Multiscale lepidochronological analysis of Posidonia oceanica (L.) Delile rhizome production in a northwestern Mediterranean coastal area

Abstract

The influence of geographical location and depth on the rhizome primary production of Posidonia oceanica was investigated over different spatial scales: large (the whole Ligurian coast), medium (the individual meadows) and small (the sites of each individual meadow). Six Posidonia oceanica meadows, separated by 30 to 60 km from each other, were sampled in summer 2002 along the 300 km of the Ligurian coast (NW Mediterranean). In each meadow, two sites, 100 to 200 m apart, were chosen and in each site 10 orthotrophic shoots were sampled at three depth zones: shallow (1.5–10 m), intermediate (10–15 m), and deep (15–26 m). The annual primary production of the rhizomes was reconstructed through lepidochronology for three previous years (1999, 2000 and 2001). Three-way analysis of variance showed no significant differences in rhizome production at small scale whereas differences at medium scale were significant. These differences were strictly confined at the shallow depths suggesting that local impacts from the coastline are likely to be responsible for the variability in the rhizome primary production among meadows.

Keywords:

• Posidonia oceanica
• lepidochronology
• primary production
• multiscale analysis
• Mediterranean Sea
• Ligurian coast

Acknowledgements

This work was partially done within the framework of RIPO Project (Italian Ministry for the Environment and CoNISMa). We are grateful to S. Bava, G. Franci, L. Mangialajo and S. Schiaparelli (University of Genoa) for their participation in field activities.