Becerro Mikel’s scientific contributions

Marine communities are steadily degrading due to increasing anthropogenic pressures, particularly in coastal zones. Whether a community may return to the pre-degrading stage depends on multiple factors, including the duration and strength of the disturbance and the capacity of the system itself to bounce back to where it was before disturbance, i.e. its resilience. As the main drivers of ecological change, humans also have the capacity to regulate their activities to minimize their impact and to maximize the resilience of natural systems. In this study we quantified site specific management index based on social factors with a strong influence on resilience, such as population density, eutrophication, or fishing pressure. We used a total of seven social factors, which were obtained from national and local databases. A score is then attributed to each factor depending of its effect on marine resilience. The management index is the sum of all scores for each site. Our results show locations where a change in management decisions could improve significantly marine resilience (e.g., some locations in Northern Spain). Because the seven social factors convey multiple management measures, our index can not only point to specific locations but also to management actions that would contribute the most to increase marine resilience. Because social activities largely influence marine resilience, our study can provide socio-ecological basis to develop new and efficient marine management guidelines.

The Alboran Sea is an ecoregion in between the South European Atlantic Shelf and the Western Mediterranean ecoregions. Oceanographic conditions in the Alboran Sea are strongly influenced by Atlantic and Mediterranean currents, which suggest that this particular ecoregion could function as a transition zone from Atlantic to Mediterranean biodiversity. The Alboran Sea ecoregion is a major contributor to species richness of temperate seas and it is consider a biodiversity hotspot, but we know very little about the resistance and resilience of this region, i.e., the capacity of the region to resist to and recover from disturbance. Both resistance and resilience are critical components for a healthy ocean and a warranty to ensure effective conservation. Our study used a resilience framework to calculate an index based on a number of indicators that are known to directly affect the resilience of temperate benthic communities. Our results showed that marine resilience increased progressively and significantly from western to eastern Alboran Sea. Maximum resilience values occurred on marine protected areas. Whether the high resilience values of protected communities are a cause or a consequence of protection remains unclear, but our study supports the hypothesis that protection increases the capacity of the system to recover from disturbance and sets forth a number of hypotheses prone to experimental testing.

Marine biodiversity along the Iberian Peninsula coast is a unique crossroad, as it is surrounded by three ecoregions of the world: the South European Atlantic Shelf, the Alboran Sea, and the Western Mediterranean. Ecoregions are characterized by distinct environmental traits and associated biodiversity. The Mediterranean Sea is a highly diverse ecoregion whose waters are known to influence nearby regions outside the Mediterranean basin. Here, we looked at the marine biodiversity along the Iberian coast to quantify how benthic communities in the Atlantic coast deviated from the Mediterranean communities. We used underwater visual census to quantify fish and invertebrates and used multivariate techniques to quantify how communities in the Atlantic deviated from the Mediterranean type community. Our data showed how Mediterranean influence weakened as we move away from the Gibraltar Straight up to the entrance of the Bay of Biscay. However, benthic communities in the Bay of Biscay become increasingly more Mediterranean-like communities as we get closer to France, reversing the trend found in Portugal and western Galicia coasts. Similarity with the Mediterranean type community decreased from over 50% in sites near the Gibraltar Strait to less than 15%, at the entrance of the Bay of Biscay. Then, and despite the larger geographic distance, communities within the Bay of Biscay steadily recovered resemblance with the Mediterranean type community as we approached France. This pattern seemed to be caused by changes in environmental variables such as sea surface temperature and confirms the Mediterranean influence on Atlantic biodiversity well beyond Mediterranean boundaries.

