Patterns of seagrass (Posidonia oceanica) flowering in the Western Mediterranean

Elena Diaz-Almela*, Nuria Marbà, Elvira Álvarez, Elena Balestri, Juan M. Ruiz-Fernández, Carlos M. Duarte

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

81 Scopus citations


The intensive reconstructive sampling (1957-2004, 39 localities), a systematic direct observation (1992-2004, 1 locality) and particular direct observations (66 localities) of Posidonia oceanica meadows were analysed together with temporal series of flowering available in the literature (19 localities). This allowed the examination of temporal and spatial variability in annual flowering prevalence (FP, the fraction of meadows flowering in a given year) and of annual meadow flowering intensity (FI, number of inflorescences per shoot) for the period 1979-2004 across the Western Mediterranean, as well as spatial variability of flowering frequency (FF, the fraction of years that a given meadow has flowered) and shoot flowering probability (Pf, fraction of flowering stalks appeared per annual segment). Each year, on an average 17% of the investigated meadows flowered, ranging from 3 to 86% of meadows among the years. The highest annual FP and FI values were obtained in 2003 (FP = 0.86 and mean FI = 0.23 ± 0.03 inflorescences shoot-1). A secondary peak of FP and mean FI occurred 9 years earlier, in 1994 (FP = 0.44 and mean FI = 0.08 ± 0.02). Both peaks of flowering occurred after hot summers. Flowering synchrony in particular years across the Western Mediterranean and clines of increased meadow flowering frequency towards the North and East, suggests the existence of large-scale environmental mechanisms controlling the floral induction. On the other hand, meadow FF and Pf were highly heterogeneous among and within the meadows, indicating that local factors also may play a significant role in flowering induction. When flowering, the Western Mediterranean meadows showed an average 0.11 ± 0.02 inflorescences shoot-1, but FI greatly varied among and along the series (from 0.002 to 0.54 inflorescences shoot-1) and decreased significantly with depth but was independent of meadow shoot density and meadow latitude or longitude. The shoot flowering probability was quite low (0.007 ± 0.002 inflorescences shoot-1 year-1) and exponentially increased with shoot age.

Original languageEnglish (US)
Pages (from-to)723-742
Number of pages20
Issue number4
StatePublished - Feb 2006
Externally publishedYes

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Aquatic Science


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