Negative direct effects of nutrient enrichment on the establishment of Fucus vesiculosus in the Baltic Sea

The direct effect of nutrient enrichment on the early life stages of Fucus vesiculosus in the brackish Baltic Sea was followed in laboratory experiments. The effects of nitrate and phosphate on the rate of attachment, on germination and on the development of the primary rhizoid were assessed. The rate of attachment was slow compared with similar studies in a marine environment. The zygotes of the control reached only 9% attachment within the first 12 h. A significant negative effect of nitrate enrichment on the attachment rate and germination was observed. Germling survival was reduced by over 20% in moderate nitrate enrichment, and by over 50% in high nitrate (21 MM) and high phosphate (1.0 muM) enrichment during the first 10 days. The effect on the development of the primary rhizoid was also significant, but less severe. The results suggest that eutrophication may have a direct negative effect on the recruitment of Fucus vesiculosus, unrelated to the secondary effects normally attributed to the decline of Fucus in the Baltic Sea.