Turtles' Battle: Surviving In A Polluted World

Pollution poses a significant threat to turtles at all stages of their lives, from eggs to adults. Marine and coastal pollution come in many forms, including sound, thermal, photic, plastics, chemical, and effluent. One of the primary concerns is plastic pollution, as turtles often mistake plastic for food, leading to intestinal blockages, malnutrition, and even death. Additionally, they can become entangled in plastic debris, choking or losing limbs, and the accumulation of plastic at nesting beaches puts baby turtles at risk. Aside from plastics, oil spills and toxic metals such as mercury also endanger turtles, causing immunosuppression, organ damage, and reproductive issues. Light and noise pollution further drive turtles away from critical habitats, disrupting their nesting and foraging behaviours. The impact of pollution on turtles underscores the urgent need for conservation efforts and a reduction in pollution to protect these ancient mariners.

How plastic ingestion affects turtles

Plastic ingestion is a serious threat to turtles, and it affects both marine and freshwater turtles. It is estimated that more than half of all sea turtles have eaten plastic, and in some populations, more than 90% of individual turtles have ingested microplastics.

Plastic ingestion can cause physical damage to turtles' intestines and lead to blockages, which can make turtles sick or even cause premature death. One study found that sea turtles who ingest just one piece of plastic have a one in five chance of premature death, and those who ingest 14 pieces have a 50% chance of dying early.

Turtles can confuse plastic for their natural food, such as plastic bags that look like jellyfish, or they may accidentally eat plastic that is present among their natural food, such as a plastic straw on the seafloor.

Plastic ingestion can also lead to what is known as plastic-induced satiety. This is when plastic accumulates in the gastrointestinal tract, leading to a false sensation of fullness and decreased food intake. This can result in underweight and emaciated turtles, and potentially negative fitness consequences.

In addition to the physical dangers of plastic, the chemicals in plastic also pose risks to turtle health. Plastics contain any mixture of at least 16,000 chemicals, including about 4,200 that are known to be hazardous, such as bisphenols (like BPA), dioxins, flame retardants, PFAS, and heavy metals. These chemicals can cause serious health problems in turtles, including hormone-disrupting effects that can feminize sea turtle populations and infertility.

While the effects of plastic ingestion on marine turtles have been more widely studied, plastic ingestion in freshwater turtles is relatively understudied. However, it is known that plastic ingestion is reported for all 7 marine turtle species, and 5 out of 352 non-marine turtle species. One study found that 7.7% of 65 freshwater turtles had ingested plastic.

Overall, plastic ingestion poses a significant threat to the health and survival of both marine and freshwater turtles, and more research is needed to fully understand the impacts of plastic on these ancient creatures.

How oil pollution affects turtles

Oil pollution can have a devastating impact on turtles at all stages of their life cycles. Sea turtles are highly migratory and inhabit different parts of the ocean as they grow, which means they are vulnerable to oil spills at every age. Oil spills can occur during the exploration, transportation, and production of oil, as well as from urban and agricultural runoff.

One of the main ways oil spills affect turtles is through direct contact with the oil slick on the surface of the water. When turtles surface to breathe, they can inhale oil and its vapours, gulping it down into their mouths and throats and damaging their lungs. They can also become coated in oil, which impairs their ability to swim and can lead to exhaustion and dehydration. Oil can also irritate the sensitive mucus membranes in their eyes, mouths, lungs, and digestive tracts. In addition, toxic oil compounds, such as polycyclic aromatic hydrocarbons (PAHs), can be absorbed into vital organs, such as the lungs and liver, causing further damage.

Ingesting oil is another serious threat to turtles. They may swallow oil directly or consume food that has been contaminated by oil. Female turtles that ingest oil can pass the toxic compounds on to their developing young, causing developmental issues and threatening their survival. Nesting sites on beaches can also be contaminated by oil, affecting the eggs and hatchlings. Oil can inhibit the development of eggs, decrease hatchling survival rates, and cause developmental deformities in those that do survive.

Oil spills can also have indirect effects on turtles by damaging their habitats and reducing their food sources. Oil can kill seagrass, a significant component of green turtle diets, and harm invertebrates and sponge populations that other turtle species feed on. The loss of these food sources can make turtles more vulnerable to predators and expose them to greater energy expenditure.

Furthermore, oil spills can hinder turtle breeding. Oil containment booms set up along beaches can prevent female turtles from reaching the shore to lay their eggs. Oil spills can also disrupt the natural balance of habitats, such as seagrass beds, mangroves, and coral reefs, that turtles depend on for feeding and shelter.

