The Nitrogen Cycle in the Sea

Abstract

i and 2) Brandt (1899) first suggested that phytoplankton organisms must, by removing from the illuminated surface layers of the sea the nutrients required for their further growth, place a limit on their continued multiplication, and he and Raben for long worked on the problem (see Brandt, 1927, for review of earlier work). The thesis has been proved true beyond all doubt by work which has followed improvements in analytical technique by Atkins and Harvey. In many waters reserves of nitrate are formed during the winter months and are used up, often completely, with the coming of longer days. Interest is now centred on the mechanism by which the nitrate reserve is built up and depleted and on the role played by other compounds of nitrogen. The time has come to review the nitrogen problem as a whole and to assess the importance of many possible reactions in which nitrogen may be involved. The plan of this paper is based on Fig. 1, in which associated reactions are N204 -»-NMejO--NHMe, + CHjO Fig. 1. The numbers indicate the reaction group in which the reaction is considered in the text.

Photochemical Processes in the Inorganic Nitrogen Cycle of the Sea 1

“…Interestingly, this reaction was reported as occurring readily by Rakestraw and Hollaender (1936) but seems to have been ignored by later writers (Cooper 1937;Svcrdrup et al 1942;Spencer 1956;and Vaccaro 1962), although they mention the more difficult photooxidation process. The reduction reaction proceeds easily enough that it may act as an indicator of incident radiation in a closed system (see Figs.…”

“…It is known that a catalyst is needed for the process, and it has been suggested that in seawater colloidal silica may serve as such ( Cooper 1937). Tropical Atlantic waters are low in silica as compared with those of the North Atlantic and of the Pacific (Sverdrup, Johnson, and Fleming 1942, p. 245).…”

“…Papers dealing with aspects of the nitrogen cycle of the sea often mention the photooxidation of ammonia as a possible process ( Cooper 1937;Waksman, Madhuk, and Hollaender 1937;Rakestraw 1936;Spencer 1956;Vaccaro 1962). Such speculations are based upon the investigations of ZoBell ( 1933) and of Rakestraw and Hollaender (1936).…”

Ultraviolet COM.BUSTION of Dissolved Organic Nitrogen Compounds in Lake Waters1

“…7). It may bc the result of photosensitizing silica adsorbed as solid oxides on colloidal particles in seawater ,as suggested by Cooper (1937Cooper ( , 1948) although <dissolution of such oxides proceeds much faster in 0.9% saline solution than in pure water ( Stijber 1967). Similar catalytic action might be expcctcd in Lawrcncc and Wintergrccn Lakes which have SiOa-Si levels (Table 2) similar to those in the oceans (Sverdrup et al 1942).…”

“…7). It may bc the result of photosensitizing silica adsorbed as solid oxides on colloidal particles in seawater ,as suggested by Cooper (1937Cooper ( , 1948) although <dissolution of such oxides proceeds much faster in 0.9% saline solution than in pure water ( Stijber 1967 Decomposition is probably a function of two processes : absorption of UV light encrgy sufficient to cleave intramolecular bonds and reduction of the resultant fragments by reactive radicals to molecular CO2 and NH&N ( McLaren and Shugar 1964). The primary reactive species in acidic, ,oxygenated solutions is likely the hydrogen atom ( Ho) created by the reaction of II+ with the hydrated electron (c,,-), whereas in neutral or alkaline oxygenated solutions it is probably the hydroperoxy radical (Oz-) (Matheson and Dorfman 1969).…”