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

二氧化碳分压（partial pressure of CO2，简称pCO2）升高引发海洋酸化，进而影响浮游植物的生长速率与元素组成。本文探讨了在不同温度、光照强度及pCO2条件下培养的威氏海链藻（Thalassiosira weissflogii）的生长速率与细胞配额的变化。所呈现的数据表明，指数生长的硅藻对环境扰动的驯化适应周期可能为数周至数月，而非数天至数周。驯化后的威氏海链藻对pCO2的响应依赖于光照强度与温度，且呈现出极强的交互性、非线性与非均匀性。在光照和温度受限的生长条件下，观测到pCO2具有极为显著的负效应；在光照受限的生长条件下，虽响应幅度较小但仍具有统计学显著性的负响应；而在光饱和生长条件下，pCO2对威氏海链藻的生长速率无显著影响。有机碳、氮或叶绿素a的细胞配额与生长速率相关联。细胞标准化的透明胞外聚合物颗粒（transparent exopolymer particles，TEP）产量与颗粒有机碳（POC）细胞配额呈正相关，光照强度与pCO2对该相关性仅存在轻微影响。TEP产量与碳细胞配额的这一相关性，与“胞外释放是细胞代谢的固有组分”这一假说相符。研究结果表明，升高的pCO2可作为威氏海链藻的（额外）代谢胁迫因子，且不同胁迫因子的交互作用以复杂的非线性关系决定了生物的生长速率与细胞特征。