Pollution's Impact On Loggerhead Sea Turtles: A Worrying Future

Loggerhead sea turtles are the most common species of sea turtle in US coastal waters. They are named for their large heads and strong jaws, which they use to feed on hard-shelled prey. While loggerhead sea turtles are a common species, they are still vulnerable to ocean pollution at all stages of life. This vulnerability is caused by the ingestion of plastic, entanglement in fishing gear, and exposure to toxic metals, chemicals, and oil.

Plastic ingestion

The ingestion of plastic can cause physical damage to the intestines of loggerhead sea turtles, leading to blockages and intestinal injuries. It can also trick turtles into feeling full when they have not consumed sufficient nourishment, resulting in sickness and even death. The impact of plastic ingestion on loggerhead sea turtles is severe, and it is estimated that approximately 1,000 sea turtles die each year from ingesting plastic, making it a leading cause of death for this species.

In addition to ingestion, plastic pollution also poses a threat of entanglement to loggerhead sea turtles. This can hinder their ability to swim, surface for air, or feed, and can cause injuries or drowning. The combination of ingestion and entanglement risks makes plastic pollution an urgent issue for the conservation of loggerhead sea turtles.

Entanglement in fishing gear

Loggerhead sea turtles are vulnerable to entanglement in fishing gear at various stages of their life cycle and in different habitats, including the open ocean, coastal areas, and beaches. This is primarily due to their habitats overlapping with fishing activities, both commercial and recreational, as well as the presence of lost or abandoned fishing gear and other types of marine debris.

The impact of entanglement on loggerhead sea turtles varies depending on their size. Smaller turtles may drown immediately if entangled in large or heavy gear. In contrast, larger turtles may be able to pull the gear off the ocean floor but still face risks of exhaustion and infection. Entanglement can also lead to physical trauma and infections as the gear cuts into their flesh.

Entanglement can hinder a loggerhead sea turtle's ability to swim, surface for air, or feed. It can also increase the risk of vessel strikes as the entangled turtles may be unable to avoid boats and ships. Even after escaping or being freed from entanglement, the wounds caused by the gear can lead to serious infections.

Untended fishing gear, including longlines, gillnets, traps, pots, trawls, and dredges, is a significant cause of mortality among loggerhead sea turtles. The impact of entanglement is exacerbated by the presence of other threats, such as coastal development, predation, and human disturbances, which further endanger the survival of this vulnerable species.

Efforts to prevent entanglement and rescue entangled loggerhead sea turtles are ongoing. Organizations like NOAA Fisheries work with partners to prevent entanglements and respond to reports of entangled animals. Specialized tools and techniques have been developed to safely disentangle turtles, and satellite tracking is used to monitor and relocate entangled individuals. Additionally, initiatives such as the Monofilament Recovery and Recycling Program aim to reduce the amount of fishing line in the environment by providing recycling bins and promoting recycling practices.

Oil spills

Loggerhead sea turtles are particularly vulnerable to oil spills due to their nesting habits. They return to the same nesting beaches every two years or so, making them susceptible to repeated exposure to oil pollution. Oil from spills washes up on these beaches, degrading the nesting habitat and impacting females and hatchlings. Oil can also accumulate in convergence zones, which are important areas for young turtle development, further endangering this vulnerable stage of their life cycle.

Additionally, loggerhead sea turtles are at risk of ingesting oil or tar balls, which are formed when crude oil degrades in water. Ingesting these contaminants can lead to health issues and even death. Oil spills contribute to the decline of loggerhead sea turtle populations, and if pollution levels are not reduced, these turtles could eventually face extinction.

To protect loggerhead sea turtles from the harmful effects of oil spills, it is crucial to reduce pollution levels and address the sources of oil spills, such as offshore oil exploration and vessel discharge.

Chemical exposure

Loggerhead sea turtles are vulnerable to chemical exposure from ocean pollution at all stages of their life. Chemicals can be ingested when turtles eat contaminated food or water, or they can be absorbed through their skin. These chemicals can cause organ damage, reproductive issues, and even death.

Chemicals can enter the ocean through oil spills, urban runoff, and the use of fertilizers and other agricultural and industrial contaminants. Oil spills can occur through intentional discharge from vessels, vessel groundings, offshore oil exploration and production, the transport of oil products, spills, and runoff from land-based sources. Oil can coat the bodies of turtles, preventing them from floating and leading to drowning. It can also damage their shells and cause respiratory issues.

Additionally, toxic metals and PCBs (polychlorinated biphenyls) can accumulate in the tissues of loggerhead sea turtles over time, leading to immunosuppression and increased susceptibility to diseases and death. PCBs can also cause depressed immune systems, illness, impaired reproduction, and the development of tumors.

The impact of chemical exposure on loggerhead sea turtles is a serious concern, and efforts to reduce and prevent marine pollution are crucial for the conservation and protection of this vulnerable species.

Light and noise pollution

Light pollution has a significant impact on the nesting behaviour of loggerhead sea turtles and the subsequent risk of predation of nests and hatchlings.

Impact on nesting behaviour

Light pollution can deter female loggerhead sea turtles from nesting. They may fail to nest after multiple false crawls, instead resorting to sub-optimal nesting spots or depositing their eggs in the ocean. In either case, the survival outlook for hatchlings is slim.

Light pollution can also cause hatchlings to become disoriented and wander inland, where they often die of dehydration or predation. This is because hatchlings have an innate instinct to head towards the brightest horizon, which is usually over the ocean. Excess lighting from nearshore buildings and streets draws hatchlings towards land, where they may be eaten by predators, run over by vehicles, or drown in swimming pools.

Solutions

• Turn off lights visible on nesting beaches or use special fixtures to shield the lights from the beach.
• Use low-pressure sodium-vapour lighting (LPS) instead of normal lights.
• Use Turtle Safe Lighting – these red lights emit a very narrow portion of the visible light spectrum, which is less intrusive to nesting sea turtles and hatchlings.
• Tint windows that face the beach.
• Close opaque curtains or blinds after dark to cover windows visible from the beach.

Case study

The Sea Turtle Conservancy (STC) is implementing a bold new programme to address the problem of artificial lighting that disorients newborn hatchlings in Florida, where about 90% of all sea turtle nesting in the US takes place. The loss of hatchlings caused by poorly managed light represents a major obstacle to the recovery of US turtle populations.

The STC has worked with over 161 properties, representing over 21 miles of beach darkened. At Gulf Islands National Seashore, approximately half the nests experience a high level of hatchling disorientation. In 1999, 33 of 65 nests (51%) that hatched had levels of disorientation where at least 25% of the hatchlings emerging from the nest cued in on the wrong direction. In 2000, 26 of 58 nests (45%) that hatched were disoriented.

Impact on other species

Light pollution near nesting beaches also threatens adult female sea turtles hauling out to nest. As they approach a beach from the sea, these females instinctually seek out dark places to deposit their eggs. Bright lights can deter females from coming ashore at all. If they do come ashore, they can be lured away from the sea.

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