Morphological variation of kelps (Alaria esculenta, cf. Laminaria digitata, and Saccharina latissima) in an Arctic glacial fjord

Abstract

Kelp forests supply many important ecosystem services that often are dependent on kelp morphological characteristics. Understanding the relationship between environmental factors and the morphological response of macroalgae is essential. The main aim of this study was to investigate the impact of factors associated with glacial activity and depth on the variability of dominant kelp species in the Arctic fjord, Hornsund. A total of 347 individuals of three kelp species (Alaria esculenta, cf. Laminaria digitata, Saccharina latissima) were collected in July 2003 at three sites located at different distances from glacier outflows (two sites under the influence of active tidewater glaciers and one site without any glacial impact) and at two depths (5 and 10 m). The length and wet weight of the thallus, blade and stipe were measured. The morphological response to environmental conditions was complex and species-specific. At one glacier-proximal site, light limitations due to seasonally increasing mineral particle flux did not affect kelp morphology, while iceberg scouring could have caused a reduction in kelp size and biomass at another site. Depth had a significant effect on the morphological traits of A. esculenta and S. latissima, which tended to have longer and heavier stipes at greater depths, most likely to improve light capture. No effect of depth on morphological traits of cf. L. digitata was noted. Regression models between thallus biomass and length, constructed for the kelp species that were studied, can be used in non-destructive kelp biomass estimations.