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Bacterial utilization of high-molecular-weight (HMW; > 1 kDa) and low-molecular-weight (LMW; < 1 kDa) dissolved organic C (DOC) was investigated in freshwater and marine systems by measuring dissolved oxygen consumption, bacterial abundance, and bacterial production in size-fractionated samples. Tangential-flow ultrafiltration was used to separate HMW and(More)
Although the principal source of marine organic matter is phytoplankton, experimental data on carbon and nitrogen mass balance during their growth cycle are lacking. Phytoplankton from diverse taxonomic groups (Synecho-coccus bacillaris, Phaeocystis sp., Emiliania huxleyi, Skeletonema costatum) were grown in synthetic seawater media, and changes in(More)
The biological pump is a process whereby CO(2) in the upper ocean is fixed by primary producers and transported to the deep ocean as sinking biogenic particles or as dissolved organic matter. The fate of most of this exported material is remineralization to CO(2), which accumulates in deep waters until it is eventually ventilated again at the sea surface.(More)
Arctic system is moving toward a new state that falls outside the envelope of glacial-interglacial fl uctuations that prevailed during recent Earth history. This future Arctic is likely to have dramatically less permanent ice than exists at present. At the present rate of change, a summer ice-free Arctic Ocean within a century is a real possibility, a state(More)
Carbohydrates are major components of marine organic matter, but few molecular-level carbohydrate analyses in seawater have been undertaken owing to the low concentrations of individual compounds. This paper presents novel data on aldose compositions and concentrations in various size fractions of particulate and dissolved organic matter from the equatorial(More)
A series of laboratory experiments was performed to measure dissolved organic carbon (DOC) production during herbivorous grazing by heterotrophic protists (ciliate Strombidinopsis acuminatum, dinoflagellate Oxyrrhis marina) and copepods (Calanus pacificus). DOC production by phytoplankton was 31~0 measured. Experiments were performed in artificial seawater(More)
The present study demonstrates that the spectral slope coefficient of chromophoric dissolved organic matter (CDOM) between 275 nm and 295 nm (S 275–295) can be used as a tracer of the percent terrigenous dissolved organic carbon (%tDOC) in river-influenced ocean margins, where rivers exert an important control on carbon dynamics and CO 2 fluxes. Absorption(More)
Heterotrophic bacterial growth and the chemical composition of dissolved organic matter (DOM) produced by bacteria from freshwater and marine environments were monitored during experiments with artificial media containing glucose as the sole carbon source. Glucose was quickly consumed, and DOM was released during bacterial growth. Percentages of(More)
Bacterial abundance and production (thymidine and leucine incorporation) were measured along a salinity gradient from the Mississippi Rlver (0 %o) to the open waters of the Gulf of Mexico (36 %a) during July-August 1990 and February 1991. Bactenal production in surface waters was maximal at intermediate salinities (15 to 30 %o). Nutrlent enrichment(More)
Bacterial biomarkers (D-amino acids and muramic acid) were measured in various organic matter size fractions collected in the North Pacific and North Atlantic, and they were used to quantitatively estimate bacterial contributions to particulate and dissolved organic carbon and nitrogen reservoirs. The origins and yields of biomarkers were determined in(More)