rials and organisms through careless land man- 

 agement and by allowing the introduction of 

 nutrients from sewers, food processing industries, 

 fertilizer plants, feed lots, and farms. As a result, 

 natural communities of aquatic life are altered 

 and the functioning of these ecosystems often 

 is changed severely or destroyed. 



To maintain natural distribution, abundance, 

 and interrelations of the aquatic biota, and to 

 control unwanted growths, it is necessary to de- 

 termine and maintain levels of dissolved materi- 

 als required for this balance. This is an extremely 

 difficult task, however, because there are a great 

 many interrelated factors that contribute to the 

 development of excessive populations of a species. 

 Although a considerable amount of work has been 

 done on the nutrition of aquatic organisms, most 

 of this work has been done on a very few different 

 species. Very little research has been done to deter- 

 mine what interaction of factors causes a shift in 

 diversity or in the kinds of species that compose a 

 community. For these reasons it is impossible to 

 set any definite requirements. At this time the only 

 meaningful thing that can be done is to develop 

 guidelines. 



Plant Nutrients: The increase of nutrients in the 

 sea is accelerated by deposition of material derived 

 from the land as sediments from the rivers, by 

 settling and filling caused by water movements 

 produced by tide or wind, and by biological activ- 

 ity. To date, no serious problems resulting from 

 abnormal enrichment of nutrients have been iden- 

 tified in the open sea except perhaps locally around 

 outfalls that extend several mUes out to sea. With 

 the increased disposal of wastes in the sea, this 

 potential problem should be carefully watched. 



Estuaries and tidal embayments have long been 

 recognized as some of our most valuable and pro- 

 ductive resources. They are the most ephemeral of 

 the natural marine habitats and consequently most 

 easily affected by man's activities. They serve as 

 sinks for most of the organic and inorganic mate- 

 rials resulting from land erosion. Because of the 

 lack of scouring and the nature of the sediments 

 that occur in some areas, anaerobic conditions 

 often develop in the beds of estuaries and bays. 

 Increases in the deposition of suspended solids 

 intensifies this condition. An excellent discussion 

 of the role of sediments in an estuary is given by 

 Carriker(1967). 



Many industries and municipalities discharge 

 nutrient-rich wastes into estuaries. Because of the 

 nature of the estuary, these are recycled and ac- 

 cumulated over a period of time. Because of this 

 recycling, effluents with low concentrations of nu- 

 trients may, in time, produce serious problems. 



The complete flushing of the estuary often takes 

 many years. With controlled water discharges, this 

 problem may become more severe. 



Plant nutrients consist of many types of chemi- 

 cals. For example, we have the chemicals com- 

 monly recognized as being important in plant 

 nutrition such as nitrate, phosphate, sulfate, car- 

 bonate, calcium, magnesium, sodium, and potas- 

 siiun. There are also the so-called "trace elements" 

 which are equaUy important but are required in 

 small amounts such as iron, manganese, molybde- 

 num, cobalt, zinc, etc. More recenfly the impor- 

 tance of organic compounds in plant nutrition has 

 been recognized. These include vitamins, such as 

 vitamin Bj,, organic forms of nitrogen, such as 

 urea, various amino acids, and amides, and the 

 simple sugars, such as glucose. 



The role of dissolved organic compounds in the 

 nutrition of plants as well as animals appears to be 

 important. Darnell (1967) refers to the aquatic 

 medium as a "vegetable soup" to indicate its rich- 

 ness in dissolved organic materials. The work of 

 Ryther (1954) points out that the organic forms 

 of nitrogen are best utilized by the less desirable 

 species {Natmachloris atomus and Stichoccus sp.). 

 Nitzschia, a desirable diatom, often grows poorly 

 in their presence. This is no doubt a major reason 

 why sewage effluents often bring about the devel- 

 opment of undesirable species. 



If the increased nutrients in a system are well 

 balanced, many species wUl have larger popula- 

 tions, the predator pressure will increase, and the 

 productivity of the whole ecosystem will increase. 

 If, however, the increased nutrients are of undesir- 

 able composition for most forms of aquatic life, or 

 not in the correct ratio, excessive blooms of spe- 

 cies with low predator pressures may develop. 

 Examples of these are certain blue-green algae. Of 

 course, environmental factors other than nutrients 

 are important in the development of blooms. Any 

 one important factor, such as temperature, light, 

 or water mass stability, if limiting, may prevent 

 blooms even though other conditions are suitable 

 for their development. As a result, blooms some- 

 times do not develop even though most of the 

 conditions are favorable. 



Nuisance Organisms: Nuisance organisms in 

 the marine environment are usually defined as 

 those organisms which interfere with the use that 

 man wishes to make of a particular water. Some 

 examples are abnormally abundant growths of or- 

 ganisms that make bathing beaches unattractive, 

 produce unpleasant odors, foul the bottoms of 

 boats, spoil the esthetic appearance of water and 

 the coastline, clog fishing nets, interfere with the 



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