Resolving the Impactsand Feedbackof Ocean Optics on Upper Ocean Ecology ........ W. Paul Bissett Florida Environmental Research Institute. Tampa, Florida USA Oscar Schofieid, Scott Glenn Rutgers University. New Brunswick, New Jersey USA John J. Cullen, William L. Miller Dalhousie University. Hafifax, Nova Scotia Canada Albert J. Plueddemann Woods Hole Oceanographic Institution • Woods Hole, Massachusetts Curtis D. Mobley Sequoia Scientific, Inc. • Redmond, Washington USA USA December 30, 1831 - "The deep water differs as much from that near shore, as an inland lake does from a little pool. - It is not only the darkness of the blue, but the brilliancy of its tint when contrasted with the white curling tip that gives such a novel beauty to the scene." --Charles Darwin, The Beagle Diaries Introduction The abundance and fecundity of life on this planet is directly related to the energy supplied by the sun. The pyramid of life starts with the absorption of a frac- tion of this energy, followed by its conversion from electromagnetic to chemical energy (photosynthesis) and its subsequent storage into biomass (primary pro- duction). This chemical energy supports, in one way or another, the myriad of food webs that exist on the earth 1. Thus, the study of food webs and their dynam- ics is to a first order defined by the basic energy inputs into the ecosystem, and therefore the study of life requires understanding of the amount of energy avail- able to feed biological systems. The study of energy propagation to the planet is called geophysical optics, and is sub-divided into two categories, meteorologic optics (energy and atmo- sphere) and hydrologic optics (energy and water; Preisendorfer, 1976). The majority of solar energy strik- ing the earth falls into two broad bands of the electro- magnetic spectrum, visible energy (approximately 400 to 700 run) and infrared energy (700 nm to 100 ~tm). As water is nearly opaque to infrared energy (Figure 1), the study of ocean optics has been primarily concerned with propagation of visible energy, i.e. light. This is also a natural starting point for the study of ocean ecology as photosynthesis is driven (with a few exceptions) by energy within the visible light spectrum, which has suf- ficient energy per photon to induce photochemistry. As phytoplankton accumulations also impact the color and clarity of the water column, there is a direct link between the studies of ocean optics and ocean ecology (Yentsch and Phinney, 1989). _r lllilllll] lilUllltln iJlU 1.5-x1033~, " " " ~ - =_i ,.o _:- - o.s 2 Z o 0.4 o.o ~.2 ~.e 2,o 2.4 ~. {~m) Figure 1. Spectrum of downwelling irradiance at the sea surface and at various depths within the upper ocean. From Kraus and Businger (1994), "Atmosphere Ocean Interaction". Copyright Oxford University Press. 1 We are ignoring chemosynthesis using reduced inorganic molecular products around hydrothermal vents. Oceanography • VoL 14 • No. 3/2001 30