Why the decline in plankton could affect us all

The smallest life forms can be the most important for example bacteria can profoundly affect your health, both beneficially and adversely. In the oceans plankton are one of the smallest forms of life yet play an important part in sustaining life on earth in two ways. They provide food for aquatic life and also provide an essential role in the planet’s carbon and biochemical cycles. If the amount of plankton in the oceans decline it can have a profound effect on our planet and the bad news is that plankton do seem to be on the decline, and global warming is thought to be the culprit.

Plankton are found in the upper layers of seas and phytoplankton are breathing and photosynthesise. By taking in carbon dioxide they convert it to carbon, which sinks to the bottom of the sea and give out oxygen, which is released into the sea and into the air. Scientists estimate that half of our oxygen is produced by the photosynthesis of plankton.

Plankton are eaten by fish larvae and larger plankton are the food of whales, so in addition to perfuming their carbon sequestration, plankton are important in the food chain. With less plankton the oceans will sequestrate less carbon and there will be less food for fish larvae which will produce fewer fish.

Writing in Nature Daniel Boyce, Marlon Lewis and Boris Worm, all at Dalhousie University in Nova Scotia, have been analysing satellite data derived from 1979 and report that plankton have declined in eight out of ten oceans with the approximate decline being in the order of 1% during that period.

They link this decline in plankton to global warming, and although that link seems to be based upon a degree of speculation, inevitably in the absence of long term data, it does not appear to be an unreasonable speculation.

The process which they think is happening is the stratification of heat in the sea. Solar thermal system designers understand stratification and use it in solar systems. In a hot water cylinder or store water will be hotter at the top than at the bottom and will stratify in different layers at different temperatures. If you had a solar heating system and a very large array of panels and a large cylinder you could draw heat from the top, where it is hottest for washing and heat from the middle where it is cooler for supporting under floor heating.

Plankton seem to thrive in cooler waters. There are less plankton in the sea when oscillations within the seas like El Nino are in their warmer cycles and more plankton when these oscillations are in their cooler cycles.

The scientists believe that as the ocean water becomes more stratified that limits the nutrients available to plankton. Nutrients are not declining everywhere; fertiliser run off increases nutrients and therefore plankton numbers increase, in coastal areas of the sea. It also seems that the Indian Ocean is not affected with plankton decline.

It is easy to blame everything bad that happens on climate change, which runs the risk of being the bogeyman of humanity. However in the case of the decline in plankton numbers there may be some substance in laying the reason for the decline at humanity’s door. By warming the planet we risk decreasing fish supplies, decreasing oxygen and increasing carbon dioxide for further warming.

4 Responses

  1. Robert,

    Great post. I was reading a BBC piece that talks about this very subject. In case you have not seen it: http://www.bbc.co.uk/news/science-environment-10781621.

  2. There are many such things happening the world over from the beginnings of life to seas shells, the Benthic layers of the oceans are going through sudden changes, pollution is more than likely the culprit, plankton will not escape either.

    The latest oil dissaster will have long reaching conscequences, and there is also huge cover up of news events,

  3. Hi, liked your article, but have to disagree with the fact that plankton seem to thrive in cooler waters. As a fishfarmer, I look at plankton samples daily, all year round. In my experience, plankton flourish in warmer waters. Spring through to fall is when our farms see the most plankton in the water. Pulling a tow sample in the winter nets you very little to look at. In British Columbia we get alot of run off in the winter and still plankton is hardly seen. I wrote an article called Harmful Plankton Blooms I’d like you to read, lets keep this discussion going. http://fishfarming.wordpress.com/2010/11/25/harmful-plankton-blooms/

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