SCIENCE 255, 1561-1564

Bulk Chemical Characteristics of Dissolved Organic Matter in the Ocean

Ronald Benner¹, J. Dean Pakulski¹, Matthew McCarthy², John I. Hedges², Patrick G. Hatcher³

¹Marine Science Institute, University of Texas at Austin, Port Aransas, TX 78373

²School of Oceanography, University of Washington, Seattle, WA 98195

³Fuel Science Program, The Pennsylvania State University, University Park, PA 16802

Dissolved organic matter (DOM) is the largest reservoir of reduced carbon in the oceans. The nature of DOM is poorly understood, in part, because it has been difficult to isolate sufficient amounts of representative material for analysis. Tangential-flow ultrafiltration was shown to recover milligram amounts of > 1000 daltons of DOM from seawater collected at three depths in the North Pacific Ocean. These isolates represented 22 to 33 percent of the total DOM and included essentially all colloidal material. The elemental, carbohydrate, and carbon-type (by ¹³C nuclear magnetic resonance) compositions of the isolates indicated that the relative abundance of polysaccharides was high (~50 percent) in surface water and decreased to ~25 percent in deeper samples. Polysaccharides thus appear to be more abundant and reactive components of seawater DOM than has been recognized.