In situ growth potential of the subtidal part of green tide forming Ulva spp. stocks

Type Article
Date 2007-10
Language English
Author(s) Merceron Michel1, Antoine Virginie2, Auby IsabelleORCID3, Morand P4
Affiliation(s) 1 : Univ Rennes 1, ECOBIO, Ctr Natl Rech Sci, F-35380 Paimpont, France.
2 : IFREMER, F-29280 Plouzane, France.
3 : IFREMER, Direct Environm, F-14520 Port En Bessin, France.
4 : Institut Français de Recherche pour l'Exploitation de la Mer, Direction de l'Environnement Littoral, quai du Commandant Silhouette, 33120 Arcachon, France
Source Science of The Total Environment (0048-9697) (Elsevier), 2007-10 , Vol. 384 , N. 1-3 , P. 293-305
DOI 10.1016/j.scitotenv.2007.05.007
WOS© Times Cited 73
Keyword(s) Nutrients, Irradiance, Photosynthesis, Ulva sp., Algal blooms, Eutrophication
Abstract Ulva spp., the algae most responsible for green tides in Brittany (France), are found on the foreshore and in the most beachward wave area (MBWA) of many bays during green tide phenomena. These algae have recently been seen drifting at greater depths (reaching -20 m). In view of the significant quantities of algae found at these depths, and the less favorable conditions for algal growth than in the intertidal zone, we attempted to determine if they could grow there. For that, during their maximum growth period (from May to July), algae were picked up at three stations located on the foreshore, in the MBWA and in the subtidal (deep) zones of the Bay of Douarnenez, and their nitrogen, carbon and chlorophyll a+b contents were determined, and their photosynthetic activity was compared in the laboratory. The intracellular concentrations did not differ much from one station to another, although in the subtidal zone, the irradiance and the nitrogen concentration in the ambient water were much lower than those measured on the foreshore and in the MBWA. Photosynthetic activity characterized by maximum amounts of oxygen produced at different irradiances and by saturating and compensating irradiance levels, was also quite similar at the three stations. The irradiance, temperature and salinity of the subtidal environment, together with the chemical and photosynthetic characteristics of the algae found in that area, are consistent with the hypothesis that they grow there, and that their nitrogen supply comes from nitrogen releases from sediments. Nevertheless, their growth rate is probably less than that of algae in the MBWA. (C) 2007 Elsevier B.V. All rights reserved.
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