6 GEORGE V SESSIONAL PAPER No. 38a A. 1916 



XIII. 



VARIATIONS IN DENSITY AND TEMPERATURE IN THE COASTAL 

 WATERS OF BRITISH COLUMBIA— PRELIMINARY NOTES. 



By C, McLean Eraser, M.A., Ph.D., akd A. T. Cameron, M.A., BjSc. 

 (With Two Charts and a Map.) 



It is well known that two of the chief factors determining the distribution of 

 marine fauna and flora are the salinity and the temperature of the containing water. 

 The series of observations embraced in this paper have been carried out in order to 

 obtain an idea as to the extent to which these factors participate in British Columbia 

 waters, and to see therefore whether a subsequent more exact series of measurements 

 is desirable. 



We are not acquainted with any extended series of observations of density and 

 temperature of these waters previously published; while scattered data almost cer- 

 tainly exist bearing on the problem, we have had no opportunity of consulting them. 

 Any previous observations by other observers have not, therefore, been taken into 

 consideration. 



Continuous observations have been made at the Biological Station, Departure 

 bay, for a period of four months. Examination of the Pacific coast kelp beds by one 

 of us afforded an opportunity of similar measurements at points over a large part of 

 the British Columbia coast. These, taken together, give data for the variation at a 

 single point (the Biological Station) and for a large number of scattered points. 

 Since the results indicate a considerable variation at the one point, a similar unde- 

 termined variation probably exists for many, if not all of the other points, at which 

 only one or very few readings could be made. Only certain general conclusions can 

 therefore be drawn from the second series of readings. 



The readings taken at the Biological Station are given in Appendix A, and 

 figured in fig. 1. Those dealing with density will be considered first. They indicate 

 variations in density between the limits 1-013 and 1-022, with a mean value 1-0185. 

 The curve is marked by repeated sudden fiuctuations in the sense of a fall with sub- 

 sequent slower rise. These fluctuations indicate sudden influxes of fresh water. The 

 possibility of tide-effects was tested in the earlier readings by taking numerous read- 

 ings at high and low tide. The corresponding points lie on the curve and show no 

 marked tidal influence. 



The position of the Biological Station is shown in the accompanying coast map. 

 Possible sources of fresh water are: (1) local, small streams flowing into the bay, 

 and the Nanaimo river flowrng into adjacent waters 4 miles south (the amount from 

 these sources is practically negligible at the height of summer) ; (2) large bodies of 

 fresh water poured into the strait of Georgia, by the Eraser river, and through Howe 

 sound and inlets farther to the north. The nearest of these more distant sources is 

 the Eraser river, 30 miles directly across the strait of Georgia. Since the amount 

 of water from this source far exceeds that from those in the near vicinity, this alone 

 need be considered under the second head. We are convinced that the fresh water 

 of the Eraser river, and not that from more local sources, is the cause of the fluctua- 

 tions here chronicled, on the following grounds: — 



(1) The readings throughout Departure bay on June 2)9 were practically con- 

 stant. On June 30 a lower reading was obtained outside than that obtained inside 



