Phosphate Utilization by Diatoms

Abstract

Routine measurements of inorganic phosphorus concentration are frequently made on standard oceanographic stations to ascertain the potential productivity of marine waters. In quantitative, ecological studies on diatom populations in the Atlantic Ocean, Riley, Stommel and Bumpus (1949) have utilized the phosphate concentration as a nutrient index. Their equation of productivity depends upon the experimental results of Ketchum (1939), who found that phosphate concentrations helow 0.55 microgram-atoms per liter limited the growth of Nitsschia clostcriitin.Riley, Stommel and Bumpus (1949) further checked the validity of this index in their photosynthetic rate equation by calculating the phosphate requirements of a growing plankton population, assuming that 100 carbon atoms to one atom of phosphorus are needed for normal metabolism. However, in studies on the fresh water diatom Astcrionella fonnosa, Lund (1950) found that the phosphate content of the plant varied by a factor of seventy in both natural and cultural populations. He stated that the cells are able to store phosphorus in excess of their immediate requirements even at very low levels of phosphate concentration.The data on the amount of phosphate contained in marine phytoplankton, as found by Ketchum and Redfield (1949), show considerable variation, making the determination of phosphate requirement difficult and uncertain. The use of phosphate as a parameter in the computation of productivity would appear to be premature therefore, until such time as definitive values of the phosphate requirement shall have been established. Even then the total mineral requirements relative to one another must be known and their seasonal and geographic abundances must be shown to vary with biological activity. The use of an arbitrary and easily measured nutrient index for correlation with diatom abundances seems to be unwarranted.The release of phosphate by marine plankton is an important factor in ecological investigations. Cooper (1935) found that one-fourth to one-half of the phosphate added as phytoplankton in sea water was set free to the environment as inorganic phosphate after one month. Seiwell and Seiwell (1938) reported similar results.

On the biology ofCalanus finmarchicusVIII. Food uptake, assimilation and excretion in adult and Stage VCalanus

“…It is present in all the major food constituents and should therefore give a good idea of the assimilationbut some caution is necessaryin interpreting the results. It has been shown by various workers (Kamen & Spiegelman, 1948;Gest & Kamen, 1948;Goldberg, Walker & Whisenand, 1951;Rice, 1953) that when algae are grown in phosphate-rich media, some of the phosphorus in the culture organisms maybe labile or verylooselybound. Rice has shownthat in cultures with low P concentrations, only about 2 % is exchangeableafter they are a week old.…”

Geochemistry of Organic Matter in the Ocean

“…Most of the phosphorus contained in the phytoplankton can be readily hydrolyzed, whereas in the calanuses it is tightly bound and requires more rigid hydrolysis for its release (Goldberg et al 1951, Conover 1961, Parsons et al 1977. The latter are most predominant in bones of animals, chitinous exoskeletons and scales.…”

The Absorption of Inorganic Ions by Chlorella pyrenoidosa.

“…Recently, Rediske and Selders (10) reported the uptake of strontium by plants to be proportional to the concentration of this element in the nutrient solution. Goldberg et al (5), working with diatoms, found the phosphate uptake to be proportional to the concentration in the medium over the range 0.5 to 3.5 ,ug/l. Similar findings were reported by Ketchum (7).…”