Oceanographic Abstracts 409

and 4 per cent was due to Sr 9°. On the basis of atom uptake, more Sr 9° was found, approximately 130 times as much. The percentage values for concentration of atoms showed a greater concentration for yg0 than for Sr 9°, presumably because of the 3592 to ! ratio of Sr 90 and yg0 in the m~.dium initially. P. subcordiformis cells selectively concentrated ygo mole than Sr 9°. On a percentage-atom- uptake basis, yg0 was concentrated to a greater degree than Sr 9°. Details of these experiments are reported in a paper by Donald W. Lear, Jr. and Carl H. Oppenheimer, Jr. (pp. xliv-lxii).

Consumption of Micro-organisms Labelled with Sr 9° and ygo by the Copepod Tigriopus californicus Experiments, entailing feeding S. marinorubra and P. subcordiformis, which had taken up Sr 9°

a n d y90, to Tigriopus californicus, were conducted to determine the rate of feeding of the copepod and the transfer of activity up this step in the food chain. Results were not conclusive. It is indicated that there was little or no concentration of activity by T. californicus in the presence of S. marino- rubra. There is, however, evidence of T. californicus grazing on P. subcordiformis and thereby accu- mulating activity from Sr 90 and yg0. Details of tbese experiments are reported in a paper by Donald W. Lear, Jr. and Carl H. Oppenheimer, Jr. (pp. lxiii-lxv).

Uptake of Fission Products by Phytoplankton Experiments were conducted between May 20 and 30, 1955, to determine the amount of radio-

activity taken up by laboratory cultures of a marine dinoflagellate, Gonyaulax polyedra, from sea water containing mixed fission products collected in the test area. A concentration of activity in the cells of this organism of about 5000 times in a period of 90 hr was indicated. From concentration factors in different dilutions of radioactive sea water, it appears that, in the range of 5 to 50 per cent dilution, the concentration factor is independent of dilution. Studies of energy spectra of the cells which had taken up activity suggest differential uptake of certain energies. The corresponding isotopes were not identified. Details of these studies are reported by W. H. Thomas, D. W. Lear, Jr., and Francis T. Haxo (pp. lxvi-lxxi).

Elemental Composition of Some Pelagic .Fishes In order to evaluate the potential uptake of fission products and the potential sites of concentra-

t ion of various elements, it was of interest to learn something of the concentration of various naturally occurring elements in the various organs of pelagic fishes. This was undertaken by studying the ele- mental composition of various organs of tunas and other pelagic fishes.

The data indicate that the elements existing most probably as cationic species in sea water (Mn, Cu, Ni, Zn, etc.) tend to be concentrated in the internal organs. The alkaline earths (Ca and Sr) concen- trate in the hard parts, and Sr appears more strongly in the flesh than Ca. Details of the analyses are given by Edward D. Goldberg (pp.lxxii-lxxv).

Uptake of Sr 9° by Pacific Mackerel An experiment was conducted to determine the uptake, retention, excretion, and sites of deposition

of Sr 9° in a representative pelagic food fish, the Pacific mackerel (Pneumatophorus diego), by feeding this isotope and studying total activity and its distribution in various organs after various periods of time up to 235 days. It was found that 95 per cent of the activity was excreted in 24 hr and that the remaining 5 per cent remained fixed in the body for the duration of the experiment. Eighty per cent of this fixed activity was located in the skeletal structures. The edible portion of the fish showed low activity per unit weight after two days. One to three days after feeding, the gills showed the highest activity per unit weight, suggesting this as the site of major excretion. Details of this experiment are contained in the paper by De Courcey Martin and Edward D. Goldberg (pp. lxxvi-lxxxi).

FIELD STUDIES IMMEDIATELY AFTER TEST TO STUDY U P T A K E OF FISSION P R O D U C T S BY MARINE ORGANISMS

Radiochemical studies of sea water, of the particulate matter in the sea water, and of the organisms were made on the basis of samples collected at the test site during the first few days after the shot.

Approximately half the activity in the sea water was found to be due to materials present in par- ticulate form.

The most active organisms during this early time, and hence the most effective concentrators of activity, were mucous, pseudopodal, and ciliary-feeding zooplankton species which, it was presumed, were ingesting the particulate matter. Limited assays of diatoms indicated low effectiveness in accu- mulating activity, although this result is somewhat doubtful owing to the possibility that the technique was faulty.

During this early period the fishes showed no significant concentrations of activity except in the stomach and gut regions, indicating that they were feeding on organisms lower in the food chain which were radioactive and that the active elements had not yet reached deposition sites in the other parts of the fish. No long-term studies for sites of accumulating of specific isotopes were conducted. Details of this are given in the paper by L. Berner, R. Bieri, E. D. Goldberg, De C. Martin, and R. L. Wisner (lxxxii-xci).