Morphological variation of northern Baltic<i>Sea Fucus vesiculosus</i>L

Abstract

Abstract The variation of northern Baltic Fucus vesiculosus morphology along the salinity gradient is described. Samples of 15–30 mature receptacle-bearing plants were collected by SCUBA diving from 19 sampling points on moderately exposed and exposed shores along the salinity gradient in the Gulf of Finland and in the Bothnian Sea. Eight morphological characteristics were measured and then analyzed using linear regression analysis and stepwise discriminant analysis. The analyses indicate considerable morphological divergence according to decreasing salinity. In both the Gulf of Finland and in the Bothnian Sea the width and length of thallus as well as distance of dichotomies and stipe dimensions decreased along the gradient. Along the exposed shores, plants are shorter and have narrower fronds. The change in morphology towards the low salinity areas is a clinal one and different morphological types can be distinguished to a certain extent. Discriminant analysis revealed that a combination of four morphological characteristics, i.e. midrib width, thallus width, plant length and stipe length is sufficient to distinguish between populations from different sites.