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Trichodesmium sp. is a filamentous, colonial cyanobacterium which contributes substantially to the input of nitrogen in tropical and subtropical oceanic waters through nitrogen fixation (N(2) fixation). We applied a N tracer technique to assess the rate of release of dissolved organic nitrogen (DON) from this cyanobacterium and compared those rates with(More)
Jellyfish blooms occur in many estuarine and coastal regions and may be increasing in their magnitude and extent worldwide. Voracious jellyfish predation impacts food webs by converting large quantities of carbon (C), fixed by primary producers and consumed by secondary producers, into gelatinous biomass, which restricts C transfer to higher trophic levels(More)
During a 3-yr study in the Gulf of Mexico, we measured dinitrogen (N 2) fixation and nitrogen (N) release by Trichodesmium and compared these rates with water column N demand and the estimated N necessary to support blooms of Karenia brevis, a toxic dinoflagellate that severely affects the West Florida shelf. Net and gross N 2 fixation rates were compared(More)
River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO(2) drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO(2) dynamics, we evaluated rbcL mRNA abundance using novel(More)
In oceanic, coastal, and estuarine environments, an average of 25 to 41 percent of the dissolved inorganic nitrogen (NH(4) (+) and NO(3) (-)) taken up by phytoplankton is released as dissolved organic nitrogen (DON). Release rates for DON in oceanic systems range from 4 to 26 nanogram-atoms of nitrogen per liter per hour. Failure to account for the(More)
Ž. Ž. Ž. We compared the persulfate PO , ultraviolet UV , and high temperature oxidation HTO methods used to analyze total Ž. dissolved nitrogen TDN concentrations in aquatic samples to determine whether the three methods differed in terms of Ž. standard parameters blanks, limits of detection and linearity, and precision or in oxidation efficiency of(More)
Humic substances are a collection of colored organic acids characterized by high molecular weight and low nitrogen (N) content that are thought to be biologically recalcitrant. We examined a suite of nonaxenic estuarine phytoplankton isolates to determine their ability to take up 15 N-labeled humic substances formed in the laboratory and supplied as the(More)
The marine nitrogen (N) cycle is a complex network of biological transformations in different N pools. The linkages among these different reservoirs are often poorly understood. Traditional methods for measuring N uptake rely on bulk community properties and cannot provide taxonomic information. (15)N-based stable isotope probing (SIP), however, is a(More)
Southern Ocean primary productivity plays a key role in global ocean biogeochemistry and climate. At the Southern Ocean sea ice edge in coastal McMurdo Sound, we observed simultaneous cobalamin and iron limitation of surface water phytoplankton communities in late Austral summer. Cobalamin is produced only by bacteria and archaea, suggesting(More)