Science Serving Maryland's Coasts
Rodger Harvey, Ph.D.
Chesapeake Biological Laboratory
Long Chain Alkenones as Biomarkers for Past and Present Sea Surface Temperatures using the Marine Algae Isochrysis galbana
The marine phytoplankton, Prymnesiophyceae, contains membrane Iipids, long chain C37 methyl alkenones. The prymnesiophyte, Emiliania huxleyi, is an open ocean species that has shown that the degree of unsaturation within the alkenone long chain changes with temperature. The unsaturation ratio, U(K/37), shows a linear response to temperature change and is presently used as a biomarker for past and present sea surface temperatures (SST) from cores of the ocean floor. A coastal prymnesiophyte, Isochrysis galbana, also contains these alkenones. Definitive-work with I. galbana and its relation to E. huxleyi has yet to be done. I. galbana and its relation to temperature and salinity of growth was the focus of this research. I. galbana was cultured in varying temperatures at a constant salinity and also in varying salinities at constant temperature. Alkenones were extracted and analyzed using a HPGC with FID. The relation of the U(K/73) to temperature (10-25°C) was linear and best fitted using the equation U(K/37) = 0.035T-0.352 with an r2of 0.9198. This equation is very similar to that of E. huxleyi:. U(K/37) = 0.033T + 0.043 showing a high correlation between slopes. This indicates that I. galbana may be used to predict SST along the coastlines. Results of I. galbana grown in varying salinities (10-30 ppt) show little change of UK and help support the use of I. galbana as a biomarker for SST.
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