Secondary metabolites of Posidonia oceanica (Posidoniaceae)

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.     

A biotic index using the seagrass Posidonia oceanica (BiPo), to evaluate ecological status of coastal waters

The development of ecologically based indices that respond to disturbances in a predictable manner has been stressed by the EU Water Framework Directive. The seagrass Posidonia oceanica, given its ecological indicator characteristics, has been identified as one of the elements to determine ecological status under the EU Water Framework Directive. The purpose of this study is therefore to develop a biotic index based on P. oceanica (BiPo), focussing on: (i) the necessity of an index that may be applied over the largest geographical extent possible, (ii) the necessity of a tool for a baseline evaluation of P. oceanica status in the Mediterranean, (iii) the compliance with WFD requirements, (iv) the efficiency of the method in terms of reliability and cost. The BiPo index is developed on the basis of all P. oceanica monitoring data available in the western Mediterranean and on a standard assessment of anthropogenic pressures. The index metrics are selected and evaluated on the basis of this pressures assessment, and are subsequently integrated for the evaluation of ecological status. The index is then tested on 15 sites around Corsica (France). The results show that the BiPo well reflects meadow health status and ecological status. Furthermore it is reliable, standard and cost-effective, and can be applied to a wide array of management and conservation purposes.     

Spatial,temporal and structural variations of a Posidonia oceanica seagrass meadow facing human activities

The Bay of Saint-Cyr (Provence, France, Mediterranean Sea) is the site of two harbours, coastal urban development, trawling, boat anchoring and a sewage outfall. The Posidonia oceanica seagrass distribution was mapped with the help of aerial photographs, side scan sonar and GIS. In addition, the temporal variations of its distribution were studied by aerial photographs and GIS from 1955 to 2000. Finally, coverage and shoot density were measured via scuba-diving. This work reveals (i) the regression of the P. oceanica meadow at sites where harbours have been built, (ii) the occurrence of spaces within the meadow free of live P. oceanica (“intermattes”), which account for 8% of its surface area, (iii) a deep area where P. oceanica coverage and shoot density are low and (iv) evidence of regression, although modest, of the meadow at its lower limit. Nevertheless, the study site also exhibits an extensive and on the whole relatively healthy meadow whose limits have changed little over time.     

The suitability of the marine biotic index (AMBI) to new impact sources along European coasts

In recent years, several benthic biotic indices have been proposed to be used as ecological indicators in estuarine and coastal waters. One such indicator, the AZTI Marine Biotic Index (AMBI), was designed to establish the ecological quality of European coasts. The index examined the response of soft-bottom benthic communities to natural and man-induced disturbances in coastal and estuarine environments. It has been successfully applied to different geographical areas and under different impact sources, with increasing user numbers in European marine waters (Baltic, North Sea, Atlantic and Mediterranean). The AMBI has been used also for the determination of the ecological quality status (EcoQ) within the context of the European Water Framework Directive (WFD).In this contribution, 38 different applications including six new case studies (hypoxia processes, sand extraction, oil platform impacts, engineering works, dredging and fish aquaculture) are presented. The results show the response of the benthic communities to different disturbance sources in a simple way. Those communities act as ecological indicators of the ‘health’ of the system, indicating clearly the gradient associated with the disturbance.     

Illegal trawling and induced invasive algal spread as collaborative factors in a Posidonia oceanica meadow degradation

Posidonia oceanica, a key seagrass species of the Mediterranean Sea, shows clear signs of regression throughout the Mediterranean and illegal trawling is recognized as one of the main causes. We examined the condition of a P. oceanica meadow in Alykes Bay (Zakynthos Island, western Greece), a typical Mediterranean littoral area where illegal trawling is common practice, in respect to the total area affected, and in terms of possible ecological substitution. A side scan sonar (SSS) survey of the seafloor provided an image of the condition of the meadow and biological sampling evaluated the ecological status in affected meadow areas. SSS images revealed that trawling has a serious effect on the meadow, with 11% of the vegetated area being abraded, and the affected areas were also found to be fully colonized by the invasive alga Caulerpa racemosa. Moreover, unusually high densities of the polychaete Sabella pavonina were detected in the affected areas among C. racemosa fronds. Recolonization by P. oceanica of the affected meadow areas that have been colonized by C. racemosa seems improbable considering the allelopathic interactions between the species, with the alga displaying phytotoxic properties through caulerpenyne production and deterioration of the sediment quality.     

