Upper Ocean Mixing: The Use of Algal Pigments as Biological Tracers for Turbulent Diffusion.

摘要

The goal of lhe proposed research was to develop an in situ method for determining upper-ocean mixing rates using algal pigments as natural biological tracers. The work focused specifically on xanthophyll-cycling, a well known series of reversible, light-sensitive pigment transformations that occur in all higher land plants and many marine phytoplankton species. Laboratory work was initiated to define the rate constants for xanthophyll-cycling in microalgal cultures, and to develop a. quantitative understanding of the influence of light intensity on the xanthophyll-cycling process. Field work was completed which verified that xanthophyll-cycling processes measured in natural phytoplankton populations indeed reproduced our laboratory observations. A Monte-Carlo computer model was developed in order to study the influence of xanthophyll-cycling on algal pigmentation under known conditions of simulated mixing. The collective results from physiological experimentation and simulation modeling were used to develop a field method for calculating ocean mixing rates (Welschmeyer and Hoepffner, 1991; Welschmeyer 1991). The work has now identified previously unrecognized relationships between xanthophyll- cycling and cellular fluorescence, which are of potential importance in exploiting single-cell characteristics as novel tracers of ocean mixing. This new work is continuing in our laboratory.