Copper (Cu) is essential for many physiological processes in phytoplankton, including electron-transfer reactions and high-affinity Fe transport systems. However, at high concentrations, Cu can have a toxic effect on phytoplankton. Phytoplankton’s tolerance to certain toxicants in marine ecosystems cannot always be solely attributed to the presence of compounds, as various environmental factors including temperature can also indirectly influence their effects on organisms. In this study, we investigated the effects of different Cu concentrations (0, 19.6, 160, 800, and 8000 nM) on the growth and physiological changes in the centric diatom Thalassiosira pseudonana (CCMP 1335) when simultaneously applied with temperature cultivation of 20 °C and 25 °C. At low (0 nM) and high (8000 nM) Cu concentrations, the growth rate of T. pseudonana was inhibited, though an increase in temperature lessened this inhibition. There were no significant changes in the POC:PON ratio during all of the treatments. However, increasing the temperature significantly decreased the POC: POP, PON: POP and BSi: POP ratios of T. pseudonana. The intracellular Cu content of T. pseudonana varied from 0.13 to 13.28 fg cell⁻¹ in response to increases in ambient Cu concentrations. Lastly, an increase in the Cu concentration decreased the transcriptional expression of CTR (copper transporter), 3Hfcp (photosynthetic protein), and Sit1 (silica shell formation) encoding genes. In conclusion, our results indicated that T. pseudonana can adapt to physiological processes and molecular mechanisms in response to varying Cu concentrations and ambient temperatures.

中文翻译：

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温度升高改变细胞外铜对假假海藻生理和转录的影响

铜 (Cu) 对浮游植物的许多生理过程至关重要，包括电子转移反应和高亲和力 Fe 传输系统。然而，在高浓度下，Cu 会对浮游植物产生毒性作用。浮游植物对海洋生态系统中某些有毒物质的耐受性并不总是仅仅归因于化合物的存在，因为包括温度在内的各种环境因素也会间接影响它们对生物的影响。在本研究中，我们研究了不同 Cu 浓度（0、19.6、160、800 和 8000 nM）对中心硅藻Thalassiosira pseudonana生长和生理变化的影响(CCMP 1335) 同时应用 20 °C 和 25 °C 的温度培养。在低 (0 nM) 和高 (8000 nM) Cu 浓度下，T的生长速率。假假假名被抑制，但温度升高减轻了这种抑制。在所有处理过程中，POC:PON 比率没有显着变化。然而，升高温度会显着降低T. pseudonana的 POC: POP、PON: POP 和 BSi: POP 比率。T. pseudonana的细胞内铜含量从 0.13 到 13.28 fg cell ^{- 1}不等以响应环境铜浓度的增加。最后，Cu 浓度的增加降低了 CTR（铜转运蛋白）、3Hfcp（光合蛋白）和 Sit1（二氧化硅壳形成）编码基因的转录表达。总之，我们的结果表明T. pseudonana可以适应不同的 Cu 浓度和环境温度的生理过程和分子机制。