The necromass of the <Emphasis Type="Italic">Posidonia oceanica</Emphasis> seagrass meadow: fate,role, ecosystem services and vulnerability

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea. Most of the primary production of the P. oceanica meadow is not directly consumed by herbivores and plays a role as dead rhizomes and roots, dead leaves and drift epibionts (hereafter necromass). The fate of this necromass is (i) sequestration within the matte, (ii) consumption by detritus-feeders within the meadow, (iii) export towards other marine ecosystems, where it constitutes a source for food webs, (iv) export towards beaches, where it constitutes banquettes, reduces the impact of waves and contributes to the beach ecosystem, and (v) export towards the terrestrial dune ecosystem. These five stocks can exchange necromass. The ecosystem services of the P. oceanica necromass are pivotal. For example, the role of P. oceanica banquettes is fundamental in protecting beaches from erosion, and the carbon sequestration within the matte contributes to the mitigation of emissions of CO₂. Human impact on each of these stocks can affect the other stocks and their ecosystem services. The removal of banquettes from beaches can have a dramatic negative impact on P. oceanica ecosystem services, including the sustaining of beaches. The erosion of matte due to trawling and anchoring can remobilize the sequestrated carbon stock.     

Genetic variability of Posidonia oceanica (L.) Delile in relation to local factors and biogeographic patterns

To evaluate genetic differences of Posidonia oceanica (L.) Delile both at smaller (within a meadow) and larger scale (Mediterranean basin), plants of P. oceanica were analyzed by PCR technique and compared using random amplified polymorphic DNA (RAPD) markers. Results were associated to known differences in phenology. At the small-scale level, P. oceanica shoots collected in the bay of Monterosso al Mare (Liguria, NW Mediterranean Sea) showed genetic differences among sampling stations, with a decrease in genetic diversity along an anthropogenic disturbance gradient. At basin level, genetic differences were detected among 11 P. oceanica shoots coming from different regions of the Mediterranean, and transplanted to the Port-Cros National Park (France) between 1989 and 1991: Izmir, Turkey; Athens, Greece; Taranto, Italy; Ischia Island, Italy; Lavezzi, France; Port-Cros, France; Banyuls, France; Palma de Majorca, Balearic Islands, Spain; Marsa Bay, Algiers. By cluster analysis two major Mediterranean groups were distinguished, the Eastern Mediterranean Group (EMG) and the Western Mediterranean Group (WMG). This suggests that eastern and western populations of P. oceanica have diverged during the colonization of the Mediterranean (after near extinction of the Mediterranean biota in the Messinian period, approximately 5.6 million years ago), and have experienced little gene flow between them. Cluster analysis also indicated that previously described phenological differences among P. oceanica populations in different sectors of the Mediterranean are not mere phenotypic responses to different climatic and hydrological conditions but may well have a genetic basis.     

Ability of invertebrate indices to assess ecological condition on intertidal rocky shores

The implementation of directives such as the European Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) has promoted the development of several tools and methods for assessing the ecological health of marine ecosystems. Within the scope of the WFD and in terms of rocky shores, several multimetric tools were developed based on the macroalgae biological quality element (BQE), in addition to those based on macroinvertebrates.The WFD requires member states to assess each BQE separately. The present work aimed to test the ability of ecological indices to distinguish sites within anthropogenic disturbance gradients caused by organic enrichment, using macroinvertebrate communities on intertidal rocky shores. Owing to the lack of more specific indices (for rocky shore), indices based on abundance, diversity and/or taxonomic composition were selected from several widely used indices in ecological studies and/or developed for soft-bottom macroinvertebrate communities.Present findings reveal several indices based on diversity and/or taxonomic composition able to distinguish sites within the disturbance gradients, showing increasing quality from the site nearest the source of organic enrichment to that farthest from it, especially indices calculated using biomass data, and in the summer season. Such results open good perspectives for the use of intertidal macroinvertebrate communities from rocky shores, and also help add the perspective of this biological quality element in the ecological quality assessment of coastal waters.     

