Multiple stressors in freshwater ecosystems

Freshwater ecosystems are particularly vulnerable to stressors from multiple sources (climate change, invasion, pollution, habitat degradation), due to their relatively small size and fragmented nature in a predominantly terrestrial landscape. These stressors almost never occur in isolation, yet our knowledge of their combined effects remains limited - an important oversight since stressors can interact to cause unpredictable outcomes that will influence how we conserve and manage natural ecosystems. The combined effect of two co-occurring stressors can sometimes be additive (the predictable sum of their independent effects), but global analyses suggest this is rare. Non-additive effects can be broadly categorised into those that are either less than, or more than, the sum of their independent effects. In the first case, the two stressors mitigate one another’s effects: an ‘antagonistic interaction’ between stressors. In the second case, the stressors amplify one another’s effects: a ‘synergistic interaction’. The drivers of this non-additivity are currently unclear and, therefore, the goal of this project is to extract and analyse existing data to address this knowledge gap. You will expand an existing database of fully-factorial multiple stressor experiments in freshwaters, and use it to assess where non-additivity arises: does it depend on stressor identity, trophic level and/or the level of biological organisation at which the response is measured?

 

Any pre-requisites: A background in ecology, with an interest in global change in aquatic ecosystems

Maximum number of students: 2

If interested please contact michelle.jackson@zoo.ox.ac.uk