Sublittoral Seaweed Survey of the Orkney Islands

Abstract

Further sublittoral seaweed surveys have been carried out around the island group of Orkney, N. Scotland. Analysis of the data gave the following quantities (tons): Shapinsay 48,194, Rapness Sound 49,150, Papa Sound 91,563, N. Ronaldsay Firth 112,600, Newark and Lop Ness Bays 127,200, Sanday Sound 127,563, Holm Sound 19,500, extending over 26,950 acres. Laminaria cloustoni was the dominant sp. in all the above areas except Shapinsay. In all 7 areas the seaweed was found to be related tq the algal cover and depth, according to the formula [image] k -[gamma]f, where d = avg. fresh wt./unit area found in total quadrats at a particular depth, C = cover at the corresponding depth and f = depth. The factor k varies with each area but is related to the tidal stream operating and [gamma] is related to the light absorption coeff. of seawater. Light in the region of 6600 A appears to be a limiting factor to growth. For these surveys, nearly 6000 quadrats were taken from the seabed by the same spring grab designed for the purpose by the author.