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Hybridization is common among plants and has been crucial in the evolution of many aquatic plant groups. However, hybrid individuals are often difficult to identify, particularly in the marine environment. We aim to confirm a hybrid origin between two seagrass species for a morphologically-intermediate plant observed in shallow subtidal environments near Perth, Western Australia. Both morphological measures and DNA markers demonstrated a clear case for hybridization among two sympatric Posidonia species from different species complexes: Posidonia australis and P. coriacea. All five samples with the intermediate morphology had the same multilocus genotype (MLG), providing evidence that it resulted from a single hybridization event, followed by local clonal (rhizome) expansion. This result highlights weak reproductive barriers within the genus Posidonia, a trait common among other seagrass genera with sympatric ranges, apparently overlapping morphologies and low phylogenetic divergence.

Posidonia oceanica is a marine phanerogam that buries a significant part of its belowground production forming an organic bioconstruction known as mat. Despite Posidonia seagrass mats have proven to be reliable archives of long-term environmental change, palaeoecological studies using seagrass archives are still scarce. Here we reconstruct four millennia of environmental dynamics in the NE coast of Spain by analysing the carbon and nitrogen stable isotopic composition of P. oceanica sheaths, the proportion of different seagrass organs throughout the seagrass mat and other sedimentological proxies. The palaeoenvironmental reconstruction informs on long-term ecosystem productivity and nutrient loading, which have been linked to global (e.g., solar radiation) and local (e.g., land-use changes) factors. The long-term environmental records obtained are compared with previous palaeoecological records obtained for the area, showing a common environmental history. First, a relative seagrass ecosystem stability at ~4000 and 2000 cal. yr BP. Then, after a productivity peak at ~1400-800 cal. yr BP, productivity shows an abrupt decline to unprecedented low values. The fluctuations in ecosystem productivity are likely explained by increases in nutrient inputs related to human activities – mostly in the bay watershed – concomitantly with changes in total solar radiation. Cumulative anthropogenic stressors after Roman times may have started to affect ecosystem resilience, dynamics and productivity, with more abrupt regime shifts during the last millennium. These results add into recent research showing the potential of seagrass archives in reconstructing environmental change and seagrass post-disturbance dynamics, hence providing unvaluable information for improving the efficiency in managing these key coastal ecosystems.

The use of seaweed biomass for energy production is under consideration in several countries of the world. This paper, after a review of other scientific papers on the subject, aims at evaluating the pros and cons of the use of Posidonia oceanica as biomass source for anaerobic digestion (AD) in territorial contexts where the presence of large quantities of beached seagrass is also a problem for the tourism economy. The case chosen is the Sardinian town of Alghero. The presence of large Posidonia leaves deposits on the beaches is responsible for some inconveniences, such as the foul odour derived from the natural decomposition process. Other problems are the reduced usability and the untidy appearance of the beach, which lays within the town’s urban context. This condition reduces the competitiveness of the hotels, bars and restaurants that are located on the seaside promenade and the quality of life of nearby residents and tourists. The methodology used to define and analyse the problem is based on the following steps: territorial analysis, evaluation of the available quantities, regulatory issues, economic and social impacts evaluation. Although the overall quantity of fresh Posidonia evaluated by the municipal authorities is of approximately 200 tonnes per year, other calculation methods show that the potential quantity of raw biomass is far superior (up to 3.500 tons). It is possible then to determine the potential CH 4 yield and the consequent thermal/electric output after an AD process. Based on the quantitative data of our analysis we are able to determine a cost structure and to evaluate, from the economic point of view, the adequacy of the choice of installing an AD plant fuelled with Posidonia oceanica in the town’s industrial area. The study has a preliminary approach, as the data used for the biogas production estimation are derived from laboratory tests. Furthermore, the effects of the removal of the seagrass from the beaches, provided that the operations are carried out in a sustainable and non-destructive way, could improve the quality of life of residents and tourists in the nearby areas. Based on our findings we can suggest that the usage of Posidonia oceanica in the studied case is potentially interesting as a resource for biogas production although further research is needed to validate this solution. The future research efforts will have to concentrate on several issues: definition of the available biomass quantities, evaluation of the biogas yield of Posidonia on an industrial scale, available co-digestion solutions, treatment and possible use of the digestate sludge.

Seagrasses are marine angiosperms that have evolved from terrestrial ancestors. Photosynthetic activity on seed has been studied before in Posidonia genus. T. testudinum and P. oceanica share some evolutionary aspects as they live in more stable environments. As in P. oceanica , T. testudinim seed is also green-coloured suggesting the presence of photosynthetic pigments. Here, the photosynthetic activity in the T. testudinum seed was examined. Measurements of photosynthetic production, pigment content and maximum PSII photochemical efficiency (Fv: Fm) were determined. Epifluorescence microscopy analysis was used to obtain evidence of photosynthetic structures within the seed. This study revealed photosynthetic activity in seed epidermis which increased linearly with increasing irradiance. T. testudinum seed displayed a higher Photosynthetic efficiency (α), and lower light saturated photosynthesis (P. max), saturation irradiance (Ek), and compensation irradiance (Ec) compared to adult leaves. Epifluorescence microscopy images of the seeds showed an epidermis composed of relatively small, regular cells, tending towards a rectangular shape, containing abundant chloroplasts. The photobiological behaviour results in the T. testudinum seed being strongly adapted to colonize environments with reduced light availability. Photosynthetic activity in T. testudinum seed shed some light on seagrass dispersal and expansion mechanisms.

Talitrid amphipods (sandhoppers and beach fleas) are typical of the supralittoral zone. They are known to thrive on stranded materials, including detrital marine angiosperms and macroalgae, as well as occasional dead animals. In this work, the gut microbiota of five species of talitrid amphipods (Talitrus saltator, Talorchestia ugolinii, Sardorchestia pelecaniformis, Orchestia montagui and Orchestia stephenseni) collected in Sardinia (Italy) has been investigated through: i) metabarcoding analysis of the amplified 16S rRNA V4 region; and ii) quantification of family 48 glycosyl hydrolase genes (GHF48), involved in cellulose degradation. Results indicate that, though talitrid gut biodiversity is not directly related to taxon or sampling locality, the animals' digestive tracts may host species-specific bacterial communities. In particular, gut microbiota of O. montagui, an inhabitant of Posidonia banquettes and macro-algae mat, showed the greatest differences in taxonomic composition and the highest proportion of GHF48 genes with respect to 16S rRNA genes. These results suggest that the different talitrid species may host species-specific bacterial communities whose function could partially reflect the different microhabitats and food preferences of their host.

Este artículo contiene 8 páginas, 1 tabla, 3 figuras., Seagrass restoration has been suggested as a Blue Carbon (BC) strategy for climate change mitigation. For Nationally Determined Contributions (NDC) and carbon crediting schemes, BC projects need to demonstrate ‘additionality’, that is enhanced CO2 sequestration and/or avoided greenhouse gas emissions following management actions. This typically requires determining soil carbon accumulation rates (CAR), which is often done using radionuclides or surface elevation tables to estimate sedimentation rates. Here we undertook a case study, using 210Pb and 14C dating, to detect possible changes in Corg stocks and CAR following the loss and partial recovery of Posidonia seagrass meadows in South Australia since 1980–90s. The 210Pb data revealed a lack of accumulation of excess 210Pb in most sites, suggesting negligible accumulation of sediments, intense mixing of the upper layers, or accumulation of reworked sediments, precluding the estimation of reliable CAR at decadal time scales. This limitation was also encountered with 14C. The inability to compare sites over analogous periods of time prevented quantifying differences in soil Corg sequestration, thereby to demonstrate additionality. The lack of significant differences in soil Corg stocks among sites which never suffered seagrass loss, those showing recovery and those with no recovery (5.7 ± 1.2, 4.5 ± 0.7 and 3.3 ± 0.3 kg Corg m-2 within the top meter, respectively) also precluded estimates of soil Corg gains or losses. Our findings demonstrate that, while 210Pb and 14C provide important information on sediment deposition dynamics, it is not straightforward to demonstrate additionality using radionuclides in low depositional seagrass habitats exposed to hydrodynamic energy, features which may be encountered in seagrass sites. We provide insights for the selection of suitable habitats for seagrass BC projects, suggest possible alternative methods for estimating additionality, and discuss the implications of the findings for the implementation of seagrass BC strategies to mitigate greenhouse gas emissions., This research was funded by Edith Cowan University, the Environmental Protection Authority of South Australia and SA Water, through ECU-Industry grant (G1001729). OS, PM and PL were supported by ARC (DE170101524, LE170100219). Funding was provided to PM through an Australian Research Council LIEF Project (LE170100219) and by the Generalitat de Catalunya (Grant 2017 SGR-1588). This work is contributing to the ICTA ‘‘Unit of Excellence’’ (MinECo, MDM2015- 0552).

