8. ORGANIC REGULATION OF PHYTOPLANKTON FERTILITY ' 



L. Provasoli 



1. Introduction 1 



A. The Problems of "Good" and "Bad'" Waters 



The search for biologically active substances in sea-water is a recent approach 

 to the age-long problem of '"bad" and "good" waters. There is no doubt that 

 water-masses differ in ability or inability to sustain growth of various organisms. 

 Most of the interest in the properties of waters has centered on the words 

 "good" and "bad" 2 for the organisms we harvest from the sea. In this respect, 

 the most fertile areas of the sea are near the coasts, above shallow bottoms 

 (banks), and in zones of water mixing (merging of different bodies of water, 

 up welling, etc.). Because all life in the sea depends on the primary producers 

 of organic matter, most of our knowledge centers on the algae and we will 

 restrict our presentation of data almost solely to them. 



The early work on the physical and chemical conditions governing growth of 

 phytoplankton in the sea was guided by the knowledge of the time that photo- 

 synthetic organisms require only mineral nutrients. Of these, nitrogen, and 

 especially phosphorus, assumed primary importance because they are essential 

 and are often present in waters in "limiting" quantities; hence the growth of 

 phytoplankton, it was thought, should correlate with the N and P content of 

 waters. This is often, but not always so : e.g. productivity along the coast of 

 California is far less than around the British Isles, yet the phosphate content 

 of California waters is many times higher. In the meantime, many nutritionists 

 found that algae need, besides N and P, some organic substances present in 

 several natural extracts (soil, peat, seaweeds, etc.) and also in sea- water (Allen. 

 1914). This led to the recognition that many algae need vitamins (reviewed by 

 Provasoli, 1956; Droop, 1957; Provasoli, 1958). 



The present interest in the organic components of waters, and particularly 

 in the biologically active substances, is, however, due to the powerful arguments 

 advanced by Lucas (1947, 1949, 1955, 1958) that some water organisms might 

 affect the growth of other organisms by producing necessary nutrients, by 

 removing inhibitory compounds, and by excreting inhibitory substances. The 

 vitamin requirements of algae, what we already know of the vitamin cycle in 

 sea-water and the production of antibiotics by marine organisms dramatically 



1 Aided in part by contract NK 104-202 with the U.S. Office of Naval Research and by 

 grant G-10783 from the National Science Foundation. 



2 The utilitarian meaning attached to the terms "fertility" and "good and bad waters'* 

 is far too general and often misleading. Waters favorable for spring diatoms are not 

 necessarily favorable for dinoflagellates, or tuna, and no water is bad enough not to 

 support some sort of community. While it is obvious that the plants and animals living in 

 the same biocoenosis share common requirements and resistance to a number of environ- 

 mental factors, we can expect that other factors are peculiarly important for each species 

 or taxonomic groups. Therefore, any discussion about the quality of waters should be in 

 reference to a specific organism or group. 



[MS received October, 1960] 16f> 



