29/10/2005

Maria Cristina Buia, Stefania Flagella, Ivan Guala, Tara Gravina, Maria Monia Flagella and Maria Michela Cigliano

Abstract

In the framework of a project focused at mapping the Posidonia oceanica meadows all around the Sardinian Island (Central Western Mediterranean Basin), the past production of P. oceanica has been estimated in 85 stations, at shallow (5 –10 m) and deep (22-27m) stands, and at the lower limit (beyond 35m).  The role of environmental (anthropogenic disturbance) and biological (flowering) factors in the timing and magnitude of inter-annual plant production was evaluated on the decadal period 1991-1999. A potential anthropogenic pressure was relevant in decreasing rhizome production: an inter-annual average of 87 ± 4.2 mg rh^-1 y^-1 was recorded in unimpacted localities while a third mean value  (54.4 ± 3 mg rh ^–1 y^-1) was recorded in impacted meadows. The same pattern was observed for the rhizome elongation rate (12 ± 0.5 mm rh^-1 y^-1 against 6.5 ± 0.3 mm rh^-1 y^-1).

Comparing flowering and non-flowering meadows, a significant reproductive decreasing effect was detected in the rhizome compartment. Taking into account only meadows in which anthesis was recorded, no differences in production rates were found in relation to the presence-absence of flowers in the shoots. At plant level, significant differences were found in the year after the flowering event. The results confirm that P. oceanica is a sensitive bio-indicator of environmental alterations. Furthermore, intrinsic factors (i.e. anthesis) can affect its inter-annual variability in growth patterns, suggesting, in this clonal plant, a translocation of storage products within the meadow during the reproductive process.

Proceedings of The Seventh International Conference on the Mediterranean Coastal Environment