The Trealla Limestone, which forms a veneer of foraminiferal-rich limestone and covers over 4000 km2 of the tectonically stable Southern Carnarvon Platform, contains the oldest evidence for seagrass meadows known in Western Australia. It belongs to Lower Tf1 Letter Stage (based on larger benthic foraminifers) of the Burdigalian, within interval 19–16 Ma, and is the only Miocene unit on the platform. The Trealla Limestone here is coeval to the deeper water lower part of the much thicker Trealla Limestone in the Exmouth Sub-basin to the northwest. A seagrass-meadow depositional environment is indicated by most of the studied microfacies based on comparisons with modern sediment composition and foraminiferal assemblages found in innermost shelf seagrass banks between 23°S and 32°S on the present Western Australian coast. Some levels in the Trealla Limestone on the platform (e.g. with abundant miliolid foraminifers, and absence of coral debris) probably were deposited in and around dense seagrass meadows similar to those present today in the metahaline (40–55 ppt salinity) reaches of Shark Bay; whereas other levels (e.g. coral floatstone) were deposited under normal-marine conditions. Based on comparisons with modern carbonate sediment and biota in the region, the biogenic composition of the Trealla Limestone on the platform suggests winter minimum sea-surface temperatures within the range of 17–22 °C. The Nullabor Limestone in the Eucla Basin, at 10° further south on the southern Australian margin, is similar, at least in part, in composition and age to the Trealla Limestone on the Southern Carnarvon Platform. Both may have been deposited during a Burdigalian sea-level rise, and during part of the Miocene climate optimum recognized elsewhere. Sediment composition and foraminiferal assemblages (including epiphytic types) found in the Trealla and Nullabor limestones are similar to those in the modern seagrass banks of the region. This suggests that seagrasses similar to the extensive Posidonia and Amphibolus stands, which are dominant today between 25°S and 35°S along the Western Australian coast, were widespread during the Burdigalian.

The study of a Posidonia sinuosa sedimentary archive has delivered a millenary record of environmental change in Cockburn Sound (Western Australia). Ecosystem change is a major environmental problem challenging sustainable coastal development worldwide, and this study shows baseline trends and shifts in ecological processes in coastal ecosystems under environmental stress. The concentrations and fluxes of biogeochemical elements over the last 3,500 years indicate that important changes in ecosystem dynamics occurred over the last 1,000 years, in particular after ~1900's, probably related to establishment of seagrass meadows in the area and to local and regional human activities (industry and coastal development), respectively. The establishment of seagrasses ~1,000 years ago in the area of study is supported by the appearance of Posidonia fibres from ~40 cm soil depth until the core top, higher δ13C values indicating a larger contribution of seagrass-matter to the soil organic carbon pool, and increased concentration of fine sediments driven by the effect of seagrass canopy in enhancing sedimentation. The comparison of organic carbon, nutrients and metal concentrations and fluxes between pre- and post-establishment of seagrasses shows that seagrass establishment resulted in up to 9-fold increase in the soil biogeochemical sink. In ~1900's, shifts in the concentrations of metals, carbonates, organic carbon, sediment grain size, and δ13C and δ15N values of the organic matter were detected, demonstrating an alteration in seagrass ecosystem functioning following the onset of European settlement. Anthropogenic activities, and in particular the construction of a causeway in 1970's, enhanced seagrass soil organic carbon and metal accumulation rates by 36- and 39-fold, respectively, showing that human-made structures can enhance the biogeochemical sink capacity of seagrasses. Here we reconstruct the impact of human activities on seagrass ecosystem dynamics and blue carbon, which can inform local management of Cockburn Sound and seagrass conservation for climate change mitigation and adaptation.

The high organic carbon (OC) stores in seagrass meadows have led to their recognition as significant Blue Carbon sinks, though the diagenetic conditions that enable OC retention in seagrass soils remain poorly understood. In this study, seagrass soils were sampled from a Posidonia australis meadow in Oyster Harbour (Albany; south-western Australia) to investigate the preservation of sedimentary OC. We analysed soil characteristics (colour, grain size and redox potential), radiocarbon age, and characterised the soil organic matter (OM) using solid state CP/MAS 13C NMR spectroscopy to examine the preservation of OM down the soil profile. There was minimal change in organic composition over 1,700 years of accumulation, indicating long-term OM preservation. Primarily, this preservation appears to be driven by the recalcitrance of seagrass detritus buried in anoxic soils. The majority (70–83%) of total sedimentary OM comprised components directly attributable to seagrass origins (lignin, carbohydrate and black carbon-like matter), while the remainder consisted mostly of protein, some of which may have been present in seagrass biomass, along with likely contributions from algae and microbes. Although black carbon originates from organic matter combustion, here we provide evidence that the 13C NMR signal identified as black carbon-like matter in our soils is possibly associated with seagrass-derived organic matter consisting of degraded lignin products or other non-pyrogenic aromatics. The increase in the relative abundance of this black carbon-like matter with aging suggests its selective preservation. The relative abundances of carbohydrates significantly decreased with age down core (i.e. they appeared to be selectively decomposed), while lignin and protein did not show any quantitative changes in relative abundance (non-selective preservation). These findings demonstrate the exceptional preservation of P. australis derived OC, which contributes to our understanding of the higher OC storage capacity of Posidonia compared to other seagrass species.

The Great Australian Bight is a large carbonate cold water environment located on the central and western portions of the southern Australia. Seagrasses (Posidonia sp.) and macroalgae benthic habitats are widely distributed in the shallow water environment of southern Australia, contributing to the carbonate factory. This study investigated the distribution of modern benthic foraminiferal assemblages in the microtidal wave-dominated inner-shelf of Esperance Bay (southwestern Australia), that lies on the western margin of the Great Australian Bight. Benthic foraminifera were taxonomically identified and biotic parameters (species richness, density, Fisher-α index, Shannon–Weaver index, dominance) were calculated. Multivariate analyses (Hierarchical Cluster Analysis, Principal Component Analysis) were performed to understand foraminiferal distribution in the context of environmental conditions. Four main Foraminiferal assemblages have been recognized: (I) a nearshore assemblage of dense seagrass meadow, dominated by Lamellodiscorbis dimidiatus, Elphidium craticulatum, Elphidium crispum, Cibicidoides lobatulus, II) a second assemblage associated with unvegetated seabed (approximately 30 m depth) with Lamellodiscorbis dimidiatus, Elphidium crispum, Quinqueloculina disparilis, III) a third assemblage in the central sector of the bay, characterized by a discontinuous and mixed seagrass-algae coverage with Lamellodiscorbis dimidiatus, Elphidium crispum, Elphidium macellum, Cibicides refulgens, and Quinqueloculina poeyana, and IV) an epiphytic assemblage of transitional zone from the coastline to the upper limit of a mixed seagrass-algae meadow, dominated by Elphidium crispum, Chrysalidinella dimorpha, Planulinoides biconcava, Planoglabratella opercularis, Rugobolivinella elegans. The spatial distribution of the four assemblages appears closely related to sediment texture, seagrass cover and depth, but it is also influenced by the shoreface morphology and the hydrodynamic energy. The understanding of the ecological parameters that influence benthic foraminiferal distribution, composition and assemblage structure within seagrass meadows is useful for paleoecological and paleoenvironmental interpretations.

This paper focuses on the detection of Posidonia oceanica in underwater images. The input image is split into a set of patches that are classified as depicting Posidonia or not. Two different Neural Networks are proposed to perform the classification. A region growing algorithm able to accurately detect the contours of the Posidonia oceanica from the output of the classifier is also described. The experimental results, performed using images gathered in coastal areas of Mallorca (Spain), show that our proposal reaches the 95.5% of accuracy, the 95.8% of precision and the 95.4% of recall with only a 4.6% of fallout. When compared to previous studies, these results surpass those of methods based on Machine Learning and are comparable, even superior in some cases, to recent Deep Learning approaches. The advantages in terms of computational requirements, which are crucial in underwater robotics, are also highlighted. In particular, our proposal works up to 8.6 times faster than other Deep Learning methods.

