The study compared the abundance and distribution of two species of plankton over a 50-year period. They found that the range of the cold-water species, Calanus finmarchicus, had contracted, while the warm-water species, C. helgolandicus, had become more common. ‘In other words, even over 50 generations (each plankton lives for one year or less), there’s no evidence of adaptation to the warmer water,’ said one of the study’s authors, Professor Graeme Hays of Melbourne’s Deakin University.
‘The consequences of this study are profound,’ he added. ‘It suggests that cold- water plankton will become scarcer as their ranges contract to the poles, and ultimately disappear. So, certainly for these animals, thermal adaptation appears unlikely to limit the impact of climate change.
‘C. finmarchicus is a key food source for fish such as cod and hake,’ he concluded. ‘So continued declines in abundance will have a negative impact on the long-term viability of cold-water fisheries in the North Sea and other areas in the southern part of their range. At the same time, the continued increase in abundance of the warm-water plankton, C. helgolandicus, will likely play a role in the emergence of new fisheries for warm-water species.’
This story was published in the December 2013 edition of Geographical Magazine