Large-Scale Variation in Combined Impacts of Canopy Loss and Disturbance on Community Structure and Ecosystem Functioning

Tasman P. Crowe (1) , Mathieu Cusson (2, 3, 1) , Fabio Bulleri (2) , Dominique Davoult (4) , Francisco Arenas (5) , Rebecca Aspden (6) , Lisandro Benedetti-Cecchi (2) , Stanislao Bevilacqua (7) , Irvine Davidson (6) , Emma Defew (6) , Simonetta Fraschetti (7) , Claire Golléty (8) , John N. Griffin (9) , Kristjan Herkül (10) , Jonne Kotta (10) , Aline Migné (4) , Markus Molis (11) , Sophie K. Nicol (1) , Laure M-L J. Noël (4) , Isabel Sousa Pinto (12) , Nelson Valdivia (13, 14) , Stefano Vaselli (15) , Stuart R. Jenkins (9)

1 School of Biology & Environmental Science
2 CoNISma - Consorzio Nazionale Interuniversitario per le Scienze del Mare [Rome, Italie]
3 DSF - Département des Sciences Fondamentales [Chicoutimi]
4 EFEB - Ecogéochimie et Fonctionnement des Ecosystèmes Benthiques
5 CIIMAR - Interdisciplinary Centre of Marine and Environmental Research [Matosinhos, Portugal]
6 Scottish Oceans Institute
7 Department of Biological Environmental Science and Technology
8 AD2M - Adaptation et diversité en milieu marin
9 Marine Biological Association
10 Estonian Marine Institute
11 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine
12 Laboratory of Coastal Biodiversity
13 Centro des Estudios Avanzados en Zonas Aridas
14 Instituto de Ciencias Marinas y Limnológicas
15 Unita de Biologia Marina

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.

Domaines: Sciences du Vivant [q-bio]; Sciences de l'environnement

Tasman P. Crowe, Mathieu Cusson, Fabio Bulleri, Dominique Davoult, Francisco Arenas, et al.. Large-Scale Variation in Combined Impacts of Canopy Loss and Disturbance on Community Structure and Ecosystem Functioning. PLoS ONE, 2013, 8 (6), pp.e66238. ⟨10.1371/journal.pone.0066238⟩. ⟨hal-01255948⟩