Patterns of seagrass (Posidonia oceanica) flowering in the Western Mediterranean |
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Authors: | Elena Diaz-Almela Nuria Marbà Elvira Álvarez Elena Balestri Juan M Ruiz-Fernández Carlos M Duarte |
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Institution: | 1. IMEDEA (CSIC-UIB), Grupo de Oceanografía Interdisciplinar, C/Miquel Marqués n° 21, 07190, Esporles, Spain 2. Direcció General de Pesca, Palma de Mallorca, Palma de Mallorca, 07006, Baleares, Spain 3. Dipartamento di Scienze dell’Uomo e dell’Ambiente, 6, I-56126, Pisa, Italy 4. Instituto Espa?ol de Oceanografía (IEO), Centro Oceanográfico de Murcia, C/ Varadero n°1 CP: 30740, San Pedro del Pinatar, Murcia
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Abstract: | 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. |
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