12 páginas, 5 figuras, 4 tablas, 4 apéndices., The study of a Posidonia australis sedimentary archive has provided a record of changes in element concentrations (Al, Fe, Mn, Pb, Zn, Cr, Cd, Co, As, Cu, Ni and S) over the last 3000 years in the Australian marine environment. Human-derived contamination in Oyster Harbor (SWAustralia) started ~100 years ago (AD ~1900) and exponentially increased until present. This appears to be related to European colonization of Australia and the subsequent impact of human activities, namely mining, coal and metal production, and extensive agriculture. Two contamination periods of different magnitude have been identified: Expansion period (EXP, AD ~1900–1970) and Establishment period (EST, AD ~1970 to present). Enrichments of chemical elementswith respect to baseline concentrations (in samples older than ~115 cal years BP) were found for all elements studied in both periods, except for Ni, As and S. The highest enrichment factors were obtained for the EST period (ranging from 1.3-fold increase in Cu to 7.2-fold in Zn concentrations) compared to the EXP period (1.1-fold increase for Cu and Cr to 2.4-fold increase for Pb). Zinc, Pb, Mn and Co concentrations during both periods were 2- to 7-fold higher than baseline levels. This study demonstrates the value of Posidonia mats as long-termarchives of element concentrations and trends in coastal ecosystems. We also provide preliminary evidence on the potential for Posidonia meadows to act as significant long-term biogeochemical sinks of chemical elements., Thisworkwas supported by the ECU Faculty Research Grant Scheme, the ECU Early Career Research Grant Scheme, and the CSIRO Flagship Marine & Coastal Carbon Biogeochemical Cluster with funding from the CSIRO Flagship Collaboration Fund. PMwas supported by a Gledden Visiting Fellowship and AAO by Obra Social “la Caixa”.

Sweet spot identification in underexplored shale gas basins needs to be based on a limited amount of data on shale properties in combination with upfront geological characterization and modelling, because actual production data is usually absent. Multidisciplinary reservoir characterization and integration of modelling approaches can aid initial site selection for exploratory drilling and de-risk exploration efforts. In this study, the potential of hydrocarbon production across underexplored shale basins is analyzed using key performance indicators. A mean indicator is defined as the harmonic mean of three performance indicators that describe the potential for hydrocarbon generation, storage, and flow stimulation. The performance indicators are based on a limited number of local shale properties, i.e. vitrinite reflectance, porosity, depth, thickness, sorbed gas content and brittleness index. Values for the indicators are calculated relative to prospective North American shales (Marcellus, Bakken, Haynesville and Barnett), so that the mean indicator can be used to rank the prospectivity of an underexplored shale relative to hydrocarbon producing shales. The mean performance indicator is also used to map out the potential for gas production in the underexplored Posidonia Shale Formation in the West Netherlands Basin. The analysis shows that the performance indicator is lower for the Posidonia than for the North American Shales, mainly due to low maturity and brittleness. Local maxima of the indicator correlate with local maxima in vitrinite reflectance and depth. Besides the low potential for flow stimulation, the potential for hydrocarbon generation and storage capacity of the Posidonia are comparable to oil-window thermal-maturity Barnett Shale. Upfront simulations of hydraulic fracture properties and gas production in the Posidonia Shale Formation are in rough agreement with observed average gas flow for Barnett wells in non-core areas that are oil mature. It shows that key performance indicators can be applied to underexplored shales to quantify prospectivity and map out sweet spots across shale basins.

In the recent decades, the rational management of agricultural residues and industrial byproducts presented an interesting approach. In this context, the valorization of Posidonia oceanica leaves and balls, a widely available marine residue in Tunisia, was carried out. This biomass was found to be an interesting source of cellulose. Thus, the cleaned and ground raw material was delignified and bleached. The extraction with alkali solution (yield 60% of cellulose) followed by bleaching gave 45% of pure cellulose. The resulting extracted cellulose was characterized by various techniques. Then, different nanocrystal suspensions were prepared from the P. oceanica cellulose and holocellulose and characterized by different methods such as TEM and nano-sizer, which gave their morphological parameters (length and size). The obtained nanocrystals were compared with those usually prepared from wood and annual plants, and it was shown that promising nanomaterials can be prepared.

Dunbarella marine marker horizon has significant stratigraphical importance for the Lublin Coal Basin — LCB (Poland). It sets the boundary between Westphalian A (Langsettian) and B (Duckmantian) and between paralic and limnic sedimentation at the same time. This marker horizon is also the base of the Lublin formation deposits where a main multi-seam coal deposits can be found. The horizon correlates with the Clay Cross Marine Band (England), the Katharina horizon (Germany, The Netherlands) and the Quaregnon horizon (Belgium). The paleontological material taken from recent boreholes provides new data about development of the Dunbarella horizon of the LCB. 32 bivalve species have been encountered and can be assigned to 28 genera. Edmondia, Posidonia, Sanguinolites, Polidevcia, Phestia and Dunbarella are the most abundant in all profiles. Slightly less numerous are gastropods (9 genera), represented mainly by Glabrocingulum and Euphemites, and cephalopods (4 genera), represented mainly by Gastrioceras and Anthracoceras. Very frequent, although not so diverse, are the brachiopods, primarily inarticulate and represented almost exclusively by Lingula. Studies of macrofauna showed the presence of marker species and faunal assemblages typical of the Dunbarella horizon. A distinctive feature of this horizon which was observed was the cyclic sedimentation and associated variability of the fauna spectrum. This is typical for Westphalian marine horizons of Northwestern Europe, including those correlated with the Dunbarella horizon.

Seagrasses of the genus Posidonia are known to be particularly vulnerable to disturbances because damaged plants are slow to recover and recolonisation by seedlings is rare. Reestablishment of denuded areas by propagules is therefore likely to rely on maximising the survivorship of seedlings or vegetative fragments. This study investigated methods for enhancing growth rates of P. australis seedlings using hormones and nutrients, which may increase establishment success of plants used for rehabilitation. Laboratory experiments compared seedlings treated with different combinations and concentrations of hormones (auxin, cytokinin, gibberellic acid) and nutrients (N, P, K). Growth rates of healthy seedlings were not significantly enhanced by any treatment and negative effects of 30 mg/L auxin and nutrients were evident. Any positive effects of hormones were limited to improving survival of small seedlings with the addition of low concentrations of auxin (5 mg/L) or cytokinin (2.5 mg/L), and 0.1 or 20 mg/L gibberellic acid. A review of hormone effects on seagrasses found few consistent results among studies, in part due to differences in methods, species and hormones used. The few studies that were comparable tended to have conflicting results and we found relatively little evidence for positive effects of hormones on the growth of any seagrass. A final experiment demonstrated that the greatest influence on growth of P. australis seedlings was the initial size of seedlings (just after being released from the fruit). Large seedlings produced significantly larger plants (1.5–2.3 fold for various above and below ground measures) over 232 d than did initially small seedlings. Rehabilitation programmes should therefore use the largest seedlings available to help maximise the chances of success.

Mediterranean seagrass Posidonia oceanica is used as a 'biological quality element' in the long-term monitoring programmes of the Water Framework Directive (WFD 2000/60/EC) for the evaluation of ecological status of coastal waters. Due to its low resilience to anthropogenic pressures, P. oceanica meadows have disappeared irreversibly along some of the Mediterranean coasts. The main objective of this survey, is therefore to compare the ecological status of coastal waters and P. oceanica meadows in two islands from Eastern (Gokceada, Turkey) and Western (Corsica, France) Mediterranean Sea based on the Posidonia Biotic Index (BiPo) and the Vitality Index besides concentrating on: (i) their consistency in different environmental conditions present in the Mediterranean Sea, (ii) their effectiveness to discriminate the ecological status of coastal waters in relation to different anthropogenic pressures and (iii) their application capacity to initiate long-term data series for monitoring the evolution of the meadows in less evaluated regions (i.e. from the Eastern Mediterranean). The measurements of several descriptors of P. oceanica are interpreted based on the BiPo and the Vitality indices for 2 regions; 9 sites from Gokceada and 15 sites from Corsica exposed to different human pressures. The mean BiPo and Vitality indices are higher in Corsica than in Gokceada, where the values correspond to a "good" status for Corsica and a "moderate" status in Gokceada. The application of these biotic indices showed their feasibility and comparability to assess the ecological status in different environmental conditions. Significant relationships between the scores of Anthropization index and the EQR values of the BiPo index (r = - 0.745, p < 0.01) and the Vitality index (r = - 0.702, p < 0.01) highlighted their efficiency to determine the seagrass degradation in the sites subjected to higher pressure levels. It can be assumed that this study initiates the development of long-term data series and also meets the essential data deficiency in less evaluated regions.

