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Marine Ecology Progress Series

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MEPS 352:39-52 (2007)  -  DOI:

Primary production enhancement by artificial upwelling in a western Norwegian fjord

Jan Aure1, Øivind Strand1, Svein Rune Erga2, Tore Strohmeier1

1Institute of Marine Research, Nordnesgaten 50, 5817 Bergen, Norway
2Department of Biology, University of Bergen, Jahnebakken 5, 5020 Bergen, Norway

ABSTRACT: To enhance primary production rate for shellfish cultivation in fjords, a large-scale artificial upwelling experiment was carried out in a western Norwegian fjord during the summers of 2004 and 2005. Pumping 2 m3 s–1 brackish surface water to a depth of 30 m created an artificial upwelling of nutrient-rich deeper water. The entrainment of deeper water into the buoyant brackish plume resulted in a transport of about 450 kg d–1 nitrate, 760 kg d–1 silicate and 75 kg d–1 phosphate to an intrusion depth of 8 to 10 m. The artificial upwelling approximately tripled mean chlorophyll a (chl a) concentration and related primary production rate during the summer within an influence area of 10 km2 near the head of the fjord. The size of the area of influence and the relative increase of the algae biomass within it depend on both the water exchange and the photosynthetic effectiveness. The relatively high silicate content of the deeper water stimulated diatom growth inside the area influenced by the artificial upwelling. A higher stable level of phytoplankton biomass, dominated by nontoxic species, would probably increase the carrying capacity of seston-feeding shellfish and could form the basis of more predictable mussel cultivation in fjords.

KEY WORDS: Artificial upwelling · Phytoplankton biomass · Primary production rate · Fjord · Mussel culture

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Cite this article as: Aure J, Strand Ø, Erga SR, Strohmeier T (2007) Primary production enhancement by artificial upwelling in a western Norwegian fjord. Mar Ecol Prog Ser 352:39-52.

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