Cruise blog

Sunday 19 July 2009

Measuring Bioluminescence at the PAP site by Charlotte Marcinko

Some small plankton species are able to produce flashes of light which can be seen in the water at night. These organisms are said to be bioluminescent. As part of the scientific work happening here on the RRS Discovery we are taking measurements to estimate the amount of bioluminescence which can be stimulated in the surface water and to identify which organisms are creating it. This is done using an instrument named Glowtracka. To make measurements with the Glowtracka we take samples of surface water collected from the niskin bottles on the CTD and because we like to take samples during the night it means staying up very late or waking up very early in the morning. The water collected is placed into a blacked out holding chamber attached to the instrument. The water sample is then left for a set amount of time in the dark before it is allowed to run from the holding chamber and through a mesh grid which stimulates any bioluminescent organism in the water to glow. The flashes of light emitted by the bioluminescent organisms are detected by a sensor called a photodiode and the signal is recorded on a computer. We then take samples of the water which can be analysed in the lab when we get back to shore and from these we hope to identify which organisms created the bioluminescent signals recorded. From a piece of equipment called Flowcam we have already identified that there are some bioluminescent organisms called dinoflagellates present in the water column. We hope that the bioluminescent signal recorded from the water samples on the computer are from these same organisms.