Inconsistent responses to substratum nature in Posidonia oceanica meadows: An integration through complexity levels?

Abstract

The endemic Mediterranean seagrass Posidonia oceanica (L.) Delile can colonise either sand or rock, but mostly builds its own substratum through the formation of the so-called matte (a terrace of interlaced rhizomes and roots trapping sediment). We studied two shallow water meadows in the Ligurian Sea (NW Mediterranean) to examine the influence of the substratum nature on three different levels of ecological complexity: individual (the plant), population (the meadow) and community (the leaf epiphytes). Responses to substratum nature showed inconsistency among the three complexity levels in that leaf surface area (plant level) was lower and shoot density (meadow level) was higher on rock, whereas no major differences were found in epiphyte cover and quali-quantitative composition (community level). We argued that responses are integrated through complexity levels up to dampening substratum influence.

Keywords:

• seagrass
• Posidonia oceanica
• plant phenology
• meadow density
• epiphyte community
• Mediterranean Sea

Acknowledgements

Paolo Guidetti (University of Lecce) provided advice with statistical analyses. Daria Bertoncin (University of Genoa) helped with field activities. Critics by Andrea Peirano (La Spezia) and an anonymous referee greatly improved the paper.