Western Channel Observatory

NERC National Capability of the Plymouth Marine Laboratory and Marine Biological Association


L4 flow cytometry data

These plots show data generated using flow cytometry since April 2007. The data can be downloaded from the Pangaea website as files for each year from 2007 – 2011 and from the BODC website from 2012. Once you are ininto either site, type Tarran L4 into the search box to find out how to access the data. Flow cytometry involves using a laser-based machine, to count particles and measure light that they scatter as well as fluoresce. A copy of the protocols can be downloaded here. Different groups of particles have different light scattering and fluorescence properties. This makes it possible for us to distinguish different groups of algae (phytoplankton) in live samples of seawater from L4 because the chlorophyll inside them fluoresces red when the laser beam shines on them. We can also count different groups of bacteria and tiny single celled zooplankton (heterotrophic nanoflagellates) by staining the same seawater samples with a dye that attaches to the DNA in the cells and fluoresces green when the laser beam shines on them. These measurements are taken every week by collecting seawater samples from 4 depths at station L4, bringing them back to the laboratory and then analysing them on the flow cytometer. We then have measurements of the plankton abundance as cells per millilitre of seawater through the water column which we use to see how their abundance changes with time as shown in the example plots below. In all plots the green and orange/red colours show where the abundance is highest.

2018 was a year of extremes in terms of weather, from significant snow and cold weather in the early part of the year to one of the hottest, calmest summers on record. Extremes were also recorded in some of the groups of plankton analysed by flow cytometry. For example, coccolithophores responded to the extended period of really calm weather, forming a bloom in the English Channel in June/July. At Station L4, abundance reached 3500-4500 cells per mL in the upper 10 m on 2 July. This is the highest abundance recorded since 2007. Synechococcus sp. cyanobacteria also reached the highest abundance recorded since 2007, with a maximum of 325,000 cells per mL in the upper 10 m on 3 September. A third group for which maximum abundance since 2007 was recorded was the Dino group. This group is most likely made up of small dinoflagellates of the genus Prorocentrum (coinciding with opservations made by microscopy). Maximum abundance was recorded in mid-September in the upper 10 m, with abundance between 1300-1900 cells per mL on the 10th of September and 4300-4400 cells per mL on 17th September. Another group of note was the HNA bacteria; bacteria with relatively high nucleic acid content. Its abundance was in excess of 1 million per mL for more than 6 months, from spring to autumn.

Concentrations of Coccolithophores Concentrations of Dinos Concentrations of Syn

About Us

The WCO is a partnership between the Plymouth Marine Laboratory and the Marine Biological Association.

How are we funded?

The core work of the WCO is funded as part of the UK Natural Environment Research Council's National Capability.

Contact Information

For more details about the WCO please contact:

Dr Tim Smyth
Western Channel Observatory
Plymouth Marine Laboratory
Prospect Place
email: tjsm@pml.ac.uk