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Este artículo contiene 18 páginas, 4 figuras., Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change., This paper was supported by Euromarine. Joaquim Garrabou acknowledges the funding by the “Severo Ochoa Centre of Excellence” (CEX2019-000928-S), the MCIU/AEI/FEDER [HEATMED; RTI2018-095346-B-I00], Interreg-Med Programme MPA-Engage (1MED15_3.2_M2_337), the European Union Horizon 2020 research and innovation programme (Futuremares SEP-210597628). Nuria Teixido acknowledges the French National Research Agency (4Oceans-MOPGA grant, ANR-17-MPGA-0001) and internal funds from the Stazione Zoologica Anton Dohrn. Gil Rilov was supported by the Israel Ministry of Environmental Protection. Hocein Bazairi, Free Spinosa, and Vasilis Gerovasileiou acknowledge the funding by the MAVA Fondation (MedKeyHabitats I Project) and the European Commission (Ecap-MED II Project; projects implemented by UNEP/MAP-RAC/SPA). Alfonso Ramos was supported the CIESM “Tropical Signals,” Stelios Katsanevakis and Maria Sini were supported by the Project “Coastal Environment Observatory and Risk Management in Island Regions AEGIS+” (MIS 5047038), implemented within the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014–2020), co-financed by the Hellenic Government (Ministry of Development and Investments) and the European Union (European Regional Development Fund, Cohesion Fund), Stelios Katsanevakis, Maria Sini and Vasilis Gerovasileiou acknowledge the support of the MARISCA Project, co-funded by 85% by the EEA GRANTS, 2009–2014, and 15% by the Public Investments Programme (PIP) of the Hellenic Republic. Ivan Guala and Daniele Grech thanks thank the support of the project “Pinna nobilis—ricerca per la sopravvivenza: un'iniziativa di Citizen Science per tracciare la mortalità di massa di Pinna nobilis in Sardegna” project and the L/7 grant (CUP 87G17000070002) funded by the Regione Autonoma Sardegna. Jean-Baptiste Ledoux was funded by an assistant researcher contract framework of the RD Unit—UID/Multi/04423/2019—Interdisciplinary Centre of Marine and Environmental Research—financed by the European Regional Development Fund (ERDF) through COMPETE2020—Operational Program for Competitiveness and Internationalization (POCI) and national funds through FCT/MCTES (PIDDAC). This research was supported by the Strategic Funding UIDB/04423/2020 and UIDP/04423/2020 through national funds provided by the FCT—Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the program PT2020. Bernat Hereu and Cristina Linares acknowledge the support of the long-term monitoring programme of the catalan Natural Parks, funded by the Departament de Territori i Sostenibilitat of the Generalitat de Catalunya. Cristina Linares acknowledges the support of the ICREA Academia programme. David Díaz acknowledges the support the research grant CTM2016-77027-R of the Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad and Program of Marines Strategies of Spain funded by MITERD. Jamila Ben Soussi was partially funded by the Fondation Albert 2 Monaco (MIMOSA Project) and the Tropical Signals Program of CIESM. Giovanni Chimienti was supported by the Italian Ministry of Education, University and Research (PON 2014–2020, AIM 1807508–1, Linea 1), by the Ente Parco Nazionale del Gargano (Research agreement with CoNISMa N. 21/2018), and by the National Geographic Society (Grant EC-176R-18). Nathaniel Bensoussan acknowledges financial support from the European Commission through the programme “Caroline Herschell” in the context of the action “Developing Downstream applications and services on BIO-PHYsical characterization of the seascape for COASTal management” (BIOPHYCOAST). Monica Montefalcone and Annalissa Azzola collected some of their data on MMEs in the frame of the project “Mare Caldo” funded by Greenpeace Italy. Núria Marbà acknowledges financial support from the Spanish Ministries of Economy and Competitiveness (CTM2012-32603, CGL2015-71809-P) and Ministerio de Ciencia, Innovación y Universidades (RTI2018-095441-B-C21). Diego K. Kersting acknowledges support by the postdoctoral fellowship programme Beatriu de Pinós funded by the Secretary of Universities and Research (Government of Catalonia) and the Horizon 2020 programme of research and innovation of the European Union under the Marie Sklodowska-Curie grant agreement No 801370.

“Introduced” species of the Algerian coast remains the most undocumented issue in the Mediterranean Sea. Only few studies were dedicated to Introduced species due to the lack of taxonomists. In-depth research on Introduced species along the Algerian coast should provide new data that could explain the spreading mechanisms in the southwestern part of the Mediterranean basin particularly near the Alboran Sea. Introduced species among other related research; of which the outcome is expected in the next few years, is in progress in the southwest Mediterranean basin. The aim of this work is to provide an inventory of available data pertaining to marine species “introduced” in Algerian waters, whether these species were introduced intentionally or accidentally. This large number of Introduced species records covers the period from 1834 to December 2017. Seventy “Introduced” species have been recorded along the Algerian coast, composed by 55.7% true aliens25.7 % range expanding species, 15.7% cryptogenic species and 2,9% vagrant species, with a clear domination of fish (38.57%) and macroalgae (30%). Approximately 348 introduction events have been reported; 64,9 % of them belong to macroalgae and one sighting out of two is done in the central region. The distribution and the status of introduced species in Algeria were evaluated. In total, 20% of the Introduced species can be considered as established along the Algerian coast, in particular the macrophyta, Codium fragile and Ulva lactuca as well as the cryptogenic species, Oculina patagonica, while Asparagopsis armata, A. taxiformis and Caulerpa cylindracea are considered as invasive.

