Phytoplankton Species' Responses to Nutrient Changes in Experimental Enclosures and Coastal Waters

Abstract

Phytoplankton growth is controlled by factors that influence intracellular processes, such as radiation, nutrients, and temperature; and factors that influence the entire cell, such as grazing, sinking, mixing, and advection. To evaluate the effects of certain of these factors on growth, small-scale containers are acceptable for short-term experiments, but continuous culture systems are recommended for long-term observations. Examining the growth of mixed phytoplankton assemblages in a multitrophic system requires large-scale facilities and very large containers. The present study examines the effects of macronutrients (nitrate, phosphate, and silicate) additions on phytoplankton species grown in large enclosures (1335 m3 ) containing multitrophic communities, during the CEPEX (Controlled Ecosystem Populations Experiment) Foodweb I experiment (Grice et al. 1980), at Saanich Inlet, British Columbia, Canada.