Biogeochemical controls

Biogeochemical explanations of variations in phytoplankton floristic composition work at two levels. The first level is qualitative, and concerns the crude distinctions between algae that require silicon (diatoms and some others) and those that don t, or between cynaobacteria able to assimilate N2 and all other pelagic photoautotrophs. The second level is quantitative, and concerns the idea that optimum ratios of the nutrient elements required for growth may 

the decrease in the dissolved Si N ratio of river water might explain an alleged increase in the frequency of non-diatom blooms in coastal waters. 

The argument goes back to Officer and Ryther (1980), who point out that it is also necessary to take account of recyling rates, which are faster for P than N and for N than Si. Silicate depleted by uptake during the spring bloom, for example, is often replaced more slowly than DAIN and phosphate, and this may force seasonal succession from diatoms to dinoflagellates or small phytoflagel-lates. 

Ammonium is held to be preferred by most algae as a source of nitrogen the uptake of nitrate must be followed by its reduction to ammonium and requires both supply of protons (from photosynthesis or stored energy) and additional iron (Flynn Hipkin, 1999). In some algae, nitrate uptake is completely 

44 phototrophs (of which 8 were myxotrophic or possibly so), 35 heterotrophs, and five flagellates whose mode of nutrition is unknown. 

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Falkowski, P. G., Barber, R. T. and Smetacek, V. (1998). Biogeochemical controls and feedbacks on ocean primary production. Science 281, 200-206. 

Feijtel T.C., Delaune R.D., Patrick Jr. W.H. Biogeochemical control on metal distribution and accumulation in Louisiana sediments. J Environ Qual 1988 17 88-94. 

Marine chemists have taken increasingly more sophisticated approaches towards modeling seawater composition. The goal of these models is to understand the biogeochemical controls on seawater composition well enough that the effects of future perturbations can be predicted. As described next, the first modeling efforts were based on a series of reactions that were assumed to reach equilibrium the next efforts took a steady-state approach as the composition of seawater was thought to have been relatively constant over time. 

Hering, J.G. and Kneebone, P.E. (2002) Biogeochemical controls on arsenic occurrence and mobility in water supplies, in Environmental Chemistry of Arsenic (ed. W.T. Frankenberger Jr.), Marcel Dekker), New York, pp. 155-81. 

Howard, A.G., Apte, S.C., Comber, S.D.W. and Morris, RJ. (1988) Biogeochemical control of the summer distribution and speciation of arsenic in the Tamar estuary. Estuarine Coastal and Shelf Science, 27(4), 427-43. 

Carrasco, J. J., Neff, J. C., and Harden, J. W. (2006). Modeling physical and biogeochemical controls over carbon accumulation in a boreal forest soil. J. Geophys. Res. Biogeosci. 111(G2). 

Dale, A.W., and Prego, R. (2002) Physico-biogeochemical controls on benthic-pelagic coupling of nutrient fluxes and recycling in a coastal inlet affected by upwelling. Mar. Ecol. Prog. Ser. 235, 15-28. 

Howarth, R.W., Marino, R., and Cole, JJ. (1988b) Nitrogen fixation in freshwater, estuarine, and marine ecosystems. 2. Biogeochemical controls. Limnol. Oceanogr. 33, 688-701. 

Voice, T. C., Rice, C. P., and Weber, J. W. J. (1983). Effects of solids concentration on the sorptive partitioning of hydrophobic pollutants in aquatic systems. Environ. Sci. Technol. 17, 513—518. Warren, L. A., and Haack, E. A. (2001). Biogeochemical controls on metal behaviour in freshwater... 

Rustad, L. E. Cronan, C. S. (1995). Biogeochemical controls on aluminum chemistry in the O horizon of a red spruce Picea rubens Sarg.) stand in central Maine, USA. 

Seyler, P., and F. Elbaz-Poulichet. 1996. "Biogeochemical control on the temporal variablity of the trace element concentrations in the Oubangui River (Centrai African Republic)." Journal of Hydrology 180 319-332. 

Warren L. A. and Haake E. A. (2001) Biogeochemical controls on metal behaviour in freshwater environments. Earth. Sci. Rev. 54, 261-320. 

Brand L. E. (1991) Minimum iron requirements of marine phytoplankton and the implications for biogeochemical control of new production. Limnol. Oceanogr. 36, 1756-1772. 

Von Damm K. L. and Lilley M. D. (2003) Diffuse flow hydrothermal fluids from 9°50 N East Pacific Rise origin, evolution and biogeochemical controls. Geophys. Monogr. (AGU) (in press). 

Overall, a meaningful synthesis of the processes influencing the distribution and cycling of aliphatic and aryl halides (Figure 11) within the context of biogeochemical controls requires a thorough... 

Biogeochemical Controls on the Occurrence and Mobility of Trace Metals in Groundwater 11 25 DISCUSSION... 

BIOGEOCHEMICAL CONTROLS ON Till OCCURRENCE AND MOBILITY OF TRACE METALS IN GROUNDWATER... 

From. Austin, W. E. N. James, R. H. (eds) Biogeochemical Controls on Palaeoceanographic Environmental Proxies. Geological Society, London, Special Publications, 303, 1-2. 

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