Temperature and nutrient supply interactively control phytoplankton growth and productivity, yet the role of these drivers together still has not been determined experimentally over large spatial scales in the oligotrophic ocean. We conducted four microcosm experiments in the tropical and subtropical Atlantic (29°N-27°S) in which surface plankton assemblages were exposed to all combinations of three temperatures (in situ, 3 °C warming and 3 °C cooling) and two nutrient treatments (unamended and enrichment with nitrogen and phosphorus). We found that chlorophyll a concentration and the biomass of picophytoplankton consistently increase in response to nutrient addition, whereas changes in temperature have a smaller and more variable effect. Nutrient enrichment leads to increased picoeukaryote abundance, depressed Prochlorococcus abundance, and increased contribution of small nanophytoplankton to total biomass. Warming and nutrient addition synergistically stimulate light-harvesting capacity, and accordingly the largest biomass response is observed in the warmed, nutrient-enriched treatment at the warmest and least oligotrophic location (12.7°N). While moderate nutrient increases have a much larger impact than varying temperature upon the growth and community structure of tropical phytoplankton, ocean warming may increase their ability to exploit events of enhanced nutrient availability.

温度和养分供应交互控制浮游植物的生长和生产力，但这些驱动因素的共同作用仍未在贫营养海洋的大空间尺度上通过实验确定。我们在热带和亚热带大西洋（29°N-27°S）进行了四次微观世界实验，其中地表浮游生物组合暴露于三种温度（原位、3°C 升温和 3°C 降温）和两种营养物质的所有组合中。处理（未修正和富集氮和磷）。我们发现叶绿素a浮游植物的浓度和生物量随着营养添加而持续增加，而温度变化的影响较小且变化较大。营养丰富导致微小核生物丰度增加，抑制原绿球菌丰度，并增加了小型纳米浮游植物对总生物量的贡献。变暖和营养添加协同刺激光捕获能力，因此在最温暖和最少贫营养的位置（12.7°N）的变暖、富营养处理中观察到最大的生物量响应。虽然适度的养分增加比温度变化对热带浮游植物的生长和群落结构的影响要大得多，但海洋变暖可能会增加它们利用养分增加事件的能力。