305 research outputs found
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
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
No full textArtificial 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
Experimental evidence of spatial signatures of approaching regime shifts in macroalgal canopies
No full textDeveloping early warning signals to predict regime shifts in ecosystems is a central issue in current ecological research. While there are many studies addressing temporal early warning indicators, research into spatial indicators is far behind, with field experiments even more rare. Here, we tested the performance of spatial early warning signals in an intertidal macroalgal system, where removal of algal canopies pushed the system toward a tipping point (corresponding to approximately 75% of canopy loss), marking the transition between a canopy- to a turf-dominated state. We performed a two-year experiment where spatial early warning indicators were assessed in transects where the canopy was differentially removed (from 0 to 100%). Unlike Moran correlation coefficient at lag-1, spatial variance, skewness, and spatial spectra at low frequency increased along the gradient of canopy degradation and dropped, or did not show any further increase beyond the transition point from a canopy- to a turf-dominated state (100% canopy removal). Our study provides direct evidence of the suitability of spatial early warning signals to anticipate regime shifts in natural ecosystems, emphasizing the importance of field experiments as a powerful tool to establish causal relationships between environmental stressors and early warning indicators
Variation in the structure of subtidal landscapes in the NW Mediterranean Sea
No full textCompounded effects of climate change and local human activities are threatening marine biodiversity worldwide. At a regional scale (10s to 100s km), comparisons among areas characterized by the prevalence of different human activities provide an insight into the effects of anthropogenic disturbances at multiple levels of ecological organization (i.e. from landscapes to assemblages). At the landscape scale (1000s m), we hypothesized that patchiness in habitat distribution and proportion of degraded assemblages would increase with increasing levels of disturbance, as a result of the decline of habitat-forming species. In addition, we hypothesized that prevailing human influences would affect the structure and variability of rocky benthic assemblages at smaller spatial scales (10s cm to 10s m). An extensive survey encompassing areas subjected to different human influences (i.e. from urbanized to protected areas) was carried out along the coasts of Tuscany (NW Mediterranean Sea). Seagrass beds and macroalgal canopy stands were the dominant habitats in relatively pristine areas, while macroalgal turfs and dead rhizomes of Posidonia oceanica were the most extended habitats in urbanized areas. In general, habitat fragmentation did not vary among areas subjected to different human influences. At a smaller scale (10s cm to 10s m), urbanization favored dominance by opportunistic species and promoted biotic homogenization. Our study shows that regional variations in the composition of landscapes and assemblages can be predicted on the basis of prevailing human activities. Our results also suggest that variations in landscape composition could be an effective descriptor of the effects of multiple human stressors in marine environments.L. Tamburello, L. Benedetti-Cecchi, G. Ghedini, T. Alestra, F. Buller
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
BIORES - Resistenza e resilienza della biodiversità costiera agli effetti sinergici di cambiamenti ambientali su scala locale e globale
No full textScopo principale del presente progetto è lo studio integrato dell'effetto del disturbo tra scale (globale vs locale) e sistemi (marini vs terrestri). Affronteremo questa
tematica svolgendo un esperimento in ambienti di duna costiera con lo stesso approccio logico ed un disegno sperimentale analogo all'esperimento nella fascia
subtidale superficiale illustrato nel modulo B dell'unità di Pisa. L'esperimento analizzerà se i popolamenti vegetali costieri terrestri rispondano in maniera analoga ai
popolamenti macroalgali marini quando sottoposti a fattori di disturbo ambientali. Verranno manipolati due fattori considerati importanti per l'ecologia delle specie
vegetali delle dune costiere, l'aerosol marino (spettro "rosso" di variabilità spaziale) ed il pascolamento di erbivori (spettro "bianco" di variabilità spaziale).
L'esperimento verrà realizzato in tre siti (Foce Bevano, Marina di Pisa, e Carovigno) in stretta collaborazione tra le tre unità di ricerca coordinate dall'Unità di
Ravenna. Il raffronto tra i risultati dei due esperimenti permetterà di confrontare la resistenza e resilienza di due sistemi all'interfaccia tra mare e terra all'effetto
sinergico dei fattori di stress globali e locali, e di identificare le relazioni tra scale di impatto e risposte in ciascun sistema
BIORES - Resistenza e resilienza della biodiversità costiera agli effetti sinergici di cambiamenti ambientali su scala locale e globale
No full textScopo principale del presente progetto è lo studio integrato dell'effetto del disturbo tra scale (globale vs locale) e sistemi (marini vs terrestri). Affronteremo questa
tematica svolgendo un esperimento in ambienti di duna costiera con lo stesso approccio logico ed un disegno sperimentale analogo all'esperimento nella fascia
subtidale superficiale illustrato nel modulo B dell'unità di Pisa. L'esperimento analizzerà se i popolamenti vegetali costieri terrestri rispondano in maniera analoga ai
popolamenti macroalgali marini quando sottoposti a fattori di disturbo ambientali. Verranno manipolati due fattori considerati importanti per l'ecologia delle specie
vegetali delle dune costiere, l'aerosol marino (spettro "rosso" di variabilità spaziale) ed il pascolamento di erbivori (spettro "bianco" di variabilità spaziale).
L'esperimento verrà realizzato in tre siti (Foce Bevano, Marina di Pisa, e Carovigno) in stretta collaborazione tra le tre unità di ricerca coordinate dall'Unità di
Ravenna. Il raffronto tra i risultati dei due esperimenti permetterà di confrontare la resistenza e resilienza di due sistemi all'interfaccia tra mare e terra all'effetto
sinergico dei fattori di stress globali e locali, e di identificare le relazioni tra scale di impatto e risposte in ciascun sistema
- …
