1,721,521 research outputs found
Resistenza e resilienza della biodiversità costiera agli effetti sinergici di cambiamenti ambientali su scala locale e globale (BIORES) Progetto PRIN
No full textThe intensification of human activities along coastlines in combination with large-scale climate events are causing major changes to marine and terrestrial
biodiversity. To develop adequate policies that guarantee the sustainable use of coastal resources, it is necessary to determine how ecological functions and services
can be maintained in the face of increasing environmental uncertainty. The traditional approach to examine the effects of anthropogenic disturbances on biodiversity
is to focus on specific drivers of change - e.g. point-source pollution. This approach is unlikely to capture the full range of environmental pressures that impinge on
coastal organisms. An alternative strategy to cope with this complexity is to focus on the fundamental difference between large-scale and local processes in terms of
the underlying patterns of variability. Whilst large-scale processes are characterised by large variability at low frequencies, localized processes that change abruptly
in space or time display large variability at high frequencies. Thus, the response of biodiversity to the simultaneous influence of local and global environmental
changes can be assessed by altering the patterns of variability of environmental drivers of change. In this project we will examine the synergistic effects of global vs.
local disturbances on the ability of two key coastal systems - subtidal rocky reefs and coastal dunes - to resist to and to recover from perturbations. Using a
combination of correlative and experimental approaches we will establish quantitative relationships between the resistance/resilience of these ecosystems and the
degree of variability of environmental driving forces. Marine and terrestrial assemblages will be exposed to series of spatially autocorrelated and spatially
independent disturbances to reflect large-scale (low frequency) disturbances and abrupt (high frequency) environmental changes, respectively. In doing so, we expect
to identify general principles that govern the response of assemblages to increasing environmental fluctuations, independently of the identity of the environmental
drivers of change. This project is expected to originate the necessary scientific understanding to anticipate the consequences of environmental variation on
biodiversity, to provide managers with better tools to halt species extinctions and to guarantee long-term ecosystem functioning in the face of increasing climate
variability
Trophic compensation stabilizes marine primary producers exposed to artificial light at night
Full text linkArtificial light at night (ALAN) is a widespread phenomenon along coastal areas. Despite in - creasing evidence of pervasive effects of ALAN on patterns of species distribution and abundance, the potential of this emerging threat to alter ecological processes in marine ecosystems has remained largely unexplored. Here, we show how exposure to white LED lighting, comparable to that experienced along local urbanized coasts, significantly enhanced the impact of grazing gastropods on epilithic microphytobenthos (MPB). ALAN increased both the photo-synthetic biomass of MPB and the grazing pressure of gastropods, such that consumers compensated for the positive effect of night lighting on primary producers. Our results indicate that trophic interactions can provide a stabilizing compensatory mechanism against ALAN effects in natural food webs
Short-term stability of rocky intertidal biofilm to nitrogen and phosphorus pulses
No full textCoastal environments experience both natural and anthropogenic inputs of nitrogen (N) and phosphorus (P). Agricultural fertilisers, organic run-offs, and edaphic characteristics of coastal environments may generate mosaics of nutrient concentrations that ultimately influence the coastal primary productivity. Here, we experimentally assessed the effects of repeated pulses of N and P on multiple components of ecological stability (sensitivity, resilience, temporal stability and recovery) of phototrophic rocky intertidal biofilm. We performed a repeated-pulses factorial experiment crossing increasing N and P concentrations chosen to reflect a range of nutrient enrichment conditions, from oligotrophic to eutrophic. N and P, regardless of concentration or whether they occurred in isolation or combination, enhanced biofilm's sensitivity (increased biomass or physiological performance compared to controls) without altering resilience. Our experiment illustrates how the stability of an essential coastal primary producer responds to increasing N and P supply levels. Furthermore, notwithstanding the importance of decomposing the multiple dimensions of stability, the transitory increase of the sole sensitivity indicated that rocky shore biofilm is robust against a wide range of nutrient enrichment
Scales of spatial variation in Mediterranean subtidal sessile assemblages at different depths
No full textAnalyses of spatial patterns of distribution of populations and assemblages along enviroromental gradients are common in marine ecology. How these patterns vary at different spatial scales has seldom been examined, despite the fact that patterns in nature are intrinsically scale-dependent. This study quantified variability in subtidal assemblages at a hierarchy of spatial scales along a depth gradient, using several univariate and multivariate techniques. Despite variation in the sizes of depth effects in time and space, there were large, significant and generally characterisable differences in the structure of assemblages at different depths. The sizes of multivariate and univariate components of variation at different spatial scales were compared at each of 3 different depths (5, 15 and 25 m), using a bias-corrected bootstrapping approach. The sizes of variance components at different spatial scales varied with depth and choice of transformation. In all cases, the largest component of variation was at the smallest scale (tens of centimeters). A pattern of decreasing residual variance with depth was seen for untransformed data, while a pattern of increasing residual variance with depth was seen for presence/absence data. In contrast, variation among locations (separated by > 1 km) and among sites (separated by hundreds of metres) was largest at intermediate depths (similar to 15 m), regardless of the transformation used. The multivariate procedures used here offer several advantages over previously used techniques, providing suitable quantitative methods for analysing, at multiple scales, the patchy and complex nature of rocky subtidal assemblages
Light pollution enhances temporal variability of photosynthetic activity in mature and developing biofilm
No full textArtificial light at night (ALAN) has been recently recognized as a threat for aquatic systems, but a comprehensive knowledge of its effects is still lacking. A fundamental question is whether and how ALAN might affect temporal variability of communities, thus undermining the stability of mature assemblages or influencing the colonization process. Here we investigated the role of ALAN on temporal variability of total biomass and maximum photosynthetic efficiency of marine autotrophic biofilms colonizing Mediterranean high-shore rock surfaces while controlling for density of their main grazers. Results showed stability in total biomass, but an increase in maximum photosynthetic efficiency from unlit to lit conditions, which suggested a temporal change in composition and/or abundance of different taxa within mature assemblages. The effect was weaker during the colonization process; in this case, density of grazers acted in the opposite direction of ALAN. We suggest that the addition of light at times when it would not be naturally present may affect the temporal variability of a variety of functioning in aquatic systems, depending on species-specific sensitivities to ALAN within microbial assemblages and/or indirect effects mediated by their consumers. We highlight to further investigate the role of this emergent topic in aquatic ecology
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Ecological feedback mechanisms and variable disturbance regimes: the uncertain future of Mediterranean macroalgal forests
Full text linkLoss of algal canopies can result in a shift towards a turf-dominated state, where variability in species life-history traits can determine new mechanisms of feedback, and influence the degraded system under variable regimes of disturbance. By focusing on rockpools dominated by Cystoseira brachycarpa, we tested the hypothesis that the alga Dictyopteris polypodioides could take advantage of extreme regimes of disturbance related to storms, and outcompete other turfs through a distinctive combination of life traits. Replacement of the canopy was initially driven by a mix of taxon-specific life-traits and resulting assemblages were susceptible to intense events of disturbance. Subsequently, D. polypodioides dominated removal quadrats, favored by density-dependent abilities to intercept more light and reach larger size than the rest of turf. These new positive feedbacks may contribute to maintain the modified state of the system and influence its ability to withstand extreme abiotic conditions
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