Chapter 5 



Ecological Systems and Transport 



57 



the coastal regions are found in the Pacific 

 sardine and the North Atlantic herring. In all 

 of these cases materials assimilated at sea may 

 be concentrated in inshore waters as a result 

 of these migrations, which may cover thousands 

 of miles. Such migrations certainly make it 

 difficult to select any area in the oceans as being 

 sufficiently remote and isolated from human 

 interest to insure that the discharge of radio- 

 isotope wastes might not be transported into 

 those areas man is most interested in protecting. 

 It should, however, be pointed out that this is 

 a quantitative problem, and our knowledge is 

 not sufficiently detailed to permit evaluating 

 the quantity of radioisotopes which could be 

 transported in mass migrations of fish. 



In addition to the movements of organisms 

 which are independent of the circulation of the 

 water resulting from gravity and vertical and 

 horizontal migrations, many populations remain 

 stationary in a flowing stream of water. The 

 organism is thus able to concentrate remarkably 

 the constituents of the water masses which pass 

 by. Harvey (1950) estimated, for example, 

 that the bottom population was nearly 70 per 

 cent of the total population at a station in the 

 English Channel (see Table 3) . 



The most apparent of these stationary popu- 

 lations are those which live on or in the bottom. 

 Much of our knowledge concerning such popu- 

 lations is confined to those which occupy shal- 

 low waters such as the clams, the oysters, and 

 other economically important species. Stationary 

 populations may be exposed to and feed on 

 populations in many cubic miles of sea water 

 during the course of an active growing season. 



Although most of our knowledge is confined 

 to shallow water forms, it is known that such 

 stationary populations are a main source of food 

 for many bottom-feeding commercial fishes. The 

 haddock and cod fisheries of New England and 

 the halibut fishery of the Pacific Coast, for 

 example, are ground fisheries. These impor- 

 tant species of fish feed on sedentary or sta- 

 tionary populations. Even in the great depths 

 of the ocean such sedentary populations have 

 been found wherever man has had the oppor- 

 tunity to search for them. Although little is 

 known of their location in the food web and 

 dynamics of the ocean, it seems certain that 

 they play a part. 



The importance of such stationary popula- 

 tions is that they can concentrate enormously 



the density of organic matter in those locations 

 suitable for their survival. In unique situations 

 they may concentrate by several orders of mag- 

 nitude the available organic matter in the ocean. 



Less obvious stationary populations are plank- 

 tonic and unattached, and one would expect 

 them to be transported away from a given area 

 by the currents. It has been found in some 

 cases, however, that in spite of horizontal cur- 

 rents of considerable velocity, the centers of 

 some planktonic populations can remain rela- 

 tively stationary. Presumably there is a con- 

 stant drain from these populations as a result 

 of the currents which carry away some of the 

 organisms, but the rate of production of the 

 population is sufficient to maintain the popula- 

 tion in spite of this drain. Examples of such 

 populations are to be found in almost all estu- 

 aries which tend to maintain endemic species 

 different from those commonly found in the 

 adjacent sea (Ketchum, 1954; Bousfield, 1955). 

 Even in the open ocean similar stationary popu- 

 lations have been found (Redfield, 1939, 1940, 

 1941 ; Johnson and co-workers, unpublished 

 observations) . It is necessary to have a rate of 

 reproduction of the population as a whole suffi- 

 cient to balance the circulatory drain. This rapid 

 rate of reproduction will, of course, lead to the 

 concentration of materials from the v»'ater mass 

 moving past. 



A special case of biological concentration of 

 materials which probably involves several of 

 the above phenomena is found in the "red 

 tide." It has been shown that the concentration 

 of total phosphorus in the colored water of 

 these dinoflagellate blooms is commonly ten to 

 twenty times as great as the concentration which 

 can be found in any of the adjacent waters 

 (Ketchum and Keen, 1948). Most of this 

 phosphorus is combined in the living cells, and 

 very little is present in the inorganic form. 

 One of the explanations for these high concen- 

 trations involves the accumulation of the organ- 

 isms at the surface because of their buoyancy, 

 and the subsequent further concentration of 

 the surface film by convergence of water masses 

 (Ryther, 1955). In the red tides which have 

 occurred in recent years off the west coast of 

 Florida, the organism involved, Gymnodinium 

 brev}s, produces a toxin which is lethal to the 

 fish and other organisms in the water, and vast 

 numbers of fish have been killed as a result 

 of these dinoflagellate blooms (Gunter, et al.. 



