Multiple stressors and aquatic life
How do increases in levels of nutrients and fine sediments, higher water temperatures, and reduced water flow, affect life in streams? What if these changes occur simultaneously? And at what point are thresholds reached where serious harm is done to aquatic life?
These are the questions tackled in a series of experiments designed to measure the typical multiple effects of land-use change on aquatic invertebrates, algae, and microorganisms – key components of life in our streams and rivers. The results confirm that there is nothing simple about the interactions between the various biological and physical components in waterways.
”The main message from our results so far is that you cannot just look at the impact of a single stressor on aquatic life forms,” says University of Otago scientist, Dr Christoph Matthaei. “Significant interactions between the stressors – nutrients, sediment, water temperature, and water flow, arecommon, so focusing on a single stressor could well lead to inaccurate predictions about impacts and recovery.”
The University of Otago is a major collaborator in NIWA’s ‘Effects-based protection and management of aquatic ecosystems’ research programme.