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The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.

Coll M, Piroddi C, Steenbeek J, Kaschner K, Ben Rais Lasram F, Aguzzi J, Ballesteros E, Bianchi CN, Corbera J, Dailianis T, Danovaro R, Estrada M, Froglia C, Galil BS, Gasol JM, Gertwagen R, Gil J, Guilhaumon F, Kesner-Reyes K, Kitsos MS, Koukouras A, Lampadariou N, Laxamana E, López-Fé de la Cuadra CM, Lotze HK, Martin D, Mouillot D, Oro D, Raicevich S, Rius-Barile J, Saiz-Salinas JI, San Vicente C, Somot S, Templado J, Turon X, Vafidis D, Villanueva R, Voultsiadou E - PLoS ONE (2010)

Bottom Line: Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea.Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth.This abstract has been translated to other languages (File S1).

View Article: PubMed Central - PubMed

Affiliation: Institut de Ciències del Mar, Scientific Spanish Council (ICM-CSIC), Barcelona, Spain. mcoll@icm.csic.es

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).

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Diel difference in biodiversity estimates obtained with trawling in the Mediterranean Sea.Reported diel differences in estimated biodiversity are obtained by two trawl hauls performed at the autumnal equinox at midday and midnight, in the same sampling location of the western Mediterranean shelf (100 m) and slope (400 m), during October 1999 (NERIT survey). (A) Number of fish, crustaceans, and cephalopod species, and Shannon diversity index (H'), and (B) Waveform analysis of four-day time series of data for catches (left) and light intensity variations as photon fluency rate (PFR; right) for representative decapods. Black rectangles depict the temporal limits of significant increases in catches. Shaded gray rectangles indicate the night duration [adapted from 425].
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pone-0011842-g014: Diel difference in biodiversity estimates obtained with trawling in the Mediterranean Sea.Reported diel differences in estimated biodiversity are obtained by two trawl hauls performed at the autumnal equinox at midday and midnight, in the same sampling location of the western Mediterranean shelf (100 m) and slope (400 m), during October 1999 (NERIT survey). (A) Number of fish, crustaceans, and cephalopod species, and Shannon diversity index (H'), and (B) Waveform analysis of four-day time series of data for catches (left) and light intensity variations as photon fluency rate (PFR; right) for representative decapods. Black rectangles depict the temporal limits of significant increases in catches. Shaded gray rectangles indicate the night duration [adapted from 425].

Mentions: Sampling biases are another source of uncertainty in the estimation of marine biodiversity. In particular, the three-dimensional character of marine ecosystems requires much more study at depths where light penetration is perceived as important but is poorly understood. Light intensity decreases with increasing depth and species perform extensive migrations within the water column or along the seabed. Endobenthic species display rhythms of emergence, including burying or burrowing within the substrate and sheltering in natural holes [425]. Marine species react to light intensity cycles, which may include movements in and out of our sampling windows [426]. Information gathered without attention to such rhythmicity will affect perceived population distribution, biomass, and estimated biodiversity [425]. These issues have been integral to land ecology since the early twentieth century [427] but have been rarely considered in the marine environment. In the Mediterranean, Sardà et al. [428] considered this problem during day-night sampling at and below the end of the twilight zone (1,000 m depth) and observed day-night fluctuations in their catches. Midday and midnight trawl catches at different depths during October showed great differences in fish, cephalopod, and crustacean species composition and relative abundance in the deeper areas (see Figure 14a). Waveform analysis of crustacean catches showed behavioral rhythms that affected presence or absence from catches made at different times during a 24-hour cycle (Figure 14b). Because trawl surveying is one of the commonest methods of sampling in marine waters [429], and is one of the most used in the Mediterranean Sea, future biodiversity studies should correct for the practice of sampling only during daytime. In addition, observations of important diel variation in the fauna associated with seagrasses include a notable increase of species richness and abundance in nighttime samples [430], [431]. This issue brings together the problem of biodiversity and climate change due to expected changes in species migrations and rhythmicity.


The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.

