Microplastics May Heat Marine Turtle Nests and Produce More Females
By Mariana Fuentes
Have you ever considered that small pieces of plastic less than 5 millimeters long, or smaller than a pencil eraser head, called microplastics, can affect large marine vertebrates like sea turtles?
My research team first discovered this disturbing fact when we started to quantify the amount and type of microplastic at loggerhead nesting grounds in the northern Gulf of Mexico, between St. Joseph State Park and Alligator Point in Florida.
Microplastics, which are created by the breakdown of larger plastic pieces into smaller ones, or manufactured as microbeads or fibers for consumer products, can change the composition of sandy beaches where marine turtles nest. Marine turtles, which are listed under the Endangered Species Act, lay their eggs in coastal areas, and the environment in which their eggs incubate can influence hatching success, the gender and size of hatchlings.
In particular, the sex of marine turtle eggs is determined by the sand temperature during egg incubation. Warmer sand produces more females and cooler sand, more males. Temperatures between approximately 24-29.5 degrees C produce males and above 29.5 to 34 degrees C, females. Since plastics warm up when exposed to heat, when combined with sand, microplastics may increase the sand temperature, especially if the pigment of the plastic is dark. This could potentially affect the nesting environment of marine turtles, biasing the sex ratio of turtles toward producing only females and affecting the future reproductive success of the species.
Coastal areas and consequently marine turtle nesting environment exposed to microplastic may also be harmed by toxic chemicals that leach out of the microplastics when they are heated.
Given the potential impacts of microplastic on marine turtle incubating environment, we did a study to determine the microplastic exposure of the 10 most important nesting sites in Florida for the Northern Gulf of Mexico loggerhead subpopulation. Microplastic was found at all nesting sites, with the majority of pieces located at the dunes, the primary site where turtles nest.
We took several samples of sand at each nesting site during the Northern Hemisphere summer months, May to August, which is when turtles are nesting in the region.
We are still unsure what the implications of these exposures are, and how much microplastic is needed to change the temperature of the nesting grounds. So, this summer we are expanding our experiments to explore how different densities and types of microplastic can affect the temperature of nesting grounds.
Regardless of the implications, it is important to consider that any alteration to our natural environment may be detrimental to species that rely on then. The good news is that there are several easy ways to reduce microplastic.
The research was conducted by undergraduate student Valencia Beckwith and Mariana Fuentes.
Sweden's reindeer have a problem. In winter, they feed on lichens buried beneath the snow. But the climate crisis is making this difficult. Warmer temperatures mean moisture sometimes falls as rain instead of snow. When the air refreezes, a layer of ice forms between the reindeer and their meal, forcing them to wander further in search of ideal conditions. And sometimes, this means crossing busy roads.
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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