Production/productivity phytoplanktonic

Probyn, T. A. (1992). The inorganic nitrogen nutrition ofphytoplankton in the southern Benguela New production, phytoplankton size and implications for pelagic foodwebs. S. Afr.J. Mar. Sd. 12, 411—420. 

Chavez, F. P., Barber, R. T., Kosro, M., Huyer, A., Ramp, S., Stanton, T. P., and Rojas de Mendiola, B. (1991). Horizontal transport and the distribution of nutrients in the Coastal Transition Zone off Northern Cahfomia— Effects on primary production, phytoplankton biomass and species composition. J. Geophys. Res. Oceans 96, 14833—14848. 

The estimated primary production (in terms of C content) for various aquatic ecosystems is shown in Table 3.3. Freshwater primary production, in lakes and streams, amounts to a little over 1% of total aquatic primary production. Phytoplankton account for c.95% of marine primary production, which totals c.40GtCyr-1, whereas coastal ecosystems make relatively minor contributions. Important macrophytes in intertidal zones include Rhizophora in mangrove swamps, turtle grass... 

Another important greenhouse gas is a product of phytoplankton oxidation of ammonium. This reaction can follow two pathways ... 

Changes in surface temperature elsewhere in the globe are likely to have a lesser impact on carbon or DMS production. For example, the warming that a doubling of atmospheric COj could produce in the Southern Ocean has been modelled to lead to decreased carbon uptake, but enhanced biological productivity, due to the temperature effect on phytoplankton growth." This would lead to an approximately 5% increase in DMS production and a lesser increase in CCN. There is thus a negative feedback here, but only of minor impact. 

Temperature also affects production rates but, through its influence on the thermal expansion of water, it also induces changes in the depth of vertical mixing and resistance to wind-stirring processes. Reactions to temperature of other components of the food chain are also important in the regulation of phytoplankton biomass by consumers. Different phytoplankton species, with important morphological differences, are differentiated selectively by the interplay of these factors. " ... 

A month-long study of the effects of ultraviolet radiation (UV) on phytoplankton and ice-algae collected from Arthur Harbor, Anvers Island, Antarctica, was carried out during November-December 1987. The parameters studied included primary production rates, photosynthetic... 

The average photosynthetic rates for each of the three experiments performed, increased with UV exclusion and decreased with increased UV exposure (Table I). However, primary production rates of phytoplankton (collected on 17 November and 3 December 1987) measured under near-ambient light conditions were low, but not statistically different from those measured under either UV-reduced or UV-enhanced conditions. Small but statistically significant increases in... 

Comparison with other Studies. How do the results of our investigation compare with similar studies Our results corroborate the data provided in a similar study of the effect of UV-B on primary productivity in the southeastern Pacific Ocean (35). In the latter study, it was noted that enhanced UV-B radiation caused significant decreases in the productivity of surface and deep samples. Compared to ambient, primary productivity decreased with increasing doses of UV-B. In another study in which in situ experiments using natural Antarctic phytoplankton populations, it was noted that incident solar radiation significantly depressed photosynthetic rates in the upper 10-15 meters of the water column (36). It was also found that the spectral region between 305 and 350 nm was responsible for approximately 75 percent of the overall inhibitory effect. 

Increases in nitrate + nitrite have been well documented in the Great Lakes (19). Relative increases over the past twenty years have been between 30 and 200% with the highest increases in the most populated and agriculturally productive basins of Lakes Ontario and Erie (29). Currently no adverse impacts due to this increase have been observed and concentrations are well below the 10 mg.L maximum acceptable drinking water concentration for the protection of human health. Changing N P ratios, however, can impact phytoplankton community structure (30). 

This equation was originally proposed for "average" plankton, a category that included both zooplankton and phytoplankton. This mean elemental ratio of C/N/P = 106/16/1 by atoms is highly conserved (Falkowski et al., 1998) and reflects the average biochemical composition of marine phytoplankton and their early degradation products. 

This is not a reversible reaction in the strict sense and does not spontaneously seek equilibrium between products and reactants. The exothermic reverse reaction, respiration, occurs in a different part of phytoplankton cells or is mediated by heterotrophic organisms. 

The released ammonia is preferentially taken up by phytoplankton relative to nitrate (Dortch, 1990) to drive regenerated production. The/-ratio is used to describe the relative amounts of new and regenerated production (Dugdale and Goering, 1967) where... 

Recently, the ocean-basin distribution of marine biomass and productivity has been estimated by satellite remote sensing. Ocean color at different wavelengths is determined and used to estimate near-surface phytoplankton chlorophyll concentration. Production is then estimated from chlorophyll using either in situ calibration relationships or from empirical functional algorithms (e.g., Platt and Sathyendranth, 1988 Field et al., 1998). Such studies reveal a tremendous amount of temporal and spatial variability in ocean biological production. 

Oceanic surface waters are efficiently stripped of nutrients by phytoplankton. If phytoplankton biomass was not reconverted into simple dissolved nutrients, the entire marine water column would be depleted in nutrients and growth would stop. But as we saw from the carbon balance presented earlier, more than 90% of the primary productivity is released back to the water column as a reverse RKR equation. This reverse reaction is called remineralization and is due to respiration. An important point is that while production via photosynthesis can only occur in surface waters, the remineralization by heterotrophic organisms can occur over the entire water column and in the underlying sediments. 

Chisholm S. W. and Morel, F. M. M. (eds) (1991). What controls phytoplankton production in nutrient-rich areas of the open sea Limnol. Oceanogr. 36, 1507-1965. 

Falkowski, P. G., Greene, R. and Geider, R. (1992). Physiological limitations on phytoplankton productivity in the ocean. Oceanography 5, 84-91. 

A more complex feedback has been proposed that involves the production of dimethylsulfide by certain classes of marine phytoplankton. Four observations in the remote marine atmosphere formed the basis of this idea ... 

Wilkerson EP, Dugdale RC, Hogue VE, Marchi A (2006) Phytoplankton blooms and nitrogen productivity in San Erancisco Bay. Estuaries Coasts 29(3) 401-416... 

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