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

Abstract

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.