Continuous Culturing of Natural Phytoplankton Communities in the Experimental Lakes Area: Effects of Enclosure, in situ Incubation, Light, Phosphorus, and Cadmium

Abstract

Continuous culture chambers containing and receiving raw lake water as an inflow were incubated in the laboratory and in situ. This was done to determine the suitability of continuous algal culture for recording the responses of lake phytoplankton to experimentally imposed perturbations simulating environmental changes. The distribution of the phytoplankton in control chambers, particularly with in situ incubation, remained similar to that of the lake. Other chambers produced changes in distribution as responses to perturbations of filtered inflow, light, a nutrient, and cadmium. These responses were consistent with existing data for lakes at the Experimental Lakes Area, including the responses to cadmium which were compared to those from tube experiments. The relative merits of these and other types of enclosures including batch cultures, large bags, and tubes are discussed.Key words: phytoplankton culture, enclosure effects, phosphorus, light, cadmium, bioassay, microcosms