Measuring the vulnerability of a community of species to a given pressure: Benthos and bottom trawl in the Barents Sea. Jørgensen, LL, Certain G, Thangstad T, Planque B Spatial workshop outputs: Annual meeting Paris 3-7 Dec 2012

How environmental disturbance affects a community of species Benthic community delivering ecosystem goods and services Benthic end member community with opportunistic species Mixture where S, A and B increase Disturbance Pearson & Rosenberg 1978

Classical, experimental approach to measure disturbance effect on biodiversity: Benthic community Environmental noise Directed disturbance (Pressure a, b or c) Natural fluctuations difficult to separate from pressure induced Need to make the link between pattern and pressure more explicit

Pointing toward the species showing the effect HillLeinster & Cobbold (2012) Zi = the average similarity of species i with the remaining species All species differs in the same way

Coding species in accordance to the effect from a defined pressure Species Traits sizegrowth Sp. 1 Sp. 2 Sp mobility Theoretical indicator species: A similarity measure is convenient if the theoretical species has some meaning ex: the most vulnerable species 0

Trawling impact 293 Barents Sea Species 6 Traits MobilitySpeedStrataBody shapeBody TextureMean weight A theoretically super-vulnerable species

From an given community sample, we can measure the community vulnerability V = community vulnerability v= species vulnerability P = frequency i=1...S species j=1...L locations

Application to Benthic communities in the Barents Sea (1) Trawled area (VMS) Benthos station

Norwegian coast Bear Island Hopen deepFrontSvalbard Community Vulnerability Application to Benthic communities in the Barents Sea (2) T nT

Statistical distribution of community vulnerability in Hopen Deep area: Expected vulnerability Frequency Benthos communities in trawled area Benthos communities in untrawled area HighLow

Conclusion This general method estimate the community vulnerability if a species vulnerability to a given pressure can be assessed. The geographical borders of the used polygons needs more evaluation Other covariates potentially affecting a community vulnerability ? New more exhaustive datasets will be included Way forward