Molecular Characterization of a Variable Tandem Repeat Sequence Determined during RAPD Analysis among Posidonia oceanica Insular and Coastline Populations

The seagrass Posidonia oceanica plays a multifunctional role in the coastal area as an important and productive component of ecosystems in the Mediterranean Sea. We detected by RAPD analysis with two arbitrary primers genetic differences in P. oceanica collected from several sites in the Southern Mediterranean. By AMOVA analysis we observed a level of about 20% genetic difference among individuals within a population and 80% among populations. A common band of 200 bp was found in all the amplified samples. Cloning and sequencing analysis of this band revealed the presence of a simple tandem repeat sequence (minisatellite) that we called PoTR (Posidonia oceanica tandem repeat). Finally, the ability of PoTR to detect genetic variability inP. oceanica genome was demonstrated by the presence of amplification products of different lengths utilizing primers internal to this sequence.     

Leaf vs. epiphyte nitrogen uptake in a nutrient enriched Mediterranean seagrass (Posidonia oceanica) meadow

In situ nitrogen uptake by leaves and epiphytes was studied in a Mediterranean seagrass (Posidonia oceanica) meadow impacted from a fish farm and a pristine meadow, using ¹⁵NH₄ and ¹⁵NO₃ as tracers. In the impacted meadow both leaves and epiphytes yielded higher N concentrations and showed higher specific N uptake, suggesting a linkage between N uptake and its accumulation. Epiphytes took up N faster than leaves in relation to their corresponding biomass, but when assessed per unit area, N uptake was higher in leaves. Leaf N uptake was negatively correlated with epiphyte N uptake. With increasing epiphyte load on leaves, N leaf uptake decreased while N epiphyte uptake increased, indicating that epiphyte overgrowth hinders N uptake by P. oceanica leaves. Epiphyte contribution to total N uptake increased, while that of leaves decreased at the impacted meadow. However, 2-3 times less N was transferred daily from the water column to the benthic compartment, through seagrass and epiphyte uptake on total, at the impacted meadow. Therefore, it is probably still the loss of the key species - the seagrass - which plays the most important role in N cycling in seagrass ecosystems.     

Use of macroinvertebrate-based multimetric indices for water quality evaluation in Spanish Mediterranean rivers: an intercalibration approach with the IBMWP index

For the European Parliament and Commission to implement the Water Framework Directive (WFD), the water-quality indices that are currently used in Europe need to be compared and calibrated. This will facilitate the comparative assessment of ecological status throughout the European Union. According to the WFD, biologic indices should respond consistently to human impacts, using multimetric approaches and water-quality classification boundaries adjusted to a common set of normative definitions. The European Commission has started an intercalibration exercise to review biologic indices and harmonize class boundaries. We used data from rivers in Spain to compare the IBMWP (Iberian Biological Monitoring Working Party) index, which is commonly used by water authorities in Spain and by several research centers, with the Intercalibration Common Multimetric Index (ICM-Star), which was used as a standard in the intercalibration exercise. We also used data from Spanish rivers to compare the multimetric indices ICM-7 (based on quantitative data) and ICM-9 (based on qualitative data) with the IBMWP. ICM-7 and ICM-9 were proposed by the Mediterranean Geographical Intercalibration Group (Med-GIG). Additionally, we evaluated two new multimetric indices, developed specifically for macroinvertebrate communities inhabiting Mediterranean river systems. One of these is based on quantitative data (ICM-10), while the other is based on qualitative data (ICM-11a). The results show that the IBMWP index responds well to the stressor gradient present in our data, and correlates well with ICM-Star. Moreover, the IBMWP quality class boundaries were consistent with the intercalibration requirements of the WFD. However, multimetric indices showed a more linear relation with the stressor gradient in our data, and less variation in reference values. In addition, they may provide more statistical power for detecting potential environmental impacts. Multimetric indices produced similar results for quantitative and qualitative data. Thus, ICM-10 (also named IMMi-T) and ICM-11a (also named IMMi-L) indices could be used to meet European Commission requirements for assessing the water quality in Spanish Mediterranean rivers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: Joel Trexler     

The fuzzy index of ecosystem integrity (FINE): a new index of environmental integrity for transitional ecosystems

