Impacts of climate change on stream benthic diatoms-a nation-wide perspective of reference conditions

Consequences of anthropogenic climate change directly affect freshwater ecosystems and their aquatic biological communities. Diatoms are amongst the most sensitive organisms to hydric stress, making them good indicators of preceding hydrological conditions. We assume that river types with low runoff and associated high temperature and mineralization host the most tolerant diatoms to climate change. We performed a cluster analysis with reference sites throughout Spain, based on their physiographic and hydrological characteristics. We obtained seven end-groups spread in the three existing ecoregions, onto which we estimated the indicator diatom taxa (IndVal). Brackish and aerophilic diatom were indicator taxa in mineralized and low discharge rivers. We simulated the impact of climate change on the river types, to conclude that under the RCP 8.5, the most impacted of all types would be the mineralized rivers. We predict higher homogenization in the diatom assemblages' composition, with higher proportion of planktonic taxa, and a potential increase of terrestrial and aerophilic diatoms, as the best adapted to the harsh conditions imposed by runoff reduction. Formulating clear predictions of climate change effects should rely on planned, long-term monitoring including accurate hydrological and biological data.

Automated summary

The consequences of anthropogenic climate change directly impact freshwater ecosystems and their aquatic biological communities. Diatoms, which are sensitive organisms to hydric stress, are good indicators of preceding hydrological conditions. River types with low runoff and high temperature and mineralization appear to host the most resilient diatoms to climate change.