Assessment of <i>Posidonia Oceanica</i>(L.) Delile conservation status by standard and putative approaches: the case study of Santa Marinella meadow (Italy, W Mediterranean)

The conservation status of the Posidonia oceanica meadow at Santa Marinella (Rome) was evaluated through both standard (bed density, leaf biometry, "A" coefficient, Leaf Area Index, rhizome production) and biochemical/genetic approaches (total phenol content and Random Amplified Polymorphic DNA marker). The bio-chemical/genetic results are in agreement with those obtained by standard approaches. The bed under study was ranked as a disturbed one, due to its low density, and high heterogeneity in leaf biometry, LAI values, "A" coefficient and primary production. This low quality ranking is confirmed by both mean phenol content in plants, quite high and scattered, and by the low genetic variability in the meadow, with a very high similarity of specimen at a local scale. Hence, these two putative approaches clearly identify the endangered conservation status of the meadow. They link plant biodiversity and ecophysiology to ecosystem 'health'. Furthermore, they are repeatable and standardizable and could be usefully introduced in meadows monitoring to check environmental quality.

Trace metals in <i>Posidonia oceanica</i>in a coastal area of the Ionian Sea (Calabria, Italy)

As, Cd, Cu and Pb concentrations were measured in Posidonia oceanica sampled from meadows located in two sites along the calabrian coast (Ionian Sea, South-eastern Mediterranean). By dating the scales and the rhizome using retrospective procedures (lepidochronology), a time series over a period of nine years (1995-2004) was analysed. Throughout the whole lepidochronological period, the arsenic content in the scales was tenfold higher than that measured in the rhizome with a peak in the lepidochronological year 1996-1997 and a general decrease in the years after. Pb concentration also showed a tendency to decrease with time, whereas the Cd and Cu concentration were increasing. A comparison of the metal level in dead sheaths (scales) and living tissue (leaves) was also performed. The detailed distribution of the trace metals along the leaf axis and in the leaves at different developmental stages (adult, intermediate and juvenile) showed some differences in the metal content. The results also indicate that the arsenic content measured in the leaf blade reflects the high As content measured at the superficial sediments at one of the two sampled sites, demonstrating, for the first time, that P. oceanica would be a good indicator for this element.

Epiphytic Diatom Communities on Sub-Fossil Leaves of <i>Posidonia oceanica</i>Delile in the Graeco-Roman Harbor of Neapolis: A Tool to Explore the Past

The Graeco-Roman harbor of Neapolis (Naples, Italy), chronologically constrained between the late 4th century BC and the 6th century AD, offers a unique sight on relationship between past and present into the history of the marine biodiversity. In fact, the digs expose fossil leaf of Posidonia oceanica with epiphytic communities of microorganisms. Posidonia oceanica is a seagrass endemic to theMediterraneanthat forms large meadows whose remains can persist in the sediment for thousands of years. In this communication, we report results of analyses carried out using both molecular and morphological techniques on sub-fossil leaves of P. oceanica and their associated epiphytic communities.

Comparative analysis of bed density, total phenol content and protein expression pattern in <i>Posidonia oceanica</i>(L.) Delile

Posidonia oceanicameadows are experiencing a progressive decline, and monitoring their status is crucial for the maintenance of theseecosystems. We performed a comparativeanalysis of bed density, total phenol content and protein expression pattern to assess the conservation status ofPosidoniaplants from the S. Marinella (Rome, Italy) meadow. The total phenol content was inversely related to maximum beddensity, confirming the relationship betweenhigh phenol content and stressful conditions. In addition, protein expression pattern profilesshowed that the number of differentially expressed proteins was dramatically reduced in the latest years compared to previous analyses. Our results support the usefulness of integrating solid descriptors, such as phenol content, with novel biochemical/molecular approaches in the monitoring of meadows.

Diet of fish populations in posidonia oceanica meadows off the Island of Ischia (Gulf of Naples, Italy):

The gut contents of fish in three Posidonia oceanica meadows off the island of Ischia (Bay of Naples, Italy) were investigated. A total of 926 individual fish belonging to 28 species was sampled by bottom trawl in the leaf canopy. Labridae, Pomacentridae, Scorpaenidae, and Serranidae were the best represented families (41%, 38%, 8% and 6% of the total number of individuals, respectively). Of the 94 taxa detected in the gut contents, 42 were identified to the species level. The most common food items were decapod crustaceans (15% of the gut contents, on average), copepods (13%), amphipods (14%), brown fragments of P. oceanica (6%), and ostracods (6%). The most abundant species of labridae, Symphodus ocellatus and S. rostratus, showed a broad spectrum of prey. This generalist feeding may positively influence their numerical abundance. Seasonal variations in the diets of fish, also at prey-species level, were demonstrated. The fish taxon plays essentially a macro-carnivore trophic role. In the investigated seagrass meadows the main trophic fluxes start from plant detritus, macrophyta, and microphyta (as primary producers) towards crustacean decapods, copepods, ostracods, and gammarid amphipods (as secondary producers) to fish. A low recycling rate (4%) within the fish community was observed. Larger fish predators (e.g., Sparidae), swimming over the leaf canopy, are the main exporters to adjacent coastal systems.

Variability in patterns of macro-epiphytic leaf community of Posidonia oceanica in the Islands of Kuriate:Western coast of Tunisia

Objective:To test the response of the epiphyte community structure and biomass of the Posidonia oceanica(P.oceanica)leaves to natural disturbance.Methods:Sampling of P.oceanica was carried in winter and summer on three sites in Kuriate Islands(western coast of Tunisia)subject to different environments disturbances.Shoots of P.oceanica were preserved in seawater-formalin(5%)solution for macro-epiphytes species identification in the laboratory.The samples were examined for leaf surface per shoot and the coverage(expressed as a percentage of leaf surface)of each morphological group,then carefully scraped with a razor blade.Epiphytes and scraped leaves were oven-dried at 60℃for 48 h.Biomass was expressed as g dry weight/shoot.Results:The biomass and the percentage cover of macro-epiphytic leaves showed seasonal variation.The highest values of epiphytic leaves were detected in summer whereas the lowest values were registered during winter.ANOVA showed that Kuriate Islands functioned as a single ecosystem in terms assemblage of macro-epiphytic leaves since no significant variation was detected for biomass and percentage cover at the scale site.Our study showed that natural disturbance had no effect on the assemblage distribution and the biomass of macro-epiphyte on the leaves of P.oceanica between the scales of site,whereas variability at the smallest scale was detected.ANOVA showed that exposure to wind and current had no effect on the biomass of macro-epiphytes leaves.Conclusions:Biomass and assemblages of macro-epiphytic leaves of P.oceanica were high in summer and homogenous between all sites investigated.Natural disturbances such as exposure to wind have no effect on the distribution and the biomass of epiphytes on the shallow meadow.