9417214 Zafiriou To better understand the mineralization of dissolved organic matter (DOM) this study will assess the CO cycle, a key species in the marine organic carbon, by evaluating independently its sources and sinks. CO serves as a tracer for budgeting other substances in the equation: 1O2+aDOM+xhv--->dHOOH+eCO+fCO2+chv-DOM (hv=photons, hv-DOM=light altered dissolved organic matter). CO production and CO losses by microbial oxidation and gas exchange in the mixed layer can be equated. Thus mixed- layer CO can be calibrated as a tracer in marine geochemical units via its sinks, and in photochemical units via its source. Then determining the terms a-f in the equation permits using their ratios to budget other photo-reactant and photo-product terms. Cruises constraining CO microbial oxidation, and sampling for laboratory studies of a-f will cover varied sites to allow generalizing globally. Time-series studies will be done in local coastal waters influenced by high- latitude rivers, the N.Atlantic gyre where optical properties driving photoprocesses vary seasonally (Bermuda) and on CALCOFI transects in productive coastal (California) waters. A Seattle-Hobart cruise will add a large-scale Pacific data set (NOAA/RITS). CO gas exchange will be estimated by traditional methods; CO microbial oxidation will be measured in incubations as CO loss or conversion of 14CO2.
