  The vulnerability to trawling on a species level is determined by a species'
individual combination of biological traits that is related to the ecosystem
functions. Trait-based indices of physical resistance RI and reproductive
potential RPI were developed and combined into an overall vulnerability index
on a species level, the RRI or Resistance and Reproductive Potential Index. The
indices are used to explore how resistance and reproductive potentia change
over a trawling gradient. The RRI allows for dividing the benthic community
into groups expressing different levels of vulnerability that can be linked to
ecosystem functions. The RRI index opens up the possibility of scenario
modelling by simulating the extinction or loss of vulnerable species and its
effects on functions. The validity of the trait-based RRI index was explored by
comparing individual species' RRI scores to empirically observed responses over
a trawling gradient based on a previously published data. RRI score and
observed responses (regression slopes) were significantly correlated providing
support for the rationality of the approach taken. Data analyses evidenced
increases of resistance and resilience indices over the trawling gradient,
demonstrating that communities lost vulnerable species with increasing
trawling. When exploring the effects of trawling on the bioturbation, we found
it to be disproportionately affected though the loss of vulnerable species. The
proposed indices provide new insights into the link of species vulnerability
and function.
