pCO2 as one of multiple stressors for Thalassiosira weissflogii - Cell Characteristics - PON per cell from UCSB MSI Passow Lab from 2009 to 2010 (OA - Ocean Acidification and Aggregation project)

<p>The increase in partial pressure of CO2 (pCO2) is causing ocean acidification, which impacts the<br />
growth rates and elemental composition of phytoplankton. Here, shifts in growth rates and cell<br />
quotas of Thalassiosira weissflogii grown under a variety of different temperatures, irradiances,<br />
and pCO2 conditions are discussed. The presented data suggest that acclimatization times of<br />
exponentially growing diatoms to environmental perturbations may be weeks to months, rather<br />
than days to weeks. The response of acclimatized T. weissflogii to pCO2 depended on irradiance<br />
and temperature and was highly interactive, non-linear, and non-uniform. A very significant<br />
negative effect of pCO2 was observed under growth conditions that were light-, and<br />
temperature-limited; a smaller, but still significant negative response was seen under<br />
light-limiting growth conditions, whereas pCO2 did not affect growth rates of T. weissflogii under<br />
light-saturated growth conditions. Cell quotas of organic carbon, nitrogen, or chlorophyll a were<br />
linked to growth rate. The cell-normalized production of transparent exopolymer particles (TEP)<br />
was positively correlated with POC cell quotas, with some minor impact of irradiance and pCO2<br />
on the relationship. This correlation of TEP production with carbon cell quotas is consistent with<br />
the hypothesis that extracellular release is an inherent component of cell metabolism. Results<br />
suggest that elevated pCO2 functions as an (additional) metabolic stressor for T. weissflogii and<br />
that the interaction of different stressors determines growth rates and cell characteristics in a<br />
complex, non-linear relationship.</p>