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- Title
Seasonal dynamics of Posidonia oceanica in Magalluf Bay (Mallorca, Spain): Temperature effects on seagrass mortality.
- Authors
Díaz-Almela, Elena; Marbà, Núria; Martínez, Regino; Santiago, Rocío; Duarte, Carlos M.
- Abstract
We recorded seasonal and interannual population dynamics of the endemic Mediterranean seagrass Posidonia oceanica in a shallow meadow, Magalluf Bay, Spain (39°30.25′N, 2°32.59′E), performing direct monthly-bimonthly censuses from June 2001 to November 2004, in 12 permanent plots. Initially, there were 568 ± 54 (mean 6 SE) shoots m22. An average decline of -63 ± 10 SE shoots m−2 yr−1 was detected. Shoot mortality (median: 1.2% month−1; range: 0% to 12.1% month−1) increased in summer, enhanced by seawater temperature. There was also substantial interannual variability characterized by very high mortality in summer-autumn 2001 and in autumn-winter 2003-2004, coinciding with hot summers and meadow flowering in autumn (2001: 2.0% ± 1.4% of shoots; 2003: 53.8% ± 10.4% of shoots), but fruiting and seedling recruitment were only observed in 2004. Annual vegetative recruitment (0.034 ± 0.007 yr−1) was 53 times higher than annual sexual recruitment (0.0006 ± 0.0007 yr−1), and total recruitment (vegetative + sexual) was on average 4.5 times lower than mortality. Specific net population growth was always negative during the study. No seasonality was detected in shoot recruitment (median: 0.002 month−1; range: 0 to 0.021 month−1), which did not correlate with solar radiation or temperature. Shoots recruited during the study had a steeper exponential depletion rate ( rr = -0.34 ± 0.05 SE yr−1) than the global population ( rN0 = -0.16 ± 0.01 SE yr−1). Shoot probability to survive to the next age class ( px) increased with shoot age. Our results suggest that the general decline of P. oceanica meadows could be enhanced by the decadal Mediterranean warming trend.
- Subjects
POSIDONIA oceanica; SEAGRASSES; PLANT population measurement; PLANT mortality; COASTAL ecology
- Publication
Limnology & Oceanography, 2009, Vol 54, Issue 6, p2170
- ISSN
0024-3590
- Publication type
Article
- DOI
10.4319/lo.2009.54.6.2170