Some of the smallest living organisms feed the largest animals. Plankton are the food supply of many marine creatures including the largest fish, the whale shark and the largest mammal, the blue whale.
Plankton are organisms that float drift around oceans, seas and other bodies of water; plankton derive their name from the Greek “planktos” which means “drifter”. These high water drifters are both plants and animals (jellyfish are plankton). The plankton plants use chlorophyll to convert energy from light into carbohydrates, soaking up carbon dioxide dissolved in water as part of the process. The animal plankton eat other animals.
Plankton are important both in terms of their impact on ecosystems and in terms of the carbon dioxide that they soak up and convert. Scientists at the IMF-GEOMAR Institute in Kiel Germany have been trying to understand what will happen in the ocean if the climate warms up.
Oceans soak up more human made carbon dioxide than any other thing and plankton, because they use dissolved carbon dioxide, enable the ocean to continue this carbon sink effect. It is thought that oceans soak up half of the human made carbon dioxide. Ocean plankton have been ignored in most climate change models until now, so the work at Kiel is important to our overall understanding of climate change processes.
There are positives and negatives from the study. The positive is that more carbon dioxide means that the plankton will prosper and in doing so will soak up more and more of the carbon emissions we pump into the atmosphere.
The negative is that increased uptake of carbon dioxide will probably cause the oceans to become more acidic. This will reduce the amount of food in the oceans that ocean inhabitants eat.
Experiments showed that higher carbon dioxide levels gave a large boost to numbers of plankton. It showed itself in a big algae bloom which then sunk to the bottom of the sea, making way for the upper part of the sea to absorb more carbon dioxide. Good.
When the deceased plankton arrived at the bottom of the ocean (or in the case of the experiment the bottom of a 27 metre tank) the decomposition of the plankton soaked up oxygen and created more acidic water. Bad.
When plankton grow they emit dimethyl sulphide, which helps in the formation of clouds. Some think that increased cloud formation would protect the planet from radiation which then it is thought would reduce the impact of climate change. I am not so sure that messing about with the weather is right.
There will be consequences that we are not wise enough o compute or understand. While all this science is debating, plankton are prospering. Large masses of jellyfish are being reported in many sea side resorts.
There have always been jelly fish, but some resorts in Australia are experiencing problems with poisonous box jellyfish which for hundreds of years were unknown in those waters. Box jellyfish were once only found on the southern (windward) side of the Hawaiian island of Oahu; now they found on the on the northern and western coasts.
This may be evidence of a shift in the ocean currents but what seems to be without doubt is that there are more jellyfish than before and this is probably due to there being warmer seas and a higher availability of carbon dioxide.
Back home in Britain the North Sea has higher levels of jellyfish. This is affecting birds that eat fish. Guillemot numbers in Shetland have been devastated, Great Skuas on Foula have not bred well, and this has been explained by there being less sand eels (a small silver fish that sea birds eat) in the North Sea. Historically this part of the North Sea has been a little to cold to support jellyfish, and the effect of climate change on the northern part of the planet is greater than on the equatorial region.
Now although plankton are prospering for now there is, so as to speak, a sting in the tail. Plankton that have skeletons cannot manufacture the calcium carbonate that they need for the skeletons in acidic waters, and acidic waters are a by product of too many plankton. In the Southern Antarctic Ocean lives an animal plankton called pteropod – which are snail like. Scientists think that its shells will not be able to withstand the acidic sea that is likely to exist by the end of this century; once you take out an important element in an ecosystem you never quite know how it will impact on the rest of the system and the impact is usually less than benign.
There is yet another sting that plankton may well deliver; I have explained how it uses carbon dioxide, but plankton also respire, emitting carbon dioxide. Until now they absorb far more carbon dioxide than they emit.
A team of scientists led by Angel López-Urrutia of the Spanish Institute of Oceanography in Gijón have some evidence that the balance between production and respiration of plankton is affected by temperature. Apparently while the rates of photosynthesis and respiration in plankton both rise with temperature, the rate of respiration goes up faster, so that the plankton will emit more carbon than they soak up.
As plankton are thought to soak up half of the human made carbon dioxide the oceans instead of becoming a carbon store may end up as a carbon emitter.