title: The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.
abstract: The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet-undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1).
authors.affiliation: Institut de Ciències del Mar, Scientific Spanish Council (ICM-CSIC), Barcelona, Spain. mcoll@icm.csic.es
authors.forename: Marta
authors.initials: M
authors.lastname: Coll
authors.forename: Chiara
authors.initials: C
authors.lastname: Piroddi
authors.forename: Jeroen
authors.initials: J
authors.lastname: Steenbeek
authors.forename: Kristin
authors.initials: K
authors.lastname: Kaschner
authors.forename: Frida
authors.initials: F
authors.lastname: Ben Rais Lasram
authors.forename: Jacopo
authors.initials: J
authors.lastname: Aguzzi
authors.forename: Enric
authors.initials: E
authors.lastname: Ballesteros
authors.forename: Carlo Nike
authors.initials: CN
authors.lastname: Bianchi
authors.forename: Jordi
authors.initials: J
authors.lastname: Corbera
authors.forename: Thanos
authors.initials: T
authors.lastname: Dailianis
authors.forename: Roberto
authors.initials: R
authors.lastname: Danovaro
authors.forename: Marta
authors.initials: M
authors.lastname: Estrada
authors.forename: Carlo
authors.initials: C
authors.lastname: Froglia
authors.forename: Bella S
authors.initials: BS
authors.lastname: Galil
authors.forename: Josep M
authors.initials: JM
authors.lastname: Gasol
authors.forename: Ruthy
authors.initials: R
authors.lastname: Gertwagen
authors.forename: João
authors.initials: J
authors.lastname: Gil
authors.forename: François
authors.initials: F
authors.lastname: Guilhaumon
authors.forename: Kathleen
authors.initials: K
authors.lastname: Kesner-Reyes
authors.forename: Miltiadis-Spyridon
authors.initials: MS
authors.lastname: Kitsos
authors.forename: Athanasios
authors.initials: A
authors.lastname: Koukouras
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Lampadariou
authors.forename: Elijah
authors.initials: E
authors.lastname: Laxamana
authors.forename: Carlos M
authors.initials: CM
authors.lastname: López-Fé de la Cuadra
authors.forename: Heike K
authors.initials: HK
authors.lastname: Lotze
authors.forename: Daniel
authors.initials: D
authors.lastname: Martin
authors.forename: David
authors.initials: D
authors.lastname: Mouillot
authors.forename: Daniel
authors.initials: D
authors.lastname: Oro
authors.forename: Sasa
authors.initials: S
authors.lastname: Raicevich
authors.forename: Josephine
authors.initials: J
authors.lastname: Rius-Barile
authors.forename: Jose Ignacio
authors.initials: JI
authors.lastname: Saiz-Salinas
authors.forename: Carles
authors.initials: C
authors.lastname: San Vicente
authors.forename: Samuel
authors.initials: S
authors.lastname: Somot
authors.forename: José
authors.initials: J
authors.lastname: Templado
authors.forename: Xavier
authors.initials: X
authors.lastname: Turon
authors.forename: Dimitris
authors.initials: D
authors.lastname: Vafidis
authors.forename: Roger
authors.initials: R
authors.lastname: Villanueva
authors.forename: Eleni
authors.initials: E
authors.lastname: Voultsiadou
mesh_terms: D000818:Animals; D044822:Biodiversity; D002965:Classification; D003196:Computer Graphics; D056727:Endangered Species / Q000706:statistics & numerical data; D008522:Mediterranean Sea; D013997:Time Factors