Renewed phytoplankton growth usually occurs in September when nutrients become available again after remineralization of organic matter. The subsequent modest autumn bloom often mainly consists of small diatom species. The image shows a young colony of the small diatom Chaetoceros socialis (Bacillariophyceae). Cells of this young colony are more or less systematically arranged in long bent chains, but that differs in older colonies, where cells are more chaotically organized.