We compiled published data in peer-review articles and grey literature reports, which we appended with our own data, to assess the changes in areal extent, cover and shoot density that P. oceanica meadows have experienced between years 1842 and 2009 in the Mediterranean basin. Our results demonstrate an overall tendency towards decline of the areal extent, cover and shoot density of P. oceanica meadows during the last 50. years, the period with the largest availability of records. Available estimates indicated that between 13% and 50% of seagrass areal extent of P. oceanica in the Mediterranean basin appear to be lost, and that the remaining meadows of the Mediterranean may have thinned shoot density by 50% for the last 20. years and have became more fragmented. Considering the changes quantified in P. oceanica areal extent, cover and density, about 6.9% of the potential P. oceanica vegetation would have been lost annually over the last 50. years. The loss of P. oceanica meadows in the Mediterranean may have lead to a substantial (between 11% and 52%) reduction of the capacity of this key coastal ecosystem to sequester carbon in the last 50. years, hence reducing the carbon sink capacity of the entire Mediterranean Sea. The major causes of P. oceanica loss were widespread local disturbances, but recently, global disturbances, such as climate change and the spread of invasive exotic species, were also seriously threatening Posidonia meadows in the Mediterranean. These findings urgently call for implementation of management measures aiming at mitigating coastal deterioration by combining local and global actions. © 2014 Elsevier Ltd., This study was funded by the projects SESAME (EU, Project no: 036949, Integrated Project of the Thematic Priority: 6.3 Global Change and Ecosystems), OPERA (EU, Project no: 308393, Collaborative Project of Theme ENV.2012.6.2-1), EstresX (Spanish Ministry of Economy and Competitivness, Ref. CTM2012-32603) and GAEM (Government of the Balearic Islands). A Gledden Visiting Senior Fellowship from the Institute of Advanced Studies, University of Western Australia, partially supported NM.

This paper describes the results of a two-year monitoring study examining the pollution of the sea urchin Paracentrotus lividus by polycyclic aromatic hydrocarbons (PAHs) in Sardinia. GC–ITMS analysis of sea urchin gonads showed the presence of 11 and 12 PAHs in the samples of Capo Pecora, and Capitana, respectively. Fluorene, naphthalene and its two degradation products, 1-methyl-naphthalene, and 2-methyl-naphthalene, were detected in all samples analyzed. The ΣPAH residues showed a similar trend over the two-year sampling period. Furthermore, the residues in the first year were slightly higher than in the second year. The information obtained by the multivariate statistical analysis PLS-DA allowed for the determination of samples based on field site and varying habitat types (rocky reef, and Posidonia seabed). The results of this study showed that Posidonia sea urchins are contaminated by high molecular weight PAHs and that Capitana samples are more contaminated due to a higher level of human activity in the area.

The suitability of Posidonia oceanica as feedstock for anaerobic digestion process was evaluated carrying out several biochemical methane potential tests. No clear evidence of process inhibition were observed during tests. Nevertheless, the very high lignin content of Posidonia did not allow the organic matter solubilization by microbial lithic enzymes, thus limiting the effectiveness of the anaerobic digestion process. Therefore, Posidonia was subjected to thermal (132 °C) and thermo-chemical pre-treatment in order to increase its anaerobic digestibility. The opportunity of reducing biomass stress due to the high salinity of Posidonia suspension (performing a washing operation before anaerobic digestion) was also evaluated. Thermal treatment and salt removal allowed only a limited increase in anaerobic digestion process efficiency. Whilst thermo-chemical pre-treatment at 132 °C in presence of HCl 0.40% resulted in a relevant increase of Posidonia biodegradability leading to a specific methane production higher than 90 mL/gVS and a VS removal efficiency of about 50%.

The persistence of seagrass meadows reflects variation in factors that influence their productivity and consumption. Sea urchins (Amblypneustes pallidus) can over-graze seagrass (Amphibolis antarctica) to create sparse meadows in South Australia, but this effect is not observed in adjacent Posidonia sinuosa meadows despite greater densities of inhabiting urchins. To test the effect of urchin grazing on seagrass biomass, we elevated the density of urchins in meadows of A. antarctica and P. sinuosa and quantified seagrass decline. Urchins removed similar amounts of biomass from both seagrass species, but the loss of leaf meristems was 11-times greater in A. antarctica than in P. sinuosa. In a second experiment to assess the recovery of seagrass, we simulated urchin grazing by clipping seagrass to mimic impacts measured in the first experiment, as well as completely removing all above ground biomass in one treatment. Following simulated grazing, P. sinuosa showed a rapid trajectory toward recovery, while A. antarctica meadows continued to decline relative to control treatments. While both A. antarctica and P. sinuosa were susceptible to heavy grazing loss, consumption of the exposed meristems of A. antarctica appears to reduce its capacity to recover, which may increase its vulnerability to long-term habitat phase-shifts and associated cascading ecosystem changes.

An acoustic method, a vertically oriented Sidescan Sonar (SSSv), is used to detect and map Posidonia oceanica meadows in the bay of Agua Amarga (SE of the Mediterranean coast of Spain). Sidescan sonar, among other active hydroacoustic techniques, has shown its ability to detect, map and monitor seagrass based on its acoustic backscatter; however, some limitations linked to its power based approach have been reported in the literature. Our method is based on the SSSv measurement of canopy height distribution, making the most use of the SSSv acoustic data and using existing algorithms as statistical mapping methods. The results show a spatially coherent and statistically consistent classification. The comparison with groundtruthing is difficult due to the steep variations in the seafloor cover found in the area of interest, nevertheless the validation is successful (proving low-order discrimination) in a zone with a large range of depth variations (0−25 m).

Rapid, easy and low cost semi-quantitative methods were tested to study the heterotrophic bacterial community of Posidonia oceanica meadows and were compared to techniques commonly used in microbial ecology. Free and pore-water bacterial densities were estimated by luminescence, and principal enzymatic activities, metabolic capabilities and benthic mineralisation processes were studied with microtitration methods: ApiZym galleries, Biolog microplates and BART™ tests. Bacterial densities varied little throughout the year and were around 5.0·105 and 6.0·106 cells ml−1 of free and pore-water, respectively. The combined use of the ApiZym gallery and the Biolog microtitration plate permitted highlighting bacterial enzymatic activities susceptible to degrade principal organic polymers present in the Posidonia meadow, and to correlate these enzymatic activities to the subsequent potential utilization of resulting monomeric products. Levels of enzymatic activities (1.80–8.36 nmolessubstrates h−1 ml−1) and energetic bacterial metabolism (1.80–6.42 nmolessubstrates h−1 ml−1) presented seasonality relying on the temperature regime and on the primary production (Posidonia and phytoplankton). Main mineralization processes of buried organic matter through sulfate and iron reduction activities were successfully detected. Despite the complexity of the studied ecosystem, results obtained by this semi-quantitative approach, compared to studies applying commonly used methods in microbial ecology, highlighted the same bacterial dominant key processes. Their low cost, rapid and easy use, and the low level of expertise and sophistication they require means that these techniques are of use to many employed in environmental surveys.

