Northwest European shelf seas - Phytoplankton pigments - 2020 to 2023

These data contain concentrations in micrograms per litre (ug/L) of the individual accessory pigments of phytoplankton measured by High Performance Liquid Chromatography (HPLC). Pigment samples were taken on Cefas fisheries surveys in the Celtic Seas, and sent to DHI laboratory in Denmark for HPLC analysis. Data was then sent back to Cefas and matched with metadata and quality controlled. Chlorophyll concentrations from this dataset have a variety of uses: for assessment of concentrations for purposes such as eutrophication assessments, validation of remote sensing derived chlorophyll estimates, as a proxy for phytoplankton biomass, or to calibrate fluorometers. Pigment concentrations can be applied like a fingerprint to derive phytoplankton functional types and give information about the phytoplankton community. 2 litre water samples were collected on board the RV Cefas Endeavour from the continuous flow ferrybox water supply (4m depth), or from Niskin bottles on a rosette fired at particular depths. Water samples were filtered through a Whatman GFF filter, and immediately frozen in a -80°C freezer on board. Pigments were stored at -80°C for 1-4 months, before being selected for analysis, then transferred to the analysis laboratory (DHI; Horsholm, Denmark) using dry ice. Pigments were extracted adding 6 ml of 95% acetone (and an internal standard, vitamin E) to each filter. The samples were sonicated in an ice-cold sonication bath for 10 min and extracted at 4 °C for 20 hours. The samples were then filtered through 0.2 µm Teflon syringe filter into HPLC vials. Buffer and samples were injected on HPLC (Shimadzu LC-10A HPLC system with LC Solution software) in the ratio 5:2 using a pre-treatment program and mixing in the loop before injection (Schlüter et al 2016). The HPLC method used was the Van Heukelem & Thomas (2005) method where the gradient was adjusted to optimise the resolution of the pigments. The raw data were stored in PostgreSQL database. Quality control was performed following methods in Aiken et al 2009. Samples were removed if they had insufficient chlorophyll (