Author contributions
Y.H. initiated the research idea. K.J.W. and Y.H. discussed with T.R.K. and codesigned the study. C.S.A. and F.V. collected and processed sediment samples.  K.J.W., M.M., and N.R. analyzed the DNA and the phylogenetic data. S.L. and K.J.W. conducted the alkenone analyses. K.J.W. and Y.H. cowrote the manuscript with contributions from coauthors.