• Energy Research

Historical exploitation of the Mediterranean Sea and the absence of rigorous baselines makes it difficult to evaluate the current health of the marine ecosystems and the efficacy of conservation actions at the ecosystem level. Here we establish the first current baseline and gradient of ecosystem structure of nearshore rocky reefs at the Mediterranean scale. We conducted underwater surveys in 14 marine protected areas and 18 open access sites across the Mediterranean, and across a 31-fold range of fish biomass (from 3.8 to 118 g m(-2)). Our data showed remarkable variation in the structure of rocky reef ecosystems. Multivariate analysis showed three alternative community states: (1) large fish biomass and reefs dominated by non-canopy algae, (2) lower fish biomass but abundant native algal canopies and suspension feeders, and (3) low fish biomass and extensive barrens, with areas covered by turf algae. Our results suggest that the healthiest shallow rocky reef ecosystems in the Mediterranean have both large fish and algal biomass. Protection level and primary production were the only variables significantly correlated to community biomass structure. Fish biomass was significantly larger in well-enforced no-take marine reserves, but there were no significant differences between multi-use marine protected areas (which allow some fishing) and open access areas at the regional scale. The gradients reported here represent a trajectory of degradation that can be used to assess the health of any similar habitat in the Mediterranean, and to evaluate the efficacy of marine protected areas.

AbstractBiological invasions represent one of the main threats to marine biodiversity. From a conservation perspective, especially in the context of increasing sea warming, it is critical to examine the suitability potential of geographical areas for the arrival of Range‐Expanding Introduced and Native Species (REINS), and hence anticipate the risk of such species to become invasive in their new distribution areas. Here, we developed an empirical index, based on functional and bio‐ecological traits, that estimates the Invasive Potential (IP; i.e. the potential success in transport, introduction and population establishment) for a set of 13 fishes that are expanding their distributional range into the Mediterranean Sea, the most invaded sea in the world. The IP index showed significant correlation with the observed spreading of REINS. For the six species characterized by the highest IP, we calculated contemporary and future projections of their Environmental Suitability Index (ESI). By using an ensemble modelling approach, we estimated the geographical areas that are likely to be the most impacted by REINS spreading under climate change. Our results demonstrated the importance of functional traits related to reproduction for determining high invasion potential. For most species, we found high contemporary ESI values in the South‐eastern Mediterranean Sea and low to intermediate contemporary ESI values in the Adriatic Sea and North‐western Mediterranean sector. Moreover, we highlighted a major potential future expansion of high ESI values, and thus REINS IP, towards the northern Mediterranean, especially in the northern Adriatic Sea. This potential future northward expansion highlights the risk associated with climate‐induced impacts on ecosystem conservation and fish stock management throughout the entire Mediterranean Sea.

Successfully enforced marine protected areas (MPAs) have been widely demonstrated to allow, within their boundaries, the recovery of exploited species and beyond their boundaries, the spillover of juvenile and adult fish. Little evidence is available about the so-called 'recruitment subsidy', the augmented production of propagules (i.e. eggs and larvae) due to the increased abundance of large-sized spawners hosted within effective MPAs. Once emitted, propagules can be locally retained and/or exported elsewhere. Patterns of propagule retention and/or export from MPAs have been little investigated, especially in the Mediterranean. This study investigated the potential for propagule production and retention/export from a Mediterranean MPA (Torre Guaceto, SW Adriatic Sea) using the white sea bream, Diplodus sargus sargus, as a model species. A multidisciplinary approach was used combining 1) spatial distribution patterns of individuals (post-settlers and adults) assessed through visual census within Torre Guaceto MPA and in northern and southern unprotected areas, 2) Lagrangian simulations of dispersal based on an oceanographic model of the region and data on early life-history traits of the species (spawning date, pelagic larval duration) and 3) a preliminary genetic study using microsatellite loci. Results show that the MPA hosts higher densities of larger-sized spawners than outside areas, potentially guaranteeing higher propagule production. Model simulations and field observation suggest that larval retention within and long-distance dispersal across MPA boundaries allow the replenishment of the MPA and of exploited populations up to 100 km down-current (southward) from the MPA. This pattern partially agrees with the high genetic homogeneity found in the entire study area (no differences in genetic composition and diversity indices), suggesting a high gene flow. By contributing to a better understanding of propagule dispersal patterns, these findings provide crucial information for the design of MPAs and MPA networks effective to replenish fish stocks and enhance fisheries in unprotected areas.

Spawning dates and pelagic larval duration (PLD) are early life traits (ELT) crucial for understanding life cycles, properly assessing patterns of connectivity and gathering indications about patchiness or homogeneity of larval pools. Considering that little attention has been paid to spatial variability in these traits, we investigated variability of ELT from the analysis of otolith microstructure in the common two-banded sea bream Diplodus vulgaris. In the southwestern Adriatic Sea, along ~200 km of coast (~1° in latitude, 41.2° to 40.2°N), variability of ELT was assessed at multiple spatial scales. Overall, PLD (ranging from 25 to 61 d) and spawning dates (October 2009 to February 2010) showed significant variability at small scales (i.e. <6 km), but not at larger scales. These outcomes suggest patchiness of the larval pool at small spatial scales. Mul- tiple causal processes underlying the observed variability are discussed, along with the need to properly consider spatial variability in ELT, for example when delineating patterns of connectivity.

ABSTRACT Marine Protected Areas (MPAs) have gained increasing popularity worldwide as tools for biodiversity conservation and management of human uses. This rise in popularity has been accompanied by an increasing body of scientific papers and books on MPA design and management, the vast majority of which are almost completely focused on coastal or insular MPAs. A small number of MPAs have also been established in the pelagic domain, however, these pelagic sites have been considered in isolation from coastal/insular MPAs, even when the sites are adjacent or nearby. Pelagic and coastal ecosystems are not at all isolated from each other, but interconnected both physically via the flow of water, and biologically, via the movement of organisms. In order to maximize the effectiveness of MPAs, it is suggested that spatial management planning encompass large areas that span both coastal and pelagic domains. This requires integrated, large‐scale spatial management, which may extend across borders and thus require international cooperation.Copyright © 2012 John Wiley & Sons, Ltd.

Abstract The positive effect of fully protected marine protected areas (MPAs) on marine biodiversity, and specifically on fishes, has been widely documented. In contrast, the potential of MPAs to mitigate the impact of adverse climatic conditions has seldom been investigated. Here, we assessed the effectiveness of MPAs, quantified as increasing fish biomass, across wide geographic and environmental gradients across the Mediterranean Sea. We performed underwater visual surveys within and outside MPAs to characterize fish assemblages in 52 rocky reef sites across an extent of over 3300 km. We used the steep spatial temperature gradient across the Mediterranean as a ‘space‐for‐time’ substitution to infer climate‐driven temporal changes. We found that, as expected, Mediterranean MPAs increased fish biomass. At the same time, higher seawater temperatures are associated with decreased fish biomass, changes in species composition, and shifts towards more thermophilic species. Importantly, we found that the rate of decrease in fish biomass with temperature was similar between protected and fished sites. Taken together, these results suggest that the capacity of MPAs to harbour higher fish biomass, compared to surrounding areas, is maintained across a broad temperature range. At the same time, MPAs will not be able to offset larger‐scale biotic alterations associated with climate change. Policy implications. Our results suggest that sustained warming will likely reduce fish biomass in the Mediterranean Sea and shift community structure, requiring more conservative targets for fishery regulations. At the same time, protection from fishing will remain an important management tool even with future high‐water temperatures, and MPAs are expected to continue to provide local‐scale benefits to conservation and fisheries.