Effects of elevated temperature and CO(2) on intertidal microphytobenthos

BACKGROUND: Microphytobenthos (MPB) are the main primary producers of many intertidal and shallow subtidal environments. Although these coastal ecosystems are particularly vulnerable to anthropogenic activities, little is known on the effects of climate change variables on the structure and productivity of MPB communities. In this study, the effects of elevated temperature and CO(2) on intertidal MPB biomass, species composition and photosynthetic performance were studied using a flow-through experimental life support system. RESULTS: Elevated temperature had a detrimental effect on MPB biomass and photosynthetic performance under both control and elevated CO(2). Furthermore, elevated temperature led to an increase of cyanobacteria and a change in the relative abundance of major benthic diatom species present in the MPB community. The most abundant motile epipelic species Navicula spartinetensis and Gyrosigma acuminatum were in part replaced by tychoplanktonic species (Minidiscus chilensis and Thalassiosira cf. pseudonana) and the motile epipelic Nitzschia cf. aequorea and N. cf. aurariae. Elevated CO(2) had a beneficial effect on MPB biomass, but only at the lower temperature. It is possible that elevated CO(2) alleviated local depletion of dissolved inorganic carbon resulting from high cell abundance at the sediment photic layer. No significant effect of elevated CO(2) was detected on the relative abundance of major groups of microalgae and benthic diatom species. CONCLUSIONS: The interactive effects of elevated temperature and CO(2) may have an overall detrimental impact on the structure and productivity of intertidal MPB, and eventually in related ecosystem services. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12898-015-0043-y) contains supplementary material, which is available to authorized users.