MadMacs – a Water JPI project

MadMacs - Mass development of aquatic macrophytes; causes and consequences of macrophyte removal for ecosystem structure, function, and services - aims to determine the causes of mass development of water plants, and to study the direct and indirect consequences of their removal on ecosystem functions and services.

MadMacs in a nutshell


  • Mass development of aquatic macrophytes (= water plants) in rivers and lakes is a worldwide problem, and substantial resources are spent on macrophyte removal. However, measures are usually inefficient and macrophyte stands either quickly grow back or their removal causes other problems.
  • The specific regional causes of macrophyte mass development are still poorly understood, most likely because there is typically a combination of factors which together cause nuisance growth (multiple pressures).
  • Macrophyte mass developments have known negative effects (e.g. causing fish kills and impairing the use of the water body for swimming or boating), but well-developed macrophyte stands also have many benefits (ecosystem services). These are often poorly known to the public or to water managers.


  • Analyze which combination of natural conditions and stressors can cause mass development of macrophytes
  • Quantify the effect of macrophyte presence/removal on structural and functional diversity of aquatic organisms (biodiversity)
  • Quantify the effect of macrophyte presence/removal on nutrient and carbon retention and greenhouse gas emission (water quality)
  • Quantify the effect of macrophyte presence/removal on the full range of ecosystem services
  • Develop a tool to assess and balance benefits and costs of macrophyte removal

Case studies

We will execute a set of “real-world experiments” in a harmonized design at six sites across five countries (Norway, Germany, France, South Africa and Brazil).

The MadMacs project is funded through the 2017 call of the Water Challenges for a Changing World Joint Programme Initiative (Water JPI), with the national funders Research Council of Norway (297202/E10), German Federal Ministry of Education and Research (033WU005), the French National Research Agency (N° ANR-18-IC4W-0004-06), the South African Water Research Commision (K5/2951), and Fundação Araucária in Brazil (N° 186/2019). Additional funding is provided by Krypsivprosjektet på Sørlandet, NIVA and NMBU to support a PhD-student in Norway.

Last updated 25.10.2019