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Introducing the MARS project: Part 1

February 17, 2014

Over the coming weeks, the BioFresh blog will be changing.  As the BioFresh project draws to a close with the ‘Water Lives’ symposium in Brussels, the blog will transition to the new MARS project

The content will still focus on issues relating to freshwater ecosystem science, conservation and policy, but will be run by MARS, and it will feature news and information on the project’s development from February 2014. 

Above is a video explaining the background of MARS, featuring project co-ordinators Daniel Hering and Christian Feld at the University of Duisburg-Essen in Germany, both of whom worked on the BioFresh project.

logo_mars_247x120pxWhat is MARS?

MARS (Managing Aquatic Ecosystems And Water Resources Under Multiple Stressors) is a new collaborative European Union Seventh Framework project which aims to identify and understand how different stressors – for example pollution, water abstraction, and habitat fragmentation – impact freshwater environments, both now and in the future.

What are stressors?

Stressors are biological (biotic, e.g. pollution) or non-biological (abiotic e.g. water abstraction) processes that have negative impacts on organisms and communities in an ecosystem.  These can be naturally occurring (e.g. flooding) or man-made (e.g. habitat fragmentation).

European freshwaters are subject to a complex set of stressors resulting from human activity. As MARS partner Steve Ormerod and his colleagues outlined in a 2010 article in Freshwater Biology (‘Multiple Stressors in Freshwater Ecosystems’) human impacts on freshwater ecosystems typically alter more than one environmental stressor.

For example, urbanisation might affect the water quantity and pollution content of runoff into a river; increase the risk of flooding; reduce the amount of habitat available for different organisms; and increase the ability of invasive species (such as Chinese mitten crabs) to disperse.

Freshwaters – lakes, rivers, estuaries and groundwater – can be polluted, abstracted, altered and fragmented by human activity, often with unpredictable results for ecosystem health and function.  In particular, the interaction of multiple stressors is poorly understood and documented.

In a 2010 paper ‘Multiple stressors in coupled river-floodplain ecosystems’, BioFresh leader Klement Tockner states ‘Predicting and understanding the effects of multiple stressors is one of the most important challenges presently facing ecological studies.’

Interactions of multiple stressors

In some cases stressors may cancel each other out (or act ‘antagonistically’).  For example, a 1996 study by Helmut Klapper and colleagues suggests that organic pollution and eutrophication may neutralise acidification from open cast mining in German lake ecosystems.

On the other hand, stressors may interact to worsen their individual effects (in the MARS project, this is termed as the stressors acting ‘synergistically’.)  For example, a 2011 study by Anika Wagenhoff and colleagues suggests that the build up of sediment pollution and nutrients can co-determine the diversity and health of invertebrate and algae communities in New Zealand streams.

Stressors, ecosystem function and ecosystem services

Stressors often negatively impact the organisms living in freshwaters – plants, fish, insects and microorganisms – directly.  These negative impacts on organisms may then affect the functioning of the ecosystem, for example the natural purification of watercourses by photosynthesising plants.  In turn, this change in ecosystem function may alter the provision of ecosystem services to humans, affecting services such as drinking water supply or fish availability for food.

For more information on these interrelations, this 2010 chapter by Rob Haines-Young and Marion Potschin at Nottingham University provides a good introduction

In short, the MARS project is looking to untangle how different stressors interact and impact the biodiversity, function and ecosystem service provision of European freshwaters.  This work will support stronger freshwater conservation and restoration initiatives at the water body, catchment and continental scale, in the context of ongoing climatic and social change.

Part two of this Introduction to MARS will explain how the project will study the impact of multiple stressors on freshwater environments at a variety of scales in order to inform and support European freshwater policy.

You can access the MARS website here:

For more information: there is an open-access set of journal articles related to the themes of MARS available online from a special issue of Freshwater Biology, published in January 2010.

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