Microsporogenesis, megasporogenesis and embryogenesis were studied using Posidonia australis as representative among three sympatric species in the seagrass genus Posidonia ( P. australis , P. coriacea and P. sinuosa ). Each flower spikelet has only one ovary (this is common to the three species). With P. australis the microspore is initially globular then becomes baton-like and finally matures into stick- or thread-like pollen. The mature embryo sac is four-nucleate comprising one polar nucleus, one egg cell and two syngerids, however as the embryo sac becomes mature, only three nucleate cells dominate, comprising one central cell (polar nucleus), one egg cell and one syngerid. After fertilization, the fertilized cell divides into two longitudinally. The basal cell ceases division, vacuolates and may function as a conduit for nutrients to the upper, dividing cell(s). The upper cell firstly divides transversely into two cells and then longitudinally into four cells, that in turn develops into a globular zygotic embryo attached by the basal cell. The globular zygotic embryo morphs into a shuttle-shaped embryo and loses attachment to the basal cell. This developmental sequence also appears to apply to P. coriacea and P. sinuosa .

Quantitative sampling in combination with classification of fish species into six major feeding guilds revealed the position and contribution of non-indigenous species (NIS) in the food web of Posidonia oceanica and sandy habitats in an area of the eastern Mediterranean. In P. oceanica beds and on sandy bottoms 10 and five species, respectively, were non-indigenous fish of Indo-Pacific origin. The proportional contribution of NIS individuals on P. oceanica beds was lower than that of sandy bottoms (12.7 vs. 20.4%) a pattern that also followed for biomass (13.6 vs. 23.4%), indicating that low diverse systems may be more liable to introductions than species-rich communities. The two habitats had similar fish feeding guilds, but the biomass contribution from NIS varied within each guild, indicating different degrees of impact on the available resources. This study showed that only few non-indigenous fish species contributed to the differences in biomass between habitats. No support could be found in postulating that taxonomic affiliation could predict invasion success. Size was considered highly important due to habitat shift of species with increased size. Two of the aspects considered in this study, the chance of establishing vs. the chance of being very dominant will depend upon competitive abilities strongly coupled to size and grounds for habitat shift. However, success of establishment will also depend on appropriate food resources in the recipient community as well as competitive abilities and level of competition in the food web within habitats.

The posidoniform bivalve species Posidonia becheri Bronn, 1828, has been identified for the first time in the Lower Carboniferous (Tournaisian) sandy limestone-dark grey shale deposits of Hakkari Province, south-eastern Turkey. Palaeogeographically, this area was located at the northern tip of the Gondwanan Arabian Palaeozoic platform at the southern Palaeotethyan margin during the Carboniferous. The closest localities to this new occurrence are the Lower Carboniferous of northern England, Germany (Kulm Basin), Poland (Walbrzych Basin), Northwest Belgium, Spain (Cantabrian Mountains), Portugal, and Northwest Turkey (Zonguldak Basin). All these locations are considered parts of the Avalonian or Perigondwanan terranes, and were located NW of the Palaeotethys. Hence, our new finding from the SE Palaeotethyan margin, together with the data from Morocco, indicates that this posidoniid bivalve had probably been transported by oceanic currents in its larval stage to lower palaeolatitudes (about 50° S) within the Palaeotethyan Ocean during the Early Carboniferous, or alternatively, the northern Arabian platform margin was located in lower latitudes than previously suggested.

Residues of the marine plant posidonia (Posidonia oceanica, PO) beached in tourist zones represent a great environmental, economical, social and hygienic problem in the Mediterranean Basin, in general, and in the Apulia Region in particular, because of the great disturb to the bathers and population, and the high costs that the administrations have to bear for their removal and disposal. In the present paper, Authors determined the heating values of leaves and fibres of PO, the main offshore residues found on beaches, and, meantime, composted those residues with mowing and olive pruning wood. The final composts were characterized for pH, electrical conductivity, elemental composition, dynamic respiration index, phytotoxicity, fluorescence and infrared spectroscopic fingerprints. The aim of the paper was to investigate the composting and energy recovery of PO leaves and fibres in order to suggest alternative solutions to the landfill when offshore residues have to be removed from recreational beaches. The fibrous portion of PO residues showed heating values close to those of other biofuels, thus suggesting a possible utilization as source of energy. At the same time, compost obtained from both PO wastes showed high quality features on condition that the electrical conductivity and Na content are lowered by a correct management of wetting during the composting.

Posidonia oceanica Delile is an endemic of the Mediterranean Sea. P. oceanica is one of the few marine higher plants of the Mediterranean and plays a significant role in coastal ecosystems of the Mediterranean Sea. In the past, a number of phytochemical investigations with different focus were carried out. The results of these investigations are summarized and appraised here. A total of 51 natural products was reported from P. oceanica, including phenols, phenylmethane derivatives, phenylethane derivatives, phenylpropane derivatives and their esters, chalkones, flavonols, 5α-cholestanes, and cholest-5-enes. Many of the compounds reported for P. oceanica were, however, not detected by appropriate phytochemical methods and some most probably represent artifacts and are no genuine natural products.

The use of data, including bathymetry, backscatter intensity and the angular response of backscatter intensity, collected using multibeam sonar (MBS) systems to recognise seabed types was evaluated in the inner shelf of central western Sardinia (western Mediterranean sea), a site characterised by a complex seabed including sandy and gravelly sediments, Posidonia oceanica seagrass beds growing on hardgrounds (i.e. biogenic carbonates) and sedimentary substrates. A MBS survey was carried out in order to collect bathymetric and acoustic backscatter data. Ground-truth data in the form of grab samples and diver observations were collected at 57 stations, 41 of which were in non-vegetated sedimentary substrate and 16 of which were in P. oceanica beds. Sediment samples were analysed for grain size. Statistical comparison between MBS backscatter and grain size data showed that backscatter intensity is strongly affected by sediment grain size, being directly correlated to the weight percent of the coarse fraction (1–16 mm) and inversely correlated to weight percent of the finer sediments (0.016–0.5 mm). Factor analysis of grain size and acoustic data identified three sedimentary facies: sandy gravels (SG), gravelly sands (GS) and slightly gravelly muddy sands (SGMS). Each facies showed different acoustic responses in terms of backscatter intensity and shape of the angular response curves. Differences in backscatter intensity among five seabed types, including the three sediment types identified by factor analysis and P. oceanica beds, growing on hardgrounds and sedimentary substrates, were tested by analysis of variance. P. oceanica on hardgrounds, P. oceanica on sedimentary substrates and GS exhibited values of relative backscatter intensity within the same range and, consequently, it was not possible to distinguish Posidonia beds and gravelly sands only on the basis of backscatter data. The similarity of backscatter intensity from P. oceanica growing on different substrates suggests that the acoustic response is mainly linked to the leaf canopy rather than the substrate it is growing on. A map of seabed classification, including sediment types and seagrass distribution was produced through a combination of information derived from backscatter data and morphological features derived from multibeam bathymetry, which were validated by ground-truth data.

Translocation of carbon (C) and nitrogen (N) was investigated in response to shading of the seagrass Posidonia sinuosa in control (ambient light) and shade (below minimum light requirement) treatments after 10 d shading. A mature leaf was incubated in situ in 13C- and 15N-enriched seawater for 2 h and the appearance of the isotopes in the young leaf and adjacent rhizome monitored over 29 d. C and N isotopes gradually reduced in the mature leaf: of 15N contained in the entire shoot (mature leaf, young leaf and 4 cm rhizome), 95% (control) and 97% (shade) was found in the mature leaf after 2 h incubation and only 75% and 60% remained in the mature leaf after 29 d; 98% and 94% of 13C was found in the mature leaf after 2 h, and it had reduced to 36% and 44% after 29 d. This corresponded to an equal increase in the young leaf + rhizome indicating that the mature leaf is a source of these nutrients to the young leaf and rhizome. C translocation from mature leaves was not significantly affected by the shade treatment. In contrast, there was an increase in 15N taken up by the mature leaves (1.9× higher in the shade), the percent of 15N translocated to the young leaf and rhizome (24% in control and 40% in shade) and N concentration in the young leaf (1.24% control and 1.41% shade) and rhizome (0.86% control and 0.99% shade). Resorption of C and N was also estimated from changes in the total C and N content of the mature leaf over 29 d. N resorption from the mature leaf contributed up to 63% of young leaf N requirements in the control treatment but only 41% in the shade treatment. We conclude that uptake and translocation of N by mature leaves is a response to shading in P. sinuosa and would provide additional N to growing leaves, enhancing light harvesting efficiency.

