Bernat Hereu

Los ecosistemas marinos costeros desempeñan un importante papel ecológico tanto por su implicación en la productividad marina como por la biodiversidad que albergan, así como por los bienes y servicios que nos proporcionan. Pero muestran una elevada vulnerabilidad frente a perturbaciones tanto de origen natural como causadas por el hombre, y muchos de ellos están en declive a escala global. Los hábitats cercanos a la costa y en particular las comunidades de la zona infralitoral están especialmente afectados por las actividades humanas debido a su proximidad y las infraestructuras que conllevan. Detectar los cambios que se producen en las comunidades infralitorales es esencial para comprender las transformaciones y los efectos de las perturbaciones en los ecosistemas, así como la efectividad de las medidas de gestión aplicadas. Los estudios de monitoreo a largo plazo son fundamentales para entender la dinámica y el funcionamiento de estos ecosistemas pero sobre todo para detectar los...

Human activities and the resultant pressures they place on the marine environment have been widely demonstrated to contribute to habitat degradation, therefore, their identification and quantification is an essential step towards any meaningful restoration effort. The overall scope of MERCES Deliverable 1.2 is to review current knowledge regarding the major marine pressures placed upon marine ecosystems in EU waters and the mechanisms by which they impact habitats in order to determine potential restoration pathways. An understanding of their geographical distribution is critical for any local assessment of degradation, as well as for planning conservation and restoration actions. This information would ideally be in the form of maps, which: (a) compile single or multiple activities and pressures over broad scales, integrating and visualizing available data and allowing direct identification of aggregations as well as gaps and (b) may be overlaid with habitat maps (or any other map ...

The spatio-temporal variability of fish distribution is important to better manage and protect the populations of endangered species. In this sense, the vertical movements of a vulnerable and protected species, Sciaena umbra, were assessed in a marine protected area (the Réserve Naturelle Marine de Cerbère-Banyuls, south of France) to study the variability of their bathymetric distribution at different time scales. Twenty adults were marked with acoustic transmitters and acoustically monitored over 2.5 years. This revealed that some individuals remained at shallow waters (< 8 m) all year round, while others presented vertical segregation at deeper waters during the cold months (mean depth of 22.5 ± 0.04 m) and all aggregated in shallow waters during the warm months. The brown meagre was more active during the night, except in June and July when peaks of activity were observed at dusk. These patterns are likely associated with foraging and reproductive behavior during the cold and...

Coralligenous communities are an important “hot spot” of Mediterranean biodiversity. These communities are presently threatened by a combination of anthropogenic impacts partly related to global change. Managers of MPAs are increasingly concerned about the capacity of coralligenous communities to endure crowds of divers, and there is a call for descriptors and for quantitative methods for estimating this capacity. A good indicator to detect the impacts on coralligenous communities should gather the following essential traits: to be a long-lived, clonal, engineering species displaying an erect shape and a large size in order to facilitate the monitoring. Among the main taxonomic groups of the coralligenous, gorgonians display several advantages and, in this study, the red gorgonian Paramuricea clavata was selected as a model species to evaluate the effects of diving impact and climate change on coralligenous communities. We present three cases of study about the demographic monitorin...

Restoration is considered an effective strategy to accelerate the recovery of biological communities at local scale. However, the effects of restoration actions in the marine ecosystems are still unpredictable. We performed a global analysis of published literature to identify the factors increasing the probability of restoration success in coastal and marine systems. Our results confirm that the majority of active restoration initiatives are still concentrated in the northern hemisphere and that most of information gathered from restoration efforts derives from a relatively small subset of species. The analysis also indicates that many studies are still experimental in nature, covering small spatial and temporal scales. Despite the limits of assessing restoration effectiveness in absence of a standardized definition of success, the context (degree of human impact, ecosystem type, habitat) of where the restoration activity is undertaken is of greater relevance to a successful outcom...

The temperate coralligenous bioconcretions are mainly built by the accumulation of encrusting coralline algae growing at low irradiance levels. They harbour approximately 10% of marine Mediterranean species (about 1600 species), including long-lived algae and invertebrates. Enhanced by climate change, several pressures affect coralligenous assemblages, leading to increased frequency of mass mortalities and dramatic loss of habitat complexity and biodiversity. The EU-funded project MERCES is developing innovative methodologies to restore macroinvertebrate habitat-forming species from three key taxonomic groups: Cnidaria/Anthozoa, Porifera/Demospongiae and Bryozoa. Restoration protocols are based on fragments/transplants from donor organisms and recruitment-enhancing devices. Collaboration with volunteers (divers and diving operators) in several phases of field activities proved crucial both to minimize underwater working time and to increase the sense of stewardship in a major users’...

