Rapid assessment of tissue nitrogen in cultivated Gracilaria gracilis (Rhodophyta) and Ulva lactuca (Chlorophyta)

  • DV Robertson-Andersson
  • DT Wilson
  • JJ Bolton
  • RJ Anderson
  • GW Maneveldt

Abstract

Tissue nitrogen content and thallus colour were quantified using a rapid assessment method based on the Pantone®matt uncoated formula guide for raft-cultivated Gracilaria gracilis Steentoft, Irvine et Farnham at Saldanha Bay and tank-cultivated Ulva lactuca Linnaeus at Jacobsbaai in 2001–2002. For Gracilaria a relationship between thallus colour and tissue nitrogen, as well as a transition between green-yellows and yellow-browns that occurs between 0.8 and 1.3 mg N per g tissue (Pantone® colours 460U–455U), was found, with the green-yellow colours indicating nitrogen-starved material and the yellow-browns indicating nitrogen-replete material. For Ulva a transition between green-yellow and green  occurred at a tissue nitrogen content of between 1.5 and 1.7 mg N per g tissue (Pantone®colours 585U–583U). This  elationship can be used by seaweed farmers for cultivation management as a quick guide to determine nutritional status of the seaweeds, and as an indication of protein content when the seaweeds are used as feeds.

Keywords: cultivated seaweeds, Pantone®; thallus colour; tissue nitrogen

African Journal of Aquatic Science 2009, 34(2): 169–172

Author Biographies

DV Robertson-Andersson
Botany Department, University of Cape Town, Rondebosch 7701, South Africa; current address: Department of Biodiversity and Conservation Biology, University of the Western Cape, Bellville 7535, South Africa
DT Wilson
Botany Department, University of Cape Town, Rondebosch 7701, South Africa
JJ Bolton
Botany Department, University of Cape Town, Rondebosch 7701, South Africa
RJ Anderson
Botany Department, University of Cape Town, Rondebosch 7701, South Africa; current address: Seaweed Research Unit, Marine and Coastal Management, Department of Environmental Affairs and Tourism, Rogge Bay 8012, South Africa
GW Maneveldt
Department of Biodiversity and Conservation Biology, University of the Western Cape, Bellville 7535, South Africa
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Articles

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eISSN: 1727-9364
print ISSN: 1608-5914