Data from: Different response-effect trait relationships underlie contrasting responses to two chemical stressors

1. Trait-based approaches predict ecosystem functioning under
environmental change by relating traits predicting changes in species
densities (response traits) to traits driving ecosystem functioning
(effect traits). Stressors can however affect ecosystem functioning not
only by altering species densities, but also by directly changing species
effect traits. 2. We first identified the response traits predicting the
cell density of 18 marine benthic diatom strains along gradients of two
chemical stressors (a pesticide and a metal, atrazine and copper). We then
tested if response traits could predict stressor-induced changes in
ecosystem functioning, i.e. changes in the effect traits driving the
diatoms’ potential contribution to primary production, sediment
stabilization and energy content in intertidal systems. Finally, we
examined if changes in density and changes in ecosystem functioning were
correlated, to assess whether species capable of growing under stressful
conditions could maintain their contribution to ecosystem functioning. 3.
The relationship between response traits and stressor-induced changes in
density and ecosystem functioning was different depending on stressor
type: a set of intercorrelated morphological traits predicted changes in
both density and ecosystem functioning under metal stress, with large
cells being more stress-resistant. Changes in density and changes in
ecosystem functioning were positively related: diatoms whose density was
least affected by the metal were also able to sustain functioning under
metal exposure. 4. In contrast, the capacity for mixotrophic growth
predicted changes in density, but not changes in ecosystem functioning
under pesticide stress. Pesticide effects on density and on ecosystem
functioning were negatively related for energy content and sediment
stabilization, indicating a limited capacity of pesticide-tolerant diatoms
to maintain their contribution to ecosystem functioning. Synthesis.
Ecosystem functioning under stress can depend on whether response traits
driving changes in density also predict direct stress effects on the
species’ contribution to ecosystem functioning. Based on our results, we
expect a disproportionate loss of functioning when traits driving species
densities do not allow to maintain ecosystem functioning under stress.

data_package_MensensEtAl2017_JournalOfEcologyThis data package contains data from the publication: Mensens, C., De Laender, F., Janssen, C.R., Sabbe, K. & De Troch M. (2017) Different response-effect trait relationships underlie contrasting responses to two chemical stressors. Journal of Ecology. Details about the content of the package can be found in the Readme.txt file in the zip folder.MensensEtAl2017JEcol.zip