赫氏圆石藻（学名：Emiliania huxleyi），经常被缩写为“EHUX”，是一种遍布全球水域的钙板金藻。它被用来研究夏季的温跃层后营养耗尽的水中形成的大范围水华。就像其他的钙板金藻一样，'赫氏圆石藻是一种包覆着独特碳酸钙盘状外壳的单细胞海洋浮游植物。虽然完整的钙板金藻个体很少见，但它们大量存在于海底沉积物中。至于“赫氏圆石藻”，不只是外壳，也是可能是被记录在沉积物里的柔软有机体。它能合成出一组具有很强的防腐能力的化学物质，这些化学物质，比如颗石藻标志物，可以在海底沉积物中那些早已腐烂的有机体中找到。颗石藻标志物成为地球科学中用来研究海洋表面温度的线索。

Emiliania huxleyi, often abbreviated "EHUX", is a species of coccolithophore with a global distribution from the tropics to subarctic waters. It is one of thousands of different photosynthetic plankton that freely drift in the euphotic zone of the ocean, forming the basis of virtually all marine food webs. It is studied for the extensive blooms it forms in nutrient-depleted waters after the reformation of the summer thermocline. Like other coccolithophores, E. huxleyi is a single-celled phytoplankton covered with uniquely ornamented calcite disks called coccoliths (also informally known as liths or scales). Individual coccoliths are abundant in marine sediments although complete coccospheres are more unusual. In the case of E. huxleyi, not only the shell, but also the soft part of the organism may be recorded in sediments. It produces a group of chemical compounds that are very resistant to decomposition. These chemical compounds, known as alkenones, can be found in marine sediments long after other soft parts of the organisms have decomposed. Alkenones are most commonly used by earth scientists as a means to estimate past sea surface temperatures.