. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 118 MARLON G. KELLY AND STEVEN KATONA during daylight hours. Since the treatment and environmental conditions were the same both day and night, it may be concluded that there is an endogenous diurnal rhythm in sensitivity to light inhibition. The similarity of the flashing rates after recovery from light inhibition to those of populations kept in continuous darkness indicates that there is no appreciably long-term effect of light exposure. The two intensities used are approximately equivalent to 2% and 12% of the mid-day sur
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 118 MARLON G. KELLY AND STEVEN KATONA during daylight hours. Since the treatment and environmental conditions were the same both day and night, it may be concluded that there is an endogenous diurnal rhythm in sensitivity to light inhibition. The similarity of the flashing rates after recovery from light inhibition to those of populations kept in continuous darkness indicates that there is no appreciably long-term effect of light exposure. The two intensities used are approximately equivalent to 2% and 12% of the mid-day surface light intensity in Eel Pond. Although the higher intensity of 8820 caused slightly greater inhibition, the flashing was never reduced by more than f. Sweeney, Haxo and Hastings (1959) noted that exposure of G. polyedra cultures to light caused inhibition of luminescence to varying degrees, depending on the intensity of the light, and that longer exposure to light altered the phase of the rhythmicity. They did not, however, mention significant variations in sensitivity to inhibition with time of day. The lack of a phase shift in the present experiments was probably due to the relatively short exposure and low intensity. Many luminescent marine organisms are known to be inhibited by light (Harvey, 1952), but only dinoflagellates and euphausids (Mauchline, 1960) are known to have 240 200 ? 160 kj 120 <0 £ so 40 00. 1-SEPT START 0830 HR 31-AUG ' START 1215 HR 2-SEPT i START 1815 HR 3-SEPT START 1510 HR 04 08 12 16 20 TIME (EOT) FIGURE 2. Flashing rates recorded using water collected from the natural environment at dates and times shown, and placed immediately in darkness. After time "A" (1600 hr.), all flashing rates fell on approximately the same curve, and only the range of flashing rates is shown by the cross-hatched Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - col
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