In order to understand the broad effects of natural moonlight on nocturnal creatures, the team organised the effects into the categories of reproduction, communication and foraging/predation, and addressed each of these categories across a variety of animal groups.
One of the most stunning behaviors the team covers in their report is a moon-induced mass-spawning event that occurs every December in Australia's Great Barrier Reef. Each year, hundreds of species of coral spawn together at the same time. A variety of environmental factors — including temperature, salinity and food availability — likely contribute to the timing of the event, but the level of moonlight appears to be the main trigger. When the light is right, hundreds of corals release their sperm and eggs in synchrony, increasing the probability of fertilisation.
In other cases, the moon's effects are more mundane. Communication patterns, for example:
- change with increased light availability at night for certain species of birds. Eagle owls use white throat feathers to communicate with other birds at night, and tend to increase this activity during nights surrounding the full moon when their feathers are more visible. Other owls, on the other hand, avoid activity during full moons, a behaviour that scientists think helps them avoid predators.
Reducing activity to avoid predation during periods of brighter light is a common way that land animals react to the lunar cycle. Marine animals, however, often react more to the opportunities associated with changes in tides. Some species of sea turtles, for example, wait for the full moon's high tide to ride waves onto shore and lay their eggs far up on the beach.
Adaptations of Pyrophytic Plants
Perhaps the most amazing fire adaptation is that some species actually require fire for their seeds to sprout. Some plants, such as the lodgepole pine, Eucalyptus, and Banksia, have serotinous cones or fruits that are completely sealed with resin. These cones/fruits can only open to release their seeds after the heat of a fire has physically melted the resin.
Other species, including a number of shrubs and annual plants, require the chemical signals from smoke and charred plant matter to break seed dormancy. Some of these plants will only sprout in the presence of such chemicals and can remain buried in the soil seed bank for decades until a wildfire awakens them.
To take advantage of the ash-fertilized soil, some plant species are able to flower prolifically after a fire. The Australian grass tree is a well-known example of this adaptation. Its conspicuous flower spikes are often the first sign that the plant survived a blaze and individuals grown in greenhouses are often subjected to blowtorching to encourage flowering. Other fire-stimulated species often bloom simultaneously a few weeks after being burned, creating lush landscapes of colorful flowers. This is especially common in annual plants that emerge rapidly from the post-fire soil seed bank. Several members of the fire lily genus (Cyrtanthus) only flower after fires and have an extremely fast flowering response to natural bush fires.
A tall crown and few to no lower branches is a strategy a number of tree species employ to reduce wildfire damage. In keeping their leaves and vital growth tissues far above the reach of most flames, these trees can often survive a fire with only minor charring to their trunks. This adaptation is common in several pine species as well as in many Eucalyptus species. Some of these trees, such as the ponderosa pine, have even evolved a “self-pruning” mechanism and readily remove their dead branches to eliminate potential sources of fuel.
How does the gravitational pull of the moon affects the seas and the tides on earth?
Tides are created by the moon (and to some degree actually, the sun) because of the moon's gravity and the rotation of the earth.The moon has a large mass that exerts a large gravitational force or 'pull' on the earth. However, because of the shape and size of the earth, the portion of the earth's oceans that are facing the moon at any time are closer to the moon than the center of the earth, and therefore will feel a greater pull, and will be pulled outward towards the moon forming a bulge, or high tide. Likewise, the portion of the earth's oceans that are on the opposite side of the earth from the Moon are farther away from the moon than the earth's center, and the center of the earth will feel the greater pull and be pulled away from the ocean on the side opposite the moon. This forms a second bulge or high tide on the opposite side of the earth. As the earth rotates on its axis, the tides will move on the surface of the earth so that the high tide remains fixed on the side directly facing, and directly opposite the moon. Many other factors can affect the path taken by tides in each ocean basin, such as the shape of surrounding landmasses, but the dominant effect is from the moon's gravitational pull.
This explains why there is a high tide once a day. However, you have probably learned that there are usually two high tides every 24 hours.
Where does the second one come from? The answer to that question is also that it is a consequence of the moon's gravity affecting the earth, but in a different way.
Whereas the first high tide is due to the fact that the moon and earth are linked into a rotating tandem by their gravity, the second high tide is a result of the moon's direct gravitational pull on the earth's oceans. When a region of the ocean is directly under the moon, the moon's gravity pulls the ocean away from the earth, increasing the size of the water bulge there.
Alterations of the circadian rhythm by the electromagnetic spectrum: A study in environmental toxicology
The nightly production and secretion of melatonin by the pineal gland, an endocrine organ near the anatomical center of the brain, provides important time-of-day and time-of-year information to the remainder of the body. In mammals, the circadian rhythm of melatonin (low levels during the day and high levels at night) is synchronized by the prevailing light: dark environment with the retinas of the eyes doing the photoreception required for the induction of this rhythm. The advent of artificial light sources has allowed animals or humans to be exposed to light at unusual times, i.e., during the night. Light falling on the retinas at night leads to a rapid depression in the production and secretion of melatonin by the pineal gland. The magnitude of the drop in circulating melatonin due to light exposure at night is related to the brightness (intensity) as well as the wavelength (color) of light to which humans are exposed. The lowered melatonin values following unusual light exposure at night provide erroneous information to a number of organs that respond to the melatonin message since the signal implies it is day when, in fact, it is still night. Besides visible light, certain ultraviolet wavelengths as well as extremely low frequency electric and magnetic fields may also disturb the melatonin rhythm. These nonvisible wavelengths may influence the circadian melatonin rhythm by mechanisms similar to those by which light causes disturbances of melatonin production and release.