Robertson-Andersson, DeborahWilson, D.T.Bolton, John J.Anderson, Robert J.Maneveldt, Gavin2013-10-262013-10-262009Robertson-Andersson, D.V., et al. (2009). A Rapid assessment of tissue nitrogen in cultivated Gracilaria gracilis (Rhodophyta) and Ulva lactuca (Chlorophyta). African Journal of Aquatic Science, 34(2): 169-1721608-5914http://hdl.handle.net/10566/778Tissue 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. A relationship between thallus colour and tissue nitrogen, as well as a transition between green-yellows and yellow-browns that occurs between 0.8 – 1.3 mg N per g tissue (Pantone® colours 460U – 455U) for Gracilaria were found, with the green-yellow colour indicating nitrogen-starved material and the yellow-browns indicating nitrogen-replete material. For Ulva a transition between green and yellow-green occurred at a tissue nitrogen content of between 1.5 – 1.7 mg N per g tissue (Pantone® colours 585U and 583U). This relationship 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.enThis is the authors' final draft following peer review. It may be displayed and circulated, subject to full acknowledgement of author and source. The published item is copyright Taylor & Francis.Cultivated seaweedsPantone®Tissue nitrogenThallus colourArticle