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Endemic Mediterranean seagrass Posidonia oceanica is highly endangered today as it lives in a narrow infralittoral zone intensely exposed to human impact. P. oceanica beds are especially endangered in the Adriatic Sea as the central and northern Adriatic could be considered as a naturally suboptimal area for P. oceanica growth. In this research, we used some standard descriptors of Posidonia meadows at different locations and depths and determined the biochemical parameters (phenolic compounds, photosynthetic pigments, and enzyme activities) in its leaves in order to find possible correlations among the measured parameters and environmental conditions. Photosynthetic pigments were shown to be sensitive biomarkers in the assessment of P. oceanica response to different light conditions, but more research is needed to elucidate the impact of other environmental factors. Overall, the results of this research show that the studied parameters are good bioindicators of a meadow's environmental state, but it is necessary to analyze a number of diverse indicators together to properly characterize the state of a particular P. oceanica meadow. This approach would be very useful in the determination of P. oceanica conservation status, which is the first step towards improving monitoring protocols and implementing appropriate conservation measures. [ABSTRACT FROM AUTHOR]

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Copyright of Monografies de la Societat ďHistòria Natural de les Balears is the property of Societat d'Historia Natural de les Balears and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of the study was to evaluate the effectiveness of the application of multiple environmental descriptors through an asymmetrical sampling design to detect possible impacts related to the Costa Concordia event on the coastal marine environment. The Costa Concordia shipwreck occurred on a submerged rocky reef in the north-western Mediterranean Sea and the wreck was removed 2 years later. To achieve the proposed objective two main coastal ecosystems, the seagrass Posidonia oceanica and coralligenous assemblages were studied using two ecological indices, PREI and ESCA, respectively. Both indices show a lower ecological quality in the disturbed sites compared with the control ones. Differences between the disturbed and control sites observed in both studied ecosystems would seem to indicate an increase of turbidity around the shipwreck as the most plausible cause of impact. The concurrent use of different ecological indices and asymmetrical sampling designs allowed detection of differences in ecological quality of the disturbed sites compared with the controls. This approach may represent an interesting tool to be employed in impact evaluation studies. [ABSTRACT FROM PUBLISHER]

Allochthonous alga Caulerpa taxifolia (Vahl) C. Agardh has been present in the Mediterranean Sea for over thirty years. Different types of negative impacts on species and entire communities have been well documented; however, studies of its impact on meiofauna are scarce. The aim of this study was to investigate the structure of meiofauna in the area impacted by the invasive alga, C. taxifolia, in the Stari Grad Bay (43.1833°N, 16.5838°E), Adriatic Sea, in December 2008 (autumn) and June 2009 (spring). To establish the nature of the impact on meiofauna inhabiting the sediment of the studied area, we compared the structure of meiofauna inhabiting bare sediments with the structure of meiofauna inhabiting sediments beneath the autochthonous seagrass ( Posidonia oceanica (L.) Delile) and invasive alga ( C. taxifolia). Furthermore, comparisons between epibiontic meiofauna inhabiting alga and seagrass were made. Multivariate statistical analysis revealed differences in the composition of meiofaunal assemblages inhabiting unvegetated and vegetated sediments ( P. oceanica and C. taxifolia), during spring. However, no significant differences in composition of meiofauna in sediments inhabited by the invasive alga and those inhabited by the native seagrass were detected. However, the observed impact of C. taxifolia on meiofauna in sediment could be characterized as negative, due to the observed decrease of meiofaunal density in sediment inhabited by the aforementioned alga. Considering the epibiontic meiofauna, our study showed that P. oceanica increases the meiofaunal density in the Stari Grad Bay ten times as much as the allochthonous, invasive C. taxifolia. However, the biodiversity of higher taxonomic categories has not been affected. [ABSTRACT FROM AUTHOR]

