An investigation of the effects of discharged wastes on kelp / [Wheeler J. North, project director].

  • California. State Water Quality Control Board.
Date:
1964
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Licence: Public Domain Mark

Credit: An investigation of the effects of discharged wastes on kelp / [Wheeler J. North, project director]. Source: Wellcome Collection.

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    100 80 60 40 20 ABSORBENCY BEFORE DILUTION 10 90 100 900 1000 above, calculations for a path length of 1 meter must be made, ultilizing equation (1). A value of 1 « 10-°° was computed for the absorption coefficient at 500 mu, representing a spectral region important for kelp photosynthesis and intermediate in the range of values for absorption coefficient over the whole spectrum. We have noted above that increasing the average absorbency by only 1% is sufficient to produce a sub- stantial change in ambient light at depths of 10 m (33 ft.) or greater, typical of the kelp bed zone. The amount of dilution required to lower the absorption coefficient so that the final mixture is increased only by 1% can be computed from a family of dilution eurves (Fig. 93) and is shown as a function of ab- sorbancy before dilution (Fig. 94). For the values of absorbancy obtained above, a dilution of at least a thousand fold seems desirable. Use of these calculations requires that the optical character of the sewage-seawater mixture does not change with the passage of time. In practice there are almost certainly profound changes, but what these are in the open sea, and exactly what influence is exerted on water clarity remains to be established. Gunnerson (1948) ascribes a major portion of the disappearance of B. coli in receiving waters to rapid sedimentation of suspended solids in the sewage-sea- water mixture. We have noted no sludge deposits in the nearshore areas of Point Loma, Palos Verdes, and Santa Barbara, but the immediate vicinity of the out- falls has not been examined (our kelp station at Santa Barbara is about 1000 feet from the outfall terminus). On calm days, however, at Palos Verdes and Santa Barbara, a fine skinlike film of ooze settles on hard surfaces but appreciable wave action brings this into suspension. Our measurements of ambient light in the sea tend to indicate that regions near outfalls can be quite turbid, and there is good indication that the Santa \e\y pase petore dition A A Wd YQ EAS SSS ] 100 A on OF DILUTION ABSORBENCY AFTER DILUTION Figure 94. Curves illustrating the variation of absorbency as a liquid is diluted with a non-absorbing fluid.