An ecosystem-based approach to assess the status of Mediterranean algae-dominated shallow rocky reefs.

A conceptual model was constructed for the functioning the algae-dominated rocky reef ecosystem of the Mediterranean Sea. The Ecosystem-Based Quality Index (reef-EBQI) is based upon this model. This index meets the objectives of the EU Marine Strategy Framework Directive. It is based upon (i) the weighting of each compartment, according to its importance in the functioning of the ecosystem; (ii) biological parameters assessing the state of each compartment; (iii) the aggregation of these parameters, assessing the quality of the ecosystem functioning, for each site; (iv) and a Confidence Index measuring the reliability of the index, for each site. The reef-EBQI was used at 40 sites in the northwestern Mediterranean. It constitutes an efficient tool, because it is based upon a wide set of functional compartments, rather than upon just a few species; it is easy and inexpensive to implement, robust and not redundant with regard to already existing indices

Collaborative database to track Mass Mortality Events in the Mediterranean Sea

Anthropogenic climate change, and global warming in particular, has strong and increasing impacts on marine ecosystems (Poloczanska et al., 2013; Halpern et al., 2015; Smale et al., 2019). The Mediterranean Sea is considered a marine biodiversity hotspot contributing to more than 7% of world\u2019s marine biodiversity including a high percentage of endemic species (Coll et al., 2010). The Mediterranean region is a climate change hotspot, where the respective impacts of warming are very pronounced and relatively well documented (Cramer et al., 2018). One of the major impacts of sea surface temperature rise in the marine coastal ecosystems is the occurrence of mass mortality events (MMEs). The first evidences of this phenomenon dated from the first half of \u201980 years affecting the Western Mediterranean and the Aegean Sea (Harmelin, 1984; Bavestrello and Boero, 1986; Gaino and Pronzato, 1989; Voultsiadou et al., 2011). The most impressive phenomenon happened in 1999 when an unprecedented large scale MME impacted populations of more than 30 species from different phyla along the French and Italian coasts (Cerrano et al., 2000; Perez et al., 2000). Following this event, several other large scale MMEs have been reported, along with numerous other minor ones, which are usually more restricted in geographic extend and/or number of affected species (Garrabou et al., 2009; Rivetti et al., 2014; Marb\ue0 et al., 2015; Rubio-Portillo et al., 2016, authors\u2019 personal observations). These events have generally been associated with strong and recurrent marine heat waves (Crisci et al., 2011; Kersting et al., 2013; Turicchia et al., 2018; Bensoussan et al., 2019) which are becoming more frequent globally (Smale et al., 2019). Both field observations and future projections using Regional Coupled Models (Adloff et al., 2015; Darmaraki et al., 2019) show the increase in Mediterranean sea surface temperature, with more frequent occurrence of extreme ocean warming events. As a result, new MMEs are expected during the coming years. To date, despite the efforts, neither updated nor comprehensive information can support scientific analysis of mortality events at a Mediterranean regional scale. Such information is vital to guide management and conservation strategies that can then inform adaptive management schemes that aim to face the impacts of climate change

Early-life dispersal traits of coastal fishes: an extensive database combining observations and growth models

Early-life stages play a key role in the dynamics of bipartite life cycle marine fish populations. Difficult to monitor, observations of these stages are often scattered in space and time. While Mediterranean coastlines have often been surveyed, no effort has been made to assemble historical observations. Here we build an exhaustive compilation of dispersal traits for coastal fish species, considering in situ observations and growth models (; https://doi.org/10.17882/91148). Our database contains over 110 000 entries collected from 1993 to 2021 in various subregions. All observations are harmonized to provide information on dates and geolocations of both spawning and settlement, along with pelagic larval durations. When applicable, missing data and associated confidence intervals are reconstructed from dynamic energy budget theory. Statistical analyses allow traits' variability to be revisited and sampling biases to be revealed across taxa, space and time, hence providing recommendations for future studies and sampling. Comparison of observed and modelled entries provides suggestions to improve the feed of observations into models. Overall, this extensive database is a crucial step to investigate how marine fish populations respond to global changes across environmental gradients

Temporal variation in vegetative development of Caulerpa scalpelliformis (Chlorophyta) from Baleia beach, Ilha Grande bay (Rio de janeiro, brazil)

