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High-resolution sonar system (MBS, SSS, Sub Bottom Profiler) was used to map and characterize Posidonia oceanica meadows, dead matte formations and to long-term monitor its progressive lower limit. Hydro-acoustic techniques allows to quickly acquire, at sufficiently low cost, a synoptic coverage of a large area and a high number of data by mean of non-destructive methods. Hence, they are recommended as useful tools for detecting and characterizing submerged aquatic vegetation.

The endemic Mediterranean seagrass Posidonia oceanica is the only marine phanerogam able to form matte, a biogenic structure representing important long-term “blue carbon” reservoir. Natural and/or anthropogenic factors can lead to the formation of a regressive structure, called “dead matte”, resulting from the disappearance of living shoots in the upper part of the matte. In the framework of TETIDE project (PON01_03112, www.progettotetide.it) a multiple sensors acoustic survey -multibeam sonar (MBS), side scan sonar (SSS), sub-bottom profiler (SBP) -was carried out in a portion of the Gulf of Augusta (Sicily, Southern Ionian Sea). The aim of investigation was to estimate the extent of dead mattethat are present in this area due to pollution from industrial activities over the last several decades. The investigated area covers a surface of about 141 ha from 3.5 m to 21.5 m of depth. MBS and SSS showed an irregular seabed morphology with rock, sand and dead mattestructures delimited by walls up to 2 m high. Dead mattecovers about 58 ha, corresponding to 41% of seabed. The seismo-acoustic data, recorded by SBP, allowed to estimate the thickness of the matteand then to calculate its volume per unit surface area of seabed. The volume of mattevaries from 0.83 m3/m2to 2.68 m3/m2with a mean value of 1.46 m3/m2. The total seabed surface affected by industrial activities concerns an area of about 3,000 ha. Considering the percentage of dead mattecoverage and its volume per unit surface area, a total volume of 18•106m3was estimated. From literature data, the amount of carbon storage inside the matteis 0.034 tons/m3on average, thus we extrapolated that total carbon accumulated is about 612 tons. These “blue carbon” reservoirs should be put into preserving in order to contrast their erosion and the consequent potentially massive CO2release into the atmosphere.

Il brevetto consiste in un sistema a basso impatto ambientale, realizzato interamente in bioplastica, per il fissaggio sul fondo marino in forma rapida ed efficace di organismi vegetali, allo scopo di garantirne l'attecchimento e la crescita, assecondandone la dinamica naturale di sviluppo.

Il brevetto consiste in un sistema a basso impatto ambientale, realizzato interamente in bioplastica, per il fissaggio sul fondo marino in forma rapida ed efficace di organismi vegetali, allo scopo di garantirne l'attecchimento e la crescita, assecondandone la dinamica naturale di sviluppo.

Marine coastal ecosystems are facing structural and functional changes due to the increasing human footprint worldwide, and the assessment of their long-term changes becomes particularly challenging. Measures of change can be done by comparing the observed ecosystem status to a purposely defined reference condition. In this paper, a geospatial modelling approach based on 2D mapping and morphodynamic data was used to predict the natural position of the upper limit (i.e., the landward continuous front) of Posidonia oceanica seagrass meadows settled on soft bottom. This predictive model, formerly developed at the regional spatial scale, was here applied for the first time at the Mediterranean spatial scale in eight coastal areas of Spain, France, Italy, and Greece showing different coastal morphologies and hydrodynamic characteristics, and affected by a number of natural and/or human local disturbances. The model was effective in measuring the regression (i.e., seaward withdrawal) of the meadow upper limit. In all the meadows investigated the upper limit was regressed, laying deeper than the reference condition, with the proportion of regression ranging from 17.7% to 98.9%. The highest values of regression were found in Spain and in France, and were consistent with the highest levels of fragmentation detected with map analysis and of coastal pressures. This geospatial modelling approach represents an effective tool to define the reference conditions when proper pristine areas or historical data are not available, thus allowing the assessment of long-time changes experienced by seagrass ecosystems due to human impacts.

Following the restoration of natural conditions by reducing human pressures, reforestation is currently considered a possible option to accelerate the recovery of seagrass habitats. Long-term monitoring programs theoretically represent an ideal solution to assess whether a reforestation plan has produced the desired results. Here, we report on the performance of a 20 m2 patch of Posidonia oceanica transplanted on dead matte twelve years after transplantation in the Gulf of Palermo, northwestern Sicily. Photo mosaic performed in the area allowed us to detect 23 transplanted patches of both regular and irregular shape, ranging from 0.1 to 2.7 m2 and an overall surface close to 19 m2. Meadow density was 331.6 ± 17.7 shoot m−2 (currently five times higher than the initial value of 66 shoots m−2), and it did not show statistical differences from a close by natural meadow (331.2 ± 14.9). Total primary production, estimated by lepidochronology, varied from 333.0 to 332.7 g dw m2/year, at the transplanted and natural stand, respectively. These results suggest that complete restoration of P. oceanica on dead matte is possible in a relatively short time (a decade), thus representing a good starting point for upscaling the recovery of the degraded meadows in the area.