This work is an overview of all available benthic data collected in the Algerian harbours between 1983 and 2001. So, total of 571 stations were reported in the 10 major Algerian harbours along the Algerian coast (1200km). Two main categories of harbours were distinguished according to their hydrodynamic regime and volume of water exchange between inner harbour basins and the entrance of the harbours. Univariate, multivariate, benthic indices and Biological Traits of Life approaches were applied on stations sampled in the late 1990s and long-term observations in six out of these ten harbours. These approaches assessed the main characteristics and ecological statuses from these south Mediterranean harbours. One of the main characteristics of the Algerian harbours was the very high species diversity (847 species). Although all the fauna was dominated by pollution-tolerant species; some harbours such as Bethioua and Djendjen hosted normal benthic communities as found in the open sea, but also included some pollution indicator species typical of a slight polluted system. On the contrary, the newly constructed port of Skikda showed perturbed benthic communities in relation to hydrocarbon pollution. Biological Traits of Life analysis reinforced the separation of benthic species along a gradient reflecting their sensitivity or tolerance to pollution. This response was related to an increase in organic matter content, probably associated with a general organic and metal contamination, from the entrance of the harbour to the innermost basins in areas with weak circulation, high sedimentation rate and concentrations of pollutants. Except for Oran harbour, where the poor to moderate ecological status remained unchanged with time, the other harbours showed an improvement or a slight degradation. A strategy of long-term monitoring should be promoted, based on a restricted and selected number of stations characteristic of the different basins and water masses occupying the harbours.

Este artículo contiene 16 páginas, 5 figurtas, 6 tablas, 3 apéndices con 3 tablas., The Biocoenosis of Well Sorted Fine Sands (WSFS) (SFBC, Sables Fins Bien Calibr es in French) is a Mediterranean community very well delimited by bathymetry (2e25 m) and sedimentology (>90% of fine sand) occurring in zones with relatively strong hydrodynamics. In this study focused on sites located along the Algerian, French, Italian and Spanish coasts of the Western Basin of the Mediterranean Sea (WBMS) we aim to compare the structure, ecological status and diversity of the macrofauna of the WSFS and examine the effects of recent human pressures on the state of this shallow macrobenthic community. We assess the ecological status and functioning of these WSFS using three categories of benthic indices: a) five indices based on classification of species into ecological groups, AMBI, BO2A, BPOFA, IQ and IP, b) the ITI index based on classification of species in trophic groups, and c) the Shannon H’ index, and the Biological Traits Analysis (BTA), which is an alternative method to relative taxon composition analysis and integrative indices. Cluster analyses show that each zone show a particular taxonomic richness and dominant species. The seven benthic indices reveal that the macrobenthos of the WSFS of the four coastal zones show good or high Quality Status, except for one location on the Algerian coast (the Djendjen site) in 1997. BTA highlights the presence of three groups of species: 1) typical characteristic species; 2) indicator species of enrichment of fine particles and organic matter, and 3) coarse sand species which are accessorily found on fine sand. Finally, the WSFS which are naturally subject to regular natural physical perturbations show a high resilience after human pressures but are very sensitive to changes in the input of organic matter., The authors thank the MEDISCAN programme for the Camargue Data, the Italian Research was funded by University of Pisa (Lardicci 308/2004) with the technical help of the Environmental Protection Regional Agency of Tuscany (ARPA Toscana).

International audience; Sampling surveys (1976-2013) of soft-bottom communities and some hard bottom communities along the Algerian coast (1,180 km) have allowed the collection of 114 species of crustacean decapods of which of 37 were reported for the first time for the Algerian decapods fauna; for these species additional comments concerning their ecological and geographical patterns are given. The inventory of all benthic and pelagic decapods recorded along the Algerian coast reaches 253 species. Three families on a total of 57 families were highly diversified: Paguridae (17 species), Polybiidae (16 species) and Processidae (13 species). The presence of the 253 recorded species along the Algerian coast has been compared with eight other areas from the Mediterranean Sea. The decapods fauna of the Algerian coast is among the most richest of the Mediterranean Sea and comparable of that of Italy.

