Algal nutrients

Sterner, R. W., and Hessen, D. O. (1994). Algal nutrient limitation and the nutrition of aquatic herbivores. Annu. Rev. Ecol. Systemat. 25, 1—29. 

Because of the importance of diatoms in oceanic productivity, silicon is an important algal nutrient in seawater. A transporter of Si(OH)4 has been isolated and sequenced (Hildebrand et al, 1998 Hildebrand et al, 1997) and the physiology of silicon uptake has been well studied (Martin-Jezequel et al, 2000). Nonetheless, the molecular mechanism of Si(OH)4 transport and silica fmstule formation in diatoms are still largely mysterious. From indirect evidence, it appears possible that the Si(OH)4 transporter may contain zinc, coordinated to cysteines, as a metal center in the portion of the protein exposed to the outside of the cell (Hildebrand, 2000 Rueter and Morel, 1981). If true, this would be an unusual example of a transport protein functioning with a metal center. 

Jassby A. D., Goldman C. R., and Reuter J. E. (1995) Longterm change in Lake Tahoe (Cahfornia-Nevada, USA) and its relation to atmospheric deposition of algal nutrients. Arch. Hydrobiol. 135, 1—21. 

For many years, however, oceanographers have had a different interest in Cd. They have discovered that the distribution of Cd in the oceans is similar to that of the major algal nutrients nitrogen and phosphorus. In view of the remarkable correlation between Cd and P concentrations observed throughout the oceans (Fig. 1), the concentration of Cd—as recorded, for example, in the CaC03 tests of fossil foraminifera—can be used as a proxy for that of P. Recently, it has become apparent that the nutrient-like behavior of Cd in the... 

Two major patterns of horizontal distribution can be discerned for Cd in the oceans (i) a much smaller concentration in the deep Atlantic compared to the deep Pacific and Indian Oceans, as is characteristic of all algal nutrients (ii) a decrease in surface concentrations from the coasts of continents to the open oceans, which is observed for many elements. Cadmium concentrations in the deep Atlantic 0.3 nM) are roughly three times lower than in the deep Pacific or Indian Oceans (0.9 nM Fig. 4) about the same factor as observed for phosphate [20-22]. This higher accumulation in the deep waters of the Pacific than in those of the Atlantic results from the simultaneous downward transport of the elements that are incorporated in settling biomass and the horizontal transport by major oceanic currents, which run toward the Atlantic at the surface and toward the Pacific in deep waters [23]. 

Table IV Activities against Enteromorpha compounds tested against Enteromorpha in sea water modified with algal nutrients.

Some important inorganic water pollutants are mentioned earlier as part of the discussion of pollutant trace elements. Inorganic pollutants that contribute acidity, alkalinity, or salinity to water are considered separately in this chapter. Still another class is that of algal nutrients. This leaves unclassified, however, some important inorganic pollutant species, of which cyanide ion, CN , is probably the most important Others include ammonia, carbon dioxide, hydrogen sulfide, nitrite, and sulfite. 

Phosphate in the form of H2P04 and HPO/ ions is the substance usually removed from secondary sewage effluent to prevent excessive algal growth and eutrophication in receiving waters. Of several possible algal nutrients, why is phosphate chosen Show with a chemical reaction the most common means of removal. 

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