Extreme environmental events can strongly affect coastal marine ecosystems but are typically unpredictable. Reliable data on benthic community conditions before such events are rarely available, ...making it difficult to measure their effects. At the end of October 2018, a severe storm hit the Ligurian coast (NW Mediterranean) producing damages to coastal infrastructures. Thanks to recent data collected just before the event on two Posidonia oceanica seagrass meadows hit by the storm, it has been possible to assess the impact of the event on one of the most valuable habitats of the Mediterranean Sea. By means of seagrass cover and depth data gathered along four depth transects positioned within the two meadows in areas differently exposed to the storm waves, and by using models (WW3® + SWAN + XBeach 1D) to evaluate wave height and bed shear stress, we showed that meadows experienced erosion and burial phenomena according to exposure. Paradoxically, meadows in good conditions suffered more damage as compared to those already suffering from previous local anthropogenic impacts. Besides the direct effect of waves in terms of plant uprooting, a major loss of P. oceanica was due to sediment burial in the deepest parts of the meadows. Overall, the loss of living P. oceanica cover amounted to about 50%. Considering that previous research showed that the loss of the original surface of P. oceanica meadows in 160 years due to anthropogenic pressures was similarly around 50%, the present study documented that an extreme environmental event can generate in a single day a loss of natural capital equal to that produced gradually by more than a century of human impact.
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•Extreme weather events may affect severely the submerged benthic habitats.•Posidonia oceanica meadows halved their living cover.•The loss of P. oceanica in one day equate that lost in 160 years by human impact.
A rapid visual assessment (RVA) approach for the characterization and assessment of the integrity of coralligenous reefs was applied in 21 stations subjected to different levels of anthropogenic ...pressure, along the French Mediterranean coasts. The reefs were characterized from both the geomorphologic and bionomic (biotic cover, conspicuous species richness, canopy-forming species, etc.) points of view, and their health status was estimated through the COARSE (COralligenous Assessment by ReefScape Estimate) index. The sensitivity of the COARSE index and the robustness of the RVA approach to observer biases were analyzed. Results showed that most coralligenous reefs were characterized by (sub) vertical cliffs or platforms with variable slope, usually dominated by biotic facies with Paramuricea clavata and/or Eunicella cavolini in healthy stations, or by algal associations or facies of impoverishment in the most impacted situations. The overall quality scores of the COARSE index generally reflected the putative level of stress of the sampling stations; differences due to observer biases resulted negligible. Coupling the RVA approach with the COARSE index proved an effective protocol for both the characterization and the evaluation of coralligenous reefs: the former is achieved by the analysis of the whole complexity of this habitat, the latter provides for the first time an indication of sea-floor integrity, differently from previous indices that aim at estimating water quality.
•The use of more indices raise possibilities of discordance among responses.•New graphical approach to obtain an overall expression of seagrass health.•Area is a measure of the overall environmental ...quality.•Circularity is a measure of the consistency among indices.•Consistency among indices is a good proxy of habitat resilience.
Biotic indices are major tools recommended by the European Directives for assessing the ecological status of marine coastal ecosystems such as Posidonia oceanica meadows. Nevertheless, the multitude of available metrics commonly adopted in the P. oceanica monitoring often provide diverging responses about the health status of the habitat. In this study, we investigated the effectiveness and consistency of a set of 11 indices and descriptors working at different level of ecological complexity of P. oceanica ecosystem (individual, population, community, and seascape), applying them on 13 seagrass meadows of the Ligurian Sea (NW Mediterranean). A new approach, named RESQUE (RESilience and QUality of seagrass Ecosystem), is here proposed and aims to provide a single and comprehensive measure of the ecological status of seagrass meadows. RESQUE is a graphical approach that involves the calculation of both the Relative Area Index (RAI) and the Relative Circularity Index (RCI) starting from a radar chart where all the different values of indices and descriptors are reported after being normalized. The RAI represents a measure of the overall environmental quality, while the RCI constitutes a measure of the consistency among indices and it is assumed as a good proxy of meadow resilience. RESQUE turned out to be an effective method to incorporate all the different indices responses, and allowed integration of relevant information into an overall expression of meadow health. Beyond the ability of merely defining the quality of the Ligurian P. oceanica meadows, this approach displayed a great potential being possibly applicable to other habitats and with ideally infinite combinations of metrics.
