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Bacterial alkaline phosphatases (APases) are important enzymes in organophosphate utilization in the ocean. The subcellular localization of APases has significant ecological implications for marine biota but is largely unknown. The extensive metagenomic sequence databases from the Global Ocean Sampling Expedition provide an opportunity to address this(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)
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)
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)
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(More)
Most of the oceanic reservoir of dissolved organic matter (DOM) is of marine origin and is resistant to microbial oxidation, but little is known about the mechanisms of its formation. In a laboratory study, natural assemblages of marine bacteria rapidly (in <48 hours) utilized labile compounds (glucose, glutamate) and produced refractory DOM that persisted(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)
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)