Marine Debris in Loggerhead Turtles: Bioindicator of the World’s Oceans

Plastic marine debris has been accumulating at a rapid rate around the world.  This debris, which comes from garbage, fishing, and ships, negatively affects marine environments and wildlife.  Marine organisms, especially turtles, are harmed when they accidentally ingest this litter. Loggerhead turtles, Caretta caretta, feed generally on invertebrates on the bottom of the ocean, but have a high range of diversity in their prey. This makes it easy for the loggerhead to mistake plastic for food. These plastics carry many chemicals and pollutants, which result in higher mortality and possible negative effects on the entire food chain. The Mediterranean loggerhead population is isolated and has distinctive characteristics such as the small size of the adult turtles. This is important in relation to maturation and the time to regain population numbers because the Mediterranean basin has a large number of turtles caught each year as by catch.  Campani et al. (2013) looked at the presence and abundance of marine debris in the gastrointestinal tract of the loggerhead sea turtles. They then worked to describe and quantify the types of plastic ingested by the turtles. Most of the turtles sampled had ingested marine debris, the most common type being user plastic, which is plastic used in everyday life .Chloe Mayne

Campani T., Baini M., Giannetti M., Cancelli, F., et al., 2013. Presence of plastic debris in
loggerhead turtle stranded along the Tuscany coasts of the Pelagos Sanctuary for Mediterranean Marine Mammals (Italy). Marine Pollution Bulletin 74, 22-230.

Campani et al. used data from 31 stranded loggerhead sea turtles that were collected along the Tuscany coast. A necropsy (dissection) was performed on each turtle to determine cause of death.  Each animal was weighed and measured and the most important organs were collected for chemical analysis.  Following a prior bird marine litter determination protocol, Campani et al. determined the marine litter present in the loggerhead turtles gastrointestinal tract. The three main parts (esophagus, intestine and stomach) were divided up and separately analyzed by removing the contents, rinsing them and placing them onto dishes to be examined and sorted under a microscope. The frequency that each type of debris occurred was recorded as well as each specific weight of the sample.  The results were then split into debris found in young, or juvenile, loggerhead sea turtles and adult loggerhead turtles.
This study found marine debris in 22 of the 31 sea turtles (71%) as there were a total of 438 pieces of marine debris. The majority of this was found in the turtles’ intestine with less in the stomach and only one item, a hook, in an esophagus. The most debris found in the loggerheads was user plastic in 91.7% of them.  One of the female loggerheads had the most marine debris of all the turtles with 90% being sheetlike user plastic.  The small and young turtles had an average of 19 pieces of marine debris while the older and larger sea turtles had an average of 27 pieces. The analysis that was performed showed a relationship between number of plastics and shell length, shell length and plastic weight, and animal weight and plastic weight.

The presence of marine debris in the gastrointestinal tract of loggerhead sea turtles was found to be high in the turtles that stranded on the Tuscany coast. The greatest amount of marine debris found in the turtles was sheetlike plastic, which is commonly found in the ocean as a result of worldwide use and its long decomposition rate. The loggerhead sea turtle is an effective bioindicator of the marine litter in the environment and the health of the oceans.

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