Loggerhead Turtles: Surviving In Polluted Waters

Loggerhead turtles are a species of sea turtle that are vulnerable to pollution at all stages of their life. They are affected by plastic pollution, both by ingesting it and getting caught in it, as well as light pollution, which disrupts their nesting behaviour.

Loggerhead turtles are the most common species of sea turtle in Florida, with some of the densest nesting habitats in the world. They are also found in the Cape Verde islands, which host the second-largest nesting aggregation of loggerhead turtles in the Atlantic.

Loggerhead turtles face threats from accidental capture and entanglement in commercial fishing equipment, coastal development, and exposure to pollutants. Climate change is also likely to negatively impact loggerhead turtles, as sea level rise and shoreline hardening will reduce the availability of nesting habitats.

Light pollution

Nesting Behaviour

Turtles are often unable to orient themselves seaward under yellow and orange lights, and can be seen crawling in circuitous paths in front of the light source for several minutes.

Predation Risk

Loss of nesting habitat

Loggerhead turtles are facing a loss of nesting habitats due to coastal development, rising sea levels, and shoreline hardening. These factors are causing a decline in the availability of suitable nesting sites and increasing the vulnerability of turtle nests to flooding and other disturbances.

Coastal development and rising sea levels are leading to the loss of critical nesting beach habitats for loggerhead turtles. The construction of buildings, roads, and other infrastructure near coastal areas can destroy or degrade the sandy beaches that loggerhead turtles depend on for nesting. Additionally, rising sea levels, caused by climate change, can result in beach erosion and inundation, further reducing the amount of suitable nesting habitat.

Shoreline hardening, such as the construction of seawalls and other structures, can also have a negative impact on nesting habitats. These structures can alter the natural topography of the beach and reduce the amount of dry sand available for nesting.

The loss of nesting habitats poses a significant threat to the survival of loggerhead turtles. It can lead to a decrease in the number of successful nests, disrupt the natural nesting behavior of the turtles, and increase the vulnerability of nests to predation and other hazards.

To mitigate the loss of nesting habitats, conservation efforts focus on protecting and restoring existing coastal habitats. This includes implementing measures to reduce coastal development, minimizing the impact of rising sea levels, and promoting nature-based solutions for shoreline protection, such as living shorelines.

Additionally, creating or modifying nesting habitats through the use of shade structures or controlled incubation programs can help maintain nesting success and optimal sex ratios, which are crucial for the long-term survival of the species.

Entanglement in fishing gear

Loggerheads can become entangled in fishing gear and other marine debris as they swim or while on the beach. This includes gear from commercial and recreational fishing, as well as lost or abandoned gear, and other types of ropes, lines, and trash.

Entanglement can cause loggerhead turtles to drown or starve, as they are restricted by the gear. It can also cause physical trauma and infections from the gear cutting into their flesh. Entangled loggerheads may also be unable to avoid vessels, increasing the risk of vessel strikes. Smaller turtles, like loggerheads, may drown immediately if the gear is large or heavy.

Bycatch

There are several fishing gear modifications that have had varying degrees of success for reducing sea turtle bycatch. In hook-and-line fisheries, the circle hook has replaced traditional J-hooks and has been shown to reduce loggerhead capture and increase post-release survival. Turtle excluder devices (TEDs) have been successful in preventing the capture of sea turtles in trawls. Other devices and techniques include changing the configuration of gillnets, introducing novel bait species, adding chain mats, and putting in trap guards.

The use of circle hooks (16/0) instead of J-hooks (size 2) on pelagic longline gear reduced the incidental capture of immature loggerhead sea turtles and did not affect the catch rates or fish size of the target species. There was also a significant difference in hook location between the two hooks, with more J-hooks being swallowed.

A study in Southern California found that a six-month average local sea surface temperature (SST) anomaly indicator with closures enacted above a threshold of 0.77 °C best predicted turtle presence and minimized opportunity costs to fishers. This can improve upon the current closure guidelines by providing a quantified and spatially explicit indicator and threshold to supplement the structured decision-making process.

Coastal development

The development can also cause pollution from runoff and litter, which can contaminate the water near the shore where turtles mate. It can further create obstacles for female turtles, making it difficult for them to navigate the beach and find suitable spots for their nests. The increased population and recreational activities that come with coastal development can also lead to more vehicles on the beaches, endangering turtles and causing failed nesting attempts.

In addition, seawall construction, a common aspect of coastal development, creates impenetrable barriers for nesting females and contributes to unnatural beach erosion. The increased coastal population also results in a higher number of boats and personal watercraft, which are responsible for a large number of sea turtle injuries and deaths due to collisions.

Light pollution from coastal buildings and pathways can also disorient hatchlings, causing them to move away from the water and towards dangerous areas such as roads and buildings. This can lead to their death from exposure, predation, or vehicle collisions.

To protect loggerhead turtles, conservation efforts should focus on preventing over-development and traffic near nesting areas, implementing nature-based solutions for shoreline protection, and enforcing existing laws and regulations that safeguard these vulnerable species.

Frequently asked questions