The accumulation of oil in the environment is a significant concern for turtle populations. Oil from spills tends to concentrate in convergence zones where ocean currents meet, which are important areas for young turtle development. The impact of oil pollution on turtles can be long-lasting and devastating, affecting their health, reproduction, and survival.

How light and noise pollution affect turtles

Light pollution from coastal developments can deter female turtles from nesting and increase the risk of predation for both adults and hatchlings. Artificial light sources can disorient hatchlings, causing them to crawl away from the ocean and towards the light source, where they may die from dehydration or be eaten by predators.

The impact of light pollution on turtles depends on its intensity and wavelength. For example, green turtle hatchlings are highly attracted to short-wave blue light and show a weaker response to long-wave red light. Yellow light, on the other hand, has been found to be less disruptive to turtle behaviour than white light, with more hatchlings exhibiting appropriate sea-finding behaviour under yellow light.

Light pollution can be mitigated by reducing the amount of artificial light that reaches nesting beaches, using low-pressure sodium-vapour lighting, using turtle-safe red lights, and shielding lights from the beach.

Noise pollution, in the form of underwater noise from passing ships and offshore construction, can cause temporary hearing loss in turtles, which rely on their hearing for environmental awareness and navigation. Noise pollution is an additional stressor for turtles, over half of whose species are threatened.

How toxic metals affect turtles

Toxic metals are a serious threat to sea turtles, affecting them at all stages of life. These metals, including mercury, cadmium, and lead, can accumulate in the liver, kidneys, tissues, and eggs of sea turtles, leading to various health issues and even death.

One of the primary ways turtles are exposed to these toxic metals is through their diet. Sea turtles feed on a variety of fish, molluscs, seaweed, and sponges, which can contain high levels of pollutants. Oil spills and agricultural and industrial runoff also contribute to the problem, as chemicals, fertilizers, and untreated waste enter the water. These toxic metals can build up in the tissues of sea turtles over time, leading to immunosuppression and an increased susceptibility to diseases.

Additionally, toxic metals can interfere with the reproductive and nervous systems of sea turtles, impacting their behaviour and ability to reproduce. They can also cause developmental problems, with studies suggesting a link between heavy metal pollution and embryotic development issues, reduced hatching success, and eggshell thinning. The accumulation of toxic metals in sea turtles can also affect their growth rates and increase their vulnerability to predation and collisions with boats.

The impact of toxic metals on sea turtles is a global issue, with studies finding evidence of their presence in sea turtles in the Mediterranean Sea, the Red Sea, and the waters of Saudi Arabia, Mexico, and Japan, among other locations. The consumption of sea turtle meat and eggs by humans is also a concern, as it can lead to the accumulation of heavy metals in the human body and various adverse health effects.

Addressing the issue of toxic metal pollution in our oceans is crucial for the conservation of sea turtles and the protection of human health. Public health campaigns and education play a vital role in raising awareness about the dangers of consuming sea turtles and the importance of reducing pollution.

How pollution affects turtles' reproduction

Sea turtles are vulnerable to pollution at all stages of their life, from eggs to hatchlings to juveniles to adults. Pollution can affect their reproduction in several ways.

One of the main ways is through the ingestion of plastic and other marine debris. Turtles can become entangled in plastic debris, such as fishing nets, plastic twine, nylon fishing line, plastic packaging, and discarded cables, which can restrict their movement and make it difficult for them to feed, breathe, and reproduce. Ingesting plastic can also cause intestinal blockage, malnutrition, reduced growth rates, and even death. Additionally, plastic pollution can alter the temperature of the sand where incubation occurs, affecting the success of reproduction.

Another way pollution impacts turtle reproduction is through the accumulation of toxic chemicals in their bodies. Pollutants such as heavy metals (including mercury), PCBs, petroleum products, and agricultural and industrial runoff can build up in the tissues of sea turtles over time, leading to immunosuppression, endocrine disruption, respiratory issues, gastrointestinal problems, organ damage, and reproductive failure. These chemicals can also impact the size of turtle eggs, with smaller eggs potentially leading to reduced hatchling fitness.

Light and noise pollution also play a role in disrupting turtle reproduction. Unfiltered lights and persistent noise in coastal areas can deter adult turtles from nesting and disorient hatchlings, impacting their survival and reproductive success.

The impact of pollution on turtle reproduction is a complex and ongoing area of research, and it is clear that pollution poses a significant threat to the survival and reproductive capabilities of sea turtles.

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