Oxygenation by wave-energy - an approach to tackle the effects of eutrophication

Michael Barfoed1, Erik Skaarup2 and Torben Lenau1*

1Department of Management Engineering, Technical University of Denmark, Building 424, DK-2800 Lyngby, Denmark
2 WPP A/S, Tagesmindevej 1, DK-2820 Gentofte
*Corresponding Author: tel: +45 4525 4811, fax: +45 4593 3435, e-mail: lenau@ipl.dtu.dk

Eutrophicated marine water areas are rarely the target of restoration projects. This paper describes an attempt to oxygenate part of a fjord using wave-energy. The aim of the investigation is to see if it is possible to make a local reserve in an area burdened with organic material and re-vitalize it. During a 14-month period a wave-energy device was placed at a test site in the fjord of Holbaek in Denmark. Upon arrival the seafloor was covered with a 5 -10 centimetre deep layer of sludge and almost lifeless. By the end of the test-period the whole set up test area (120x120 m) was clear of sludge and the centre covered by higher life forms, dominated by echinoderms. The method we have developed gives hope for restoration of marine areas benefiting their ecological quality. An oxygen level of 4 mg 02/l above the seafloor is considered the minimal level for many fish species. Although the recorded oxygen level of the fjord never dropped bellow this in the 14-month test period, life only thrived bellow the oxygen device. This paper therefore questions if this oxygen level of 4 mg 02/l is enough in order to maintain life in eutrophicated areas.

Key words: oxygenation, marine restoration, eutrophication, wave-energy, marine reserves.