DOI: 10.5061/dryad.kv5h0
title: Data from: Compounded perturbations in coastal areas: contrasting responses to nutrient enrichment and the regime of storm-related disturbance depend on life-history traits

description: 1.Natural systems are exposed to compounded perturbations, whose changes
 in temporal variance can be as important as those in mean intensity for
 shaping the structure of assemblages. Specifically, climate-related
 physical disturbances and nutrient inputs due to natural and/or
 anthropogenic activities occur concomitantly, but experimental tests of
 the simultaneous effects of changes in the regime of more than one
 perturbation are generally lacking. Filling this gap is key to understand
 ecological responses of natural assemblages to climate-related change in
 the intensity and temporal patterning of physical disturbance combined
 with other global stressors. 2.Responses to factorial manipulations of
 nutrient enrichment, mean intensity and temporal variability of storm-like
 mechanical disturbance were examined, using benthic assemblages of
 tide-pools as model system. 3.Response variables were mean abundance
 values and temporal variances of taxa with different life-traits.
 Consistent negative effects of disturbance intensity were observed for the
 mean cover of long-living taxa (algal canopies and the polychaete
 Sabellaria alveolata), whose temporal fluctuations were also reduced by
 more severe mechanical stress. More resilient taxa (ephemeral algae,
 mostly green of the genus Ulva) increased under enriched conditions,
 particularly when low intensity events were irregularly applied over time.
 Opposite effects of disturbance intensity depending on nutrient
 availability occurred on filamentous algae (e.g. red of the genus
 Ceramium). This was probably due to the fact that, although nutrient
 enrichment stimulated the abundance of both algal groups, when this
 condition was combined with relatively mild physical disturbance the
 competitively superior ephemeral green algae tended to become dominant
 over filamentous red algae. The same did not occur under high intensity of
 disturbance since it likely damaged large, foliose fronds of Ulva-like
 forms more than small, filamentous fronds of Ceramium-like forms. Grazers
 were positively affected by nutrients, likely responding indirectly to
 more food available. 4.A direct relationship between the mean abundance of
 most organisms and their temporal fluctuations was documented. However,
 all organisms persisted throughout the study, even under experimental
 conditions associated to the largest temporal variation of their
 abundance, likely due to their ability to resist to/quickly recover from,
 the applied perturbations. Therefore, in systems with great recovery
 abilities of dominant organisms (e.g. rocky intertidal, grasslands),
 effects of traits of the regime of disturbance and nutrient enrichment may
 modulate the fluctuations of populations not through the elimination and
 substitution of species, but through changes in relative abundances of the
 same species. This contrasts with the theory that temporal variation in
 abundance would be directly related to the risk of local extinction.
 Present findings enable more accurate predictions of the consequences of
 climatic and non-climatic scenarios on the biodiversity of marine and
 terrestrial systems sharing analogous functional traits of organisms.
 Future more intense physical disturbances are expected to exert negative
 effects on slow growing/recovering species (e.g. habitat-formers)
 irrespectively of the temporal patterning of the same disturbances and
 nutrient inputs. On the contrary, more resistant species (e.g. encrusting
 algae on rocky shores or below-ground vegetation in grasslands) are
 expected to benefit from intense physical disturbance. Species whose
 abundance is more directly related to the availability of nutrients (e.g.
 filamentous and ephemeral algae or herbs) are expected to generally
 increase under enriched conditions, but their ability to eventually become
 dominant would depend on their ability to grow fast and attain cover large
 enough to overwhelm any possible control of concomitant disturbance
 intensity on their abundance. If, such as in the present examined system,
 virtually all organisms can persist, over the temporal scale of the
 experiment, under any combination of physical disturbance and nutrient
 availability, the resulting overall diversity is not predicted to change
 drastically. Nevertheless, low intensity events evenly distributed and
 high intensity events irregularly distributed appear as the conditions
 supporting the highest richness of taxa, independently of the availability
 of nutrients.
description: Abundance data of
 mirpho-functional groups of benthic organisms from tidepools along the
 northern Portuguese coastData are from field
 visual sampling, reporting abundances (number of individuals for mobile
 animals, i.e. grazers; percentage cover for sessile organisms, i.e. all
 the rest) in replicate 35 x 35 cm quadrats. Six morpho-functional groups
 are listed (column O: canopy-forming algae; column P: encrusting algae;
 column T: filamentous algae; column X: ephemeral green algae; column: AB:
 grazers; column AC: polychaete Sabellaria alveolata). Each of these
 columns is preceded by the list of individual taxa belonging to each
 category, with abbreviated names corresponding (easy matching) with the
 detailed list reported in the Appendix S2 associated to the paper. The
 final column (AD) reports the total number of sampled taxa in each
 replicate. The structure of the sampling (time and corresponding date,
 nutrient level, Intensity, variance, sequence of mechanical disturbance,
 three tidepools in each combination of these factors; each set of three
 entries for each pool includes three replicate quadrats sampled in each
 pool) is reported in columns from A to G, consistently with detailed
 information provided in the Methods of the paper.Bertocci&al_FE_Data
 Functional groups.xls