When friends ask me what I do, I normally say I work at the Sir Alister Hardy Foundation for Ocean Science, as a plankton analyst. People always look at me puzzled, then I explain, and soon they are fascinated.

When at the seaside, you see the beach and the ocean, but you fail to realise the plankton that is out there and the important role it plays. Plankton comes from the Greek ‘planktos’ which means ‘to drift’, plankton are the tiny organisms that drift on the currents in the ocean. There is phytoplankton, which is plant plankton and zooplankton, which is animal plankton. They are tiny organisms, not seen by the naked eye.

The Victorians already knew about their beauty and made diatom slides, which took a tremendous amount of effort to make, shifting individual plankton cells into an arrangement. www.victorianmicroscopeslides.com/slideexb.htm

People do not realise that plankton produce every other breathe we take. We worry about the rainforest, as it is so visual, but we forget about the other major contributor to our oxygen production, the tiny plankton that live in the sea.

There is more life in a drop of seawater than anyone realises.

In the early 1930s Alister Hardy devised a little torpedo shaped machine, with an opening to let seawater through, to record plankton. It is called a Continous Plankton Recorder, or CPR for short.

These CPRs are towed by ‘Ships of Opportunity’, or in other words, anyone willing to tow our recorder. There is a tremendous goodwill in the shipping industry and interest in the work we do, which is very fortunate. SAHFOS sample the North Sea, North Atlantic and North Pacific on a regular basis, with occasional tows in the Arctic, Antarctic and other areas of interest. We also have sister surveys in Australia, South Africa, Japan, Cyprus and Brazil. This means we have one of the most spatially extensive marine surveys in the world.

When the CPRs arrive at our lab in Plymouth, to be processed, they are divided into 10 nautical mile sections. The colour is assessed, the greenness is a good indication for the amount of phytoplankton (plant plankton). The analysts identify a proportion of the phytoplankton and zooplankton in each section. It is a great job being a plankton analyst, the plankton can be so pretty.

My personal favourites are silicoflagellates, star shaped phytoplankton and dictyocysta, which looks like a crocheted mushroom.

Sir Alister Hardy devised this machine to look at the movements of fish, as plankton is at the base of the foodchain and as such gets eaten by fish. Where there is plankton, there is fish and birds. This same method has been used since 1958, recording one of the longest marine time-series as well as the spatial extension. It allows us to look at changes through time, and shows us annual cycles as well as human impacts on the environment. Alister Hardy was knighted for his work in 1957.

We have seen some major changes happening in our oceans, for example what we call a regime shift. Looking back through time, plankton always used to have a distinct spring bloom, and then another distinct autumn bloom. In the mid-1980s a shift appeared, and we now have a continuous plankton bloom season from spring until autumn.

Another change we have seen is a northwards movement of cold water plankton by as much as 1000 km. This is a major change, as it shows how our oceans have warmed. It takes about 4000 times more energy to heat a litre of water compared to a litre of air. About 70% of our world is oceans, so to increase the surface temperature of the oceans by 0.5°C, takes a tremendous amount of energy, yet this is what we have seen and the plankton react to it. Cold water species are being replaced by warm water species, and diet mismatches can occur for fish. This is why we now catch more cod near the colder waters of Greenland than around the UK island coast.

In the Arctic, the plankton has shown us how the summer ice is retreating. We found a phytoplankton called Neodenticula seminae in the North Atlantic, which has been a North Pacific plankton species for over 800,000 years. The summer ice retreating in the Arctic meant it found a passage to the North Atlantic and it showed up in our samples. We are continuing to investigate the changes that are happening in our oceans and ensuring that policy makers are aware of what is happening in our oceans. Plankton is now a new indicator for the Marine Framework Directive, which means that plankton will tell us how well our marine environment is doing.

We also see the impacts of human interaction with the environment, for example the effects of our continuous input of carbon dioxide in the atmosphere. This is not only being taken up in the air, but part of the carbon dioxide dissolves in the oceans or gets taken up by the plankton and when they die, will be transported to the bottom of the oceans. As a result, our oceans are getting less alkaline. As many of the plankton species have a carbonate shell, the lower pH means they may be unable to form shells. Corals can also be affected and have been known to start bleaching in less alkaline conditions. We have a dataset of over 70 years of in situ data, which is real environment data, not laboratory experiments. Our research has shown that for now, plankton is adapting to the changes, but we don’t know for how much longer.

We have seen invasive species entering our coastal waters through ballast water, with increasing shipping traffic, and our oceans warming, we may see more invasive species thriving in our coastal waters and taking over communities.

These are interesting times, we should all care about our plankton.

After all, where would many of us be without fish? I think we would all miss the dolphins and we cannot live without oxygen!

Think about the plankton, next time you visit the seaside.

Astrid Fischer, Golberdon.