Habitat heterogeneity is a major component of biodiversity as it determines species distribution and abundance. Habitat loss, with its associated loss of species, food resources, and ecosystem functioning, is identified as one of the major threats to marine biodiversity. Traditionally, the analysis of taxonomic diversity dominates community level approaches. But species losses or additions can generate major or minor impacts in multiple ecosystem processes depending on their functional traits. Recently, there are an increasing number of researches that approach ecosystem dynamics based on species functional traits. Yet, we still have no description of habitats based on their functional characteristics. Here, we carried out a functional level characterization of the different habitats present on Spanish littoral reefs. We have used underwater visual census that follow the Reef Life Survey methodology to quantify fish, invertebrate, and sessile communities in more than 250 locations scattered over the Spanish and Portuguese coasts. We have quantified the sessile community with over 5.000 photoquadrats distributed along five marine ecoregions: Alboran Sea, Macaronesian, Saharan upwelling, South European Atlantic Shelf and Western Mediterranean. We have described 16 functional traits, including algae, sessile animals, and substrate types. These traits have allowed us to determine 13 functional marine habitats differentially distributed over the coast of Portugal, Spain, and associated archipelagos. The largest functional habitat covers 18% of the rocky reefs and it is dominated by corticated macrophytes (28%), filamentous algae (20%), and bare rock (18%) functional groups. Functional habitats dominated by leathery functional group and filamentous functional group account of 2% and 3% of rocky reefs and are not represented in marine protected areas. Our results suggest that Spain and Portugal have a large number of functional habitats heterogeneously distributed in their coastal waters. Because each habitat is restricted to a specific range in the functional space, effective conservation of each habitat is mandatory to maximize the functional diversity of rocky reefs. Our characterization of functional habitats is a first approach to increase our understanding of the functional diversity of marine benthic communities, which can lead to more effective conservation actions.

Human population growth and dynamics are causing man-made coastal structures to steadily increase, often replacing natural substrates with artificial alternatives. Yet, it is unclear whether artificial substrates can function as the natural substrates they replace or they cause significant shifts in marine biodiversity. We hypothesized that biodiversity in artificial substrates deviates from that of natural reefs because the new conditions may favor and disfavor a different subset of species than those represented in the natural substrate, resulting in significant community differences between natural and artificial substrates. Additionally, common, widely distributed species with high mobility may colonize artificial reefs faster than rare species with low mobility, resulting in shifts in species occurrence and abundance between natural and artificial reefs. However, these differences may decrease over the long term making artificial substrates suitable environments to maintain or surpass preexisting levels of marine biodiversity. Using standardized, quantitative visual censuses of fish, invertebrate, and sessile organisms in 10 artificial and nearby natural substrates, we tested for differences in species composition and abundance between natural and artificial reefs. We classified species as high, medium, or low occupancy species based on their presence in the 10 locations investigated. Artificial substrates showed lower number and abundance of low occupancy species, which represented over 50% of the species quantified in our study. Invertebrate, cryptic fish, and sessile species are significantly reduced in artificial substrates, a trend that showed no variation over time. Our results suggest than artificial substrates are causing a long lasting decrease in marine biodiversity that significantly undermines our coastal biodiversity.

Human activities associated with the rise of the world population are a major driver of ecological change and have a large toll in global biodiversity including that in world oceans. Marine protected areas are one of the main conservation actions to preserve marine biodiversity and recover fish stocks. Protected areas in the Spanish waters include marine protected areas, natural parks, and other conservation areas with a variety of status (MPAs, in general). Our study tested whether MPAs are effective tools to recover fish stocks in terms of richness, abundance, or biomass, and to preserve marine biodiversity as measured with the Shannon diversity index. We used standardized underwater visual censuses as specified by the citizen-based Reef Life Survey program to quantify the number and abundance of fish and invertebrates. Abundance and size information were used to calculate fish biomass. This species-level database allowed quantification of a number of biodiversity indicators inside and outside numerous MPAs distributed along the coasts of Spain and Portugal. We used an ANOVA design to test for differences in community organization inside and outside MPAs. We also used abundance data to calculate a number of metrics such as biomass, Shannon diversity or species richness. We ran a nested ANOVA to test for difference in these metrics as a function of 4 marine ecoregions of the world (Mediterranean, South Atlantic, Alboran Sea and Macaronesia), local geographic areas (nested within ecoregion), and level of protection of each point (protected and unprotected, orthogonal). Overall, protected areas have larger fish abundance and biomass. However, we observed significant differences between areas of the same ecoregion and between MPAs. Our results showed that protection efficiency varied between MPAs. At the community level, benthic invertivores, particularly wrasses and blennies, showed the most differences between protection levels. Despite some metrics showed higher values in protected than in unprotected areas, most metrics varied as a function of geographic area, which suggests for the need to create effective MPAs in multiple geographic locations should we aim to provide more efficient measures to preserve marine biodiversity.