The sensitivity of Posidonia oceanica at environmental variations is well known since long time. The capability of quantifying environmental space-time modification is very interesting in order to establish seagrasses cover changes. The use of aerial colour photos, after the necessary manipulations, can be useful for investigative aims. Thanks to ortorectification and mosaicing processes, a georeferenced space representative of the study area is reconstructed without optical distortions. The images are processed to highlight the area covered by P. oceanica and the recif barriere in particular. This permitted to obtain a set of themes representative of the underwater vegetable cover and to analyze the space-time changes between 1987 and 1999.

Elemental carbon and nitrogen levels and isotope ratios were assessed in different biological compartments of a Northwest (NW) Mediterranean bay to trace the various sources of nutrient input from natural (river runoffs) and anthropogenic (harbor outflows, fish farms and urban sewage outfall) sources. Samples from transplanted mussels and natural sea grass communities (Posidonia oceanica leaves and epiphytes) were harvested from different locations throughout the bay during the touristic summer and rainy seasons. The results from the nitrogen analysis revealed that sewage and harbor outflow promote higher nitrogen levels, enrichment of 15N in the tissues, and a higher seasonal variability in sea grass and epiphytes. In mussel tissues, the d15N was also influenced by sewage and harbor outflow, whereas d13C was influenced by terrestrial inputs. These results suggest that natural and anthropogenic nutrient inputs have a temporary and localized influence and affect the sensitivity of natural isotopic ratios to changes in hydrologic conditions, especially to rain and tourism.

In the present work, we studied the chemical modification of Posidonia with maleic (AM) and phthalic (AP) anhydrides, and in the absence of any solvent. We used tripropylamine (TPA) as a catalyst and the mixture underwent an ultrasonic pretreatment. The influence of ultrasonic pretreating time, reaction time, temperature, anhydride concentration, was investigated. The extent of maleation and phthalation was measured by the percent of ester groups (TE), which increased when there was a parallel increment of anhydride concentration, reaction time, and temperature. Evidence of maleation and phthalation of the waste Posidonia biomass was provided by FT-IR and CP/MAS 13 C NMR. Thermogravimetric investigation of chemically modified Posidonia indicated a better thermal stability in comparison with the untreated Posidonia .

The present work describes the preparation of new chelating materials derived from Posidonia for adsorption of heavy metal ions and dye in aqueous solution. The first part of this report deals with the chemical modification of Posidonia with succinic anhydride. Thus, we have obtained materials with various succinyl groups contents (from 29.8 to 39.2%). The obtained materials were characterized by infrared and CP/MAS (13)C-RMN spectroscopy. The rate of succinyl content of the modified Posidonia was determined by saponification. The second part is devoted to the evaluation of the adsorption capacity of metal ions such as Pb(2+) and dye such as direct red 75 (DR75) for raw and modified Posidonia materials. Two possible ways for the adsorption of these pollutants are studied: adsorption of each pollutant alone onto these supports, and cumulative adsorption of both metal ions and dye on the same supports. In the last case, the pollutant is adsorbed successively from two different solutions. The effects of pollutants concentration, support dose, pH, contact time and temperature on adsorption of each pollutant were evaluated. The results showed that the raw and modified Posidonia show a high capacity for Pb(2+) adsorption. The capacity of modified Posidonia saturated with Pb(2+) to adsorb DR75 was found 147.12 mg g(-1). While the adsorption capacity of the nonsaturated modified Posidonia was equal to 81.63 mg g(-1). The pseudo-second-order model was the best to represent adsorption kinetics of DR75. The pseudo-first-order model would be better for fitting the adsorption kinetic process of Pb(2+) onto raw and modified Posidonia. The adsorption isotherms of Pb(2+) could be described by the Jossens equation model. Any of the tested models can describe the adsorption of DR75 onto the studied materials. These results confirm that the adsorption of DR75 from aqueous solution was multilayer.

This paper describes the PREI (Posidonia oceanica Rapid Easy Index), a method used to assess the ecological status of seawater along Mediterranean French coasts. The PREI was drawn up according to the requirements of the Water Framework Directive (WFD 2000/60/EC) and was tested on 24 and 18 stations in PACA (Provence-Alpes-Cotes d'Azur) and Corsica, respectively. The PREI is based on five metrics: shoot density, shoot leaf surface area, E/L ratio (epiphytic biomass/leaf biomass), depth of lower limit, and type of this lower limit. The 42 studied stations were classified in the first four levels of status: high, good, moderate and poor. The PREI values ranged between 0.280 and 0.847; this classification is in accordance with our field knowledge and with our knowledge of the literature. The PREI was validated regarding human pressure levels (r(2)=0.74). (http://eurex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2000: 327:0001:0072:EN:PDF). (C) 2009 Elsevier Ltd. All rights reserved.

Productivity measurements from carbon uptake have been suggested as good indicators of the physiological health of seagrasses. As seagrasses acquire carbon from the surrounding water, the rate of uptake often provide a good measure of the efficiency at which seagrasses meet their resource demands for growth. This rate is often used to assess the photosynthetic efficiency of the plants, a proxy for the physiological status of seagrass. This has special relevance to the Adelaide region as over 5000 ha of seagrasses have been lost from Adelaide coastal waters over the last 70 years, with much of this loss attributed to nutrient inputs from wastewater, industrial and stormwater discharges. This study used an in-situ inorganic carbon isotope-labelling and spike approach to obtain ecologically relevant estimates of seasonal variability in carbon uptake and its allocation in two species of temperate seagrass common to this coast ( Amphibolis antarctica and Posidonia angustifolia ). Uptake of carbon by the seagrass complex (leaves, roots, phytoplankton and epiphytes) was affected by both season and species. Carbon uptake rates of phytoplankton were generally higher than other components of the system. Uptake rates ranged from 0.01 mg C g − 1 DW h − 1 (summer) to 0.61 mg C g − 1 DW h − 1 (spring) in Posidonia and 0.02 mg C g − 1 DW h − 1 (summer) to 0.93 mg C g − 1 DW h − 1 (winter) in Amphibolis . Carbon uptake by the Amphibolis complex was higher than in the Posidonia complex. The Amphibolis complex had higher uptake rates in summer whereas the Posidonia complex was higher in spring. Fine sediments probably from a nearby dredging operation, are likely to have resulted in lower carbon uptake and a reduction in the above-ground and below-ground biomass in summer.

Free-drifting fragments represent an abundant potential source of recruits to the invasive alga, Caulerpa taxifolia . Here we examine how this fragment pool interacts with real and artificial habitat structure in estuarine environments. Specifically, we tested two hypotheses; (i) the fragment pool was unrelated to the structural complexity of Caulerpa beds and, (ii) fragment accumulation and retention was unrelated to canopy height of seagrass meadows. We examined fragment accumulation and retention using artificial seagrass units (ASUs) mimicking seagrasses with long (20 cm) leaves ( Posidonia/Zostera ) and short (5 cm) leaves ( Halophila spp.). Both hypotheses were rejected. Fragment biomass was a positive function of the blade height and cover of Caulerpa taxifolia . ASUs with structure had greater fragment accumulation than controls, but we did not detect differences between ASUs of different canopy heights. However, fragment accumulation within ASUs was strongly affected by site, with the site experiencing the strongest tidal flows accumulating the most fragments. Structurally complex ASUs also retained more fragments relative to the bare control, but the degree of complexity did not affect retention and we could not distinguish between ASUs of different canopy height and the procedural control (metal frame lacking ‘leaves’). Overall, we conclude that the entanglement of C. taxifolia fragments is facilitated by structurally complex habitat and likely contributes to the successful establishment of this invader.

