Phytoplankton abundance data from pelagic surveys in the Celtic Seas and English Channel for autumn 2017 to 2023

Peltic is an ongoing annual autumn pelagic survey on the research vessel Cefas Endeavour in the English Channel, Celtic Sea and Bristol Channel running from 2012-present. This dataset comprises phytoplankton abundance and size data for CEND19 _ 17, CEND17 _ 18, CEND15 _ 19, CEND16 _ 20, CEND16 _ 21, CEND16 _ 22, CEND15 _ 23. Samples were collected from the continuous flow FerryBox water supply (approx. 4m water depth) in a 500 ml container and fixed with 2-3 ml of 25% acidified Lugol iodine solution. Phytoplankton species and abundance (cells per litre) were determined after sedimentation of the samples in 5 - 25 ml glass chambers, and using an inverted microscope. Sizes of most common taxa were measured with a micrometer. Abundances of phytoplankton species were then grouped based on functional groups (e.g. centric diatoms, pennate diatoms).