Coll M, Piroddi C, Steenbeek J, Kaschner K, Ben Rais Lasram F, Aguzzi J, Ballesteros E, Bianchi CN, Corbera J, Dailianis T, Danovaro R, Estrada M, Froglia C, Galil BS, Gasol JM, Gertwagen R, Gil J, Guilhaumon F, Kesner-Reyes K, Kitsos MS, Koukouras A, Lampadariou N, Laxamana E, López-Fé de la Cuadra CM, Lotze HK, Martin D, Mouillot D, Oro D, Raicevich S, Rius-Barile J, Saiz-Salinas JI, San Vicente C, Somot S, Templado J, Turon X, Vafidis D, Villanueva R, Voultsiadou E - PLoS ONE (2010)

Diel difference in biodiversity estimates obtained with trawling in the Mediterranean Sea.Reported diel differences in estimated biodiversity are obtained by two trawl hauls performed at the autumnal equinox at midday and midnight, in the same sampling location of the western Mediterranean shelf (100 m) and slope (400 m), during October 1999 (NERIT survey). (A) Number of fish, crustaceans, and cephalopod species, and Shannon diversity index (H'), and (B) Waveform analysis of four-day time series of data for catches (left) and light intensity variations as photon fluency rate (PFR; right) for representative decapods. Black rectangles depict the temporal limits of significant increases in catches. Shaded gray rectangles indicate the night duration [adapted from 425].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2914016&req=5

pone-0011842-g014: Diel difference in biodiversity estimates obtained with trawling in the Mediterranean Sea.Reported diel differences in estimated biodiversity are obtained by two trawl hauls performed at the autumnal equinox at midday and midnight, in the same sampling location of the western Mediterranean shelf (100 m) and slope (400 m), during October 1999 (NERIT survey). (A) Number of fish, crustaceans, and cephalopod species, and Shannon diversity index (H'), and (B) Waveform analysis of four-day time series of data for catches (left) and light intensity variations as photon fluency rate (PFR; right) for representative decapods. Black rectangles depict the temporal limits of significant increases in catches. Shaded gray rectangles indicate the night duration [adapted from 425].
Mentions: Sampling biases are another source of uncertainty in the estimation of marine biodiversity. In particular, the three-dimensional character of marine ecosystems requires much more study at depths where light penetration is perceived as important but is poorly understood. Light intensity decreases with increasing depth and species perform extensive migrations within the water column or along the seabed. Endobenthic species display rhythms of emergence, including burying or burrowing within the substrate and sheltering in natural holes [425]. Marine species react to light intensity cycles, which may include movements in and out of our sampling windows [426]. Information gathered without attention to such rhythmicity will affect perceived population distribution, biomass, and estimated biodiversity [425]. These issues have been integral to land ecology since the early twentieth century [427] but have been rarely considered in the marine environment. In the Mediterranean, Sardà et al. [428] considered this problem during day-night sampling at and below the end of the twilight zone (1,000 m depth) and observed day-night fluctuations in their catches. Midday and midnight trawl catches at different depths during October showed great differences in fish, cephalopod, and crustacean species composition and relative abundance in the deeper areas (see Figure 14a). Waveform analysis of crustacean catches showed behavioral rhythms that affected presence or absence from catches made at different times during a 24-hour cycle (Figure 14b). Because trawl surveying is one of the commonest methods of sampling in marine waters [429], and is one of the most used in the Mediterranean Sea, future biodiversity studies should correct for the practice of sampling only during daytime. In addition, observations of important diel variation in the fauna associated with seagrasses include a notable increase of species richness and abundance in nighttime samples [430], [431]. This issue brings together the problem of biodiversity and climate change due to expected changes in species migrations and rhythmicity.

Bottom Line: Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea.Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth.This abstract has been translated to other languages (File S1).

View Article: PubMed Central - PubMed

Affiliation: Institut de Ciències del Mar, Scientific Spanish Council (ICM-CSIC), Barcelona, Spain. mcoll@icm.csic.es

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).

Show MeSH
Related in: MedlinePlus