Caulerpa scalpelliformis grows on rocky and sandy bottoms at different depths in Jacuacanga Cove, Ilha Grande Bay, where it can form dense patches. The invasive behavior of this and other species of Caulerpa is well documented in the literature. This study analyzed the variation of the vegetative development of C. scalpelliformis from Baleia Beach (23º01'63''S and 44º14'18''W) in Jacuacanga Cove, from June 2003 to September 2004, including plants from rocky and sandy substrates. Morphometric and dry weight data from the erect and prostrate portions were used. Plants were collected from 20 x 20 cm² plots (n=3), randomly positioned on the rocky boulders (≅1.5 m depth) and on contiguous sandy bottom (≅3.0 m depth). During the study period, C. scalpelliformis occurred on both substrates as a pseudo-perennial species, showing partial loss of the erect portions from winter to spring; the height and dry weight of the erect portions increased from summer to autumn on both substrates. The temporal variation of C. scalpelliformis vegetative development in Baleia Beach was similar to that described for the invasive C. racemosa and C. taxifolia from different geographical regions of the world.Caulerpa scalpelliformis cresce sobre substrato rochoso e arenoso a diferentes profundidades na Enseada de Jacuacanga, Baía da Ilha Grande, onde pode formar bancos densos. O comportamento invasor desta e de outras espécies de Caulerpa é bem documentado na literatura. Este estudo analisou a variação do desenvolvimento vegetativo de C. scalpelliformis da Praia da Baleia (23º01'63''S e 44º14'18''W), Enseada de Jacuacanga, de junho de 2003 a setembro de 2004, considerando plantas do substrato rochoso e do fundo de areia. Dados morfométricos e de peso seco das porções prostrada e ereta foram usados. Plantas foram coletadas em quadrados de 20 cm de lado (n=3), posicionados aleatoriamente sobre o substrato rochoso (profundidade ≅ 1,5 m) e sobre o substrato arenoso (profundidade ≅ 3,0 m). Durante o período de estudo, C. scalpelliformis ocorreu nos dois substratos como espécie pseudo-perene, mostrando perda parcial das porções eretas do talo do inverno para a primavera; altura e massa seca das porções eretas mostraram tendência de aumento do verão para o outono nos dois substratos. A variação temporal do desenvolvimento vegetativo de C. scalpelliformis na Praia da Baleia foi similar à descrita para C. racemosa e C. taxifolia, espécies invasoras em diferentes regiões do mundo

Marine Invasion in the Mediterranean Sea: The Role of Abiotic Factors When There Is No Biological Resistance

The tropical red alga Womersleyella setacea (Rhodomelaceae, Rhodophyta) is causing increasing concern in the Mediterranean Sea because of its invasive behavior. After its introduction it has colonized most Mediterranean areas, but the mechanism underlying its acclimatization and invasion process remains unknown. To understand this process, we decided i) to assess in situ the seasonal biomass and phenological patterns of populations inhabiting the Mediterranean Sea in relation to the main environmental factors, and ii) to experimentally determine if the tolerance of W. setacea to different light and temperature conditions can explain its colonization success, as well as its bathymetric distribution range. The bathymetric distribution, biomass, and phenology of W. setacea were studied at two localities, and related to irradiance and temperature values recorded in situ. Laboratory experiments were set up to study survival, growth and reproduction under contrasting light and temperature conditions in the short, mid, and long term.Results showed that, in the studied area, the bathymetric distribution of W. setacea is restricted to a depth belt between 25 and 40 m deep, reaching maximum biomass values (126 g dw m−2) at 30 m depth. In concordance, although in the short term W. setacea survived and grew in a large range of environmental conditions, its life requirements for the mid and long term were dim light levels and low temperatures. Biomass of Womersleyella setacea did not show any clear seasonal pattern, though minimum values were reported in spring. Reproductive structures were always absent. Bearing in mind that no herbivores feed on Womersleyella setacea and that its thermal preferences are more characteristic of temperate than of tropical seaweeds, low light (50 µmol photon m−2 s−1) and low temperature (12°C) levels are critical for W. setacea survival and growth, thus probably determining its spread and bathymetric distribution across the Mediterranean Sea

Environmental and benthic habitat factors structuring the spatial distribution of a summer infralittoral fish assemblage in the north-western Mediterranean Sea

