Abstract
Behavioral rhythms of marine animals have often been investigated in the field by use of an artificial light at night. This study was carried out to test whether such lighting affects the timing of behavior, thus causing a modification of the rhythmic patterns. Emergence patterns of a marine midge and several small crustaceans monitored without light showed various degrees of synchrony with day-night and tidal cycles; patterns of some species are well-demarcated, and others show only a weak rhythmicity. In comparison, artificial lighting may indeed have affected the number of specimens collected, but the characteristics of each species' emergence pattern were unchanged. The animals may not respond positively to the artificial light except initially, and then they may escape it. We speculate that light habituation takes place in the animals, and that because of this, night activity patterns monitored using the field light are very similar to those monitored without the light. In conclusion, use of a field light for monitoring the activity of animals at night is fully acceptable procedure.