International audience; Between 1995 and 2001, the soft-bottom communities along the 1180 km of the Algerian coast were sampled in nine gulfs and 12 harbours, providing a total of 655 samples. Eight macrozoobenthos-based biotic indices (S, N, H', BQI, AMBI, BENTIX, BO2A and ITI) were selected to describe the general patterns of the coastal water quality status and to establish a quality diagnosis for the different zones subjected to anthropogenic pressure (e.g., harbour construction, industrial and urban pollution). Reference values were determined for each of the eight indices selected by analyzing the indices' parameter distribution. The Ecological Quality Ratio (EQR) was estimated for each index, resulting in an EQR Mean Score and an EQR Bad Score. From these EQR, we defined an EQS for each sample. The agreement between these EQS was analysed using the Kappa method in order to propose a survey strategy for the Algerian coastal waters that would take into account the soft-bottom biological compartment. The results clearly indicate that high and good quality assessments are prevalent in the gulfs, while quality assessments in harbours vary greatly from bad to good. The effect of pollution observed in the harbours can be classified in two main groups, according to when they were constructed and their relative degree of openness to the sea, which permits better water circulation and probably dilutes the pollution

Recent sampling surveys (2011–2012) of the shallow (0–50 m) hard-bottom communities and re-examination of some soft-bottom communities (5–143 m) along the Algerian coast have allowed the collection of 33 species (five Caprelloidea, 27 Gammaridea and one Hyperiidea), which were not recorded before in the inventory of the marine amphipod fauna of Algeria (Bakalem & Dauvin, 1995; Grimes et al., 2009). This paper reports the number of specimens sampled for each of these 33 species and provides data on their geographical distribution and habitats. Fourteen of the species (43%) are considered to be endemic to the Mediterranean Sea; 15 others are north-eastern Atlantic and Mediterranean species, and the four last are cosmopolitan species. Twenty-nine of the new records are known for Italian waters and 19 in Greek waters where there is intensive amphipod inventory. The total number of marine amphipod fauna in Algeria is now 332.

International audience; The Mediterranean Sea is known as a biodiversity hot spot, with 16,848 species reported. Biodiversity is higher in coastal areas and decreases with depth. However, knowledge about the southwestern sector remains scarce. For the last three decades, sampling of soft-bottom communities along the 1180 km of the shallow Algerian coast (0–136 m) has recorded 1642 macrobenthic species. There is a decreasing west–east species-richness gradient, especially for the total species richness and the amphipods. In addition, quantitative sampling in Bou Ismail Bay in summer 1988 (98 sampling sites for a total of 841 species) shows that diversity indices (i.e. species richness, >100 species for 0.2 m−2; Shannon diversity, >6.0; and ES50, >34) are among the highest for similar sand and muddy-fine sand communities in the Mediterranean Sea and the northeastern Atlantic Ocean. Bou Ismail Bay appears to have the highest species richness among Algerian bays, probably because of its variety of benthic habitats and the absence of significant pollution in this area. Monitoring must be undertaken to survey this high biodiversity, and a national strategy should be proposed to preserve high diversity zones.

International audience; The interest in benthic indicators for soft-bottom marine communities has dramatically increased after a rather long period of relative stagnation due to the need for new tools to assess the status of marine waters, called for by the Clean Water Act and the Water Framework Directive. Our expertise on ben- thic communities has permitted us to gather a vast amount of data from diverse water bodies under unpolluted and polluted conditions (e.g., accidental oil spill, sewage, long-term anthropogenic estuarine constraints) in tidal estuaries, harbours, and on the coastal shelf from Atlantic Ocean and Mediterranean Sea. We compared the results of four biotic indices on the various available datasets: Shannon-Wiener H diversity, AMBI and BO2A, which divide the species into Ecological Groups, and ITI, which divides the species into trophic groups, and the agreement of Best Professional Judgement (BPJ) on the assessment of ecological conditions. Benthic indicators as "sentinel species", which is a particular species that by its presence or its relative abundance warns of possible unbalances in the surrounding environment or dis- tortions in community functions, was also tested. Indicators, BPJ and opportunist sentinel species gave similar ECoQS for the different sampling sites. We discuss the use of Biological Indicators as 'objective' or 'subjective' alternatives for assessing soft-bottom communities, and propose to employ simple methods such as BPJ and taxonomy sufficiency in such diagnostic approaches.

Recent sampling surveys (1995–2001) of the shallow (3–136 m) soft-bottom communities along the Algerian coast in nine bays and gulfs and twelve harbours have allowed 206 species of marine amphipod to be recorded. Among the species recorded, 45 species appear to be new in terms of the inventory of the marine amphipod fauna of Algeria (Bakalem & Dauvin, 2005). This note reports on the number of specimens sampled for each of these 45 species and provides data on sediment type and depth at which they were sampled. Sixteen of these species are considered to be endemic to the Mediterranean Sea, twenty-six are north-eastern Atlantic species, and the last three have a wide geographical distribution in the Indo-Pacific and the Atlantic Oceans. The sampling also permitted the confirmation of the presence of five other Atlantic amphipod species not already reported in the inventory of the Mediterranean amphipod fauna (Bellan-Santini et al., 1998). The total number of marine amphipod fauna in Algeria is now 298.