L4 phytoplankton time-series
Preserved samples, for the enumeration of phytoplankton and microzooplankton species abundance and biomass, have been collected on a weekly basis since 1992. The data were initially generated by Derek Harbour (1992-2004) who subsequently trained Claire Widdicombe to enumerate and identify individual cells to genus/species level (2005 to date).
Paired samples are collected from a depth of 10m and preserved with 2% Lugol's iodine solution (Throndsen, 1978) and 4% buffered formaldeyde. Between 10 and 100 ml of sample, depending on cell density, are settled for >48 hours and cells are identified where possible to species level and enumerated. Cell volumes are calculated according to the equations of Kovala and Larrance (1996) and converted to carbon using the equations of Menden-Deuer and Lessard (2000). Please note that previous versions of the phytoplankton dataset have used the equations of Eppley et al (1970) to derive carbon biomass.
Further details of methods used are given in Widdicombe et al., (2010) Phytoplankton dynamics in the Western English Channel. Journal of Plankton Research, 32 (5) 643-655
The species recorded and identified at the L4 time-series station are verified using the World Register of Marine Species (WoRMS) and separated into eight functional groups. PHYTOPLANKTON: diatoms; dinoflagellates; coccolithophores; phyto-flagellates. MICROZOOPLANKTON: colourless dinoflagellates; ciliated protozoa; zoo-flagellates; sarcodines.
We view it as essential for all users of L4 plankton data to establish and maintain contact with the nominated current data originators as well as fully consulting the metadata. While not impinging on free data access, this ensures that this large, species-rich but slightly complex species database is being used in the correct way, and any potential issues with the data are clarified. Furthermore, a proper dialogue with these local experts on the time series will enable where appropriate the most recent sampling timepoints to be used.