Mid Sweden University

The marine intertidal Fucus vesiculosus from the Norwegian Sea (34 practical salinity units, psu) and the sublittoral F. vesiculosus from the brackish Bothnian Sea (5 psu) have been compared with respect to the production of water soluble organic compounds during treatment in varying salinities. Nuclear magnetic resonance (NMR) 13C spectra revealed that there were differences in the content of water soluble organic compounds between the marine and the brackish F. vesiculosus and that production of these compounds was independent of salinity.

The marine intertidal Fucus vesiculosus from the Norwegian Sea (34 practical salinity units, psu) and the sublittoral F. vesiculosus and F. radicans from the brackish Bothnian Sea (5 psu) have been compared physiologically with respect to changes in salinity and seasons. The initial maximum quantum yield of photosystem II photochemistry (Fv/Fm) did not vary between the marine and brackish ecotypes or between the seasons but showed different responses to the experiment condition at different seasons. In general, there were no differences in the ability to withstand salinity changes, measured as Fv/Fm, between the marine and brackish ecotype. The tolerance is in a broad range for both of the ecotypes. The marine ecotype of F. vesiculosus had 30 % more mannitol than the brackish F. vesiculosus and there was 35 % more mannitol in May compared to November. The mannitol content in the marine ecotype responded differently to salinity changes in May compared to November, probably partly due to different initial concentrations. No changes in mannitol content could be detected in brackish F. vesiculosus. No significant differences were shown in Fv/Fm and mannitol content between brackish F. vesiculosus and F. radicans.

Ecotypes of Fucus vesiculosus L. from the Norwegian Sea (34 psu, marine ecotype) and Bothnian Sea (5 psu, brackish ecotype) have been compared with respect to the ability to withstand desiccation at different temperatures (0, 10, and 20°C). The aim was also to investigate the importance of salinity and light for the availably energy reserves, osmotic adjustment, and pigment content. The maximum quantum yield of photosystem II photochemistry (Fv/Fm) values revealed that the marine ecotype was more able to resist desiccation. The brackish algae showed a decrease in Fv/Fm as a response to desiccation at all temperatures, but the decrease was most pronounced at 20°C. The brackish ecotype recovered from desiccation within 5 h only when treated at 0°C. When the two ecotypes were treated at different levels of salinity in darkness and light, the results suggested that both salinity and irradiance are main factors in the differences in mannitol content between the two ecotypes. Chlorophyll (Chl) measurements showed 25% higher Chl α and 60% higher Chl c in the brackish ecotype in comparison to the marine ecotype. Darkness had a more pronounced effect on the Chl content than the salinity and initiated an increase in the amount of Chl, especially Chl c in the brackish ecotype.

The sublittoral Fucus vesiculosus from the brackish Bothnian Sea is adapted to a salinity of 4-5 practical salinity units (psu). This study investigated the effect of different salinities (5, 10, 20 and 35 psu) on maximum photosynthetic capacity (Pmax) and the relative amount of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). The results revealed a higher Pmax at higher salinities with the maximum at 10 psu. Higher salinities also resulted in increased relative amounts of Rubisco but this was not well correlated with the increased Pmax. Therefore, the amount of Rubisco doesn�t appear to be the main reason for the increased Pmax in higher salinities.