Patterns of distribution of a Mediterranean fish assemblage, with special attention to juvenile labrids, were studied at different depths on the basis of their relationships with environmental and benthic habitat features on a rocky coast at Marseille, south-eastern France. Fish species were distributed according to depth, with juveniles and small individuals being found in shallow waters, whereas larger individuals were found in deeper waters. However, depth by itself was not a significant factor in explaining fish species pattern, whereas sandy bottom habitat was significant. The most significant factors explaining fish species distribution were small and large blocks, and rock cover. Juvenile labrids, such as the most abundant ones Coris julis and Symphodus ocellatus, were only rarely observed deeper than 10 m, and the distribution of these juveniles was mainly correlated with a cover of macroalgae, rubble and small blocks. Fish density and fish biomass were higher in shallow than in deeper waters, although some species displayed an opposite pattern, such as the adult of C. julis and Diplodus sargus. The most significant factors explaining the fish density pattern found were the presence of macroalgae, Posidonia oceanica sea grass and sand cover. Among environmental factors assessed in this study, exposure to dominant winds was never significant, either for the whole fish assemblage or for juvenile labrids, or for the communities at any of the depth strata investigated. Depth was a significant factor influencing the distribution of juvenile labrids, whereas its significance in explaining fish density was lower. Bottom slope was generally more significant than depth, and thus constituted the most significant environmental factor. Benthic habitat characteristics were all significant, except for rubble cover, in explaining both fish species and fish density distributions. However, the amplitude of the relationships between substrate variables and fish assemblages was dependent on the descriptor studied (i.e. species distribution, including considerations of fish sizes, and fish density), suggesting that extrapolation of a particular relationship to other components of a fish assemblage would most likely be unfounded. Our results as a whole indicate that benthic habitat use by fish on Mediterranean rocky infralittoral coast is clearly non-random, and suggest that differences in habitat and/or environmental characteristics have significant effects at a small spatial scale on these fish assemblages.</jats:p

Artificial reefs do increase secondary biomass production: mechanisms evidenced by stable isotopes

A large complex of artificial reefs was deployed in the Bay of Marseilles, North-Western Mediterranean, forthe enhancement of commercial fisheries stocks. Carbon and nitrogen stable isotope and stomach contentanalyses were performed on 23 fish species collected on the artificial reefs to assess their trophic position andfeeding behaviour. Results indicated that fish diets were not modified on the artificial reefs compared to naturalenvironments, nor was the structure of their trophic network. Artificial reefs, with their complex design, providediverse and abundant food sources for fishes. Ranges of δ13C and δ15N of artificial reef fishes were comparable tothose recorded in natural Mediterranean environments, with a similar trophic organization. However, somediscrepancies appeared when comparing fish trophic level based on isotopic or diet results, which calls for acareful interpretation of stable isotope values as direct indicators of trophic level

Canopy-Forming Seaweeds in Urchin-Dominated Systems in Eastern Canada: Structuring Forces or Simple Prey for Keystone Grazers?

Models of benthic community dynamics for the extensively studied, shallow rocky ecosystems in eastern Canada emphasize kelp-urchin interactions. These models may bias the perception of factors and processes that structure communities, for they largely overlook the possible contribution of other seaweeds to ecosystem resilience. We examined the persistence of the annual, acidic (H2SO4), brown seaweed Desmarestia viridis in urchin barrens at two sites in Newfoundland (Canada) throughout an entire growth season (February to October). We also compared changes in epifaunal assemblages in D. viridis and other conspicuous canopy-forming seaweeds, the non-acidic conspecific Desmarestia aculeata and kelp Agarum clathratum. We show that D. viridis can form large canopies within the 2-to-8 m depth range that represent a transient community state termed ‘‘Desmarestia bed’’. The annual resurgence of Desmarestia beds and continuous occurrence of D. aculeata and A. clathratum, create biological structure for major recruitment pulses in invertebrate and fish assemblages (e.g. from quasi-absent gastropods to .150 000 recruits kg21 D. viridis). Many of these pulses phase with temperature driven mass release of acid to the environment and die-off in D. viridis. We demonstrate experimentally that the chemical makeup of D. viridis and A. clathratum helps retard urchin grazing compared to D. aculeata and the highly consumed kelp Alaria esculenta. In light of our findings and related studies, we propose fundamental changes to the study of community shifts in shallow, rocky ecosystems in eastern Canada. In particular, we advocate the need to regard certain canopy-forming seaweeds as structuring forces interfering with top-down processes, rather than simple prey for keystone grazers. We also propose a novel, empirical model of ecological interactions for D. viridis. Overall, our study underscores the importance of studying organisms together with cross-scale environmental variability to better understand the factors and processes that shape marine communities

Teneurs en éléments traces des téléostéens des herbiers de posidonie

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