An effect of dissolved nutrient concentrations on alkenone‐based temperature estimates

Abstract

The ratio of 37‐carbon diunsaturated to diunsaturated and triunsaturated alkenones (U K′ 37 ) produced by some haptophytes is widely used as a proxy for past sea surface temperatures. However, our isothermal culturing experiments with Emiliania huxleyi clone CCMP372 show U K′ 37 values to also vary with nutrient availability and cell division rate. These results provide a reasonable explanation for large isothermal variation in U K′ 37 values of single coccolithophorid strains grown in culture. They also suggest that alkenone‐based estimates of past sea surface temperatures may have been influenced by dissolved nutrient concentrations as well as by temperature.