The European Water Framework Directive (WFD) (2000/60/EC) requires assessing the ecological quality status of water bodies, and gives great importance to the biological components of the ecosystem. Within this framework, a multimetric, fuzzy-based index for the evaluation of environmental quality (FINE: fuzzy index of ecosystem integrity) has been developed using data from several Italian coastal lagoons, gathered with seasonal frequency at diverse sites in each lagoon. The rationale of FINE is that certain attributes, selected on the basis of established principles of benthic ecology, are fundamental for lagoon ecosystem function. FINE is composed of seven ecosystem attributes (variables) each of which have ecological relevance for lagoon ecosystems. Individually, all these attributes are themselves useful indices of environmental conditions. However, the combination of these attributes into a single fuzzy index, provides a more robust, overall index of the response of the natural communities to environmental perturbations and avoids misleading or ambiguous results. Each variable is not represented by a single numerical value, but by several categories that describe its properties: in the present model we considered a total of seven variables: two with four modalities (low–medium–high–very high), one with three (low–medium–high) and three with two (low–high), plus a qualitative variable (yes–no), that altogether generate 768 rules. FINE is a low-cost, flexible and robust routine index of lagoon ecosystem impairment and could be of particular benefit to environmental managers and policymakers who require tools capable of expressing the degree of degradation or environmental quality of different lagoon habitats. For its relative simplicity in the application, FINE could be a good candidate to assess the environmental quality of Mediterranean transitional ecosystems. Guest editors: A. Razinkovas, Z. R. Gasiūnaitė, J. M. Zaldivar & P. Viaroli European Lagoons and their Watersheds: Function and Biodiversity     

Modelling the spatial distribution of the seagrass Posidonia oceanica along the North African coast: Implications for the assessment of Good Environmental Status

Posidonia oceanica (L.) Delile, 1813 is a seagrass species endemic to the Mediterranean Sea, which is considered as an indicator of environment quality in coastal areas. This species forms large meadows, which are sensitive to several anthropogenic pressures and the decrease in their extension is considered a priority issue for the Mediterranean Sea. The aim of this study was to develop a Species Distribution Model for P. oceanica, to be applied to the Mediterranean North African coast, in order to obtain an estimation of the potential distribution of this species in the region. The Species Distribution Model was calibrated using high resolution data from 4 Mediterranean sites, located in Italy and Spain, as the study area is a data-poor zone with regard to seagrass distribution (i.e. only for some areas detailed distribution maps are available). The model was then validated using available data concerning the North African coast. The probability of presence of the species in a given area was modelled using a binomial generalized linear model as a function of the bathymetry and water transparency, dissolved organic matter, sea surface temperature and salinity, mainly obtained from satellite data. Model selection procedure suggests that water transparency plays a major role, but also other variables, such as salinity and sea surface temperature, are important at larger spatial scales in explaining meadows distribution. The availability of high resolution time-series of input data allowed us to apply the validated model to the whole North African coast. Suitable areas are strongly related to the coastal realm, and cover a large portion of North African coasts, with Tunisian and Lybian ones being the most relevant zones for this species. In particular, the shelf of the Gulf of Gabes includes large areas with environmental conditions suitable for the species. Based on model predictions, we developed a robust indicator of potential habitat suitability, which could be used for the assessment of Good Environmental Status, as requested by the Ecosystem Based Approach, to be implemented at the scale of the whole Mediterranean basin in the framework of the Barcelona Convention.     

Seagrass light acclimation: 2-DE protein analysis in Posidonia leaves grown in chronic low light conditions

