Diatoms in general, and Thalassiosira weissflogii (T. weissflogii) in particular, are among the most ubiquitous phytoplanktonic species, while phosphorus (P) is an essential nutrient that limits productivity in many oceanic regimes. To investigate how T. weissflogii cultures grown under different P regimes are chemically altered before and during their prokaryotic degradation, T. weissflogii cells were cultivated under two contrasting P conditions; “P-stress” and “P-replete”. Biodegradation experiments were conducted in natural seawater comprising a natural prokaryotic community. The particulate fraction was monitored for 3 weeks for organic carbon (POC), nitrogen (PON), biogenic silica (bSiO2), total carbohydrates (PCHO) and individual monosaccharides, including prokaryotic counting. Results indicated that P-stress induced changes in the chemical composition of the T. weissflogii cells, causing a decrease in the Si/N (1.1–0.46) and Si/C (0.17–0.08) ratios. The “P-stress T. weissflogii” cells were characterized by high amounts of galactose (23% of PCHO), xylose (21%) and glucose (19%), compared to the “P-replete T. weissflogii” cells. The latter were dominated by ribose (20% of PCHO), further indicating the exhaustion of ribose-rich molecules (e.g., ATP) in T. weissflogii under “P-stress” conditions. The degradation experiments showed that bSiO2 produced under “P-stress” conditions dissolved more rapidly than bSiO2 formed under “P-replete” conditions, whereas POC and PON exhibited higher degradation rate constants in the “P-replete T. weissflogii” than in the “P-stress T. weissflogii” experiment. Overall, these observations show that submission of T. weissflogii to P-limitation results in changes in its initial biochemical composition, increased frustule dissolution rates, and decreases the degradation of T. weissflogii-organic matter by marine prokaryotes.

中文翻译：

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磷限制影响海藻的分子组成，导致生物二氧化硅溶解增加和细胞碳水化合物的高降解率

一般而言，硅藻，尤其是 Thalassiosira weissflogii (T. weissflogii) 是最普遍的浮游植物物种之一，而磷 (P) 是限制许多海洋区域生产力的必需营养素。为了研究在不同磷条件下生长的 T.weissflogii 培养物在原核降解之前和过程中如何发生化学变化，在两种不同的磷条件下培养 T.weissflogii 细胞；“P-压力”和“P-充满”。生物降解实验在包含天然原核生物群落的天然海水中进行。监测颗粒部分 3 周的有机碳 (POC)、氮 (PON)、生物二氧化硅 (bSiO2)、总碳水化合物 (PCHO) 和单个单糖，包括原核计数。结果表明，P 应力诱导 T.weissflogii 细胞的化学成分发生变化，导致 Si/N (1.1–0.46) 和 Si/C (0.17–0.08) 比率降低。与“P-replete T.weissflogii”细胞相比，“P-stress T.weissflogii”细胞的特征在于高含量的半乳糖（PCHO 的 23%）、木糖（21%）和葡萄糖（19%）。后者以核糖（PCHO 的 20%）为主，进一步表明 T.weissflogii 中富含核糖的分子（例如，ATP）在“P 压力”条件下耗尽。降解实验表明，在“P-stress”条件下产生的 bSiO2 比在“P-replete”条件下形成的 bSiO2 溶解得更快，而 POC 和 PON 在“P-replete T.weissflogii”中的降解速率常数高于“P-stress T.weissflogii”实验。全面的，