A review of 573 studies on active restoration actions in the marine environment, published in the last 25 years, was carried out at global scale. We assessed how, where, at which spatial and temporal scales and under which socio-ecological settings restoration studies have been carried out, from very shallow to deep sea habitats. Results show that restoration efforts across habitats are increasing, especially in seagrasses and coral reefs, but never approached at ecosystem level. Targets, methods, response variables and standards are still very heterogeneous. Of the factors considered in the review, habitat, human impact intensity, realm and methods of restoration were found to be good determinant of restoration success. Short project duration (one-two years), small restoration areas (< 1 ha), lack of controls and knowledge of baselines are still a limit for deriving generalities. Finally, restorations rarely consider future challenges linked to global change this impairing long-...

Aims: Aquatic and terrestrial realms display stark differences in key environmental factors and phylogenetic composition. Despite such differences, their consequences for the evolution of species life history strategies remain poorly understood. Here, we examine whether and how life history strategies vary between terrestrial and aquatic species. Location: Global. Time period: Variable, the earliest year being in 1906 and the most recent in 2015. Major taxa studies: Macroscopic animals and plants species. Methods: We use demographic information for 638 terrestrial and 117 aquatic animal and plant species, to derive key life history traits capturing their population turnover, and investments in survival, development, and reproduction. We use phylogenetically corrected least squares regression to explore the differences in the trade-offs between life history traits in both realms. We then quantify the life history strategies of aquatic and terrestrial species using a phylogenetically ...

Long-term ecological studies are crucial to understand how and why natural ecosystems change over time and space. Through a revision of historical data and a comparison with current in situ field data, we contribute to the understanding of how the Mediterranean coastal seascape has changed in the last decades. Here we describe the large decrease of the main habitat-forming species Codium vermilara along the Catalan coast (NW Mediterranean). We have analyzed data on presence/absence, abundance and biomass. Since the 70s-80s, when the species reached its highest abundances, the species has totally disappeared from 45% of the revisited sites, and showed a decrease in 95% of its abundance and 97% of its biomass. Codium vermilara has also shown a reduction in its depth range, from 30 to the first 20m depth. This study highlights the importance of having historical data to detect and describe changes in ecological systems.

Dispersal and recruitment are fundamental processes for population recovery following disturbances in sessile species. While both processes are well understood for many terrestrial species, they still remain poorly resolved for some macroalgal species. Here we experimentally investigated the effective dispersal and recruit survival of a mesophotic Mediterranean fucoid, Cystoseira zosteroides. In three isolated populations, four sets of settlement collectors were placed at increasing distances (from 0 to 10 m) and different orientations (North, South, East and West). We observed that effective dispersal was restricted to populations' vicinity, with an average of 6.43 m and not further than 13.33 m, following a Weibull distribution. During their first year of life, survival was up to 50%, but it was lower underneath the adult canopy, suggesting a negative density-dependence. To put our results in a broader context we compared the effective dispersal of other fucoid and kelp specie...

It is important to account for the movement behaviour of fishes when designing effective marine protected areas (MPAs). Fish movements occur across different spatial and temporal scales and understanding the variety of movements is essential to make correct management decisions. This study describes in detail the movement patterns of an economically and commercially important species, Diplodus sargus, within a well-enforced Mediterranean MPA. We monitored horizontal and vertical movements of 41 adult individuals using passive acoustic telemetry for up to one year. We applied novel analysis and visualization techniques to get a comprehensive view of a wide range of movements. D. sargus individuals were highly territorial, moving within small home ranges (< 1 km2), inside which they displayed repetitive diel activity patterns. Extraordinary movements beyond the ordinary home range were observed under two specific conditions. First, during stormy events D. sargus presented a shelter...

Résumé/Abstract Depuis 1994, de nombreuses missions ont été effectuées dans la Réserve Marine de Scandola afin d'étudier la structure, la dynamique à long terme et la reconstitution des communautés à Cystoseira des étages infra littoral et circa littoral. Dans ce travail ...

ABSTRACT Although recruitment is considered an essential process regulating populations of many marine species, there is still a lack of knowledge about the ultimate factors that influence it. This is especially true for seaweeds, where population dynamics studies are also lacking. The main objective of this study was to investigate the main mechanisms driving the recruitment patterns of an emblematic deep-water alga in the NW Mediterranean, Cystoseria zosteroides, and its influence on their population dynamics. Five C. zosteroides populations were monitored annually at different sites along the coast of Spain by using permanent transects over three to four years. Some of these populations suffered mass mortality events from natural or anthropogenic disturbances, allowing us to study the influence of such events. Our findings agreed with the expected results for a long-lived species. Under low frequency of disturbances, C. zosteroides populations displayed few fluctuations over time given the longevity of the adults, and they were poorly influenced by the dynamics of early life stages because of negative density-dependent control of conspecifics. Moreover, disturbances had a great influence on population dynamics because the removal of adults decreased the effects of density-dependent processes, and enhanced the recruitment. Nonetheless, a high mortality was found for early life stages (~50% yr-1), contrasting with the high survival of adults (~90% yr-1). This study confirmed the slow population dynamics of these deep assemblages, demonstrated the influence of density in the C. zosteroides population dynamics and highlighted their vulnerability to the increase of natural and human-induced disturbances.

