RIVSTRESS Project: Effects of multiple stressors on biodiversity and river functions

Global change is accelerating the emergence of stressors that impact river ecosystems, affecting their biodiversity, ecological functions and, as a consequence, the ecosystem services they provide to society. The RIVSTRESS project aims to understand how these stressors, common in Mediterranean rivers (such as water stress, increased water temperature, excess nutrients and the presence of pesticides), affect river ecosystems in different situations. The project pays special attention to:

1. The order of appearance of stressors, such as sequences from least intense to most intense, or vice versa.
2. The way stressors manifest themselves, whether continuously, in the form of increasing cramps or through pulses.
3. The legacy effect, which defines what previous stressors can leave on ecosystems, conditioning their resistance and capacity for recovery.

The project combines field and laboratory experiments, using micro- and mesocosms, to understand the general mechanisms that govern these interactions. The experiments focus on key biological communities, such as microorganisms (bacteria, algae, fungi) and invertebrates, to analyze both their structure (functional diversity, alpha and beta) and the ecosystem functions they perform, including water purification (decomposition of organic matter and removal of nutrients), primary production, respiration and energy transfer through the food chain. We are now developing an experiment with mesocosms within the ICRA artificial river facilities ( photos). In this experiment, biofilm communities from permanent and intermittent rivers have been exposed to the combined stress of urban pollution (input of wastewater) and drought. We want to determine the recovery capacity of these communities once the stressors are removed, and to determine the extent of the inherited effect on their resilience and recovery capacities. The RIVSTRESS project is funded by the Ministry of Science and Innovation within the call for R&D+i Projects 2020 (ref. PID2020-115708RB-C22), coordinated with the University of Barcelona (UB). The results will provide recommendations to anticipate and mitigate the impacts of multiple stressors on Mediterranean rivers in a context of global change.