PRINCIPAL 

 INVESTIGATOR(S) 



Ronald Benner 



Marine Science Institute 



The University of Texas at Austin 



P.O. Box 1267 



Port Aransas, TX 78373-1267 



J. Dean Pakulski 



Marine Science Institute 



The University of Texas at Austin 



P.O. Box 1267 



Port Aransas, TX 78373-1267 



PROJECT TITLE 



MECHANISMS OF DISSOLVED ORGANIC CARBON 

 CYCLING IN AN OCEAN MARGIN 



AMOUNT OF FUNDING FY 1994: $101 K 



SUMMARY OF GOALS 



Dissolved organic carbon (DOC) is the largest organic carbon reservoir in the ocean. It 

 is important to understand the processes by which DOC is cycled because changes in the oceanic 

 DOC pool could affect atmospheric carbon dioxide concentrations. Phytoplankton are the 

 dominant source of marine DOC, but the mechanisms and pathways of DOC formation are poorly 

 understood. This study will focus on the production of DOC during herbivorous grazing on both 

 eucaryotic and procaryotic phytoplankton. Herbivory is likely the major pathway for the 

 transformation of organic matter from particulate to dissolved form by grazers. A combination 

 of laboratory and field experiments will be used to determine the following: 



- the relative importance of herbivory for DOC production, 



- the rates and chemical characteristics of DOC production by natural communities and 

 particular species of phytoplankton, micro- and mesozooplankton, 



- the effect of phyto- and zooplankton species on the quantity, molecular size, and 

 composiion of released DOC, 



- the degree of coupling between DOC production and bacterial utilization. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



We propose characterizing herbivorous grazing and DOC release at inner, mid and outer 

 shelf locations within the framework of process-oriented "transformation cruises." The 



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