PRINCIPAL 



INVESTIGATOR(S) A. M. Wood 



Department of Biology 

 University of Oregon 

 Eugene, OR 97403 



PROJECT TITLE PHYTOPLANKTON EXCRETION REVISITED: HEALTHY 



CELLS MAY NOT DO IT, BUT HOW MANY CELLS ARE 

 HEALTHY? 



AMOUNT OF FUNDING FY 1994: $99 K 



SUMMARY OF GOALS 



The primary purpose of this research is to develop molecular tools for determining the 

 health of marine phytoplankton on an individual cell basis. Since the definition of healthy in 

 phytoplankton cells elusive, we are developing markers for several different metabolic process 

 indicative of physiological state: photosynthetic activity, esterase activity, accumulation of storage 

 products (ie. lipids), and membrane potential. One underlying motivation is to develop methods 

 which will allow us to evaluate the hypothesis that, while healthy cells release very little DOC, 

 many phytoplankton communities are comprised of unhealthy or physiologically stressed cells 

 which release a large proportion of total photosynthate into the pool of labile DOC. Another 

 motivation is the goal of determining the growth state of bloom-forming phytoplankton cells 

 when they are observed in samples from the water column or sediment traps. 



During the OMP field year, we are particularly interested in 1) identifying and 

 enumerating net phytoplankton in the study area; 2) evaluating their contribution to total biomass; 

 and 3) using the molecular probes we are developing to evaluate the role(s) these large cells play 

 in material and energy flux on the continental margin. 



In this work, the physiological state of individual cells is emphasized. It differs from 

 more traditional approaches based on bulk measurements. The traditional approach effectively 

 hides any differences in the relative contribution of different taxa or individuals to overall 

 productivity even though most flux processes are sensitive to physiological and taxonomically- 

 determined differences among members of the community. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



This approach is relevant to, and compatible with, the study of material and energy flux 

 in marine ecosystems on a variety of time and spatial scales. Discrete samples (net tows, bottle 



131 



