, Volume 128, Issue 2, pp 281-293

First online:

Algal propagule banks modify competition, consumer and resource control on Baltic rocky shores

  •  Affiliated withInstitut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • ,  Affiliated withInstitut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • ,  Affiliated withInstitut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


We hypothesized that supply from macroalgal propagule banks may influence the relative abundance of annual and perennial algae and that this may alter the effects of grazers and nutrients on species composition. In a factorial field experiment in the Baltic Sea littoral system we tested the effects of manipulating propagule banks, the abundance of crustacean and gastropod grazers, and nutrient supply on recruitment and growth of macroalgae over a year. Moreover, we determined seasonal patterns of macroalgal propagule dispersal at the experimental site and quantified algal abundance and recruitment at 25 locations throughout the Baltic Sea. Experimental manipulations had minor effects on adults of the dominating perennial alga, Fucus vesiculosus. Instead, we found that species composition was determined by processes operating at early life stages. Propagule supply from a propagule bank strongly favored the fast-growing annual alga Enteromorpha spp. which then blocked settlement and recruitment of Fucus. Grazers reduced the abundance of annual algae and indirectly favored Fucus recruitment. There was an apparent trade-off between gains from the propagule bank and losses to herbivory in five of seven colonizing species. Nutrient enrichment overrode grazer control of annual algae and accelerated the decline of Fucus only when annual algae had already achieved high densities through the propagule bank. Corroborating the experimental findings, field surveys across the Baltic showed that Fucus recruit densities can be predicted from the cover of annual algae during the period of Fucus reproduction and settlement. Recruitment inhibition by annual algae, which is driven by the abundance of annuals in the propagule bank, increasing nutrient levels, and declining consumer control, is suggested as a mechanistic explanation of the current decline of perennial algae in the Baltic Sea.

Dormancy Eutrophication Fucus vesiculosus Grazing Nutrients