Piet Verdonschot, Mariëlle van Riel & Ralf Verdonschot

macrofauna, benthos, voedselrelaties, bioturbatie, bio-irrigatie, nutriëntenstromen

Gaan we met de huidige maatregelen in het Markermeer het doel van de Rijksnatuurambitie, het bereiken van een robuust, dynamisch en veerkrachtig watersysteem, wel realiseren? Meer inzicht in het functioneren van het Markermeer roept gerede twijfel op. De meeste aandacht gaat naar de waterkolom, terwijl een belangrijk deel van de oplossing voor de problemen in het Markermeer juist te vinden is in de bodem. Een analyse van voedsel- en niet-voedselrelaties van bodembewonende macrofauna laat zien waarom.

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Healthy benthos as the key to a robust lake Markermeer

Piet Verdonschot, Mariëlle van Riel & Ralf Verdonschot

macrofauna, benthos, food relationships, bioturbation, bio-irrigation, nutrient flows

Central in the policies for lake Markermeer, including the EU Water Framework Directive and N2000, is the pursuit of a robust and resilient nature in synergy with other uses. Recently, various measures have been taken to fulfill these policy goals. The question arises whether these measures will provide successes. Therefore, we studied the benthos that plays a key role in lake functioning and determines 55-75% of the food relationships for the recently strongly declined fish and bird species. A decline may be due to the poorly developed benthos. Worms currently dominate lake Markermeer, at a distance followed by quagga mussels. Compared to natural reference lakes, macroinvertebrate numbers are low
(meaning a low food availability), and bioturbation and bio-irrigation levels are limited. The poorly developed benthos indicates that the current stock of particular organic material is insufficient. Therefore, the benthos is hindered to connect lakebed and the water column. Strengthening the natural f lux of organic material and nutrients is the missing link in restoring lake Markermeer functioning. By connecting impounded and new marshlands as well as by creating shallow littoral zones, organic material cycling will be initiated and enforced, and landscape, biotope and habitat heterogeneity will be strongly improved.

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