Marine phytoplankton eukaryotic

Trick, C. G., R. J. Andersen, N. M. Price, A. Gillam, and P. J. Harrison (1983b), Examination of Hydroxamate Siderophore Production by Neritic Eukaryotic Marine Phytoplankton, Mar. Biol. 75, 9-17. 

Phosphate transporters have been characterized in many model organisms, though relatively little mechanistic work has been done in marine phytoplankton. Phosphate transport is elfected by high and low affinity transporters and dependent on ATP, Na, and Mg " " in several diatoms (Cembella et al., 1984). These observations are found to be consistent with the well known active transport system of yeast (Raghothama, 1999). The dependence of phosphate transport on Mg " " in diatoms and yeast suggests that eukaryotes may transport an uncharged cation phosphate complex (MeHP04, where Me may be Ca +, Mg +, Co +, Mn ) as has been observed in heterotrophic bacteria (van Veen, 1997). 

Whether marine plankton could have contributed is a moot question. Modern marine phytoplankton in the Gulf of Mexico have an isotopic signature of around 5 C —21%o (Jasper Gagosian 1993). Modern phytoplankton are of course very dilferent from Archaean, although there are reasonable grounds to infer that cyanobacteria, and in addition, eukaryotes were probably present even 2.7 Ga ago (Brocks et al. 1999). Just possibly, phytoplankton debris may account for some of the carbon isotope values. 

In the earlier taxonomic studies of marine phytoplankton, only eukaryotes were determined, as the prokaryotes were too small to be measured using the available methodologies. Kimor etal. (1987) reported that the most common eukaryotes were coccolithophores, followed (numerically) by diatoms and dinoflagellates. On some occasions silicoflagellates were reported but they were rare. Large species >65 pm in diameter occasionally occurred at low concentrations. An example was the prasinophyte Halosphaera virtidis that was found at the DCM but not in the surface water. 

Figure 10 The <5 0 vs. <5 N in nitrate as it is progressively assimilated by four eukaryotic species of marine phytoplankton. Both (5 N and <5 0 in nitrate increase as nitrate is consumed, and they do so with an 0 N ratio for isotopic discrimination ( ) of 1. Dashed lines show slopes of 1.1 and 0.9 for comparison. Modified from Granger J, Sigman DM, Needoba JA, and Harrison PJ (2004) Coupled nitrogen and oxygen isotope fractionation of nitrate during assimilation by cultures of marine phytoplankton. Limnology and Oceanography 49 1763-1773.

The first evidence that cadmium had a beneficial biological function came from growth data in laboratory cultures of the diatom Thalassiosira weissflogii [43,45]. As shown in Fig. 10, cultures of this coastal diatom grow slowly when the unchelated Zn concentration in the medium is reduced to about Zn = 3 pM. pM. These same cultures grow much faster when Cd is added to the medium at unchelated concentrations >5 pM [46]. This effect, which is particularly obvious at low Co concentrations, has now been observed in other families of marine phytoplankton. For example, Cd enhances the growth rate of the cosmopolitan coccolithophore Emiliana huxleyi when the unchelated Zn and Co concentrations in the medium are below 1 pM (Fig. 10) [42]. From similar laboratory studies, it appears that Zn, Cd, and Co can substitute for each other in many marine eukaryotic phytoplankton [47-51]. 

Falkowski PG, Katz ME, Knoll AH, Quigg A, Raven JA, Schofield O, Taylor FJR (2004) The evolution of modem eukaryotic phytoplankton. Science 305 354-360 Flynn KJ (2005) Castles built on sand dysfunctionality in plankton models and the inadequacy of dialogue between biologists and modellers. J Plankton Res 27 205-210 Fontana A (2007) Chemistry of oxylipin pathways in marine diatoms. Pure Appl Chem 79 481 490... 

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