Knowledge about key demographic processes is required to understand and to predict the response of populations to environmental change. Recruitment is an essential process regulating population abundance and dynamics of many marine species. From the initial settlement of propagules to the first appearance in the population, algae are likely to experience substantial mortality. Notwithstanding, there is a poor knowledge about factors controlling their recruitment success. Cystoseria zosteroides is an emblematic species of deep-water Mediterranean forests, thriving on rocky bottoms between 15 to 80 m depth. The perennial character of this species has a marked influence on these communities, which show slow dynamics and harbour a high biodiversity of sessile invertebrates and encrusting algae. However, a global decline of Cystoseira assemblages throughout the Mediterranean has been observed during the last decades To date, few studies have focused on C. zosteroides populations, showing...

ABSTRACT There is growing evidence that processes other than predation have a critical role in determining sea urchin populations, causing unexpected responses to existing top-down control models. Although the biology and ecology of sea urchins have been widely studied, the long term dynamics of their populations are still poorly understood. This lack of knowledge is caused mainly by the scarcity of monitoring studies that are long and frequent enough to integrate interannual variability with low-frequency processes, which can be essential in determining the structure and dynamics of sea urchin populations. The aim of this study is to describe temporal variability in abundance and size-structure of the sea urchins Paracentrotus lividus and Arbacia lixula in rocky habitats in the northwestern Mediterranean. Two long-term monitoring series of data in two different marine protected areas are compared: Medes Islands Marine Reserve and the nearby unprotected area (measured annually from 1991 to 2012) are compared with the Port-Cros National Park (measured annually from 1983-1984 and 1994-2003). These series of data show how different processes, such as recruitment, predation or competition between both species, interact with other factors acting at different scales, such as a mass mortality episode that occurred in Port-Cros in 1982-1983, or the effects of an exceptional storm in Medes Islands in 2008, or the increase of sea temperature during the study period.

An important principle of environmental science is that changes in single components of systems are likely to have consequences elsewhere in the same systems. In the sea, food web data are one of the few foundations for predicting such indirect effects, whether of fishery exploitation or following recovery in marine protected areas (MPAs). We review the available literature on one type of indirect interaction in benthic marine ecosystems, namely trophic cascades, which involve three or more trophic levels connected by predation. Because many indirect effects have been revealed through fishery exploitation, in some cases we include humans as trophic levels. Our purpose is to establish how widespread cascades might be, and infer how likely they are to affect the properties of communities following the implementation of MPAs or intensive resource exploitation. We review 39 documented cascades (eight of which include humans as a trophic level) from 21 locations around the world; all but...

ABSTRACT: The dusky grouper Epinephelus marginatus pair spawns in summer in the NW Mediterranean. Only a few spawning sites have been identified, mostly in marine reserves. Because the dusky grouper is vulnerable to fishing, there is a need to identify and predict ...

An important principle of environmental science is that changes in single components of systems are likely to have consequences elsewhere in the same systems. In the sea, food web data are one of the few foundations for predicting such indirect effects, whether of fishery exploitation or following recovery in marine protected areas (MPAs). We review the available literature on one type of indirect interaction in benthic marine ecosystems, namely trophic cascades, which involve three or more trophic levels connected by predation. Because many indirect effects have been revealed through fishery exploitation, in some cases we include humans as trophic levels. Our purpose is to establish how widespread cascades might be, and infer how likely they are to affect the properties of communities following the implementation of MPAs or intensive resource exploitation. We review 39 documented cascades (eight of which include humans as a trophic level) from 21 locations around the world; all but two of the cascades are from shallow systems underlain by hard substrata (kelp forests, rocky subtidal, coral reefs and rocky intertidal). We argue that these systems are well represented because they are accessible and also amenable to the type of work that is necessary. Nineteen examples come from the central-eastern and north-eastern Pacific, while no well-substantiated benthic cascades have been reported from the NE, CE or SW Atlantic, the Southern Oceans, E Indian Ocean or NW Pacific. The absence of examples from those zones is probably due to lack of study. Sea urchins are very prominent in the subtidal examples, and gastropods, especially limpets, in the intertidal examples; we suggest that this may reflect their predation by fewer specialist predators than is the case with fishes, but also their conspicuousness to investigators. The variation in ecological resolution amongst studies, and in intensity of study amongst systems and regions, indicates that more cascades will likely be identified in due course. Broadening the concept of cascades to include pathogenic interactions would immediately increase the number of examples. The existing evidence is that cascade effects are to be expected when hard-substratum systems are subject to artisanal resource exploitation, but that the particular problems of macroalgal overgrowth on Caribbean reefs and the expansion of coralline barrens in the Mediterranean rocky-sublittoral will not be readily reversed in MPAs, probably because factors other than predation-based cascades have contributed to them in the first place. More cascade effects are likely to be found in the soft-substratum systems that are crucial to so many large-scale fisheries, when opportunities such as those of MPAs and fishing gradients become available for study of such systems, and the search is widened to less conspicuous focal organisms such as polychaetes and crustaceans.