Marine Biology

Harmful Effects of light

Light which is very essential for the photosynthesis of plants and generally beneficial to animals may sometimes be harmful. The violet and ultra-violet parts of the spectrum have harmful effect on animals. In order to avoid these harmful effects, many animals become nocturnal. By taking up a nocturnal habit, these animals also avoid the predators which can easily spot them in good light.

Diatoms react to excessive light by clumping. Many animals avoid excessive illumination by diurnal migrations. Animals like corals which cannot move about, open their polyps only in dim light and close them when there is bright light.

Intertidal animals also become nocturnal. Ligia oceanica comes out from crevices only in night. Mytilus edulis closes its shells in excess of light and opens only in night. Chiton also lives in areas where shade is available. It is negatively phototropic when young. As regards the zooplankton, the young stages do not live at the same level as their adults.