As an author I take responsibility for the fact that we have quoted the wrong paper describing variation in bacterioplankton diversity at the L4 site and the derivation of data used in this study. The correct reference is Gilbert, J. A., Steele, J. A., Caporaso, J. G., Steinbrück, L., Reeder, J., Temperton B., Huse, S., McHardy, A., Knight, R., Joint, I. R., Somerfield, P., Fuhrman, J. A., Field, D. (2012) Defining seasonal marine microbial community dynamics. ISME Journal 6:298-308. DOI: 10.1038/ismej.2011.107. In this paper the derivation of the time-series data, and analyses demonstrating the importance of seasonal cycles correlated with (but unlikely to be driven by) day-length, are described.