Here we review the multiple interactions between the endemic Mediterranean seagrass, Posidonia oceanica, and coastal geomorphologic processes as an outstanding example of biogeomorphology, taking into account recent advances in the field. Seagrass meadows are among the most important elements for the functioning of marine coastal ecosystems, and represent a major focus for research and conservation. Being considered a priority habitat, P. oceanica meadows are protected by several European Union directives and national laws. In this paper we examine: the role of sedimentary features in controlling the development of the meadows; the interplay between P. oceanica leaf litter (i.e. beached necromass) cast ashore and erosional-depositional processes on the beaches; the interactions between meadows and nearshore hydrodynamics, and; possible linkages between geomorphological features of the seafloor and the architecture of meadows. Finally, we provide perspectives for future research on P. oceanica and other Mediterranean seagrass meadows in a biogeomorphological context with specific reference to climate change. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A study was undertaken of the patterns of spatial variability, epiphytic biomass and distribution of epiphytic fauna and flora of Posidonia oceanica. Samples were taken at four stations located approximately 4 km apart, exposed to different current conditions. Stations A and B, situated near the Oued Mimoun tidal channel with its relatively strong bi-directional flows, were affected by high current tide. The other two stations, North Oued Mimoun (L1) and South Oued Mimoun (L2), were located further from the channel, in low current tide conditions. Sampling was conducted in the Attaya area of Kerkennah Island (Tunisia) in August 2009 at depths between 2 and 3 m, with the results indicating differences among the stations. Shoot density decreased when exposed to high levels of hydrodynamic activity generated by current tides whereas the epiphytic biomass of P. oceanica leaves decreased at sheltered stations located far from the channel. Epiphytic algae such as Heterokontophyta, Rhodophyta and Chlorophyta, and epiphytic fauna represented by Bryozoa, Hydrozoa, Annelida, Porifera and Tunicata, dominated the epiphytic assemblages and were abundant at the station most exposed to high current tide hydrodynamics. Cyanobacteria, however, were dominant in stations exposed to low current tide. [ABSTRACT FROM AUTHOR]

The study evaluated patterns of spatial variability of mobile macro-invertebrate assemblages associated withPosidonia oceanicaleaves within a meadow at three different depths and three different coastal wave-exposures. A total of 171 taxa was found, among them two Nemertea, 65 Mollusca, 91 Arthropoda, eight Annelida and five Echinodermata. The total number of taxa per sample was higher in intermediate and deep stands than in shallow ones, while no significant differences among coastal wave-exposures were observed. Multivariate analyses detected significant differences in the structure of assemblages in relation to depth and coastal wave-exposure. Mollusca were more abundant in shallow stands, while Crustacea and Echinodermata increased in intermediate and deep stands. Moreover, patterns of spatial variability changed with depth: shallow and intermediate assemblages showed high small-scale (tens of metres apart) variability, while deep assemblages showed high variability at intermediate scale (hundreds of metres apart). [ABSTRACT FROM AUTHOR]

A new alien species of Caulerpa, corresponding morphologically to Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini, already known from Turkey, Sicily, and Cyprus, was first discovered in Malta in June 2013. The original record was of but a few fronds, and surveys made during winter at the same site did not locate any plants. A survey conducted during July 2014, however, located two patches of the alga occupying a total area of ca 125m2 in the 4-6m depth range, with a mean frond density of 276.3 (± 51.21 SD) per m2. Also in July 2014, two patches with a total of 520 fronds in an area of 0.37m2 at 14-15m depth were found at a second site ca 7.4 km along-coast distance from the first site. The alien algae formed part of a photophilic assemblage growing on rock in clearings adjacent to Posidonia oceanica (Linnaeus) Delile stands. The most likely source of the Maltese populations is Sicily, and the most likely vector is recreational and/or commercial shipping. [ABSTRACT FROM AUTHOR]

The aim of this survey was to study the cover and the composition of macroepiphytic species on the leaves of Posidonia oceanica in the east of Tunisia. Surveys were conducted in December 2009 (winter period), March (spring period) and August 2010 (summer period) in a fringing reef located in Chebba. At each sampling date, 15 adult leaves were randomly collected and divided into basal and apical parts. The inner face of each part was examined with ocular glasses and microscope to estimate species cover by orthogonal projection. PERMANOVA and ANOSIM were used to test for differences of cover between sampling dates and leaf parts. SIMPER, cluster analysis, and PCA were used to ordinate species assemblages. Comparison of epiphytic cover along leaf blades showed significant differences for all groups, except cyanophycea, with high cover of hydrozoans and bryozoans in the basal part and high cover of algae in the apical part. The species composition and cover also vary with sampling date; minimum values were detected in December and the epiphytic community was composed of a few pioneer species, whereas maximum epiphytic cover values were registered in August, with the epiphytic community being composed of a more mature and more diverse community, termed 'climax'. The main regulatory factors for this distribution are discussed. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the temporal dynamics of rhizome epiphytes and sessile animals living on the rhizomes of the seagrass Posidonia oceanica in the east of Tunisia. Surveys were conducted in October 2009, and in January, April and August 2010 on a fringing reef located in Chebba. Rhizomes were sampled by SCUBA diving at three stations. Samples were examined with a microscope to estimate the cover of macroinvertebrate and macroalgal organisms on the top 10 cm of each rhizome. Results revealed a high diversity of epiphytes on P. oceanica rhizomes with a dominance of red and brown algae, ascidians, and bryozoans. Distinct temporal changes were observed in Oued Lafrann, with a high January cover (winter period) for all groups. These winter increases can be attributed to: (i) the low phenological parameters of P. oceanica in winter that reduce the effects of shading, (ii) life cycles of the epiphytes and invertebrates, (iii) water motion and (iv) grazing. [ABSTRACT FROM AUTHOR]

