Primary Production and Nitrogen Fixation

The simulated in situ method incubates samples taken from different water depths on deck of the ship in a temperature-controlled incubator. The samples were exposed to their original light intensity by coating them with gray screens of appropriate light transmission characteristics. 

Besides direct rate measurements, primary productivity can be calculated on the basis of nutrient consumption, increase in POC-H DOC, or decrease in total CO2 in the water (Wasmund et al., 2005a). These methods deliver integrated values and overcome the low representativeness of the pointwise rate measurements. For data of respiration and exudation, the literature should be consulted (Kuparinen, 1984 Witek et al., 1997 Olesen et al.. 

the problem of new and regenerated production is not dealt with (Sorensson and Sahlsten, 1987 Heiskanen, 1998 Wasmund et al., 2005a). 

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Moisander, P.H., and Paerl, H.W. (2000) growth, primary productivity, and nitrogen fixation potential of Nodularia spp. (Cyanophyceae) in water from a subtropical estuary in the United States. J. Phycol. 36, 645-658. 

Penhale, P. A., and Capone, D. G. (1981). Primary productivity and nitrogen fixation in two macro-algae-cyanobaceria associations. Bull. Mar. Sci. 31, 164—169. 

Ammonium, the primary product of nitrogen fixation, is transported to the host cell cytoplasm where it is assimilated into amides and, in some cases, further converted into ureides before being transported to the shoot. Since the physiological environment within the nodule is apparently different from the other parts of the plant, nodule-specific or nodule-abundant forms of several enzymes of the nitrogen and carbon assimilation pathways have evolved, and are induced to improve the efficiency of nitrogen and carbon metabolism in nodules. 

Fig. 10-13. The links between the cycling of C, N, and O2 are indicated. Total primary production is composed of two parts. The production driven by new nutrient input to the euphotic zone is called new production (Dugdale and Goering, 1967). New production is mainly in the form of the upward flux of nitrate from below but river and atmospheric input and nitrogen fixation (Karl et al, 1997) are other possible sources. Other forms of nitrogen such as nitrite, ammonia, and urea may also be important under certain situations. The "new" nitrate is used to produce plankton protoplasm and oxygen according to the RKR equation. Some of the plant material produced is respired in the euphotic zone due to the combined efforts...

Environmental quality parameters such as oxygen depletion, changes in primary productivity, and changes in the processing of nutrients such as mineralization of organic matter or fixation of atmospheric nitrogen... 

Welsh, D. T., Bartoh, M., Nizzoli, D., CastaldeUi, G., Riou, S. A., and Viaroli, P. (2000). Denitrification, nitrogen fixation, community primary productivity and inorganic N and oxygen fluxes in an intertidal Zostera noltii meadow. Mar. Ecol. Prog. Ser. 208, 65—77. 

Nitrogen is generally considered the most important limiting plant nutrient in the oceans. The processes that determine the total concentration of fixed nitrogen in surface seawater—particularly N2 fixation and denitrification—thus exert a fundamental control on marine primary production and on the resulting seques-... 

Nitrogen fixation counteracts denitrification losses of N from surface waters and is fundamental to replenishing fixed forms of N in all aquatic ecosystems. It is thought to be the main process responsible for maintaining surplus inorganic N in lakes and streams. It is therefore basic to the concept that primary production in most lakes and streams is limited by phosphorus (72). 

Bebout, B.M., Paerl, H.W., Bauer, J.E., Canfield, D.E., and Des Marais, DJ. (1994) Nitrogen cycling in microbial mat communities the quantitative importance of N-fixation and other sources of N for primary productivity. In Microbial Mats (Lucas, J., and Caumette, P., eds.), pp. 32-42, Springer-Verlag, Berlin. 

Garcia, N., Raimbault, P., and Sandroni, V. (2007). Seasonal nitrogen fixation and primary production in Southwest Pacific (New Caledonia) Some evidence for nanoplanktonic diazotrophy and rapid transfer of newly fixed nitrogen to picoplankton organisms. Mar. Ecol. Prog. Ser. 343, 25-33. 

Welsh, D. T. (2000). Nitrogen fixation in seagrass meadows Regulation, plant-bacteria interactions and significance to primary productivity. Ecol. Lett. 3(1), 58—71. 

Piehler, M. F., Thompson, S., Dyble, J., Moisander, P., Fear, J., and Paerl, H. W. (2002). Biologically mediated nitrogen dynamics in eutrophying estuaries. Assessing denitrification, nitrogen fixation and primary productivity responses to proposed N loading reductions in the Neuse River Estuary 339, Water Resources Research Institute of the University of North Carolina, Raliegh, NC. 

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