Filamentous, nitrogen-fixing cyanobacteria form extensive summer blooms in the Baltic Sea. Their ability to fix dissolved N2 allows cyanobacteria to circumvent the general summer nitrogen limitation, while also generating a supply of novel bioavailable nitrogen for the food web. However, the fate of the nitrogen fixed by cyanobacteria remains unresolved, as does its importance for secondary pro...

The expansion of aquaculture and the recent development of more intensive land-based marine farms require efficient and cost-effective systems for treatment of highly nutrient-rich saline wastewater. Constructed wetlands with halophytic plants offer the potential for waste-stream treatment combined with production of valuable secondary plant crops. Pilot wetland filter beds, constructed in trip...

Over half of the total nitrogen, phosphorus, silicate and dissolved organic carbon (DOC) loading was discharged from the Vène River into the Thau Lagoon waters within the first five days of what was considered to be the autumn flash flood period. Such loads represented about 8% and 3% of the yearly averaged total nitrogen and phosphorus load in Thau Lagoon, respectively. Although this event aff...

a r t i c l e i n f o Little is known about the distribution and dynamics of dissolved organic nitrogen (DON) within Arctic Ocean surface waters, though seasonal inputs from both rivers and marine phytoplankton production are likely important. Here we combine multiple datasets to provide the first quasi-synoptic view of DON concentrations in the summertime Arctic Ocean Polar Surface Layer (PSL)...

The filamentous non-heterocystous cyanobacterium Plectonema boryanum fixes dinitrogen at a high rate during microaerobic growth in continuous illumination by temporal separation of oxygen-evolving photosynthesis and oxygen-sensitive dinitrogen fixation. The onset of nitrogen fixation is preceded by a depression in photosynthesis that establishes a sufficiently low level of dissolved oxygen in t...

In the Baltic Sea, floating blooms of nitrogen-fixing cyanobacteria occur yearly during late summer. These blooms can sometimes be limited by iron. Due to extensive foresting around the Baltic Sea, iron is entering the Baltic Sea partly bound to dissolved organic material (DOM) via rivers. An experiment was performed in 300 l laboratory mesocosms to test the hypothesis that riverine highmolecul...

A combination of above-normal precipitation during the winter and spring of 2007-2008 and extensive rainfall during June 2008 led to severe flooding in many parts of the midwestern United States. This resulted in transport of substantial amounts of nutrients and sediment from Iowa basins into the Mississippi River. Water samples were collected from 31 sites on six large Iowa tributaries to the ...

Conventional wisdom postulates that leaching losses of N from agriculture systems are dominated by NO(3)(-). Although the export of dissolved organic nitrogen (DON) into the groundwater has been recognized for more than 100 yr, it is often ignored when total N budgets are constructed. Leaching of DON into stream and drinking water reservoirs leads to eutrophication and acidification, and can po...

RÉSUMÉ M. D. DOVAL *,Fernando FRAGA and Fiz F. PEREZ Instituto de Investigaciones Marinas de Vigo (CSIC), Eduardo Cabello, 6, E-36208 Vigo, Spain. * Corresponding author. E-mail:[email protected] Received 15/02/96, in revised form 04/12/96, accepted 16/01/97. An update of the Kjeldahl method is presented for the direct determination of dissolved organic nitrogen (DON) in seawater. Dissolved in...

Measurements of chlorophyll, oxygen, and particulate and dissolved forms of nitrogen and phosphorus made over a year were used in a one-dimensional diffusion model to calculate rates of generation or loss of these substances in the hypolimnion of Lake Rotoiti, New Zealand. During summer stratification the hypolimnion was always a sink for chlorophyll, particulate nitrogen (PN), particulate phos...