Oyster Insomnia Results From Light Pollution As the Artificial Illumination Disrupts the Bivalve’s Circadian Rhythm

Artificial light at night has been known to affect human health negatively, causing increased risk for depression, obesity, diabetes, breast cancer, and sleep disorders. Scientists discovered that it can also disrupt the circadian rhythms of wildlife, such as insects, birds, amphibians, birds, mammals, and plants. Just recently, an experiment revealed that light pollution can also impact marine organisms such as oysters.

Troubled Bivalve

At the French National Centre for Scientific Research, a team of scientists experimented with the effects of artificial light on marine species. Led by marine scientist Damien Tan, the researchers placed four tanks of Pacific oysters in various rooms where they were exposed to a different intensity of artificial light at night. They compared the oysters' responses with the responses of animals in a control tank that experienced complete nighttime darkness.

Each morning, the lights come up slowly in the marine lab, mimicking the natural light of the rising sun. However, the rooms never fully darken at night due to the dim glow that simulates light pollution.

Unlike other bivalves like scallops with eye-like organs, oysters are believed to detect light using patches of specialized cells on their skin. Experts have yet to identify these cells and figure out how they work.

It was discovered that artificial light at night disrupts the behavior of oysters and alters the mechanisms of their important genes, which keep their internal clocks ticking. Even the lowest level of nighttime light below the intensity of the full moon was enough to disrupt the bivalve's circadian rhythm.

Research co-author Laura Payton explains that due to the absence of eyes in oysters, they can only observe the animal's behavior through shell movement. To monitor when the oysters opened their shells, the team fitted half of the animals in each tank with electrodes.

In the control tank, oysters were found to be most active in the middle of the day and started to close when the lights went out. In the other four tanks, exposure to artificial light caused the oysters to stay open at inappropriate times, with peak activity in the early evening. Although oysters have certain genes that turn "on" during the day and others that turn on at night, the difference was eliminated by their exposure to nighttime light.

Oysters have an equivalent of a mammal gene that works like melatonin and is usually more active at night. The research team observed that this gene remained highly active during the day and eclipsed the natural circadian rhythm. This behavior is identical to insomnia in humans, and it can negatively affect the oyster's health as they can become more vulnerable to diseases in the long run.

Negative Effects of Artificial Light

Plants and animals depend on the daily cycle of light and dark to maintain life-sustaining behaviors like nourishment, reproduction, sleep, and protection from predators. Humans have disrupted this cycle by lighting up the night with artificial illumination.

Light pollution alters the nighttime environment of nocturnal animals by turning night into day. Some species of animals use darkness as cover from predators, which use light to hunt. Light pollution also affects wetland habitats, home to amphibians like frogs and toads, whose nighttime croaking is important in their breeding ritual. The artificial lights disrupt this nocturnal activity, interfering with reproduction and reducing animal populations.