III. STATEMENT OF POTENTIAL PROBLEMS OF REFLECTED LIGHT Several discrete types of biological activities were considered potentially important in evaluating the disruptive effects of additional environmental light. 1. Daily Behavioral and Physiological Rhythms: The vast majority of animals (except for perhaps some completely subterranean or cave-dwelling forms) exhibit some degree of daily activity rhythms, e.g., crepusular, diurnal or nocturnal. In many cases, the timing of these rhythms is at least partially dependent on environmental illumination, normally the daily photoperiod set by sunrise and sunset. Additional ambient light during normal daytime periods would not be expected to have significant or even measurable effects as long as it was of low to moderate levels compared to solar radiation. However, even relatively dim and brief light pulses during the "night" might act as potential stimuli to disrupt normal diurnal activity rhythms. Additional detrimental effects of interrupted nights due to reflected light might occur through disruption of numerous daily physiological rhythms other than overt activity per se. Virtually every aspect of physiological function (metabolism, kidney function, mitotic activity, etc.) shows some degree of daily rhythmicity in animals, and, in many cases, these can also be synchronized by daily photoperiods. Abnormal light stimuli during otherwise dark periods (scotophase) could potentially reset such rhythms and lead to their dissociation from other processes. Such dissociation between separate rhythms may greatly modify the entire physiological status of the animal. For example, the quantitative and qualitative actions of pituitary hormones, such as prolactin, may depend on their daily phase relationship to other
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