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plankton blooms

18 January 2015
Climate change

At http://phys.org/print340618543.html … the accepted theory on what causes plankton blooms is under attack by a marine botanist. Currently, a phyto plankton hot spot in the mid Atlantic has been chosen as the point of study – funded by NASA. Presumably this is an effort to understand the carbon cycle in the oceans.

Phyto plankton are present in abundant proportions in all the world's oceans. They capture sunlight and convert it into sugar and then become the food of zooplankton, the animal version of plankton. These, in turn, are eaten by other organisms – and so on up the food chain. In colder, nutrient rich waters they periodically undergo seasonal population blooms, leading to exploding numbers. It has been thought this was due to spring-time increases in sunlight – and warming temperatures (following the winter). Warmer oceans should therefore coincide with bigger and bigger blooms, which should release more for for ocean dwelling life. We are supposed to be living in a warming world – so blooms should have increased exponentially. Presumably this is one reason why the theory is being questioned – without asking if the world might only be warming in the models.

Satellite images have been monitoring global plankton for a few years. These appear to show blooms occurring when they should not be. For example, during winter months. A new theory on blooms is being developed – one based on winds mixing the upper layers of the ocean, a process that involves the thermal convection in which colder water inks and warmer water rises as a result of the wind disturbance. This in turn disperses the phyto plankton making them harder to locate by the zoo plankton and as a result their population numbers go  up – very quickly.

However, as with all new theories, some debris will be left behind. For example, chalk is composed of plankton from the dinosaur age (the Cretaceous period). The chalk geology is so thick that plankton and algal blooms are blamed, in order to create such a quantity. This was fine and dandy with the old theory as it is also supposed global warming was a feature of the dinosaur age – and soaring temperatures had led to ice free poles – and plankton blooms.

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