MEPS 246:115-126 (2003)  -  doi:10.3354/meps246115

Importance of benthic nutrient regeneration during initiation of macroalgal blooms in shallow bays

Kristina Sundbäck1,*, Alison Miles1, Stefan Hulth2, Leif Pihl3, Pia Engström2, Erik Selander3, Anders Svenson3

1Department of Marine Ecology, Marine Botany, Göteborg University, Box 461, 405 30 Göteborg, Sweden
2Department of Chemistry, Analytical and Marine Chemistry, Göteborg University, 412 96 Göteborg, Sweden
3Department of Marine Ecology, Kristineberg Marine Research Station, Göteborg University, 450 34 Fiskebäckskil, Sweden

ABSTRACT: Fast growing ephemeral algae are increasingly observed in shallow coastal waters worldwide. This is generally considered a symptom of coastal eutrophication. It has been suggested that the reoccurrence of macroalgal mats, despite ongoing efforts to decrease nutrient loadings, may be explained by the fact that sheltered bays function as self-regenerating systems through benthic regeneration of nutrients. The importance of benthic nutrient regeneration during the initiation of the growth of filamentous green algal mats was investigated in 2 shallow-water bays on the west coast of Sweden. Nutrient regeneration was assessed in situ and in the laboratory, using sediment-water light/dark incubations and pore water distribution patterns. Benthic efflux of inorganic nutrients could supply up to 55 to 100% of the estimated nitrogen demand and 30 to 70% of the phosphorus requirements for the initial macroalgal growth from May to June. However, the availability of the pore water nutrient pool was influenced by the amount and functional type of infauna, and by competition from microphytobenthos. Because of the internal nutrient source of the embayments, it is suggested that there may be a significant time lag between a decreased nutrient supply to coastal waters and improved conditions of shallow water embayments.

KEY WORDS: Nitrogen · Nutrient flux · Sediment · Green algae · Infauna · Microphytobenthos · Autotrophy · Heterotrophy

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