Primary Production Measurements in Eleven Florida Springs and a Marine Turtle-Grass Community1

During July and August, 1955, primary production measurements were made in eleven Florida spring communities and a marine turtle-grass community in the Florida Keys by means of the diurnal curve method. Diurnal measurements of oxygen and carbon dioxide made at a station downstream from the main springs were used in estimating gross primary production and community photosynthetic quotients. These curves show in detail the course of production hour by hour under various conditions in whole natural communities. The primary production values obtained ranged from 0.7 g oxygen/m2/day in a small, heavily shaded, anaerobic spring on a rainy day to 64 g oxygen/m2/day on a sunny day in an aerobic spring where the plant beds trailed at the water surface. A comparison of the chemostatic properties in the springs studied suggests that oxygen, phosphate, nitrate, and carbon-dioxide levels are relatively unimportant in determining the magnitude of primary production in these spring communities. Light as influenced by cloud cover, trees, and water depth is the main controlling factor. Approximate efficiencies found were 0.5 to 10% (mean 4%) of the visible light energy reaching plant level. Downstream increases in planktonic chlorophyll and oxygen suggested a steady state in 7 km of longitudinal succession in Rainbow Springs River. Net production of benthic algae of 1.5 g/m2/day was estimated in Orange Springs from the rate of bubble release into funnels placed on the bottom.