A model developed for Zostera marina was adapted and used to select suitable areas for Posidonia oceanica transplantation in the Gulf of Palermo, where recent rehabilitation programmes have reduced human pressure. This model consists of three steps: (1) habitat selection, by calculation of the Preliminary Transplant Suitability Index (PTSI); (2) field assessments and test-transplanting, to evaluate the site suitability and to estimate the effects of tearing on transplant units (about 50%); (3) identification of suitable restoration sites, by calculation of the Transplant Suitability Index (TSI). A new parameter was added to the literature model: the number of grids detached, which is linked to factors (hydrodynamic regime, anchoring, fishing) that have a potentially great effect on the final outcome of the transplant. Only one site (TSI = 16) in the Gulf of Palermo was indicated as potentially suitable for restoration with P. oceanica. In this site, a transplant of 40 m2 was implemented. From 2008 to 2014, transplant effectiveness was evaluated in terms of establishment, detachment and mortality of cuttings and shoot density. The long-term monitoring (6 years) allowed us to detect changes in the structural conditions of the transplanted meadow and to identify the possible turning point in P. oceanica recovery (2 years after transplanting). Moreover, 6 years after transplantation the P. oceanica meadow has exceeded the transplant shoot density of about 16%, with a mean and a maximum value of 11.6 and 17 shoots per cutting, respectively.

Di Maida, G., Tomasello, A., Luzzu, F., Scannavino, A., Pirrotta, M., Orestano, C., and Calvo, S. 2011. Discriminating between Posidonia oceanica meadows and sand substratum using multibeam sonar. – ICES Journal of Marine Science, 68: 12–19. High-resolution, multibeam sonar (MBS) (455 kHz) was used to identify two typologies of seabed 8 m deep: Posidonia oceanica meadow and sandy substratum. The results showed that the heterogeneity of the architecture of the P. oceanica canopy and the relatively simple morphology of a sandy substratum can be detected easily by statistical indices such as standard deviation or range-of-beam depth. Based on these indices, an automated classification was performed for seabed mapping. The overall classification accuracy was as high as 99 and 98% in October and January, respectively. The probability that P. oceanica in situ was omitted on the map was

A high-resolution echosounder was used to acquire seismo-acoustic records of P. oceanica dead matte patches in the Gulf of Palermo. Seismo-acoustic profiling enabled detection of dead matte structures that are invisible to visual inspection, being hidden by variable layers of sandy sediment. The thickness of the dead matte measured reaches a maximum of 2.2 m. The mean volume of the matte per unit area of seabed surface (MEIx) varies from 0.2 to 2.2 m 3 /m 2 , with an average value of 1.6 m 3 /m 2 and a total volume estimated at 73,000 m 3 . From literature data and from the volume of dead matte calculated in the present work we estimated that total carbon accumulated in the matte is about 2,484 tons. Seismo-acoustic technologies proves to be a powerful, non-destructive method to measure the thickness, extension, volume of dead matte and its potential carbon content.

Despite the large body of work published in the last two decades on the reproduction of the sea urchin Paracentrotus lividus, the reproductive aspects linked to hydrodynamic conditions and their influence on gonad production remain poorly understood. The present paper aims to evaluate the effect of hydrodynamism on the reproductive cycle of P. lividus. Variability in the gonadosomatic index (GSI) of P. lividus was estimated seasonally from 2007 to 2008 at two shallow sub-littoral flat basaltic areas at Ustica Island (Western Mediterranean). GSI was higher in the sites characterized by low hydrodynamism than in those with high hydrodynamism. Results also suggest a possible role for hydrodynamism in triggering processes of resource limitation (food shortage), probably by interfering with P. lividus feeding activity.

All seagrass species known from the Mediterranean basin have been recorded along the Sicilian coast, where studies have been carried out at a very local scale and information is fragmented or confined to the grey literature. The objective of this article is to summarise and evaluate current knowledge on seagrass species on the Sicilian coasts, providing an overview of species distribution, genetic diversity, biology and ecology, based on the literature and unpublished data. Most literature studies have been carried out on Posidonia oceanica meadows because of their wide distribution, complexity and ecological importance. In this study, the analyses carried out on P. oceanica structural and functional features show that the Sicilian meadows are in good condition with respect to the Mediterranean average, probably because of relatively low anthropogenic pressure and favourable ecological conditions. The available data on this species summarised in this article represent an important starting point from which to build effective plans for understanding levels of environmental threats and for supporting conservation strategies for these important ecosystems. Conversely, the limited information available on other seagrasses only allows the description of some structural and functional features, and does not permit to drive overall conclusions on their general health status.

In the Mediterranean Sea, high densities of the sea urchins Paracentrotus lividus and Arbacia lixula may promote and maintain formation of areas overgrazed by sea urchins, usually referred to as urchin barrens, leading to drastic changes in ecosystem functioning. Urchin barrens are habitats of low primary production and habitat structure, that negatively affect local biodiversity. At Plemmirio MPA, abundance of both sea urchin species increased dramatically after the start of enforcement in 2005 consequently triggering the formation of “barren” seascape, evidence of a desertification process. This study focuses on the results of a high-resolution Side scan sonar (Klein 3900) surveying carried out in the July of 2010 to acquire sonograms along the shallow rocky coasts of the Plemmirio MPA. The track lines were performed by R/V “Antonino Borzì” using a navigation software that showed as background a morpho-bathymetric map previously acquired by a Multibeam Sonar System (Reson SeaBat 8125). Side scan sonar mapping confirmed that urchin barrens were present within the MPA, above all in the B zone. Our results put in evidence that sonar is an excellent tool for mapping and monitoring barren habitats.