La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Links Between Bottom-Water Anoxia, the Polychaete Nereis diversicolor, and the Growth of Green-Algal Mats
Auteurs :	Anna Engelsen, Auteur ; Kristina Sundback, Auteur ; Stefan Hulth, Auteur
Type de document :	Article
Dans :	Estuaries and Coasts (33(6) NOV 2010)
Article en page(s) :	1365-1376
Résumé :	Sediment-water incubations were used to study effects of episodic anoxia on filamentous Ulva sp. Treatments included undisturbed sediment with (AnoxSed) and without (NatSed) exposure to 5 days of anoxia, and cores with only the top 0.5 cm of sediment (SurfSed; no macrofauna, restricted pore-water nutrient pool). All three treatments contained Ulva propagules. An Ulva mat developed in the SurfSed, and after the anoxic period in the AnoxSed cores. No growth was observed in the NatSed treatment. In the AnoxSed, Ulva was progressively removed upon reoxygenation through grazing by Nereis. The results suggest that episodic anoxia stimulates the growth of macroalgal mats not only by increasing the availability of nutrients from the sediment, but also by reducing macrofaunal grazing pressure. Infauna (grazing and bioturbation), benthic microalgae (nutrient competition and retention), and pore-water nutrients appear key components in a biogeochemical network with complex feedbacks controlling the growth of green-algal mats in shallow-water systems.

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