Research Proj. Part 3 Re-Post

Sea Turtles: Pollution Effects on a Threatened Species


Pollution in the world’s oceans has only recently become a complex issue that scientists and environmentalists are becoming increasingly aware of. Before the 1950’s, most human litter disposed of in the ocean was biodegradable, which meant it was broken down by the ocean water into organic, non-harmful components. The recent increase in the widespread use of plastics, with its durability and inexpensive qualities, has resulted in the accumulation of these materials in the oceans. Unfortunately, the durability that makes it useful to humans makes plastic detrimental to the ocean waters and the life within it. The buoyant characteristic of plastic also makes it especially harmful because it is able to travel for long distances in ocean currents (Sheavly, 301). Plastic accumulation puts marine life and ecosystems at severe risk. Plastic debris includes things like plastic bags, ropes, nets, and rings from six-packs of soda. Other harmful marine debris that is present in massive amounts are styrofoam, oil, tar, and glass (Mascarenhas, 354). Perhaps one of the most adversely affected and thus most extensively researched examples of this is the marine turtle. Although pollution items have historically not always been a direct threat to sea turtles, marine pollution is having a deleterious effect on the well being of these animals because of plastic ingestion, toxic chemical retention in tissues, and ingestion of several other anthropogenic materials.

Sea turtles, with a lifespan of up to 80 years, live predominantly in aquatic environments, except when females use beaches to lay their eggs. They live in both tropical and subtropical oceans, in many different areas of the world’s oceans. Unfortunately, these once abundant creatures’ populations are decreasing, and all seven species of sea turtle are now either classified as threatened or endangered species (NOAA.gov). One of the main reasons behind this dwindling in their populations is being accredited to anthropogenic issues; the deposition of oil and the “persistent plastics” that are disposed of in our oceans. Ingestion of plastics that may resemble prey to the turtle, especially species with a low discrimination in what they feed on, can cause direct affects to the turtle (Tomas, 211). These items also have implications in altering feeding habits, and degrading their habitats (Bugoni, 1330). When sea turtles ingest debris, the nature of the debris can be directly harmful, or it can make the turtle feel full and have no appetite. They then become nutrient deprived and more susceptible to sickness and death (Tomas, 211). Additionally, fishing nets have also become a pollutant in the waters and are harmful to turtles because the often get caught in them and drown because they cannot swim up to breathe (Sheavly, 302). In fact, it is estimated that oceans are the depot for about 52 metric tons of fishing gear per year (Pichel, 1207).

The ingestion of debris is a common cause of sickness and death in marine turtles. A significant amount of debris ingestion research has been done on turtles found dead on beaches, or turtles that are illegally captured by fishermen. In one study, a research team analyzed 54 sea turtles that were captured illegally in the Spanish Mediterranean Ocean. Upon dissection of the sea turtles’ bodies, several types of debris were found in nearly 80% of the turtles. The debris items included tar, paper, hooks, lines, and nets; the most abundant material, though, was plastics, accounting for 75% of the total debris (Tomas, 211). In another area of the world, in east and west coastal areas of Florida, another study was performed using 51 sea turtles that washed up dead onto beaches. 56% of the total turtles were found to have debris in their stomachs. They concluded that two of the turtles had died as a direct result of the debris clogging the digestive tract and mangling of gut tissue (Bjorndal, 154).

Two studies conducted using sea turtles from Brazilian waters showed debris intake by the animals. One small study documented the analysis of two turtles, one dead, one alive, found on the shore of Paraiba, Brazil. The turtle that was deceased was dissected and was noted to have several pieces of hard plastic and a part of a plastic bag. Two weeks later, the turtle expelled debris, became lethargic, and died after nearly one month. Necropsy showed that the turtle had died from a perforation in its duodenum causing it not to be able to process the food in its stomach (Mascarenhas, 354).

