LIGHT PENETRATION IN THE GULF OF MEXICO 



By WILLIAM S. SHOEMAKER, Rochester Institute of Technology 



Although the interest and study of submarine 

 illumination has increased throughout the past 

 years, there has not been a proportionate increase 

 in investigation of this subject in the Gulf of 

 Mexico. This paper will attempt to summarize 

 the present knowledge and recent efforts in under- 

 water illumination as applied to this area. It is 

 hoped that the meagerness of the information will 

 be an incentive to future endeavor. 



The major part of the known data presented 

 here was calculated from Secchi disc depths. 

 Clarke (1941) points out that Secchi disc deter- 

 minations are in reasonable accord with measure- 

 ments obtained from the photronic photometer. 

 The relationship of K=1.7/D, where "D" equals 

 the depth in meters when the disc just disappears 

 and "K" denotes the coefficient, was introduced 

 bj' Poole and Atkins (1929) to convert Secchi 

 disc values into extinction coefficients. The 



standard equation,-^ =e~^^, where L is the depth 

 of water expressed in meters in which the intensity 



of illumination is lowered from /q to /, is of ad- 

 vantage for further manipulation of the extinction 

 coefficient. 



Several institutions located in tlie area have 

 studied illumination in the Gulf, l)ut their figures 

 are not yet available. 



E. R. Fenimore Johnson, under the auspices of 

 the Smithsonian Institution, conducted studies 

 dealing with the translucence of water as related 

 to visual and photographic transparency in the 

 area under discussion. This information is at 

 present being prepared for publication. 



Table 1 represents submarine illumination data 

 that are available at the time of writing. Source 

 material marked WHOI represents information 

 from the Woods Hole Oceanographic Institution's 

 files; D indicates Dana reports (Schmidt 1929). 

 The footnoted entries denote photronic photom- 

 eter derived extinction coefficients. 



Taylor (1928), in connection with his algal 

 studies in the Dry Tortugas area, recorded data 

 obtained from the Secchi disc. Tliis information 



Table 1. — Submarine illumination data according to the Woods Hole Oceanographic Institution (WHOI) and Dana reports (D) 



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