Green sea turtle. Photo by L. Ilyes. Wikimedia Commons
(Click on the following link to listen to an audio version of this blog … Sea Turtles
Sea turtles are incredibly charismatic and critically endangered components of our marine ecosystems. There are seven, living species of sea turtles and five of them are found in Florida: the green sea turtle (Chelonia mydas), the loggerhead sea turtle (Caretta caretta), the leatherback sea turtle (Dermochelys coriacea), the hawksbill sea turtle (Eretmochelys imbricata) and Kemp’s Ridley sea turtle (Lepidochelys kempii).
In the past 100 years, global populations of sea turtle species have declined by 67%. Estimates of the number of sea turtles remaining in the Earth’s ocean range from 1.1 million individuals to 6.5 million individuals. This very broad range reflects the near impossibility of actually seeing and counting these ocean dwelling organisms unless they have emerged on land to lay their eggs. Even with the precise, yearly counts of those emergent females, though, the number of males must be estimated (typically considered to be 10% of the female count) and the yearly non-breeding female cohort must also be estimated since sea turtle females do not lay eggs every year. Depending on the species, an individual’s egg laying may occur only once every two to six years! The population estimate formula, then, is quite complex and open to broad interpretations!
Loggerhead sea turtle. Photo by Strobliomyces. Wikimedia Commons
Each year hundreds of thousands of sea turtles become trapped in longlines and nets of both commercial and small scale fishing operations. Many of these turtles are severely injured or killed outright because of these “by-catch” entanglements. Many sea turtles also die each year because they mistakenly ingest a wide variety of plastic debris that increasingly is found in our ocean waters. These plastics and other foreign materials accumulate in the turtles’ digestive tracts leading to blockages and, often, a slow, painful death. Over one million sea animals (including mammals, fish, sharks, turtles and birds) die each year from eating plastics.
Humans have also interfered with the ability of sea turtles to come ashore and lay eggs. Artificial lighting on shore repels gravid, female turtles. Sea walls and rock revetments block the turtles’ access to the dunes, and human activity on the beaches (especially at night and especially involving motorized vehicles) can disrupt nesting or interfere with the migration of recently hatched nestlings to the sea.
Pollution of the ocean has also caused suppression of the immune systems of sea turtles leaving them vulnerable to infections and viral caused cancers (like fibropapillomatosis). Climate change, though, may be one of the most severe threats to sea turtles with rising ocean levels inundating nesting sites and increasingly severe storms destroying coastal habitats.
Leatherback sea turtle. Photo by USFWS, Public Domain
Why are sea turtles important?
Certain species of sea turtles (especially among our five Florida species the loggerhead, leatherback and Kemp’s Ridly sea turtles) eat incredible quantities of jellyfish and sponges. There are a number of models (including the one published by J. Jackson in Science back in 2001) that indicate that the oceans are likely to become clotted masses of algae and jellyfish if overfishing and human interference with marine ecosystems do not stop (see Signs of Winter 4, December 27, 2018). Sea turtle conservation might be one way to avert this marine catastrophe.
Sea turtles (especially the green sea turtle) eat incredible quantities of seagrass. In fact, green sea turtles eat so much seagrass that their body tissues and especially their fat tissues turn green! Their seagrass grazing stimulates seagrass growth, mobilizes and disperses nutrients and maintains the health and vitality of the seagrass ecosystems. Sea turtles (along with manatees) are keystone species in these vital marine ecosystems (see last week’s blog for a discussion for the ecological importance of seagrass!).
Hawksbill sea turtle. Photo ny NOAA. Public Domain
Sea turtle nesting delivers much needed nutrients to the nutrient-poor sands of the nesting site beaches and sand dunes. The growth of stabilizing dune grasses and other vital dune plants depend upon the sea turtle delivered soil nutrients and also the decomposition of the failed eggs and hatchlings. Also, the sea turtle hatchlings are an important food source for a number of mammal, bird and invertebrate species (sadly, only 1 out of every thousand sea turtle hatchlings is expected to survive even its first few hours of life!).
Sea turtles, then, are a seldom seen but absolutely vital component of our shoreline ecosystems. It turns out, though, that it is possible to see a remarkable number of sea turtles right here in the Florida Keys! Next door to our rented beach house was a place that all of us had our “must see” lists for our “American Tropics” vacation: The Turtle Hospital!
Turtle Hospital, Marathon, Florida. Photo by A. Evenstead. Flickr
The Turtle Hospital occupies the buildings and grounds and salt-water swimming pool of a former, shore-side motel. Established in 1986, The Turtle Hospital provides advanced, veterinary care for injured sea turtles, and , as we noted above, lots of things can happen them! They can get tangled up in fishing lines and damage their flippers, they can hit by boats and lose limbs and get terrible breaks in their shells, they can swallow a wide range of human-generated debris (especially plastics!) and get intestinal obstructions and blockages, and they can suffer from fibropapillomatosis which, although is not a malignant cancer, can cause tumors to form all over the bodies (especially in green sea turtles and loggerhead sea turtles) making movements difficult and, sometimes, if the tumors involve the eyes, causing blindness.
Two turtles at Turtle Hospital. Photo by Y. Wang. Flickr
The Turtle Hospital working with the University of Florida and the University of Georgia College of Veternary Medicine has shown that fibropapillomatosis is caused by water pollution and toxins from harmful algae blooms (HAB’s or “red tides”) suppressing the immune systems of sea turtles. This suppression causes the turtles to be unable to control the herpes-like virus that causes the tumors. They have also shown that the causal virus can spread from turtle to turtle! It is, then, very unusually, a contagious form of cancer!
At The Turtle Hospital we saw a number of green and loggerhead sea turtles that were being treated for their injuries. Most of these turtles will be rehabilitated and then released back into the wild. There were a few sea turtles, though, whose injuries were so severe that they will have to stay in captivity for the rest of their lives. These sea turtles are referred to as “permanent residents.” These permanent residents include five turtles that are available for “adoption” by members of the public.
Montel. Poto by The Turtle Hospital
Our daughter and son-in-law adopted one of these permanent resident sea turtles for Deborah and I as a Christmas present. Our turtle is named “Montel.” She is a green sea turtle who was brought to The Turtle Hospital in 2001. Montel is a “poster child” for all of the things that can put a sea turtle in the hospital: she lost one front flipper due to an entanglement with some monofilament fishing line, she lost half of her other front flipper while she was entangled in the fishing line to a shark attack, she has shell damage due to a boat strike and, consequently, air has become trapped inside her shell disrupting her ability to dive under water (“positive buoyancy syndrome” (also called “bubble-butt syndrome”)), and,to top it all off, she lost one of her eyes to fibropapilloma tumors.
We watched Montel swimming around in the large, sea water pool at the hospital. She grabbed tossed food when it landed on her left (good eye) side and slowly circled around the pool edge. She maneuvered herself with effort (the floatation drag of the air trapped inside her shell made swimming and diving difficult), but, even though she only had one functional front flipper, she showed a great deal of focus and determination (or maybe I am just remembering her like a proud, adoptive parent!). Apparently, according The Turtle Hospital website, Montel likes to sneak up behind hospital workers when they enter the swimming tank and give them nips on their legs. Just stirring the drink, eh, Montel? I like her attitude very much!