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.
In 2016, Synechococcus sp. cyanobacteria (Syn) abundance was, on average, lower than in previous years, only managing to reach a maximum of 22,000 cells per mL in August in the upper 10 m. This was an order of magnitude lower than 2015.The highest abundance of low nucleic acid bacteria (LNA) since 2007, of 1.86 million cells per mL was recorded in mid-June. The timing of this peak was uncharacteristic as on several previous years the peak in LNA abundance has been later in the year. In 2016, this resulted in LNA bacteria having two peaks in abundance: June and October. Both of the main algal groups: picoeukaryotes and nanoeukaryotes maintained abundances consistent with previous years.