Bioluminescence* occurs widely among animals, especially in the open sea, but the ones known as sparkling phosphorescence in a surface sea layer are most often caused by plankton. One example of bioluminescent plankton is the dinoflagellate Noctiluca scintillans, commonly known as ‘ the sea sparkle’. These rather translucent organisms are difficult to spot in daylight, even when they bloom**, but in the dark you can see the almost magical effect: blue glowing water.
Their blooms are common for warmer areas, but sometimes they occur in Dutch coastal waters as well. Earlier this month, along the Dutch coast, there were many photographed reports of this visually spectacular effect (e.g. Katwijk, Scheveningen, Duindorp).
Most Noctiluca cells are around 0.5-1mm, sometimes even reaching 2 mm in size, which makes them too big to be analysed with most imaging flow cytometers, since they are getting clogged by such cells. CytoSense can run high loadings of particles (concentrations up to 10^11 cells per liter) without getting clogged thanks to our specially designed flow cell. Additionally to the bright field images, laser excited scatter and fluorescence signals are also recorded for each particle. These 'scans' allow the detection of picoplankton but also the analysis of very long particles to over 2 mm in length. This enables size and biomass/ biovolume analysis of cells that can’t be imaged in full (like bigger cells of Noctiluca scintillans).
Altogether, Noctiluca bloom presented a good opportunity to show how CytoSense can analyse much bigger cells than other instruments, so we collected a sample of sea water from the Kijkduin beach and analysed it with the CytoSense.
The CytoSense used for analysis has an imaging system with an image frame of 441 x 528 μm in the object plane, therefore from most Noctiluca cells only a part was caught on photo (Image 1). Nevertheless , due to their pulse shape scans (Image 2), we got an info of their accurate size: most of them were between 600 and 800 µm.
This demonstrates that the CytoSense analyses anything from submicron to 0.8 millimeter diameter and 2mm length, including Noctiluca. No filtration or other fractionation of samples is required. All cell sizes are measured with the CytoSense without hardware changes like flow-cell swapping or the like.
The analysis was done with a standard CytoSense, while in order to image larger organisms a camera sensor of 2048x2592 pixels of 4.8μm or 614 x 778 μm in the object plane can be mounted. Additionally, a special CytoSense version with larger fluidics and flow cell orifice (1.5mm) is also available upon request. Contact us at firstname.lastname@example.org for more information!
*The word “bioluminescence” comes from “bio,” meaning life, and “lumin,” meaning light and in 1929 was defined as “emission of light by living organisms”
**An algal bloom is a rapid increase or accumulation in the population of algae in water systems