Described as the ‘flaming seas’ by Aristotle and ‘billows of liquid phosphorus’ by Charles Darwin, the eerie beauty of bioluminescence has been documented for centuries. While most of us have only seen it in CGI-soaked fantasy films such as Avatar and Life of Pi, bioluminescence is a very real and mysterious phenomenon.
For reasons unknown, the blue glow is emitted by thousands of living organisms when they are disturbed in the water. By monitoring the tiny organisms themselves, a team of marine biologists from the National Oceanography Centre (NOC) in Southampton has developed a promising method of forecasting the blue plumes.
The organisms responsible are certain species of dinoflagellates, a type of plankton. The types of dinoflagellates that produce bioluminescence thrive in calm waters and calm winds which allow for an unmixed, stratified water column. ‘When the environmental conditions suit them they begin to grow and divide very fast,’ explains ocean biogeochemist and director of the study, Dr Charlotte Marcinko. That is, when they are not being eaten by zooplankton. ‘For a bloom, growth rate has to be faster than death rate by natural causes or grazing zooplankton.’
However, some dinoflagellates glow brighter than others; the different species have different intensities. By combining species light intensity with data from plankton recorders in the northeast Atlantic, the NOC modelled how dinoflagellates and bioluminescence might change seasonally. The plankton recorders, run by the Sir Alister Hardy Foundation for Ocean Science, have been continuously monitoring plankton levels in the world’s oceans since 1931 and provided a wealth of data to model organism growth.
‘Our model indicated that emissions of bioluminescence would be highest in the northeast Atlantic when dinoflagellate abundance reaches its maximum in July,’ explains Marcinko. ‘Emissions would be lowest in winter.’
Bioluminescence can alert to underwater presences and movements such as internal waves and shoals of fish. It supposedly gave away the position of the last German U-boat to be sunk during the First World War. Predicting when and where the plumes might occur in different parts of the world could also help assess ocean fish stocks. At certain times of year, in regions where bioluminescent dinoflagellates are very abundant, whole shoals of fish can stimulate light as they move through the water. If the bioluminescence forecast model was applied to other parts of the world, it could even be possible to record light emissions from many shoals. This light could be recorded by specially intensified cameras attached to small aircraft flying above the surface of the sea. With enough data, these patterns could be used to determine the sizes of the fish shoals and assess global fish stocks.