Ocean Pollution's Impact On Sea Turtles' Lives

Marine pollution is a serious threat to sea turtles, affecting them at every stage of their life. From eggs to adults, sea turtles are vulnerable to a range of pollutants, including plastic, toxic metals, oil, and agricultural and industrial runoff. One of the primary ways pollution affects sea turtles is through ingestion, either directly or by consuming food contaminated by oil, tar balls, or microplastics. This can lead to intestinal blockage, malnutrition, reduced growth rates, and even death. Additionally, pollution can degrade sea turtle habitats, impacting nesting sites and the survival of hatchlings. Light and noise pollution also drive turtles away from critical foraging and nesting habitats. The accumulation of debris at nesting beaches can further affect female nesting activity, embryo development, and hatchling survival.

Plastic ingestion

Sea turtles are affected by plastic ingestion at every stage of their life. From the moment they are born, they face the risk of injury or death from ingesting plastic. Sea turtles often mistake plastic for food. For example, plastic bags can look very similar to jellyfish, and fishing nets can resemble tasty seaweed. As a result, turtles end up welcoming harmful substances into their digestive tracts.

The consequences of ingesting plastic can be severe. Plastic can cause intestinal blockages, malnutrition, reduced growth rates, and even death. It can also pierce the intestinal wall, causing internal bleeding. In some cases, the presence of plastic in a turtle's stomach can create the sensation of being full, leading to starvation as the turtles neglect to seek out other food sources.

Research has found that a turtle has a 22% chance of dying if it eats just one piece of plastic. The likelihood of death increases with the amount of plastic ingested. For example, once a turtle had 14 plastic items in its gut, the probability of death rose to 50%. It is estimated that over half of all sea turtles worldwide have ingested plastic, and many will starve to death with stomachs full of plastic.

The impact of plastic ingestion on sea turtles is a critical issue that threatens the survival of these ancient mariners. It is important to address this problem through education, reduced plastic consumption, and proper waste disposal to protect sea turtles and the marine ecosystems they inhabit.

Entanglement in plastic

Sea turtles are affected by plastic at every stage of their lives. Entanglement in plastic debris is a significant threat to their survival. From the moment they are born, they face the risk of injury or death due to entanglement in plastic waste.

Turtles can get entangled in various plastic items, such as lost fishing nets, plastic twine, nylon fishing lines, six-pack rings, plastic packaging straps, plastic balloon strings, kite strings, discarded anchor lines, and seismic cables. These entanglements can lead to choking, loss of limbs, and other severe injuries.

Research by the University of Exeter found that 91% of turtles entangled in discarded fishing gear died. The same study surveyed 106 marine experts, 84% of whom had directly witnessed the death of turtles due to plastic entanglement.

The risk of entanglement is not limited to the ocean's surface but also extends to underwater and beach areas. More than 1,000 turtles are estimated to die each year from entanglement in plastic, and this number is likely an underestimate as many dead turtles are never recovered.

Plastic debris on nesting beaches can also impact female nesting activity, embryo development, and hatchling survival. The accumulation of trash on beaches can make it difficult for female turtles to dig holes to lay their eggs, leading to a decrease in successful reproduction.

Additionally, hatchlings and young turtles are particularly vulnerable to entanglement as they make their way to the ocean. They can get caught in plastic debris, trash, and fishing gear, disorienting them and preventing them from reaching the sea.

Oil and chemical pollution

Oil spills and urban runoff of chemicals and fertilisers through drains and rivers from cities may contribute to up to 36% of all marine pollution from oil. Oil spills tend to accumulate along the food chain and therefore affect the sensitive habitats that sea turtles depend on, such as seagrass beds, mangroves, and coral reefs. On a larger scale, oil from offshore spills concentrates along convergence zones, which are important areas for young sea turtle development. These may also accumulate on nesting beaches, thereby impacting nests, nesting females, and hatchlings.

Pollutants such as heavy metals (including mercury) and PCBs can concentrate in the liver, kidneys, tissues, and eggs of sea turtles. Other pollutants include petroleum products and agricultural and industrial runoff of contaminants, such as fertilisers, chemicals, nutrients, and untreated waste. Sea turtles may be harmed by these pollutants through direct or indirect exposure. Pollutants building up in tissues over time could lead to immuno-suppression (often associated with fibropapillomatosis disease), disruption of endocrine function, respiratory inflammation, gastrointestinal ulceration, organ damage, and reproductive failure in sea turtles.

Direct links to pollution sources, especially non-point sources, are difficult to ascertain. Furthermore, toxicology (the vertical transfer of pollutants from mother to offspring) and quantitative links between pollutants and specific impacts are currently not well understood. However, it is known that even a single piece of plastic ingested can cause intestinal blockage, malnutrition, reduced growth rates, and death in sea turtles.

Noise and light pollution

Light and noise pollution can have a significant impact on sea turtles, affecting their nesting and foraging habits.

Light Pollution

Sea turtles are sensitive to light, and artificial lighting near nesting beaches can deter female turtles from coming ashore to lay their eggs. Bright lights can also lure nesting females away from the sea, causing them to lay eggs in suboptimal locations or even abandon their nesting attempts altogether.

Artificial lighting also poses a threat to sea turtle hatchlings. When they emerge from their nests, hatchlings typically follow the brightest direction, which on a natural beach, would be the ocean horizon. However, bright lights from coastal developments, such as streetlights, hotels, and residences, can disorient hatchlings, causing them to crawl towards the artificial light sources instead of towards the ocean. This phenomenon, known as "light pollution," can lead to thousands of hatchling deaths each year as the confused hatchlings become dehydrated, preyed upon, or crushed by vehicles.

To address light pollution, some coastal communities have passed ordinances requiring residents to turn off beachfront lights during the turtle nesting season. Additionally, the use of turtle-safe lighting, such as red lights with narrow light spectrums, can reduce the impact on sea turtles without compromising human safety.

Noise Pollution

Sea turtles are also sensitive to noise, and persistent, abrupt low-frequency noise can disturb and even damage their hearing. Underwater noise pollution, caused by passing ships and offshore construction, can lead to temporary hearing loss in sea turtles. This hearing loss can impair their environmental awareness, navigation, and detection of predators, putting them at further risk.

While noise pollution has been studied in other marine animals like dolphins and fish, its impact on sea turtles is only recently gaining attention, highlighting the need for further research and conservation efforts to protect these vulnerable creatures.

Impact on nesting

Sea turtles are dependent on beaches for nesting. Uncontrolled coastal development, vehicle traffic on beaches, and other human activities have directly destroyed or disturbed sea turtle nesting beaches around the world. Trash on nesting beaches means adult sea turtles must crawl through collected debris to find a place to nest, and hatchlings can get caught in the debris as they make their way to the ocean. Tiny bits of plastic in the sand can also affect nests and hatchlings. Artificial lighting near the shore also causes hatchlings to become disoriented and wander inland, where they often die of dehydration or predation. Excess lighting from buildings and streets draws hatchlings toward the land, where they may be eaten, run over, or drown in swimming pools.

Light and noise pollution drive turtles away from critical foraging and nesting habitats. Unfiltered lights in coastal areas disorient hatchlings and deter adult turtles from nesting. Persistent and abrupt low-frequency noise, such as seismic tests for energy exploration, disturbs turtles and may even damage their hearing.

Oil from offshore spills washes up on beaches, degrading nesting habitats and impacting nests, nesting females, and hatchlings. Oil spills tend to accumulate along the food chain and therefore affect sensitive habitats that sea turtles depend on, including seagrass beds, mangroves, and coral reefs.

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