sunlight reaching the lake.