•Data of ESCA index from 2009 to 2018 were collated and reviewed.•ESCA values of 42 sites were compared with an anthropization index.•ESCA detected differences among sites subjected to different ...levels of pressure.•ESCA discriminated disturbed and control sites in three impact evaluation studies.•ESCA was stable respect to the regional spatio-temporal variability.
This paper aims at collating and reviewing all data collected using the ESCA (Ecological Status of Coralligenous Assemblages) index from 2009 to 2018 during different local applications, in order to evaluate at large spatial scale its effectiveness and temporal variability. To this scope, the large-scale response of ESCA to anthropogenic disturbance was tested comparing ESCA values calculated at 42 sites of the Western Mediterranean Sea with the anthropization index. Moreover, the sensitivity of ESCA to punctual human disturbance and the robustness of the index across the natural space and time variability were evaluated. The large spatial scale study showed significant correlation between ESCA and the anthropization index, while very low correlation was detected when descriptors of ESCA (i.e., sensitivity levels, α-diversity, and β-diversity) were considered separately. The three impact evaluation studies highlighted significantly lower values of the ESCA index in disturbed conditions than in the control ones. The coastal monitoring study confirmed the robustness of the index which showed a high ecological quality of coralligenous reefs in reference conditions compared to more anthropized sites, and this pattern was maintained throughout the ten years study period. Application of the ESCA index to different situations tested positively its sensibility to different levels and type of human disturbance and its stability with respect to regional spatio-temporal variability. This confirm the reliability of the ESCA index already tested on the local and annual scale, thus broadening its range of application and validating it on a wider space–time scale.
A rapid temperature increase in the 1980-90s has been accompanied by dramatic and unprecedented changes in the biota and communities of the Ligurian Sea. This review uses existing historical series ...(a few of which have been purposely updated) to assess extent and consequences of such changes. A number of warm-water species, previously absent or occasional in the comparatively cold Ligurian Sea, has recently established thanks to warmer winters. Occurrence among them of invasive alien species is causing concern because of their capacity of outcompeting autochthonous species. Summer heatwaves, on the other hand, caused mass mortalities in marine organisms, some of which found refuge at depth. New marine diseases appeared, as well as other dysfunctions such as the formation of mucilage aggregates that suffocated and entangled benthic organisms. Human pressures have combined with climate change to cause phase shifts (i.e., abrupt variations in species composition and community structure) in different habitats, such as the pelagic environment, seagrass meadows, rocky reefs, and marine caves. These phase shifts implied biotic homogenization, reduction of diversity, and dominance by invasive aliens, and may be detrimental to the resilience of Ligurian Sea ecosystems. Another phase of rapid warming has possibly started in the 2010s and there are clues pointing to a further series of biological changes, but data are too scarce to date for proper assessment. Only well addressed long-term studies will help understanding the future dynamics of Ligurian Sea ecosystems and their possibilities of recovery.
The study aimed at contributing to the knowledge of alternative stable states by evaluating the differences of mobile and sessile macro-zoobenthic assemblages between sea urchin barrens and ...macroalgal forests in coastal Mediterranean systems considering a large spatial scale. Six sites (100 s km apart) were selected: Croatia, Montenegro, Sicily (Italy), Sardinia (Italy), Tuscany (Italy), and Balearic Islands (Spain). A total of 531 taxa, 404 mobile and 127 sessile macro-invertebrates were recorded. Overall, 496 and 201 taxa were found in macroalgal forests and in barrens, respectively. The results of this large-scale descriptive study have met the expectation of lower macrofauna complexity and diversity in barrens rather than in macroalgal forests, and have allowed estimating the differences in levels of diversity and the consistency of variability across Mediterranean sites. Some peculiar patterns in barrens, related to both abundance of specific taxa and to high values of beta diversity, have been evidenced.
•Macro-zoobenthic assemblages of barrens and macroalgal forests were studied.•Six sites were studied throughout the Mediterranean Sea.•A total of 531 taxa, 404 mobile and 127 sessile macro-invertebrates were recorded.•496 and 201 taxa were found in macroalgal forests and in barrens, respectively.•A lower macrofauna complexity and diversity were found in barrens.
► Geospatial model of human pressures/ecosystems status relationship was developed. ► Approach applied on a MPA coexisting with a commercial harbor. ► Ecosystems status due to variation in the ...cumulative human pressure was predicted. ► MPA conservation effort is expected to balance harbor influence. ► Model implemented into GIS is a decision-support tool for ecosystem management.
