Consequences of Mediterranean warming events in seagrass (Posidonia oceanica) flowering records

Elena Diaz-Almela*, Nuria Marbà, Carlos M. Duarte

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

147 Scopus citations


Posidonia oceanica, a seagrass endemic to the Mediterranean forms extended and extremely persistent meadows. It is a clonal plant with an apparently irregular pattern of flowering events. An extensive bibliographic review allowed the reconstruction of past flowering events of this species around the Mediterranean, with a high degree of confidence for the last 30 years. The data series on annual flowering prevalence (FP, flowering records per total records) and flowering intensity (FI, fraction of flowering shoots) produced have been compared with four series on Sea Surface annual Temperature maxima (SSTmax) obtained for the NW Mediterranean (averaged from the local data series of l'Estartit and Villefranche: 1957-2005) and for the Eastern, Western basin and the whole Mediterranean sea (extracted from NCEP Reynolds interpolated SST maps: 1982-2005). Significant warming trends are detected in the Mediterranean SST max series, at a rate of (mean+SE) 0.04±0.01°Cyr-1 (R2 = 0.24, P <0.01, N = 24 years), in the Eastern basin series (0.06±0.01° Cyr-1, R2 = 0.43, P <0.001, N = 24 years) and in the long SSTmax series of the NW Mediterranean (0.02±0.01 Cyr-1, R2 = 0.12, P <0.02, N = 49 years). The magnitudes of the SST max anomalies around the absolute warming trend do not increase with time in any SSTmax series. Peaks of FP and FI in the Mediterranean seem to occur each 9-11 years, and coincide with peaks of annual SSTmax. Annual FP and FI increase with the residuals of annual SSTmax warming trend in all Mediterranean basins (FPMED: R2 = 0.27, P <0.01, N = 23; FPNW: R2 = 0.34, P <0.01, N = 31; FPE: R2 = 0.20; P <0.10, N = 23). An outstanding event of P. oceanica flowering across the Mediterranean has been registered in Autumn 2003; 1 month after the highest annual SSTmax recorded in the series. The hypothesis of flowering induction by thermal stress as the possible cause of this relationship is discussed, as well as the potential use of P. oceanica flowering record as early indicator of biological change induced by global sea warming in Mediterranean marine ecosystems.

Original languageEnglish (US)
Pages (from-to)224-235
Number of pages12
JournalGlobal change biology
Issue number1
StatePublished - Jan 2007
Externally publishedYes


  • Angiosperms
  • Biological footprints
  • Climate change
  • Flowering
  • Life history
  • Mediterranean
  • Posidonia oceanica
  • Sea-surface temperature
  • Seagrass
  • seawarming

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Ecology
  • General Environmental Science


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