Assessment of the ecological structure of Posidonia oceanica (L.) Delile on the northern coast of Lazio, Italy (central Tyrrhenian, Mediterranean)

Valentina Gnisci,Viviana Piermattei,Alessandro Belmonte,Carla Micheli,Simone Bonamano,Selvaggia Cognetti De Martiis,Marco Marcelli

doi:10.3897/italianbotanist.9.46426

Abstract

The ecological structure of Posidonia oceanica (L.) Delile meadows was evaluated on the northern coast of Lazio, Italy (central Tyrrhenian, Mediterranean sea). This is an infra-littoral zone with a wide range of anthropogenic activities and high geo-morphological variability, which reflects heterogeneity in shoot density, leaf morphology and biomass in fragmented patches. Genetic variability in populations corresponds to the formation of 3 sub-clusters, in the diverse impacted zones (north, centre and south), being correlated to the geographical distance between sites. AMOVA estimated a high genetic variation showing 43.05% individual differences within populations with a marked differentiation among the populations (56.9%) indicated by Fst value (0.57). These results revealed the role of the genetic structure of seagrasses for determining selectivity of fragmented habitat, in response to natural drivers. They showed that site-specific self-recruitment is related to biodiversity capacity and to the geo-morphological characteristic of the coast.

Highlights

Coastal areas are characterized by environmental disturbances due to both natural process and anthropogenic activities, with consequent impacts on marine ecosystems (Benoit and Comeau 2005)
The first population has been identified in the northern area, corresponding to sampling sites between Civitavecchia harbour and Marina di Tarquinia, an area mainly dominate by the presence of the Mignone river floodplain
According to other authors (Di Maida et al 2013; Balestri et al 2004; Pergent et al 1995), the meadows that we found are fragmented, discontinuous and are characterized by a wide range of shoot density and substrate coverage which reflect a spatial heterogeneity of P. oceanica meadows, probably due to the complex nature of the seafloor (Tables 1, 2)

Summary

Introduction

Coastal areas are characterized by environmental disturbances due to both natural process and anthropogenic activities, with consequent impacts on marine ecosystems (Benoit and Comeau 2005). In the Mediterranean Sea, P. oceanica forms widespread ecosystems with high levels of biodiversity and productivity (Boudouresque et al 1984; 2006; 2012) and, like other seagrasses, it is important from the ecological, geological and economic point of view (Costanza et al 1997; Spalding et al 2003; Vassallo et al 2013). This plant colonizes different types of substrates (e.g. sand, rocky, etc.) and generates meadows that occur in a wide range of morphotypes, ranging from continuous beds on the seafloor to fragmented patches of different shape and size (Molinier and Picard 1952; Den Hartog 1970; Semroud 1993; Boudouresque et al 2012; Bonhomme et al 2015). A new suite of descriptors has been proposed to assess the ecological status of P. oceanica meadows (Rotini et al 2013), taking into account the physiological features of the plants by means of biochemical (Arnold et al 2012) and genetic markers (Micheli et al 2005, 2015; Procaccini et al 2007; Macreadie et al 2014) as standard indicators

Objectives

Methods

Discussion

Conclusion