Turtles

Carapace Sea Turtle. © Free Pixabay License

Marine turtles have survived on Earth for more than 200 million years, and today seven species of marine turtles inhabit the world's oceans (Spotila, 2004). In Europe, turtles can be primarily found in the Mediterranean Sea, where the green turtle (Chelonia mydas) and the loggerhead turtle (Caretta caretta) nesting populations are considered as indigenous.

Another three species of turtle are visitors to the Mediterranean Sea and the North-east Atlantic Ocean (especially around Madeira, the Canary Islands and the Azores). The leatherback turtle, the largest species of turtle, is the most regularly sighted visitor (Casale and Margaritoulis, 2010).

Turtles can provide good indicators of marine environmental health, as their population numbers are closely associated with the health of their environment. Turtles play an important role in ocean ecosystems. For example, loggerhead turtles provide habitat maintenance through their foraging behaviour. This foraging behaviour affects the compaction, aeration, and nutrient distribution of the seabed sediment. It also affects the species diversity and dynamics of the benthic ecosystem (Lazar et al., 2011; Bjorndal and Jackson, 2002).

According to the Habitats Directive data from the 2007-2012 reporting period, 60% of reports showed unfavourable status and 40% unknown for the loggerhead and green turtle in the Mediterranean region (to be updated with the data from the 2013-2018 period). Marine turtles have not been observed in the Baltic Sea and are very rare visitors to the Black Sea.

General outcomes of the regional assessments

In the North-East Atlantic and the Mediterranean Sea both the loggerhead and leatherback turtles are listed as threatened and/or declining species (OSPAR Commission, 2019; UNEP-MAP, 2018).

In the Mediterranean, most nesting sites of the loggerheads are located in the eastern and central basins (Greece, Turkey, Cyprus and Libya), while for the green turtle these are all in the eastern basin (Turkey, Syria and Cyprus). Foraging and wintering sites of green turtles have been primarily documented along the Levantine basin but also in Greece and the north coast of Africa (Broderick et al. 2007; Stokes et al. 2015; Margaritoulis & Teneketzis 2003).

Outcomes from the MSFD assessments

In 2018, Member States had to update the Good Environmental Status (GES) assessments performed under Marine Strategy Framework Directive Article 8. The present dashboard displays the overall status reported by countries for the features, where the results show which is the percentage of assessments where GES has been achieved, not achieved or is unknown or not assessed.

References

  • Bjorndal, R. and Jackson, J., 2002, 'Roles of sea turtles in marine ecosystems: Reconstructing the past', in: The Biology of Sea Turtles Volume II, CRC Marine Biology Series,CRC Press, Boca Raton, Florida (USA), pp. 259–273.
  • Broderick AC, Coyne MS, Fuller WJ, Glen F. & Godley BJ. 2007. Fidelity and overwintering of sea turtles. Proceedings of the Royal Society, London B Biological Sciences, 274, 1533–1538.
  • Casale, P. and Margaritoulis, D., 2010, Sea turtles in the Mediterranean: Distribution, threats and conservation priorities., IUCN, Gland, Switzerland.
  • Lazar, B., Gračan, R., Katić, J., Zavodnik, D., Jaklin, A. and Tvrtković, N., 2011, 'Loggerhead sea turtles (Caretta caretta) as bioturbators in neritic habitats: an insight through the analysis of benthic molluscs in the diet', Marine Ecology 32(1), pp. 65–74.
  • Margaritoulis D, Teneketzis K. 2003. Identification of a developmental habitat of the green turtle in Lakonikos Bay, Greece. In First Mediterranean Conference on Marine Turtles (Margaritoulis D & Demetropoulos A eds) Barcelona Convention - Bern Convention - Bonn Convention (CMS), Rome, pp 170-175.
  • OSPAR Commission, 2019. List of Threatened and/or Declining Species & Habitats
  • Spotila, J. R., 2004, Sea turtles, Johns Hopkins University Press, Baltimore, London.
  • Stokes KL, Broderick AC, Canbolat AF, Candan O, Fuller WJ, Glen F, Godley BJ. 2015. Migratory corridors and foraging hotspots: critical habitats identified for Mediterranean green turtles. Diversity and Distributions.
  • United Nations Environment Programme - Mediterranean Action Plan (UNEP-MAP), 2018. Barcelona Convention - Mediterranean 2017 Quality Status Report
  • Wallace, B. P., et al., 2011, ‘Global Conservation Priorities for Marine Turtles’, PLOS ONE 6(9), p. e24510. DOI: https://doi.org/10.1371/journal.pone.0024510