This is the first in a series of stories we’ll be publishing over the next few weeks, looking at why sea turtles are so important to the marine environment, what threats they face, the role WVI plays in saving sick and injured turtles, and how we’d like to build on what we already do to safeguard the future of these amazing animals. This is in the run-up to our Big Give Christmas Challenge campaign at the end of November, which this year will have a special focus on sea turtles.

‍Please save the date now! 28^th November to 5^th December

‍How Sea Turtles Safeguard Ocean Health

“Sea turtles play an important role in ocean ecosystems by maintaining healthy sea grass beds and coral reefs, providing key habitat for other marine life, helping to balance marine food webs and facilitating nutrient cycling from water to land.”                 Why Healthy Oceans Need Sea Turtles (Report by oceana.org)

It’s hard not to love a sea turtle. But these extraordinary, prehistoric animals represent far more than just another incredible species under threat of extinction as a result of human actions. They are an important sentinel species for monitoring the health of marine ecosystems.

There is no doubt that our oceans are in trouble, under threat from over-fishing, pollution and climate change, and as sea turtle numbers decline, so does their ability to perform vital ecosystem functions to support ocean health. It’s a vicious circle.

Protecting sea turtles and maximising the chances of survival of every individual washing up on beaches and arriving in rescue centres is a vital piece of the puzzle when it comes to restoring the health and resilience of our oceans.

Take the role of green turtles in influencing the growth and health of seagrass, for example.

 What is sea grass and why does it matter?

Seagrasses have roots, stems and leaves just like land grasses, and they photosynthesise in the same way too, creating and releasing oxygen and storing carbon dioxide. This makes them an important carbon sink, in the same way rainforests help carbon capture on land, and illustrates the importance of seagrass in helping combat climate change. Just one square metre of sea grass can generate around 10 litres of oxygen a day.[1]

Apart from functioning as the proverbial ‘lungs of the sea’,sea grass also has an important role to play in preventing coastal erosion by trapping wave energy, stabilising the sea bed and helping maintain water quality. It also provides an important breeding and nursery ground for many species of fish, shellfish and crustaceans, including plaice and herring,[2] many of which are food sources for other animals, including humans. Taking a wider One Health view of sea turtle conservation makes it clear their protection is in the interests of all species who share the planet, ourselves included.

 How do green turtles help keep sea grass healthy?

An adult green sea turtle will eat around 2kg of sea grass every day, typically cropping the grass just a few centimetres from the bottom of the blade. Through their grazing, turtles ‘increase the productivity and nutrient content of seagrass blades’.[3] Without the action of the turtles, seagrass beds become overgrown, blocking light, triggering decomposition and encouraging the growth of slime moulds[4]and generally impeding the provision of ecosystem services associated with healthy seagrass meadows; water quality protection, erosion control, enhanced biodiversity, fisheries production and climate change mitigation.[5]

 Role of other turtle species

Meanwhile, other species of sea turtle play equally important roles in keeping ocean ecosystems balanced.

The hawksbill turtle helps maintain the health of coral reefs, by feeding on marine sponges which would otherwise dominate reef communities, limiting coral growth and modifying local ecosystems. Most other fish and marine mammals are not able to predate on sponges due to their unique physical and chemical defences.

Leatherback turtles live on jellyfish, consuming as much as 200kg in day[6] – that’s about the equivalent of a small motor cycle, or a very large male gorilla. This is important in a world where overfishing of some fish populations has allowed jellyfish to multiply to fill the resultant ecological gaps; a situation which is further exacerbated by the jellyfish’s tendency to feed on fish eggs and larvae, making recovery of fish numbers particularly challenging.

Loggerhead turtles feed on hard shelled prey, breaking up the shells as they forage and increasing the rate at which nutrients are recycled.By foraging in sand on the bottom of the ocean, they also aerate the sea bed and change the nutrient distribution of the natural sediment, boosting underwater health.

In addition, the eggs of all species of sea turtle help supply high-quality nutrients to nesting beaches  - both to vegetation (which in turn stabilises sand dunes and provides food to other animals) and as a food source for predators.

Although not all these processes and their wider implications are yet well understood, it is clear that sea turtles play an important role in maintaining marine ecosystem health, through their impact on sea grass, coral reefs and the sea bed, as well as in helping balance food webs and nutrient cycling.

Protecting these incredible animals, and making sure that rescue centres can access appropriate veterinary expertise to give sick and injured turtles the best chance of recovery and a successful life when they return to the wild, is in the interests of all of us who share the planet. This is where Wildlife Vets International plays a vital role, working with turtle rescuers and rehabilitators to make sure they are trained in the most effective techniques to treat turtles that have suffered deliberate injuries, become entangled in discarded fishing gear or other rubbish (often resulting in drowning, decompression sickness and loss of flippers), ingested plastic or fishing hooksor been hit by boats.

Watch out for our next article, which will look in more detail at the threats sea turtles are facing, including the scourge of plastic pollution, and what is being done to tackle them.  

Find out more about the threats sea turtles face. https://bit.ly/46i0s2B

Find out more about how microplastics are affecting both turtles and humans. https://bit.ly/3Flyl6H

Find out more about what work.  https://bit.ly/45Ji8De

Find out more about what we want to do next. https://bit.ly/3QShFKy

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[1] https://seaturtlespacecoast.org/sea-turtles-and-the-environment/

[2]https://saveourseabed.co.uk/about-our-seabed/seagrass-maerl/

[3] https://oceana.org/reports/why-healthy-oceans-need-sea-turtles/#:~:text=Sea%20turtles%20have%20played%20vital,to%20beaches%20and%20coastal%20dunes.

[4]Zieman, J.C., Fourqurean, J.W., and Frankovich, T.A. 1999. Seagrassdie-off in Florida Bay: Long-term trends in abundance and growth of turtlegrass, Thalassia tertudinum. Estuaries 22(2B): 460-470.

[5] https://www.frontiersin.org/articles/10.3389/fmars.2014.00028/full

[6] https://oceana.org/reports/why-healthy-oceans-need-sea-turtles/#:~:text=Sea%20turtles%20have%20played%20vital,to%20beaches%20and%20coastal%20dunes.

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