Large-scale variation in combined impacts of canopy loss and disturbance on community structure and ecosystem functioning.

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.

Stressed but stable: canopy loss decreased species synchrony and metabolic variability in an intertidal hard-bottom community.

The temporal stability of aggregate community properties depends on the dynamics of the component species. Since species growth can compensate for the decline of other species, synchronous species dynamics can maintain stability (i.e.

Sampling epifauna, a necessity for a better assessment of benthic ecosystem functioning: an example of the epibenthic aggregated species Ophiothrix fragilis from the Bay of Seine.

Sampling the sea bottom surface remains difficult because of the surface hydraulic shock due to water flowing through the gear (i.e., the bow wave effect) and the loss of epifauna organisms due to the gear's closing mechanism.

BENTHIC METABOLISM ON A SHELTERED ROCKY SHORE: ROLE OF THE CANOPY IN THE CARBON BUDGET(1).

While the importance of canopy-forming algae in structuring ecosystems is recognized, their role in the carbon budget is still not well understood. To our knowledge, no measurements of rocky shores primary production and respiration under emersion periods have been carried out in situ. A benthic chamber coupled to a CO2 -infrared gas analyzer was used to measure gross primary production and respiration on the Ascophyllum nodosum (L.