Ecological impact

The water net has negative and positive impacts on freshwater systems on the biota in lake systems.

Negative impacts

The water net is a serious nuisance alga because it clogs waterways and irrigation ditches, taints potable water, causes economic losses to trout fisheries, smothers aquatic plants and fauna and has an adverse impact upon boating, fishing, swimming and tourism.

Shallow water mats 

  • smother beds of aquatic macrophytes causing their collapse and decay

Extensive surface floating mats 

  • reduce the aesthetic appeal of  waters 
  • interfere with recreational activities by 
    • blocking marinas  
    • hampering intakes of boat engines 
    • swimming and fishing

On beaches water net accumulates in large drifts, decaying and causing localised anoxic conditions.

Positive impacts

Some studies have demonstrated water net having a beneficial impact on invertebrates.

Climate change response

The rapid spread of the water net in the British Isles is believed to be a climate change response relating to elevated and extended summer water temperatures and low river flows.

The sudden appearance of small (>2cm long), cylindrical colonies in May and June on the surface of a lake near Helston in Cornwall (UK) was associated with the water reaching 15°C. Such colonies increased in size several thousand fold within a few days and gave rise to entangled, cylindrical-shaped colonies blanketing the surface.