Sun, Sea and Turtles: Solar Appreciation Day

Throughout 2018 our marine biologists here at Love The Oceans will be doing blog posts on topics of Named Days throughout the year. To keep up to date, follow this blog, also found under the ‘News’ tab on our website. Without further ado, in celebration of Solar Appreciation Day, I introduce our fourth blog in this marine series:

Sun, Sea and Turtles: Solar Appreciation Day

Today is Solar Appreciation Day, a day where we can all appreciate the star that our lives revolve around (literally)! I know what you’re thinking, why on earth is a marine conservation organisation celebrating Solar Appreciation Day?! Solar has nothing to do with marine conservation. Well, it does. And here’s why:

The sun influences a huge array of ocean activities. Besides the obvious like providing energy for photosynthesis and warming the planet, it does lots of small things too, like regulating the diel vertical migration of organisms like copepods, squid and fish, which is actually the greatest biomass migration in the entire world (DVM is when animals move up to the surface at night and descend back down to the depths during the day). Solar has an enormous impact on every ocean activity that it would be impossible to cover them all in one blog, so for the purposes of today’s post, we’re going to focus on the influence of solar on sea turtles.

Surf School

There are 7 species of sea turtles on this planet, 5 of which reside in Mozambique. All 7 species are listed as Critically Endangered, Endangered or Vulnerable on the IUCN Redlist, with the exception of the Flatback sea turtle that is Data Deficient. The 5 species in Mozambique are: Leatherbacks, Loggerheads, Green Turtles, Hawksbills and Olive Ridleys, all of which are threatened worldwide and have been protected in Mozambique for over 45 years.

These animals are pretty spectacular creatures and they’re reliant on solar energy from beginning to end. Peak nesting season in Mozambique is in March and we’ve been lucky enough to witness a hatching event already this year! The sun partially controls tides and the space between high tide and where the vegetation begins is where turtles lay their nests. Nesting usually occurs at night and these huge animals crawl up the beach, dig a hole and lay up to 300 eggs in one clutch and a female typically lays around 1 – 8 clutches per season. They then cover up the hole and make their way back to the sea. During 2 weeks of their incubation period, the temperature of the sand determines their sex. In this way, solar influences them right from the beginning, as warmer sand (>30°C) will mean the clutch hatches female, and cooler sand (<27°C) will result in a male bale. Turtles also rely on solar for body temperature regulation to some degree throughout their lives too. Most sea turtles are poikilotherms which means their body temperature varies largely. Turtles are reptiles and although they’re not fully cold-blooded, green turtles in particular have been known to haul their bodies out of the water to warm up in the sun on rocks.

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Turtle Hatching Source

The babies emerge from nests after around 60 days and make their way back to the sea where they drift in the ocean for most of their juvenile years feeding on small floating organisms – hence the importance of events like the diel vertical migration. Unfortunately, they have so many predators and threats that even once they’re in the ocean only around 1 in 1000 hatchlings survive to adulthood. It is thought that the location they’re born in is imprinted in their olfactory organ which means they often return to their birth site to lay their eggs. Loggerheads, which we had most recently on our beaches, reach sexual maturity at around 25 years old so it’s pretty impressive they can remember their birth beach for that long!

So why are turtles so important and why have we focussed on them today?  We have sea grass in our bay, which is awesome and a big indicator of nursery grounds. Sea grass is really important for juvenile fish development and turtles graze on sea grass, which maintains its health and encourages growth.

Turtles are really important in maintaining a balanced marine ecosystem. Leatherbacks prey predominantly on jellyfish. This is really important as jellyfish blooms are a common occurrence in imbalanced ecosystems. Leatherbacks are key in controlling these blooms and ensuring re-balance. On top of this, other species feed on bottom-dwelling organisms with hard shells. Through crushing these shells and discarding the pieces this boosts nutrient recycling and the foraging behaviour affects seabed compaction and aeration.

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Leatherback feasting on a jellyfish. Image from Brian Skerry

We’re privileged enough to have these amazing animals in Mozambique and we know for a fact they nest on our beach right in front of our base.  We feel passionately about protecting them and we’ve seen some nests have been raided. Given the low survival rate of these animals, we want to ensure they at least make it to the ocean! LTO has designed a turtle patrol protocol and we’ll be running turtle patrols with our marine biologists throughout March and April on our programs. If you’d like to join us on these in Mozambique please click here.

Turtles are just some of the animals that rely on solar energy to survive. Solar is so important for so many animals as well as a providing an alternate energy source which reduces the exploitation of the seas through the likes of oil rigs.

So, we would like you to join us in celebrating #solarappreciationday today and its importance in conservation efforts…

“The sun doesn’t struggle to rise and neither should we!”