A second Brazilian study was conducted on the coast of the Rio Grande do Sul State in Southern Brazil. A group of university researchers from the area utilized 50 sea turtles that were found dead on the beach for an analysis of stomach contents. Three different species were involved. Upon analysis, plastic bags were found to be the debris that was most predominantly ingested by the sea turtles. The debris found within the sea turtles’ stomachs and intestines was the direct cause of death in 13.2% of the green turtles (the species that was the majority of the sample). Moreover, the researchers found an astonishingly large amount of fishing hazards to be the cause of death for the sea turtles (Bugoni, 1330).

In addition to being a direct threat to sea turtles by mere ingestion, ocean debris can cause more indirect harmful effects. Anthropogenic material is often slowly broken down into toxic chemical components that can build up in animal tissues (Andreani, 287). A few of the toxins that have been studied include trace metals like copper, zinc, iron, magnesium, and cadmium, as well as mercury, methylmercury, organochlorine, and polychlorobiphenyls (PCB’s) (Andreani,287; Day, 1421; Kampalath, 1816; Gardner, 1082). One study by a group of researchers in South Carolina looked at blood mercury levels in loggerhead sea turtles and their correlation to key health characteristics of the turtles. To conduct this study, they took blood samples from the turtles and analyzed the blood for total mercury levels, as well as levels of several types of indicative cells. Findings showed that high mercury levels were a likely cause of a decrease in lymphocyte cell levels, which are important immune system cells. High mercury levels in the marine environment are shown to be toxic to overall immune system function of sea turtles (Day, 1425).

It seems that the world’s increasing population and urbanization is having very serious consequences on the world’s oceans. When creatures that have thrived for millions of years are suddenly becoming rarities in the waters, there is obviously something very wrong with their environment. Big cities, especially in coastal areas, and the industries that are booming within them need to establish stricter regulations on waste disposal. The fishing industry needs to become more aware of the hazards posed to marine life by fishing nets, hooks, and other gear. Marine pollution currently places a huge impact on sea turtles because of what they ingest and the chemicals that pollutants release. If action is not taken to clean up the oceans, sea turtle population will continue to dwindle until extinction.



Works Cited

1) Andreani, G. "Metal Distribution and Metallothionein in Loggerhead (Caretta Caretta) and Green (Chelonia Mydas) Sea Turtles." Science of the Total Environment 390 (2008): 287-294.
2) Bjorndal, Karen. "Ingestion of Marine Debris by Juvenile Sea Turtles in Coastal Florida Habitats." Marine Pollution Bulletin 28 (1994): 154-158.
3) Bugoni, Leandro. "Marine Debris and Human Impacts on Sea Turtles in Southern Brazil." Marine Pollution Bulletin 42 (2001): 1330-1334.
4) Day, RD. "Relationship of Blood Mercury Levels to Health Parameters in the Loggerhead Sea Turtle (Caretta Caretta)." Environmental Health Perspectives 115 (2007): 1421-1428.
5) Gardner, Susan. "Organochlorine Contaminants in Sea Turtles from the Eastern Pacific." Marine Pollution Bulletin 46 (2003): 1082-1089.
6) Kampalath, Rita. "Total and Methylmercury in Three Species of Sea Turtles of Baja California Sur." Marine Pollution Bulletin 52 (2006): 1816-1823.
7) Mascarenhas, Rita. "Plastic Debris Ingestion by Sea Turtle in Paraiba, Brazil." Marine Pollution Bulletin 49 (2004): 354-355
8) National Oceanic and Atmospheric Administration. NOAA Fisheries- Office of Protected Resources. Aug. 2007. 10 Oct. 2008 .
9) Pichel, William G. "Marine Debris Collects within the North Pacific Subtropical Convergence Zone." Marine Pollution Bulletin 54 (2007): 1207-1211.
10) Sheavly, SB. "Marine Debris & Plastics: Environmental Concerns, Sources, Impacts and Solutions." J Polym Environ 15 (2007): 301-305.
11) Tomas, J. "Marine Debris Ingestion in Loggerhead Sea Turtles. Caretta Caretta, from the Western Mediterranean." Marine Pollution Bulletin 44 (2001): 211-216.