Abstract
Ecosystems are under pressure from multiple human disturbances whose impact may vary depending on environmental context. We experimentally evaluated variation in the separate and combined effects of the loss of a key functional group (canopy algae) and physical disturbance on rocky shore ecosystems at nine locations across Europe. Multivariate community structure was initially affected (during the first three to six months) at six locations but after 18 months, effects were apparent at only three. Loss of canopy caused increases in cover of non-canopy algae in the three locations in southern Europe and decreases in some northern locations. Measures of ecosystem functioning (community respiration, gross primary productivity, net primary productivity) were affected by loss of canopy at five of the six locations for which data were available. Short-term effects on community respiration were widespread, but effects were rare after 18 months. Functional changes corresponded with changes in community structure and/or species richness at most locations and times sampled, but no single aspect of biodiversity was an effective predictor of longer-term functional changes. Most ecosystems studied were able to compensate in functional terms for impacts caused by indiscriminate physical disturbance. The only consistent effect of disturbance was to increase cover of non-canopy species. Loss of canopy algae temporarily reduced community resistance to disturbance at only two locations and at two locations actually increased resistance. Resistance to disturbance-induced changes in gross primary productivity was reduced by loss of canopy algae at four locations. Location-specific variation in the effects of the same stressors argues for flexible frameworks for the management of marine environments. These results also highlight the need to analyse how species loss and other stressors combine and interact in different environmental contexts.
Highlights
Ecosystems are threatened by a range of pressures and damage to their structure and functioning, which can have important consequences for society [1]
This study examined variation in the separate and combined effects of the loss of key functional taxa and of physical disturbance on rocky shore ecosystems
The species making up the canopy varied among locations, but in each case were considerably larger than the other members of the algal assemblage and formed an extensive layer above them: at the northern locations it was Fucus serratus, in Lecce it was Cystoseira amentacea, in Livorno Cystoseira compressa and in Porto a mixture of small canopy species: Mastocarpus stellatus, Chondrus crispus and Gigartina pistillata (Table 1)
Summary
Ecosystems are threatened by a range of pressures and damage to their structure and functioning, which can have important consequences for society [1]. For example through harvesting and habitat destruction, is a key threat to ecosystems [1] It can be thought of as a stressor and is known to affect a range of ecosystem functions and properties, including productivity, respiration and stability [7],[8], [9]. Certain species can buffer against large disturbances and enhance resistance of communities to stressors The loss of these key species, may make ecosystems more susceptible to the increased levels of physical disturbance forecast as part of global climate change [12], but we cannot predict these effects with our current knowledge of most systems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