Addition of nutrients to sediments has been proposed as a means of enhancing transplantation success in seagrasses. The effects of nutrient and iron additions to natural sediments on the growth and morphology of Posidonia australis transplants were evaluated in underwater plots in two contrasting environments: a coastal embayment (Princess Royal Harbour) with sandy sediments and little riverine input, and an estuary (Oyster Harbour) with organic-rich sediments and subject to seasonal river flow from a large rural catchment. Sixty six planting units spaced 1 m apart were transplanted in situ in each location. Nitrogen (N) and phosphorus (P) were added in a randomized factorial design using slow release fertilizer granules at the start of the experiment and repeated every 4–5 months for 2 years. In a concurrent experiment, chelated iron Fe EDTA was added to modify the sediment sulphur cycle . In Oyster Harbour, the addition of N significantly increased leaf N concentrations but reduced total biomass and biomass of leaves. Addition of P significantly increased leaf P concentrations and number of living leaves per transplant, leaf area, leaf length, length of longest rhizome axis and total rhizome length. Combined N + P addition resulted in a significant increase in leaf P concentrations and leaf area per plant only. In Princess Royal Harbour, addition of N produced significant increases in leaf variables (total and leaf biomass, number of shoots and living leaves, leaf area, and leaf length) but there were no significant differences observed in below ground plant parts (rhizomes). Addition of P had no significant effects on any growth measurements. Addition of N + P combined increased number of living leaves and leaf area significantly. δ15N in mature leaf tissue were significantly more negative for N and N + P treatments at both locations. Our results indicated that N limitation was occurring in the coastal embayment, Princess Royal Harbour whereas in the more estuarine Oyster Harbour, P was limiting plant growth. Addition of FeEDTA produced equivocal results at both sites and we suggest these results are confounded by the addition of N and C in the EDTA. We caution the use of nutrient addition to transplants of slow growing seagrasses such as P. australis without a thorough understanding of the nutrient status of the system, estuarine or coastal embayment, in which they are to be transplanted.

Changes in photosynthetic activity during transplantation of Posidoniasinuosa Cambridge et Kuo, from Cockburn Sound, Western Australia, were assessed using a Diving-PAM fluorometer. Two transplantation methods, sprigs and plugs (5, 10 and 15 cm diameter) were examined and photosynthetic activity was compared before, during and after transplantation. Maximum electron transport rate (ETRmax) of transplanted sprigs took 1–2 months to increase to the same level recorded at a control meadow, primarily due to desiccation stress suffered during transport. Effective quantum yield ( ) of sprigs decreased below 0.2 after transplantation, but fully recovered after 3 months and the ETRmax of transplanted plugs took up to 1 week to recover to control meadow values. Once transplanted, the survival of sprigs was reduced due to strong currents and heavy epiphytic fouling, while that of plugs declined due to winter storms and swells. Since the leading human-controlled cause of transplant stress was desiccation, future rehabilitation efforts may be improved by keeping seagrasses submerged at all times during the transplanting process.

The key species Posidonia oceanica is the dominant endemic seagrass in the Mediterranean Sea and its meadows are considered as one of the most important and productive ecosystems in coastal waters. Covering the seabed from the surface down to about 40 m, meadows of P. oceanica are often affected by mechanical direct damages caused by boat anchoring and mooring activities. Negative effects of these activities have been shown to be recorded by P. oceanica at two different levels: the individual level (phenology of the plant) and the population level (structure of the meadow). We investigated the effect of an anchoring chain system on the P. oceanica meadow of Prelo cove (NW Mediterranean Sea) at two different depths (shallow, deep) and at three different situations of P. oceanica bottom cover (high, medium, low). Several standardized descriptors of the meadow health, working either at the individual or at the population level, were analysed in order to quantify the impact of the deployment of the chain system. A symmetrical BACI design was adopted to detect the impact, where multiple disturbed sites were contrasted with multiple controls in two distinct times, i.e. right few days after the chain settling (early) and 4 months later the disturbance (late). The anchoring chain system has been shown to strongly affect the meadow in terms of shoot density decline and rhizome baring, especially in the deep portions and where the cover of the meadow was low. All descriptors working at the population level proved effective in detecting the impact of the anchoring system. In contrast, descriptors working at the individual level did not show a consistent response to the impact. Our results pointed out the imperative necessity to proper regulate the boat anchoring and mooring activities on the P. oceanica meadows and the adoption of seagrass friendly mooring technology is thus recommended.

Transplant trials of the seagrass Posidonia australis were carried out after loss of seagrasses following eutrophication and increased turbidity in two marine inlets on the south coast of Western Australia. A pilot study in Oyster Harbour measured survival and growth in situ for 4 years. Long-term survival rates were high (96–98%), providing plants were anchored into the sediment. All unanchored plants were lost in the first winter. Following the success of the pilot study, a more comprehensive program began 3 years later with over 500 transplant units collected from either actively growing edges of nearby patches (plagiotropic growth form) or within established meadows (orthotropic growth form). Transplant units from edges expanded at a faster rate compared to units from mid-meadow but increases in shoot numbers were similar. Growth rates in the first 2.5 years averaged 10–20 cm yr−1 horizontal rhizome extension, depending on the source of the transplant units, and 4–12 shoots per initial shoot yr−1, depending on the initial shoot number of the transplant unit. After 5 years, shoot numbers of individual transplants were similar to shoot densities recorded for natural meadows, >500 shoots m−2. Approximately, 10% of transplants from mid-meadow flowered in the first year, whereas transplants from edges flowered only after 5 years. Transplant trials were also established in nearby Princess Royal Harbour at a site selected to test the effect of disturbance by bioturbation from large sand-burrowing worms or by sediment erosion. Survival was lower than in Oyster Harbour, 75–89% in areas with bioturbation but only 14% in areas where sediments were eroded. Growth was poor, This study showed that Posidonia australis could be transplanted with a high degree of success into a protected embayment previously vegetated with seagrass meadows. After 4 years, flower and seed production had occurred, and transplants spaced 1 m apart began merging. By the fifth year, individual transplant units could no longer be distinguished and planted areas resembled a natural meadow. These findings have important implications for restoration of impaired Posidonia habitats in Australia, using conventional low-cost techniques for transplantation once the sources of injury have abated.

Coastal development can impact on ecologically significant seagrasses. We sought to determine whether the construction of a pier and associated boat launching facilities would impact on Posidonia australis within Jervis Bay Marine Park, New South Wales, Australia. Using a modified ‘beyond BACI’ analysis we tested for impacts at three spatial scales; directly beneath the pier deck, within metres of the pier and approximately 50 m from the construction zone. We compared shoot density, leaf length and epiphytic cover prior to the commencement of construction to 7 months and 46 months later. Impacts were highly localised; we detected significant seagrass loss directly below the open-mesh deck of the pier, but not at the scale of metres and tens of metres relative to two non-impacted reference locations. Our data also supported the use of the trigger point approach to initiate management intervention; shoot density beneath of the deck of the pier fell below the 30th percentile, ending 73% lower than the mean after 46 months. If similar developments occur in waterways supporting seagrass species of high conservation significance, then management agencies need to weigh the inevitable loss of a small area of meadow with the advantages the development will provide.

Beach-cast wrack is a prominent feature of beaches of south-western Australia. We examined the fauna of these beaches to explore the generalisation [Polis, G.A., Hurd, S.D., 1995. Extraordinarily high spider densities on islands: flow of energy from the marine to terrestrial food webs and the absence of predation. Ecology 92, 4382–4386] that beach-cast wrack from highly productive marine ecosystems subsidises low productivity of terrestrial ecosystems, to establish whether this generalisation is relevant to oligotrophic marine systems. We sampled three beaches with high and three beaches with low volumes of beach-cast wrack to determine if: (1) the presence of wrack influences the abundance of macroinvertebrates; (2) wrack acts as a food source for beach macroinvertebrates; and (3) the influence of wrack varies between zones above the high water mark. We measured wrack volume and composition, sediment characteristics, the abundance of different epibenthic and infaunal macroinvertebrates taxa, and δ 13 C and δ 15 N of macrophytes and macroinvertebrates. The mean volume of wrack on high-wrack beaches was 0.27–1.07 m 3 wrack m −2 compared to 0.00–0.09 m 3 wrack m −2 on low-wrack beaches. There were no significant differences in sediment grain size, moisture content or loss on ignition between the two types of beaches or zones. Epibenthic fauna and infauna were consistently abundant on high-wrack beaches (20–291 and 0.5–3.5 individuals 0.64 m −2 , respectively), but either absent or extremely rare in low-wrack beaches (0–3 and 0–0.1 individuals 0.64 m −2 , respectively). Within high-wrack beaches, there were no significant differences in the abundance of epifauna or infauna among beaches or between zones. The δ 13 C values of macroinvertebrates at all sites were most similar to red and brown algae, with the exception of beetles from two beaches, which were closest to seagrasses. Mixing model (Isosource) results for mesograzing amphipods and dipteran flies suggested carbon was assimilated mostly from the seagrass Posidonia spp., the dune grass Spinifex longifolia and red algae for amphipods and from brown algae, red algae and dune vegetation for dipteran flies. We conclude that the presence of marine-derived wrack plays a major role in subsidising production of macroinvertebrates on beaches of south-western Australia. We suggest that marine subsidies can play a role in supporting terrestrial production, even in oligotrophic marine environments.

