Radioactivity in the Marine Environment (1971) / Chapter Skim
Currently Skimming:
ECOLOGICAL INTERACTIONS OF MARINE RADIOACTIVITY
ECOLOGICAL INTERACTIONS OF MARINE RADIOACTIVITY
Pages 200-222
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 200... ...
It is likely that this size factor is chiefly responsible for the longer food chains of the oceans. The continuity of the physical environment, however, has another important consequence: Other than the efficiency factor, there is no bar to short-circuiting of their food chains by higher trophic levels.
|
From page 201... ...
, in fact, was so impressed by the parallelism in this respect between transmittal of some elements and energy along food chains that he proposed the use of radionuclides of zinc or phosphorus as "indices of energy flow" in ecosystems. It has been frequently concluded that man, in drawing little food from marine primary producers, only moderate amounts from marine grazers, and most from predators at fairly high trophic levels, places an effective barrier between himself and radioactive nuclides introduced to the oceans (National Academy of Sciences-National Research Council, 1962, p.
|
From page 202... ...
(to be published) , the ranges of concentration factors, for a variety of elements, observed in a variety of primary producers and grazers as well as predators at various trophic levels in the marine environment.
|
From page 203... ...
Our ignorance of the genetic diversity within marine species still prevents any useful attempt to consider the genetic effects of increased radiation on pelagic ecosystems, although consideration of the histories of radiation exposure have long-term LDso's for 60Co irradiation of 215 and 300 rads, respectively-values quite like those exhibited by man. Examination of this question, they found, was further complicated, in the cases of Fundulus and ofArtemia salina, by a strong inverse correlation between environmental salinity and radiation tolerance.
|
From page 206... ...
r_ ^ ° i: nen -- .cj] - ci -- ' -- a FIGURE 1 Ranges of element concentration factors in marine organisms at various trophic levels (data from Table 2)
|
From page 207... ...
It may be further argued that radiation predation would be especially dangerous for the planktonic species of the open sea: Most of these species undergo cyclic reductions to very low abundances, at which the population may not be able to withstand further predation; these periods of low abundance are followed by periods of very rapid multiplication during which the radiosensitivity of individuals-by analogy with all experimental organisms so far studied -- may be expected to increase in proportion to the rate of cell division. It appears possible also to argue that the more closely interdependent are the species of an ecosystem -- and we believe that those of marine environments are especially closely linked, and to a greater diversity of mutually interdependent species -- the more especially radiosensitive will be the system.
|
From page 208... ...
Marine radioactivity has been and is now a basic tool in extending this understanding, and the regulation of releases of radioactive materials to the marine environment should continue to be designed with this use in mind. As ecosystems, the oceans are continua to an extent not exhibited by any other systems subjected to human exploitation save the atmosphere, and like the atmosphere, the world ocean in something like its present ecologicalgeochemical dynamism is essential to life on earth.
|
From page 209... ...
As Polikarpov points out, however, in a nonuniformly labeled environment, where organisms-cither prey or predatorsmigrate from higher to lower levels of radioisotope contamination, the food chain may be expected to be a major variable in an organism's accumulation of radioactivity. Data presented in Chapter 3 show that over very long periods of time after any radionuclide is introduced, and invariably for short-lived nuclides, nonuniform labeling of the marine environment is precisely what will exist.
|
From page 210... ...
, however, pointed out that as much as 40 percent of the 1964-1968 world fishery harvest was represented by "herring-like fishes" feeding at the first or second trophic level above the planktonic plants. Although this did not offer encouragement that large gains in fishery yield would come from transfers of effort to still lower trophic levels, Schaefer's calculations of "probable potential yield" of the world ocean (based on estimates of
|
From page 211... ...
Extensive long-term studies of food organisms from the Irish Sea near Windscale and from the northeast Pacific Ocean off the Columbia River indicate that the health and safety of human beings has been a primary consideration in release limits of radionuclides. Marine Radioactivity as a Basic Research Tool in Ecology The tracer experiment provided to scientists by the two periods of intense atmospheric testing of nuclear explosives offered a unique opportunity to explore details, especially of rates of transfer, of marine geochemistry and hydrography.
|
From page 212... ...
If, as suggested, marine species are both more closely linked than those of other ecosystems, and if unique -- or very limited -- species interdependences are here more common, then the radiation resistance of marine ecosystems will often be strongly limited by that of the least resistant species. No marine radioactivity levels have yet approached possible danger points, but this is argued as one of several aspects of the oceans needing fuller consideration in these contexts.
|
From page 213... ...
1964. On the concentration factors of radioactive Cs, Sr, Cd, Zr and Ce in marine organisms.
|
From page 214... ...
1964. Radioactivity and its relationship to the oceanic food chains.
|
From page 215... ...
1971. Radioecological investigations of plutonium in an arctic marine environment.
|
From page 216... ...
1961. On the concentration factors of some important radionuclides in the marine food organisms.
|
From page 217... ...
However, for man, this acceptance rests on ethical considerations with respect to the individual and on the fact that genetic anomalies are not reparable in an individual. When considering the marine environment, however, we are not primarily concerned with individual organisms, but with populations, and at the population level genetic damage is reparable by natural selection.
|
From page 218... ...
Our intention in this chapter is to consider only that research pertinent to the prediction of what might occur in the marine environment; therefore, we have not considered all of the studies that have been carried out using marine organisms in radiobiological research. NATURAL RADIOACTIVITY The sources contributing to the natural background radiation dose of organisms in the marine environment are cosmic rays and the natural radioactivity in the earth's crust, present in seawater sediments and biota (Folsom and Harley, 1957)
|
From page 219... ...
Falaemonetes pugio ^QL 40 60 80 Time After Irradiation (Days) 100 FIGURE 2 Mean lethal dose time curves for several species of marine invertebrates showing the dose-time combinations at which 50 percent of the experimental animals died.
|
From page 220... ...
Various crosses were made, some of which were reirradiated at 1.3 R/day to a total dose of 95 R The initial dose chosen was about 40 times the calculated maximum dose that the germ cells and young salmon could receive in the Columbia River before migration to the sea.
|
From page 221... ...
In addition, more data are required on the effects of other environmental parameters before significant radiation effects can be demonstrated. Of particular significance in the work from the Soviet Union is the unique concentration effect response (Polikarpov, 1966)
|
From page 222... ...
All of these experiments used very high levels of radionuclides, which would not normally be experienced in a contaminated aquatic environment, as the controlled disposal of radionuclides is limited to lower levels by man's use of the environment. However, the data from these ingestion experiments help to keep observations of the body burdens of radioactivity in field-contaminated fish in proper perspective with respect to potential radiation damage in fish in general.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.