Plankton monitoring by microscopy offers long-term ecological perspective of plankton communities but is biased towards those organisms that can be distinguished using the microscope. Genetic identification of marine plankton has become standard but is still not used. This study is a comprehensive study genetically measured taxa in the Western Channel of UK using a small-volume automated water sampler deployed on the CPR platform. The study present one year of high-throughput sequencing data focussing on smaller plankton and separate community to that measured by microscopy that can complement each other for a holistic view of plankton. Quantitative tests of two harmful algae show relatively high abundance of the Pelagophyte Aureococcus anophagefferens during 2011 with low nitrite levels. Three years of Pseudo-nitzschia delicatissima quantitative monitoring also shows a greater abundance of this potentially harmful taxa in 2011. Flow cytometry reveals distinct seasonal cycles with distinct timings.