Seagrasses are the only angiosperms that have invaded the marine environment. Fossil seagrasses are rare and received only little attention to date. However, among the scarce plant fossils in the marine deposits of the Maastrichtian type area, remains of seagrasses are relatively common. The present paper provides a detailed description of the morphology and anatomy of the leaves. Maastrichtian and Danian material is considered here as a single species: Thalassotaenia debeyi gen. nov., sp. nov. Campanian material is assigned to Zosterites , but this is not necessarily a seagrass. Thalassotaenia includes the oldest anatomically preserved material of seagrass leaves. Comparison with extant seagrasses shows that there is not an easy match with any of the extant genera or families. Amphibolis and Thalassodendron (Cymodoceaceae) and Posidonia (Posidoniaceae) show the greatest resemblance. Possibly, Thalassotaenia represents the leaves of an ancestor of the Cymodoceaceae–Posidoniaceae (–Ruppiaceae) clade found in several phylogenetic analyses. Because Thalassotaenia also shows some features not found in extant seagrasses, it might also represent an extinct clade of seagrasses.

8 pages.-- ArXiv pre-print: http://arxiv.org/abs/q-bio/0608018.-- Final full-text version of the paper available at: http://dx.doi.org/10.1016/j.physd.2006.09.015., We build networks of genetic similarity in which the nodes are organisms sampled from biological populations. The procedure is illustrated by constructing networks from genetic data of a marine clonal plant. An important feature in the networks is the presence of clone subgraphs, i.e. sets of organisms with identical genotype forming clones. As a first step to understand the dynamics that has shaped these networks, we point up a relationship between a particular degree distribution and the clone size distribution in the populations. We construct a dynamical model for the population dynamics, focussing on the dynamics of the clones, and solve it for the required distributions. Scale free and exponentially decaying forms are obtained depending on parameter values, being the first type obtained when clonal growth is the dominant process. Average distributions are dominated by the power law behavior presented by the fastest replicating populations., This research was funded by a project of the BBVA Foundation (Spain), by project NETWORK (POCI/MAR/57342/2004) of the Portuguese Science Foundation (FCT) and by the project CONOCE2 (FIS2004-00953) of the Spanish MEC. S.A.H. was supported by a postdoctoral fellowship from FCT and the European Social Fund and A.F.R. by a post-doctoral fellowship from the Spanish Ministry of Education and Science.

A soft-bottom community (6–8 m depth) within a seagrass bed in Prelo Bay (Eastern Ligurian Sea) was studied between April 1990 and August 1991. Samples were collected using a suction device and were sieved through a 1-mm mesh size. Cluster analysis showed seasonal fluctuations in the macrofauna density with highest values in summer 1990 (maximum 2870.0 ± 2029.4 ind. m −2 in August 1990) and lowest in late spring 1991 (100.0 ± 37.8 ind. m −2 at the end of May 1991). On the whole, the community was characterised by a high number of species (184 species plus 17 higher taxa) but only 12 accounted for 78% of the total density, so diversity was relatively low. Dissimilarity between seasons was high (on average 74.7 ± 8.3) and the principal discriminating species was the amphipod Siphonoecetes dellavallei , whose successful recruitment dominated community density in summer 1990. Total macrofauna biomass ranged between 166.1 ± 67.8 mg AFDW m −2 (May 1991) and 2399.8 ± 1073.2 mg AFDW m −2 (June 1991); molluscs being the major contributors (ca. 61%) with single large individuals. Secondary production reached on average 0.4 ± 0.2 g C m −2 y −1 . Notwithstanding the relative low biomass, deposit-feeders were the major contributors to secondary production (38%), indicating their high efficiency in utilizing their food resource (detritus-associated bacteria). The seagrass bed seems to play only an indirect role in the structure and function of macrofaunal assemblages.

There is increasing interest among ecologists about how the type of matrix surrounding a habitat patch influences the organisms living in that patch. This question is virtually unstudied in marine systems. In this paper I show that the mobile faunal assemblage in seagrass patches does depend on the surrounding matrix. Faunal assemblages in patches of Posidonia surrounded by sand are different than in those surrounded by Heterozostera , another seagrass, having more than double the abundance of both amphipods and polychaetes. However, the differences are not simply due to spillover from the matrix habitat, but rather are an emergent property of the patch context that cannot be predicted. Posidonia surrounded by sand actually has an assemblage that is intermediate between Heterozostera and Posidonia surrounded by Heterozostera . Differences in habitat structure do not account for this pattern, as seagrass biomass did not vary, and the same result was found in artificial seagrass. The faunal assemblage did not vary depending on the location within the patch (edge or centre) for Heterozostera , Posidonia or artificial seagrass. Patch size, however, did have an effect for Heterozostera , with smaller patches having 2–3 times as many isopods per sample as large, but less than half the number of some amphipod families. These results suggest that the landscape context is as important in marine systems as it is known to be in terrestrial systems.

The main aim of this study was to develop and validate a suite of sensitive responses (biomarkers) for monitoring conservation status and ecotoxicological impact in Posidonia oceanica meadows. Analytical methods were developed for NADPH cytochrome c reductase, ethoxycoumarin-o-deethylase (ECOD), guaiacol peroxidase (GPOX) and superoxide dismutase (SOD) assays. A preliminary proteomic approach using 2-D electrophoresis was also proposed as a biomarker. These techniques were initially tested on samples of posidonia exposed experimentally to various contaminants. Once validated, this approach was applied to posidonia in a field study. Samples of the seagrass were collected at four sites with potentially different environmental impact along the northern Tyrrhenian coast. The results showed that reductase activity was significantly induced in the various sampling areas with respect to the reference site. GPOX and SOD showed a similar trend; the highest activities were found in samples collected off a chlor-alkali plant and near a river estuary. Analysis of trace elements, polycyclic aromatic hydrocarbons (PAHs) and organochlorine compounds (OCs) in posidonia leaves showed differences between sites. A significant correlation was found between Hg concentrations and GPOX activity and between Cr, Al and As concentrations and reductase activity. The results validated these biomarkers in posidonia for the assessment of ecotoxicological impact on the coastal ecosystem.

The location of big SWRO plants is usually limited by environmental restrictions such as the presence of the Posidonia habitat in the Mediterranean coast. The unknown impacts of brine on the flora and fauna associated at sea grasses has caused environmental damages either high cost disposal solutions of doubtful viability. Previous to the construction of 160.000 m3/day SWRO Plant in the southeast coast of Spain, an unique research study was carried out in the Mediterranean coast by some of the most advanced Spanish Research Centres in cooperation with two Spanish universities. The knowledge of the Posidonia limits can help not only to locate Desalination plants but to design disposal devices. This paper reports the results of two years study testing the salinity impact on Posidonia habitat lab and field with brine produced with a SWRO pilot plant. Additionally a brine disposal model has been developed to support the design of a full scale disposal system.

Satellite imagery was used to detect the change in seagrass and macroalgal communities of a shallow coastal lake over a period of 14 years. The lake benthic material was classified into sets of spectral classes representing the patterns and texture of the ecosystem, and then linked to environmentally relevant labels through a radiative transfer model. The classification results for 2002 achieved an accuracy of 76% for the least understood areas; other areas were significantly better, but not quantified. Classification results of 1988, 1991, and 1995 were consistent with past surveys and maps. Based on the change detection from 1988 to 2002 Posidonia, Ruppia and Halophila change slightly in the 14 year period from 1988 to 2002. However, Zostera has undergone significant change and adaptation. Early in the time series (between 1988 and 1991) a reduction in Zostera beds was evident, especially in the middle and south of the lake with some areas not returning by 2002. Epiphytic growth over Zostera could be a confounding factor here, but the Landsat sensors do not have sufficient spectral resolution to detect these subtleties. Hyperspectral remote sensing could resolve this issue more clearly.