210 PROVASOLI [CHAP. 8 



Mn, Zn and Co ; (c) the same mixture but 1 : 1 chelated with EDTA. It is possible 

 that a differential assay of this type may distinguish between the gradations 

 of the four possible combinations, i.e. waters (1) rich both in chelators and 

 trace metals ; (2) rich in trace metals and deficient in chelators ; (3) deficient in 

 trace metals but rich in chelators ; (4) deficient in both trace metals and che- 

 lators. If these different combinations exist in sea-water then it is conceivable 

 that the favorable effect of mixing may depend on mutual compensation of 

 multiple deficiencies as well as a straight enrichment in nutrients by deeper 

 waters. 



Johnston was encouraged by his results with the addition of chelating agents 

 to sea-water to reopen the question of artificial fertilization of sea-water, 

 proposing to lower the cost of the operation by employing a chelator and 

 minimal doses of N and P to be determined experimentally. Promising, in- 

 expensive results were obtained by Buljan (1957): to 70-801. of sea-water 

 were added 5 1. of commercial concentrated H2SO4, 100 kg of superphosphate, 

 and two spades-full of garden or forest soil. The phosphates were dissolved with 

 stirring and sea-water added up to 2001., the whole being allowed to drain 

 slowly into the water of the bay from a moving boat. Use of sulphuric acid 

 permitted the solution of such cheap sources of phosphorus, as finely crushed 

 phosphate, degreased bone meal, guano, etc. ; the soil added vitamins, chelators 

 and trace metals. A total of 37 mg of P-PO4 was added in one year per ton of 

 bay water. Blooms of surface algae and a conspicuous increase of phytobenthos 

 resulted from the fertilization of the sheltered, shallow inlet of Valiko Jezero 

 in the Adriatic Sea. The area became an excellent feeding ground for oysters 

 (0. edulis). Growth of oysters was four times larger than it was for individuals 

 of the same age during the two years preceding fertilization ; the weight of 

 oysters showed an average growth of 26 g per individual per year, and the rate 

 of weight increase was five times larger than in the unfertilized part of the bay. 



One of the most attractive features of fertilization experiments is that they 

 provide a means of judging whether in laboratory experiments, or in analysis 

 of sea-water for a limited number of constituents, the really important factors 

 may have been missed. Perhaps experimental ecology will gradually reduce the 

 "trial-and-error" procedures that have characterized fertilization experiments 

 in the past. 



Addendum 



Since the preparation of the MS a few publications worth mentioning have 

 appeared. 



Vishniac (1961) perfected a fungus bioassay for thiamine in sea-water 

 (sensitive to 25 mfxg/1.). 



The occurrence of vitamin B12 in the Sargasso Sea (Menzel and Spaeth, 

 1962) has been measured for one year using the diatom Cyclotella nana (for 

 the bioassay method see Ryther and Guillard, 1962). The quantity of B12 

 in waters above 50 m fluctuates from undetectable to 0.03 mfxg/1. from May to 

 October and this paucity of B12 seems to control the species composition of 



