There arose one of the most important ecological transitions in Earth’s history approximately 750 million years ago during the middle Neoproterozoic Era (1000 to 541 million years ago, Ma). Biomarker evidence suggests that around this time there was a rapid shift from a predominantly bacterial-dominated world to more complex ecosystems governed by eukaryotic primary productivity. The resulting ‘Rise of the algae’ led to dramatically altered food webs that were much more efficient in terms of nutrient and energy transfer. Yet, what triggered this ecological shift? In this study we examined the theory that it was the alleviation of phosphorus (P) deficiency that gave eukaryotic alga the prime opportunity to flourish. We performed laboratory experiments on the cyanobacterium Synochystis salina and the eukaryotic algae Tetraselmis suecia and examined their ability to compete for phosphorus. Both these organisms co-occur in modern European coastal waters and are not known to have any allelopathic capabilities. The strains were cultured in mono and mixed cultures in chemostats across a range of dissolved organic phosphorus (DIP) conditions to reflect modern and ancient oceanic conditions of 0.2 μ M P and 2 μ M P, respectively. Our results show that the cyanobacteria outcompete the algae at the low input (0.2 μ M P) treatment, yet the eukaryotic algae were not completely excluded and remained a constant background component in the mixed-culture experiments. Also, despite it’s relatively large cell size, the algae T. suecia had a high affinity for DIP. With DIP input concentrations resembling modern-day levels (2 μ M), the eukaryotic algae could effectively compete against the cyanobacteria in terms of total biomass production. These results suggest that the availability of phosphorus could have influenced the global expansion of eukaryotic algae. However, P limitation does not seem to explain the complete absence of eukaryotic algae in the biomarker record before ca. 750 Ma.

中文翻译：

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真核藻类的全球爆炸：磷的潜在作用？

在新元古代中期（1000至5.41亿年前，Ma）出现了地球历史上最重要的生态转变之一。生物标志物的证据表明，在这段时间里，已经从以细菌为主的世界迅速转变为由真核初级生产力决定的更复杂的生态系统。由此产生的“藻类上升”导致食物网发生了巨大变化，在营养和能量传递方面更加有效。但是，是什么引发了这种生态转变？在这项研究中，我们检查了以下理论：正是磷（P）缺乏的缓解才使真核藻类得以繁衍。我们对蓝藻Synochystis salina和真核藻Tetraselmis suecia进行了实验室实验，并检查了它们竞争磷的能力。这两种生物均在现代欧洲沿海水域共存，并且不具有任何化感能力。在一系列溶解的有机磷（DIP）条件下，将这些菌株分别在化粪池中进行单培养和混合培养，以分别反映现代和古代的海洋条件，分别为0.2μMP和2μMP。我们的研究结果表明，在低输入量（0.2μMP）处理下，蓝细菌比藻类更胜一筹，但在混合培养实验中，真核藻类并未被完全排除，并且仍是恒定的背景成分。同样，尽管藻类T. suecia的细胞大小相对较大，但它对DIP的亲和力很高。由于DIP的输入浓度接近现代水平（2μM），真核藻类可以有效地与总生物量产生的蓝细菌竞争。这些结果表明磷的可用性可能已经影响了真核藻类的全球扩展。然而，P限制似乎不能解释大约在生物标记之前大约完全没有真核藻。750毫安。