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. Samples for flow cytometry have been collected at the WCO since 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 into 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.

The Western Channel Observatory, in 2020, was in the privileged position of being granted permission to continue its monitoring mission of the water column during the first lockdown due to the Covid-19 pandemic. This has meant that there has been no gap in the time series. During 2020, coccolithophores, cryptophytes, heterotrophic nanoflagellates and total bacteria were similar to long-term averages, whilst Synechococcus sp., picoeukaryote and nanoeukaryote algae were below their long-term averages. The ‘stand out’ period for the year was the 2 weeks from 16 June – 1 July. There was a large coccolithophore bloom in the Channel during June and July. On 16 June the highest surface abundance of coccolithophores since 2012 was recorded at station E1 (Figure 1 B. 7339 cells per mL), followed by the highest recorded surface abundance of coccolithophores at station L4 (Figure 1 A. 4800 per mL) since 2007 on 1 July. In the intervening week (23 June) high numbers of appendicularians were recorded (4800 m-3). Appendicularians are zooplankton that produce mucous nets that are very effective at filtering out small algae and bacteria, which they eat. This high abundance of appendicularians coincided with the lowest recorded abundance of total heterotrophic bacteria at station L4 since 2007 (Figure 2A. 54487 per mL, as opposed to a long-term summer average of 1.3 million per mL). Within the total bacteria, the HNA bacteria (which have relatively high DNA in their cells) reached as few as 535 per mL (Figure 2B, compared to a long-term summer average of 784,000 cells per mL). This day also had the lowest abundance of eukaryotic algae since 2007 at 298 cells per mL (Figure 2C, compared to a long-term summer average of 15,000 cells per mL).

Concentrations of Coccolithophores Concentrations of Bacteria

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