Abstract
Automated instrumentation is described that performs time-course incubation experiments directly in situ where natural conditions of temperature, light, hydroastatic pressure, etc. can be maintained. The sampler incubation devise (SID) takes a 1-liter sample from the water and simultaneously introduces and appropriate radiotracer. During subsequent in situ incubation, 50-ml subsamples are with-drawn from the main sample at equally spaced intervals and preserved for laboratory analysis. Representative experiments revealed nonlinear carbon utpake within 0.5-1.0 h, emphasizing that even brief end-point analyses can lead to large errors in estimating phytoplankton production rates. Studies of the rapid fluctuation in phytoplankton activity resulting from cloud-induced variations in light intensity and the application of cellular fractionation methods for measuring the intracellular distribution of newly fixed carbon illustrated the utility of instrumental time-course techniques for studying phytoplankton physiology and community metabolism in situ.