Measurement of Adenosine Triphosphate (ATP) in Two Precambrian Shield Lakes of Northwestern Ontario

Profiles of the adenosine triphosphate (ATP) concentrations occurring in the particulate material of two experimental shield lakes were obtained with respect to time. Large seasonal changes were evident, as were specific sites of high biological activity due either to natural stratification or to deliberate manipulation. Chlorophyll a, particulate carbon, and direct count data were found to be misleading in specifying the changes or the sites of biological activity. Analysis of the ATP data on the basis of the relative abundance of different size fractions was found to be useful. An ATP filtration error could not be demonstrated, indicating that cell breakage is not a source of the filtration error inherent in some 14C primary and secondary productivity studies.

Primary Production and Phytoplankton in the Experimental Lakes Area, Northwestern Ontario, and other Low-Carbonate Waters, and a Liquid Scintillation Method for Determining 14C Activity in Photosynthesis

A modified 14C method is described for measuring phytoplankton production in low-carbonate waters. The procedure includes the use of the Arthur and Rigler (Limnol. Oceanogr. 12: 121–124, 1967) technique for determining filtration error, liquid scintillation counting for determining the radioactivity of membrane filters and stock 14C solutions, and gas chromatography for measuring total CO2.Primary production, chlorophyll a, and total CO2 were measured for two dates in midsummer from each of several lakes in the Experimental Lakes Area (ELA), ranging from 1 to 1000 ha in area and from 2 to 117 m in maximum depth. Phytoplankton species abundance and biomass were determined for the same dates. Production ranged from 0.02 to 2.12 gC/m3∙day and from 0.179 to 1.103 g C/m2∙day. Chlorophyll ranged from 0.4 to 44 mg/m3 and from 5 to 98 mg/m2 in the euphotic zone. The corresponding ranges for live phytoplankton biomass were 120–5400 mg/m3 and 2100–13,400 mg/m2. Chrysophyceae dominated the phytoplankton of most of the lakes.A system for classifying the lakes in terms of phytoplankton species composition and production–depth curves is developed.

Nutrient Supply and Primary Production in Clear Lake, Eastern Ontario

Clear Lake, a small Canadian Shield lake that has been influenced little by human activity, was found to be more productive than expected from chemical and optical properties and geological surroundings. Production during the ice-free season ranged from 0.10 to 2.57 g C/m2 per day and averaged 250 g C/m2 per year for the lake as a whole. Other limnological factors studied (phytoplankton standing crop, oxygen, temperature, and nutrient regimes) were typical for an oligotrophic lake.The high production values are partially explained by the high correction for filtration error, which averaged 3.2 times for all occasions tested.Atmospheric precipitation is undoubtedly the major source of supply of the nutrients nitrogen and phosphorus to Clear Lake. Calcium and magnesium also appear to be largely carried in by precipitation, although most of the sodium, potassium, and silica entering the lake is weathered from the terrestrial watershed.