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EFFECTS OF INCREASING SEAWATER CARBON DIOXIDE CONCENTRATIONS ON CHAIN FORMATION OF THE DIATOM ASTERIONELLOPSIS GLACILIS Barcelos e Ramos, Joana1, Kai G.Schulz2 and Eduardo B. Azevedo1 Some marine diatom species form chains, thereby potentially influencing buoyancy, predator evasion, light absorption and nutrient uptake. Chain length has been observed to vary with temperature and nutrient availability as well as being positively correlated with growth rate. However, the potential effect of enhanced carbon dioxide concentrations and consequent changes in seawater carbonate chemistry are still unknown. Adjacent cells in chains establish connections through different processes. In the case of Asterionellopsis glacilis cells attach at the valve apices by exuded mucilage pads. Here we report on laboratory experiments with semi-continuous cultures of the freshly isolated diatom Asterionellopsis glacilis grown under increasing CO 2 levels, ranging from 330 to 4100 µatm. Our results show that the number of cells comprising a chain increases with increasing CO 2 concentrations. Moreover, while cell division might slightly increase between 330 and 750 µatm, it decreases again towards higher levels. Further analysis of production of particulate organic carbon, nitrogen and phosphorus, chlorophyl a and nutrient uptake rates are being conducted to understand the mechanisms behind the observed trends and infer implications for nutrient uptake of the species and potential effects on their sinking rates in the future ocean. 1 Centre of Climate, Meteorology and Global Change of the University of the Azores, Rua Capitão d'Ávila, São Pedro, PT - 9700-042 Angra do Heroísmo, Açores - Portugal, [email protected] 2 GEOMAR | Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg, D-24105 Kiel, Germany
