The natural history of the Hardangerfjord

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Abstract
As a part of a general survey of the natural history of the Hardangerfjord, in the county of Hordaland, Norway, a study of the benthonic algal vegetation was made; this was carried out mainly in summer. The area includes the outer coastal area, the outer fjord area (archipelago) and the fjord proper, where glacier-fed rivers discharge very turbid water during summer floods. The algal vegetation changes in composition from the outer to the inner reaches of the area, the “fjord effect” consisting mainly in an impoverishment of the littoral as well as the sublittoral flora. On entering the fjord proper, the lower limit of the vegetation rises from about 30 m to 10–15 m. This level was recorded throughout the fjord, even in the fjord branches where turbidity is very high in summer. The environmental factors which appear to be mainly responsible for the gradual reduction in the number of species are salinity range and water movement (turbulence, exposure). The latter is also suggested as responsible for the change in depth limit on entering the fjord proper. The fjord effect upon the algal vegetation seems to be far more pronounced in the Hardangerfjord than in other Norwegian fjords investigated, apparently as a result of its topography. Detailed records of distribution are given for all species together with charts of distribution for selected species.