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Marine Ecology Progress Series

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MEPS 335:31-41 (2007)  -  doi:10.3354/meps335031

Community metabolism in temperate maerl beds. II. Nutrient fluxes

Sophie Martin1,2,*, Jacques Clavier1, Laurent Chauvaud1, Gérard Thouzeau1

1LEMAR, Laboratoire des Sciences de l’Environnement Marin, UMR CNRS 6539, Institut Universitaire Européen de la Mer, Technopôle Brest-Iroise, Place Nicolas Copernic, 29280 Plouzané, France
2Present address: Laboratoire d’Océanographie de Villefranche-sur-Mer, CNRS, and Université Pierre et Marie Curie–Paris VI, BP 28, 06234 Villefranche-sur-Mer Cedex, France

ABSTRACT: Maerl community ammonium (NH4+), nitrate + nitrite (NO3 + NO2), dissolved silicic acid (DSi) and phosphate (PO43–) fluxes were measured seasonally in the Bay of Brest (France). Nutrient exchanges at the sediment–water interface were assessed using benthic chambers. Nutrient fluxes differed between light and dark conditions, and fluctuated seasonally, with minimum values in winter and spring and maximum values in summer and autumn. In the dark, net community fluxes of NH4+, NO3 + NO2, DSi and PO43– varied from 53 to 226 µmol N m–2 h–1, –107 to 70 µmol N m–2 h–1, 18 to 180 µmol Si m–2 h–1 and 5 to 19 µmol P m–2 h–1, respectively. In the light, NH4+, NO3 + NO2, DSi and PO43– fluxes ranged from 17 to 110 µmol N m–2 h–1, –223 to –10 µmol N m–2 h–1, –34 to 112 µmol Si m–2 h–1 and 1 to 12 µmol P m–2 h–1, respectively. Temperature, community respiration, gross community production and bottom water dissolved oxygen and nutrient concentrations mainly controlled seasonal fluctuations of benthic nutrient fluxes. Annual net community fluxes of dissolved inorganic nitrogen (DIN), DSi and PO43– were 6 g N m–2 yr–1, 10 g Si m–2 yr–1 and 2 g P m–2 yr–1, respectively. Annual gross community uptakes of DIN, DSi and PO43– were 12 g N m–2 yr–1, 9 g Si m–2 yr–1 and 1 g P m–2 yr–1, respectively. Nutrient supply from the maerl community to the water column contributed potentially to between 18 and 55% of the annual phytoplanktonic production in the Bay of Brest.

KEY WORDS: Calcareous algae · Community metabolism · Nutrient fluxes · Nitrogen · Phosphorus · Silicon

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