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. Once into the site, type Tarran L4 into the search box. 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 both plots the green and orange/red colours show where the abundance is highest. Some groups of phytoplankton such as the cryptophytes tend to peak in late summer and on into autumn. Coccolithophores however, have been more variable. In June 2011 their abundance reached 2000 cells per mL, the highest since the start of the time-series in 2007.