Young sea turtles and floating debris in sargassum habitat
Sea turtle hatchlings emerge from sandy beaches, swim offshore, and, in a few days, reach Sargassum-dominated surface-pelagic drift communities (or Sargassum habitat). The Sargassum habitat provides protection and food for these sea turtles during the first few years of their lives. We have found that these turtles are opportunistic omnivores, apparently feeding on anything that fits into their mouths including synthetic materials that can harm them. Sargassum, plastics, and other floating objects gather at surface convergence zones that are typically located at the edges of ocean currents. After exposure to ultraviolet rays and other aspects of the ocean environment, large-size plastics are broken down into smaller fragments that are then bite-sized for the young sea turtles in Sargassum habitat. Alarmingly, we have observed a high prevalence of plastics included in the diets of these turtles.
Because of late-summer to fall storm events, some post-hatchlings, which are only a few weeks to a few months old and have been living in Sargassum habitat, are washed back on the beaches, mainly along the East Coast of Florida. These wash-backs are often in poor condition. Some are found dead and others die later at rehabilitation facilities. Since the early 2000s, we have been examining the gut contents of wash-backs that died. The percentage that had ingested plastics was about 80% during the early 2000s but has reached 100% during recent years. When ingesting plastics, the wash-backs seem to have no preference in color; we see a wide range of colors of plastic in their GI contents, with the majority being translucent and white as these are the most abundant types in the Sargassum habitat. By dry weight, about 30% of the gut contents from these turtles were plastics.
In addition to our study of wash-backs, we have also been capturing and studying post-hatchlings in the offshore Sargassum habitat. When comparing these two groups, we’ve found that the body condition index of the wash-backs was significantly lower than that of the post-hatchlings that were captured offshore. Although the relationship between plastic ingestion and cause of death is often not clear, the ingestion of plastic may result in nutritional dilution (non-nutritious material contributing to a feeling of satiation and reducing the urge to continue feeding) or may cause an impaction of the digestive tract.