Many studies have been performed to investigate invasions in marine habitats, but little is known about the consequences of the simultaneous presence of more alien organisms in the same area. The aims of this work were to quantify the colonization of alien macroalgal species co-occurring in a harbour area of the northwestern Mediterranean Sea and to compare the structure of native phytobenthic communities in invaded and control areas. To achieve these objectives, invasions of four introduced macroalgae ( Acrothamnion preissii , Womersleyella setacea , Caulerpa taxifolia and C. racemosa ) have been quantified in three different habitats (rocks, matte and Posidonia oceanica meadows) throughout one year. A combination of multivariate and univariate analyses was used to detect differences among macroalgal assemblages in control and invaded areas. Results showed that introduced species represented a very high percentage of macroalgal abundance in all the habitats studied. In Posidonia oceanica meadows, the macroalgal assemblage was almost completely represented by introduced turf-forming Rhodophyta. On rocks and matte, invasive species constituted about 50% of the cover of the macroalgal assemblage throughout the year. Both univariate and multivariate analysis showed that, in the study area, the structure of macroalgal assemblages was very different in invaded and control areas. Total percentage cover and diversity were lower in invaded areas than in control areas in all three habitats investigated and temporal modifications in macroalgal assemblages appeared to be linked to the growth cycle of invaders. The results of this study show that the co-occurrence of more alien algae does not seem to limit the total cover of invaders, which reached similar values independently of the dominant species. [ABSTRACT FROM AUTHOR]

Some species of seagrasses (e.g., Zostera marina and Posidonia oceanica) have declined in the Mediterranean, at least locally. Others are progressing, helped by sea warming, such as Cymodocea nodosa and the non-native Halophila stipulacea. The decline of one seagrass can favor another seagrass. All in all, the decline of seagrasses could be less extensive and less general than claimed by some authors. Natural recolonization (cuttings and seedlings) has been more rapid and more widespread than was thought in the 20th century; however, it is sometimes insufficient, which justifies transplanting operations. Many techniques have been proposed to restore Mediterranean seagrass meadows. However, setting aside the short-term failure or half-success of experimental operations, long-term monitoring has usually been lacking, suggesting that possible failures were considered not worthy of a scientific paper. Many transplanting operations (e.g., P. oceanica) have been carried out at sites where the species had never previously been present. Replacing the natural ecosystem (e.g., sandy bottoms, sublittoral reefs) with P. oceanica is obviously inappropriate in most cases. This presupposes ignorance of the fact that the diversity of ecosystems is one of the bases of the biodiversity concept. In order to prevent the possibility of seagrass transplanting from being misused as a pretext for further destruction, a guide for the proper conduct of transplanting is proposed. [ABSTRACT FROM AUTHOR]

Seagrasses as Posidonia oceanica reproduce mostly by vegetative propagation, which can reduce genetic variability within populations. Since, in clonally propagated species, insurgence of genetic variability can be determined by the activity of transposable elements, we have estimated the activity of such repeat elements by measuring their expression level in the leaves of plants from a Mediterranean site, for which Illumina complementary DNA (cDNA) sequence reads (produced from RNAs isolated by leaves of plants from deep and shallow meadows) were publicly available. Firstly, we produced a collection of retrotransposon-related sequences and then mapped Illumina cDNA reads onto these sequences. With this approach, it was evident that Posidonia retrotransposons are, in general, barely expressed; only nine elements resulted transcribed at levels comparable with those of reference genes encoding tubulins and actins. Differences in transcript abundance were observed according to the superfamily and the lineage to which the retrotransposons belonged. Only small differences were observed between retrotransposon expression levels in leaves of shallow and deep Posidonia meadow stands, whereas one TAR/Tork element resulted differentially expressed in deep plants exposed to heat. It can be concluded that, in P. oceanica, the contribution of retrotransposon activity to genetic variability is reduced, although the nine specific active elements could actually produce new structural variations. [ABSTRACT FROM AUTHOR]