Phytoplankton growth

Other limitations on phytoplankton growth are chemical in nature. Nitrogen, in the form of nitrate, nitrite and ammonium ions, forms a basic building material of a plankton s cells. In some species silicon, as silicate, takes on this role. Phosphorus, in the form of phosphate, is in both cell walls and DNA. Iron, in the form of Fe(III) hydroxyl species, is an important trace element. Extensive areas of the mixed layer of the upper ocean have low nitrate and phosphate levels during... 

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. 

The results of two successful iron-fertilization experiments in the eastern equatorial Pacific have clearly shown that phytoplankton growth rate is limited by iron at that location (Martin et al., 1994 Coale et al., 1996). The species composition and size distributions of the ecosystem are influenced by iron availability (Landry et al., 1997). In particular, large diatoms do not grow at optimum rates in the absence of sufficient iron. Loukos et al. (1997) used a simple... 

Martin, J. H. and Fitzwater, S. E. (1988). Iron deficiency limits phytoplankton growth in the northeast Pacific subarctic. Nature 331,341-343. 

Urea has been of interest to the biological oceanographer because of its role as an excretion product of protein metabolism, its function in osmoregulation, and its reported use as a nitrogen source for phytoplankton growth. 

Howarth, R.W. and J.J. Cole. 1985. Molybdenum availability, nitrogen limitation, and phytoplankton growth in natural waters. Science 229 653-655. 

Jackson, G. A. and Morgan, J. J. (1978). Trace metal-chelator interactions and phytoplankton growth in seawater media theoretical analysis and comparison with reported observations, Limnol. Oceanogr., 23, 268-282. 

Sunda, W. G. and Huntsman, S. A. (1997). Interrelated influence of iron, light and cell size on marine phytoplankton growth, Nature, 390, 389-392. 

Gavis, J. (1976). Munk and Riley revisited nutrient diffusion transport and rates of phytoplankton growth, J. Mar. Res., 34, 161-179. 

Riebesell, U., Wolf-Gladrow, D. A. and Smetacek, V. (1993). Carbon dioxide limitation of marine phytoplankton growth rates, Nature, 361, 249-251. 

Pigment distribution is useful for quantitative assessment of phytoplankton community composition, phytoplankton growth rate and... 

Some of the NPP models are based on the color imagery and some are not. In the latter, phytoplankton growth is estimated from coupled global circulation and biogeo-chemical models in which water motion controls nutrient availability. The water motion is controlled by climatic factors, such as temperature gradients and wind stress. The latest effort to compare model outputs was conducted with 31 different models and foimd that global estimates for a test year (1998) differed by as much as a factor of 2 The mean results from this model intercalibration experiment are shown in Table 23.7. 

At mid-latitudes (Westerlies domain), seasonal changes in light availability, mixed layer depth, and temperature support two plankton blooms, one in the spring and a lesser one in the fall (Figure 24.10). In the winter, phytoplankton growth is light limited. (The carbon fixation reaction is also slower at lower temperatures.) Thus as heterotrophic microbes remineralize detrital POM, DIN concentrations rise. 

The interplay of physical controls is less complicated in the Polar and Trade (tropical) domains. As shown in Figure 24.11a, only one phytoplankton bloom occurs in the Polar domain, but is larger in amplitude than at mid-latitudes (Westerlies). Phytoplankton growth in the subpolar region is prolific because uniformly cold atmospheric temperatures suppress density stratification of the water column. Abundant winds ensure that... 

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