State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, Fujian, China.
Provincial Key Laboratory of Cultivation and High-Value Utilization of Marine Organisms, Fisheries Research Institute of Fujian Province, Xiamen, Fujian, China.
J Phycol. 2023 Dec;59(6):1347-1352. doi: 10.1111/jpy.13398. Epub 2023 Oct 16.
Increases of atmospheric CO cause ocean acidification (OA) and global warming, the latter of which can stratify the water column and impede nutrient supply from deep water. Phosphorus (P) is an essential nutrient for phytoplankton to grow. While dissolved inorganic phosphorus (DIP) is the preferred form of P, phytoplankton have evolved alkaline phosphatase (AP) to utilize dissolved organic phosphorus (DOP) when DIP is deficient. Although the function of AP is known to require pH > 7, how OA affects AP activity and hence the capacity of phytoplankton to utilize DOP is poorly understood. Here, we examined the effects of pH conditions (5.5-11) on AP activity from six species of dinoflagellates, an important group of marine phytoplankton. We observed a general pattern that AP activity declined sharply at pH 5.5, peaked between pH 7 and 8, and dropped at pH > 8. However, our data revealed remarkable interspecific variations in optimal pH and niche breadth of pH. Among the species examined, Fugacium kawagutii and Prorocentrum cordatum had an optimal pH at 8, and Alexandrium pacificum, Amphidinium carterae, Effrenium voratum, and Karenia mikimotoi showed an optimal pH of 7. However, whereas A. pacificum and K. mikimotoi had the broadest pH niche for AP (7-10) and F. kawagutii the second (8-10), Am. carterae, E. voratum, and P. cordatum exhibited a narrow pH range. The response of Am. carterae AP to pH changes was verified using purified AP heterologously expressed in Escherichia coli. These results in concert suggest OA will likely differentially impact the capacity of different phytoplankton species to utilize DOP in the projected more acidified and nutrient-limited future ocean.
大气 CO2 的增加会导致海洋酸化（OA）和全球变暖，后者会使水柱分层，并阻碍来自深层水的营养供应。磷（P）是浮游植物生长的必需营养物质。虽然溶解无机磷（DIP）是 P 的首选形式，但当 DIP 缺乏时，浮游植物已经进化出碱性磷酸酶（AP）来利用溶解有机磷（DOP）。虽然 AP 的功能已知需要 pH 值>7，但 OA 如何影响 AP 活性，从而影响浮游植物利用 DOP 的能力，人们对此知之甚少。在这里，我们研究了 pH 值条件（5.5-11）对六种甲藻（海洋浮游植物的一个重要群体）AP 活性的影响。我们观察到一个普遍的模式，即在 pH 值为 5.5 时，AP 活性急剧下降，在 pH 值为 7 到 8 之间达到峰值，然后在 pH 值>8 时下降。然而，我们的数据显示，最佳 pH 值和 pH 值生态位的种间变异显著。在所研究的物种中，Fugacium kawagutii 和 Prorocentrum cordatum 的最佳 pH 值为 8，而 Alexandrium pacificum、Amphidinium carterae、Effrenium voratum 和 Karenia mikimotoi 的最佳 pH 值为 7。然而，A. pacificum 和 K. mikimotoi 的 AP 具有最宽的 pH 生态位（7-10），F. kawagutii 的 pH 生态位第二（8-10），而 Am. carterae、E. voratum 和 P. cordatum 则表现出狭窄的 pH 范围。使用在大肠杆菌中异源表达的纯化 AP 对 Am. carterae AP 对 pH 变化的响应进行了验证。这些结果表明，OA 可能会对不同浮游植物物种在未来酸化和营养受限的海洋中利用 DOP 的能力产生不同的影响。
