Effects of increasing seawater carbon dioxide concentrations on chain formation of the diatom Asterionellopsis glacialis

• Main Authors: Barcelos e Ramos, Joana, Schulz, Kai Georg, Brownlee, Colin, Sett, Scarlett, Azevedo, Eduardo Brito
• Format: Dataset
• Language: English
• Published: PANGAEA 2014
• Subjects: Alkalinity; total; Aragonite saturation state; Asterionellopsis glacialis; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; organic; dissolved exudation; per cell; particulate; production per cell; Carbon/Nitrogen ratio; Carbon/Phosphorus ratio; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Laboratory experiment; Nitrogen/Phosphorus ratio; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Open ocean; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate organic carbon; Particulate organic nitrogen per cell; Particulate organic phosphorus per cell; Pelagos; Percentage; pH; Phosphorus; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.836367; https://doi.org/10.1594/PANGAEA.836367

Diatoms can occur as single cells or as chain-forming aggregates. These two strategies affect buoyancy, predator evasion, light absorption and nutrient uptake. Adjacent cells in chains establish connections through various processes that determine strength and flexibility of the bonds, and at distinct cellular locations defining colony structure. Chain length has been found to vary with temperature and nutrient availability as well as being positively correlated with growth rate. However, the potential effect of enhanced carbon dioxide (CO2) concentrations and consequent changes in seawater carbonate chemistry on chain formation is virtually unknown. Here we report on experiments with semi-continuous cultures of the freshly isolated diatom Asterionellopsis glacialis grown under increasing CO2 levels ranging from 320 to 3400 µatm. We show that the number of cells comprising a chain, and therefore chain length, increases with rising CO2 concentrations. We also demonstrate that while cell division rate changes with CO2 concentrations, carbon, nitrogen and phosphorus cellular quotas vary proportionally, evident by unchanged organic matter ratios. Finally, beyond the optimum CO2 concentration for growth, carbon allocation changes from cellular storage to increased exudation of dissolved organic carbon. The observed structural adjustment in colony size could enable growth at high CO2 levels, since longer, spiral-shaped chains are likely to create microclimates with higher pH during the light period. Moreover increased chain length of Asterionellopsis glacialis may influence buoyancy and, consequently, affect competitive fitness as well as sinking rates. This would potentially impact the delicate balance between the microbial loop and export of organic matter, with consequences for atmospheric carbon dioxide.