Posidonia oceanica meadows are among the most valuable coastal systems in the Mediterranean basin. They provide nursery and forage areas for many commercially important species, including juvenile mollusc, finfish, and crustaceans. In the Mediterranean Sea, P. oceanica beds have recently suffered from progressive die-offs attributed to lower light availability from elevated water turbidity. In order to understand adaptive low-light responses of this seagrass, we compared the protein expression in plants collected from turbid waters (low-light) with plants collected from pristine-clear waters (high-light). More than 2600 proteins were detected in leaves from both sites. Among them, 26 proteins were differentially expressed in low-light conditions, 12 of which were identified through MASCOT analyses. The remaining 14 proteins, did not receive significant identity scores due to a lack of genomic and proteomic information in available databases. Nevertheless, we observed a 30% down-regulation of RuBisCo large subunit in low-light acclimated leaves. Whereas, enzymes involved in carbohydrate cleavage (1-fructose-bisphosphate aldolase, nucleoside diphosphate kinase, and beta-amylase) were upregulated in low-light conditions. Electron microscopy studies also revealed substantial changes in the stroma lamellae/grana ratios in chloroplasts receiving low-light, possibly as a mechanism for re-establishing optimal PSI/PSII ratios. Furthermore, under low-light conditions, four components of the ubiquitin/mediated proteolysis pathway (26 S proteasome regulatory, proteasome beta type 1, proteasome 7 D beta type, and proteasome alpha 7), and the perchloric acid soluble translation inhibitor protein, were upregulated. This suggests that, in P. oceanica leaves, enhanced protein turnover mediates acclimation to low-light conditions. Also, enzymes involved in defending against cellular stress (superoxide dismutase, pyridoxine, and 2-caffeic-acido-methyl transferase) were differentially expressed in low-light regime. Subsequent aquaria studies involving P. oceanica transplants maintained in low- and high-light conditions, also demonstrate RuBisCo down-regulation and proteasomes upregulation in low-light acclimated plants.     

Effects of Posidonia Oceanica Beach-Cast on Germination,Growth and Nutrient Uptake of Coastal Dune Plants

Seagrass meadows play an important role in marine ecosystems. A part of seagrass production is also exported to adjacent coastal terrestrial systems, possibly influencing their functioning. In this work we experimentally analyzed the effect of Posidonia oceanica beach-cast on plant germination, growth, and nutrient uptake of two plant species (Cakile maritima and Elymus farctus) that grow on upper beaches and fore dunes along the Mediterranean coasts. We compared plants growing in simple sand (control) with those growing in a substrate enriched with P. oceanica wrack (treatment) in laboratory. P. oceanica wrack doubled the N substrate pool and kept the substrate humid. Plants growing in the treated substrate grew faster, were twice as large as those growing in the control substrate, while tissues were enriched in N and P (Cakile by the 1.3 fold in N and 2.5 fold in P; Elymus by 1.5 fold in N and 2 fold in P). Our results suggest a positive effect of seagrass litter for the enhancing of dune species, highlighting its role for the conservation of coastal dune ecosystems.     

A comparative approach of assessing ecological status in two coastal areas of Eastern Mediterranean

This work presents an assessment of the ecological quality status of two marine coastal areas in the Aegean Sea (Greece, Eastern Mediterranean) based on the benthic macroinvertebrate quality element. S. Evvoikos and Thessaloniki gulfs, two coastal areas subjected to slight and heavier anthropogenic pressures, were selected to test the biotic index Bentix developed for the assessment of the ecological status. Other ecological indicators, such as the Shannon diversity index (H′), the species richness (S) and the AMBI biotic index were also applied and evaluated comparatively. Faunistic data were also used to interpret results. The resulting classification was validated with the use of physicochemical parameters and pressure information. This work also provides an insight into the structure of the Bentix classification scheme within the scope of its use in Water Framework Directive (WFD) implementation.     

Cartography of littoral rocky-shore communities (CARLIT) as a tool for ecological quality assessment of coastal waters in the Eastern Adriatic Sea

Littoral cartography is a valuable tool which uses shallow water macroalgal communities for monitoring ecosystem health and water quality. Cartography of littoral rocky-shore communities (CARLIT) is a European Union Water Framework Directive-compliant monitoring method widely used in the Western Mediterranean Sea. This non-destructive method is based on a visual observation of the type and length of coast occupied by rocky-shore communities in the upper-sublittoral zone. Here we present the first wide-scale application of CARLIT in the Adriatic Sea. The reference values calculated specifically for the Croatian coast (Eastern Adriatic Sea) ensure accurate calculation of the ecological status. The measured ecological quality ratio values (EQR) show a good linear relation with the Land Uses Simplified Index (LUSI) and appropriately reflect an increase in nutrient concentrations. The results suggest that this method can be used as a reliable biomonitoring tool in the Eastern Adriatic Sea. This study highlighted that Cystoseira forests thrive in 39% of the surveyed coastline and 23% of the coastline seems to be subjected to overgrazing by sea urchins. Our results provide a spatially accurate information on the abundance of different upper-sublittoral communities and the associated ecological status, which can be used in future management plans for improving water quality.