The capacity of bacteria for degrading dissolved organic nitrogen (DON) and remineralising ammonium is of importance for marine ecosystems, as nitrogen availability frequently limits productivity. Here, we assess the capacity of a widely distributed and metabolically versatile marine bacterium to degrade phytoplankton-derived dissolved organic carbon (DOC) and nitrogen. To achieve this, we lyse...

In the past decade a series of studies have shown that the active transport of inorganic carbon and nutrients by diel vertical migration of zooplankton is an important component of the biological pump. Less well known is how excretion of dissolved organic material (DOM) by migrating zooplankton enhances this export by creating a migratory DOM pump. We measured ammonia (NH4 ) and dissolved organ...

Organic nitrogen (N) uptake by plants has been recognized as a significant component of terrestrial N cycle. Several studies indicated that plants have the ability to switch their preference between inorganic and organic forms of N in diverse environments; however, research on plant community response in organic nitrogen uptake to warming and grazing is scarce. Here, we demonstrated that organi...

The biological variables consist of a single population each of phytoplankton and grazers, which are denominated in phosphorus units (mmol m23) in the constant (Redfield) ratio model (CRM) and are given the symbols Pp and Pz. In the variable ratio model (VRM), there are separate state variables for phytoplankton carbon (Cp), nitrogen (Np), phosphorus (Pp), and chlorophyll (M). Grazer biomass is...

Hansell, D.A., 1993. Results and observations from the measurement of DOC and DON in seawater using a high-temperature catalytic oxidation technique. Mar. Chem., 41: 195-202. Operating temperatures for the high-temperature catalytic oxidation of dissolved organic matter (DOM) in seawater were evaluated for optimization of total dissolved nitrogen analysis. In addition, the possibility of NO2 be...

The marine macrophyte Ulva prolifera is the dominant green-tide-forming seaweed in the southern Yellow Sea, China. Here we assessed, in the laboratory, the growth rate and nutrient uptake responses of U. prolifera to different nutrient treatments. The growth rates were enhanced in incubations with added organic and inorganic nitrogen [i.e. nitrate (NO3(-)), ammonium (NH4(+)), urea and glycine] ...

Photochemical and microbial degradation of external inputs of dissolved organic matter (DOM) from both natural (forests) and anthropogenic (swine and equine pastures) non-point sources to rivers were examined through field and laboratory microcosm experiments. Little or no photochemical degradation of DOM to inorganic N or P occurred in either the agricultural or forest runoff. The dissolved or...

Rivers are critical links in the carbon and nitrogen cycle in aquatic, terrestrial, and atmospheric environments. Here riverine carbon and nitrogen exports in nine large rivers on the Tibetan Plateau - the "Water Tower of Asia" - were investigated in the monsoon season from 2013 to 2015. Compared with the world average, concentrations of dissolved inorganic carbon (DIC, 30.7mg/L) were high in r...