Phytoplankton requirements

Central Pacific, Southern Ocean) can be Fe rather than N or P limited (Behrenfeld and Kolber, 1999 Martin et al, 1994). These regions have dissolved inorganic N and P concentrations in excess of phytoplankton requirements, indicating that N enrichment is not likely to impact eutrophication potentials of these waters and that any eutrophication effect of N enrichment is rehant on parallel new Fe inputs (Kolber et al., 2002). 

Pacific, and the North Pacific subarctic) are never completely consumed in support of primary production, because low levels of iron limit phytoplankton growth (Martin and Fitzwater, 1988 Martin et al, 1994 Coale et al, 1996 Boyd et al, 2000). Diatoms, which, unlike other dominant members of the phytoplankton, require silicon for growth, are often limited by low concentrations of silicic acid in surface waters (Brzezinski and Nelson, 1996 Nelson and Dortch, 1996). Growth of diazotrophic (N2 fixing) phytoplankton such as the cyanobacteria, Trichodes-mium, wiU be more susceptible to phosphorus and iron limitation, of course, than to nitrogen limitation. Even the concentration of dissolved CO2 in seawater (especially in the midst of a phytoplankton bloom) may limit instantaneous rates, although not ultimate levels, of primary production (RiebeseU et al, 1993 Wolf-Gladrow et al, 1999). 

Possible health benefits of consuming fish oils and omega-3 fatty acids have been reviewed by various authors (1-5). These oils can also be obtained from phytoplankton (6-8). Oils obtained from phytoplankton do not contain cholesterol. Phytoplankton require very simple nutrients in easy-to-maintain growth conditions. They can be harvested in short culture cycles. They can be manipulated by genetic engineering to increase their yield and their resistance to environmental stresses. 

In this way, the near-linear chlorophyll-phosphorus relationship in lakes depends upon the outcome of a large number of interactive processes occurring in each one of the component systems in the model. One of the most intriguing aspects of those components is that the chlorophyll models do not need to take account of the species composition of the phytoplankton in which chlorophyll is a constituent. The development of blooms of potentially toxic cyanobacteria is associated with eutrophication and phosphorus concentration, yet it is not apparent that the yield of cyanobacterial biomass requires any more mass-specific contribution from phosphorus. The explanation for this paradox is not well understood, but it is extremely important to understand that it is a matter of dynamics. The bloom-forming cyanobacteria are among the slowest-growing and most light-sensitive members of the phytoplankton. ... 

Nickel is required by plants when urea is the source of nitrogen (Price and Morel, 1991). Bicarbonate uptake by cells may be limited by Zn as HCOT transport involves the zinc metal-loenzyme carbonic anhydrase (Morel et al., 1994). Cadmium is not known to be required by organisms but because it can substitute for Zn in some metalloenzymes it can promote the growth of Zn-limited phytoplankton (Price and Morel, 1990). Cobalt can also substitute for Zn but less efficiently than Cd. 

Ocean prevents eutrophication. Much more water flows into the Mediterranean Sea than is required to replace evaporation from it. The excess, high salinity water exits Gibraltar below the water flowing in af fhe surface. Nufrients that enter the Mediterranean Sea from pollution sources are utilized by marine phytoplankton that sinks and exits with the outflow. Another example is that estuaries often have lower salinity or even freshwater at the surface with a denser saline layer at the bottom. An estuarine circulation occurs with nutrients being trapped in the saline bottom water. 

Phytoplankton are easily sampled with fine-mesh nets. However, samples require considerable processing before analysis to remove zooplankton, detritus, or other particulates. Sampling would not measnrably affect target popnlations, even in the smallest lakes. 

Phytoplankton DMS producers <20 Phaeocystis and small autotrophic flagellates Produce dimethylsulfoniopro-pionate (DMSP) and convert it into DMS using an extracellular enzyme (DMSPIyase). Thus, they affect the atmospheric sulfur cycle. Have high P requirement Particularly abundant in coastal areas, where they are often observed in colonies. Calcifiers are also important for the DMS cycle... 

Dominant microphytoplankton. Comprises most of the primary production and biomass in spring blooms at temperate and polar regions. They require more Fe and P than most of the smaller nano-and pico-phytoplankton... 

Nitrogen fixation The process by which some bacteria and phytoplankton are able to convert Nj into organic nitrogen. The energy required is large because a triple bond must be broken. 

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