Light utilization and photoinhibition of photosynthesis in marine phytoplankton.

摘要

Introduction to Phytoplankton. Based on the record of the oldest identifiable fossils, the first oxygenic photosynthetic organisms appeared about 2 (times) l0(sup 9) years ago in the form of marine single celled, planktonic procaryotes (Riding, 1992; Sarmiento and Bender, 1993). In the intervening eons, phytoplankton have evolved and diversified; presently they represent at least 11 classes of procaryotic and eukaryotic photoautotrophs. While the carbon of these organisms cumulatively amounts to only 1 to 2% of the global plant biomass, they fix between 35 and 50 gigatonnes ((times) 10(sup 9) metric tons) of carbon annually, about 40% of the global total (Falkowski and Woodhead, 1992). On average, each gram of phytoplankton chlorophyll converts about 6% of the photosynthetically active radiation (440 to 700 nm) incident on the sea surface to photochemical energy (Morel, 1978). Despite a great deal of variability in ocean environments, this photosynthetic conversion efficiency is relatively constant for integrated water column production (Morel, 1978; Falkowski, 1981; Platt, 1986; Morel, 1991). Here we review the factors determining light utilization efficiency of phytoplankton in the oceans, and the physiological acclimations which have evolved to optimize light utilization efficiency.