Om Gracilaria vermiculophyllas mulige anvendelse som biofilter i dansk havbrug: On the potential use of Gracilaria vermiculophylla as biofilter in Danish marine aquaculture

Urd Steendahl Grandorf, Tina Rauff Hansen, Christina Søegren & Ronja Windfeld

Studenteropgave: Semesterprojekt

Abstrakt

The need for food increases as the population of the Earth increases. This has resulted in a rise in the number of aquacultures, including mariculture. In maricultures approximately 2/3 of the fish fodder is released into the surrounding ecosystem as waste, which causes extensive environmental problems. The aim of this report is to investigate to what extent it is possible for Gracilaria vermiculophylla (Rhodophyta), cultivated near Danish maricultures to reduce the eutrophication in the surrounding environment. In order to investigate this, three laboratory experiments has been conducted: A nutrient experiment, a light experiment and a temperature experiment. We found that G. vermiculophylla was able to accumulate substantial amounts of nitrogen and phosphorous in a short period of time. Thus, it was possible to obtain a tissue concentration of 4,00±0,63% N DW and 0,35±0,05% P DW in the course of five weeks. These concentrations are equivalent to 6 kg nitrogen and 0,5 kg phosphorous per ton FW algae. The growth rate of G. vermiculophyllas rose proportionally with increasing light intensities and the highest growth rate was measured as 0,04±0,004 d-1 at a light intensity of 97±28 μmole photons m-2 s-1. The temperature experiment showed a growth rate of 0,105±0,018 d-1 at 25°C, 0,058±0,007 d-1 at 15°C, and the lowest of 0,019±0,013 d-1 at 5°C. An assessment of the effect of G. vermiculophylla as a biofilter shows that 1 ha G. vermiculophylla will be able to reduce the emission of nutrient by 0,6%. Therefore the use of G. vermiculophylla cannot be supported solely by the ecological aspects. Further knowledge of the production of G. vermiculophylla is needed to counterbalance the economical aspects versus the expenses connected with the planting of G. vermiculophylla.

UddannelserMiljøbiologi, (Bachelor/kandidatuddannelse) Bachelor el. kandidat
SprogDansk
Udgivelsesdato22 dec. 2009
VejledereMorten Foldager Pedersen

Emneord

  • rødalge
  • Gracilaria
  • nitrogen
  • Gracilaria Vermiculaphylla
  • Nutrient
  • biofilter
  • næring
  • Havbrug
  • Aquaculture
  • fosfor