Human use of ecosystem resources and services is increasing worldwide, generating pressures that alter ecosystem structure, functioning and provision of services. Unexpected ecosystem change is becoming frequent, and the complex ways through which multiple human pressures may interact leave conservation practitioners and natural resource managers faced with high uncertainty. We developed a geospatial approach for modeling the complex relationships between multiple human pressures and coastal ecosystems status. This framework was then used to produce maps of the expected status of marine coastal ecosystems resulting from variation in the cumulative human pressure. The geospatial modeling approach we developed was tested on an emblematic study case requiring marine spatial planning, i.e. a recently established marine protected area (MPA) that will have to coexist with the expansion of a close commercial harbor. In the study case presented, our modeling approach was used to predict the status of coastal ecosystems resulting from different management alternatives. Results showed that should Port Authority support MPA in reducing human pressures in the area, coastal ecosystems would not be expected to further deteriorate as a consequence of harbor expansion. Our approach proved effective in modeling complex interaction among multiple pressures (e.g. synergisms) and predicting potential future scenarios. The implementation of this approach into geographical information systems (GIS) allows managers to represent the expected outcomes of their planned conservation efforts, thereby representing an important decision-support tool for finding efficient management solutions in the face of complex interactions and high uncertainty.
The endemic Mediterranean seagrass
Posidonia oceanica is a key species in coastal waters and it is widely employed as an ideal biological indicator for assessing the quality of water bodies, in ...accordance to the Water Framework Directive (WFD), as well as for assessing the health status of coastal ecosystems. In this contribution the current situation of the
P. oceanica monitoring programs in the Mediterranean Sea is reviewed focusing on those descriptors adopted commonly by researchers and local administrators. The application of recently introduced approaches based on a set of synthetic ecological indices, namely the Conservation Index (CI), the Substitution Index (SI) and the Phase Shift Index (PSI), is also reviewed discussing their effectiveness in the context of ecosystem health assessment and of the requirements of the WFD. The CI, the SI and the PSI go beyond the quality of the water and, thus, the WFD, as they provide additional indications on past events of disturbance that affected a meadow, on potentiality of a meadow to recover, on quality of sediments, on biological pollutants. An integrated approach based on the descriptors of the water quality together with the three ecological indices of the ecosystem health (CI, SI, and PSI) is thus recommended in order to discriminate the main components affecting the status of coastal ecosystems. Application of the CI, the SI and the PSI should be experienced in different areas of the Mediterranean Sea for selecting appropriate reference sites and for formulating more generalized classifications that shift the requirements of the WFD toward the perspective of the ecosystem health evaluation.
The epiphyte community structure of the
Posidonia oceanica leaves in three impacted meadows occurring in urbanised coastal areas was contrasted with that observed in three meadows located within ...Marine Protected Areas in the Ligurian Sea. Samplings were carried out in two distinct periods, at the beginning and at the end of the summer season, in order to individuate early changes in the epiphyte community structure. Differently from the descriptors commonly adopted for evaluating the health status of
P. oceanica ecosystem, the epiphyte community structure was able to detect alterations in the water quality already after 4
months. The impacted meadows showed an immature epiphyte community characterised by large development of brown algae. Leaf
P. oceanica epiphytes are, thus, proposed as appropriate biological quality elements (BQEs) able to show early responses to environmental alterations and they should be included in the monitoring programs for the conservation and the management of coastal areas.
Seagrass meadows are complex ecosystems representing an important source of biodiversity for coastal marine systems, but are subjected to numerous threats from natural and human-based influences. Due ...to their susceptibility to changing environmental conditions, seagrasses are habitually used in monitoring programmes as biological indicators to assess the ecological status of coastal environments. In this paper we used a non-destructive photo mosaicing technology to quantify seagrass distribution and abundance, and explore benefits of micro-cartographic analysis. Furthermore, the use of photogrammetric tools enhanced the method, which proved to be efficient due to its use of low-cost instruments and its simplicity of implementation. This paper describes the steps required to use this method in meadows of Posidonia oceanica, including: i) camera calibration procedures, ii) programming of video survey, iii) criteria to perform sampling activities, iv) data processing and micro-georeferenced maps restitution, and v) possible study applications.
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