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As a consequence of anthropogenic perturbations the global ocean is warming, acidifying, losing oxygen and sea ice, and sea level is rising. While drastic reduction of the emission of greenhouse gases is urgently needed, which includes ocean energy substitution for fossil energy, we show that the ocean offers numerous opportunities to reduce the causes and consequences of climate change, globally and locally. A wide range of ocean-based measures to enhance societal climate adaptation are currently implemented worldwide to deal either with coastal risks or changes in ocean resources. Ocean-related measures should not be considered as a substitute for climate mitigation on land or non ocean-based adaptation measures, which must be strongly pursued for the benefit of the atmosphere, the ocean, and socio-ecological systems worldwide

The biogeochemical cycle of silicon was studied at the Kerguelen Fixed Station (KERFIX) between 1992 and 1994. The timeseries shows a seasonal use of the stock of silicic acid decoupled from that of nitrate. Thus, silicon probably plays an important role in limiting the primary production of diatoms in that area, characteristic of the permanently open ocean zone. Despite this, given their very low growth rates, the dominant diatoms are strongly silicified. The results of KERFIX are compared with more recent KEOPS (Kerguelen Ocean and Plateau compared Study) results and provide a complement to KEOPS in terms of understanding interannual and seasonal variability.

Concentrations of organic matter have been evaluated in South Western Brittany coastal seawaters,in april 1970. Dissolved organic carbon and nitrogen, dissolved free fatty acids and particulate organic carbon, have been determined. Concentrations of nitrate and nitrite, obtained when measuring concentrations of organic nitrogen are also reported. Coastal influence and hydrological conditions explain the relatively high level and noticeable variations of the concentrations of dissolved organic matter. Free fatty acids represent only one or two per cent of dissolved organic matter.

Les écosystèmes côtiers sont soumis à de multiples forçages physiques et chimiques qui agissent à des échelles de temps très différentes. Pour décrire et prédire l’impact de ces forçages sur les écosystèmes, il est impératif de mesurer à long terme les caractéristiques physiques, chimiques et biologiques des eaux côtières. Depuis plus de 15 ans, un partenariat réunit l’IUEM/UBO, l’IFREMER et l'INSU pour assurer le suivi régulier et à long terme de la physico-chimie des eaux côtières à l’interface de la rade de Brest et de la mer d’Iroise (site de Ste Anne du Portzic, 48°21’60 N, 4°33’04 W ). Ce suivi repose sur une stratégie combinée de mesures à basse fréquence (série SOMLIT-Brest - Service d’Observation en Milieu LITtoral) et de mesures à haute fréquence (série MAREL-Iroise - Mesure Automatisée en Réseau de l’Environnement Littoral).