Methodology:

Water samples for chlorophyll analysis were collected on board DY098 with a Sea-Bird Scientific SBE 911 CTD (Sea-Bird Scientific, Bellevue, Washington). Samples were collected from Niskins fired at six depths (400 m, 200 m, 100 m, 50 m, 5 m and the chlorophyll maximum (chl-max)). Duplicate samples of 100 ml water from each depth were taken and water was filtered onto a 25 mm diameter GF/F, wrapped in tinfoil, and stored at -20 °C until later analysis. Upon return to the home laboratory, chlorophyll filters were removed from the freezer, extracted in 10 ml 90 % acetone for 24 hours at -20 °C, and chlorophyll-a and phaeophytin-a concentrations (mg l-1) were measured on a Turner Trilogy Fluorometer (Turner Designs, San Jose, USA) using the acidification module, in order to account for the presence of degradation products.

Data collection:

Sea-Bird Scientific SBE 911 CTD (Sea-Bird Scientific, Bellevue, Washington)

Turner Trilogy Fluorometer (Turner Designs, San Jose, USA)

Data quality:

Two replicate samples were taken at each station. NAs in the data relate to Station 105 where there was no obvious chlorophyll max as the top 100 m was uniform, and Station 116 where the bottle misfired at 50 m. No 400 m sample was taken at Station 5.