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So! There are 177+ microbes, plants, animals in freshwaters of Britain that were plonked there by people. They didn’t ask to be put there, but were either nabbed by a Victorian traveller, released by a disorganized/lazy pet keeper, accidentally picked up on someone’s boots or a ship’s ballast water, or hitched a ride on another exotic species. On arrival they may have difficulty settling in and getting on with the locals. In fact, they may get on terribly with the locals, and either bully them, push them around, make them sick, ruin their homes or even KILL AND EAT THEM!!!!!!!!!!!!!!!!!!!! Well, maybe. It certainly happens for certain species, such as American Signal Crayfish doing all of the above, causing great trouble for the native White Clawed Crayfish. Another new arrival is the Chinese Mitten Crab, hitched a lift on trading ships. It is happy living in rivers when grown up, and it is spreading round rivers in Europe, including the Thames. Their impacts are still uncertain, other than their keen burrowing activities in river banks. If you like river banks, this is a problem!

So that’s two of the 177. What about the rest? Is it just the one, similar species they affect? Do they have an effect on the whole ecosystem? Do they form a new ecosystem? If we keep adding foreign species, can we improve the biodiversity and ecosystem functioning? Should the “old woman” of Britain’s freshwater ecosystems keep “swallowing” things to “catch the fly”?

Work I do involves first seeing what lives in rivers where exotic species such as American Crayfish have invaded. I then make experiments where ecosystems are created then challenged with these invasive species. I measure what different creatures live in these ecosystems (biodiversity) after the aliens have been added, as well as how much oxygen is used up, indicating the productivity of the whole ecosystem. I also look at the structure of the food webs – what eats what, the shape of the pyramid, etc.  This is done in isolation from other freshwater ecosystems to make sure we don’t release further creatures into uninvaded sites. To decipher finer scale influences, I do laboratory experiments on things such as leaf litter decomposition in response to different alien species – this is an important aspect of aquatic ecosystem processes.

Always lots to do. Of course it might start in front of a computer, but could then be in a workshop making experimental streams, or on the university’s farm digging in water tanks for other experiments. There are days I go out with a net and catch aquatic invertebrates, or trap crayfish. Or check on the crabs and crayfish being kept in the lab, experimenting to see how quickly they break down leaf litter. During the summer I could be running the water tanks, each one replicating a small lake ecosystem, some with crayfish in, some without. And there are days when I either sit and consult the scientific literature over a coffee or attend talks by my colleagues in Geography and Biology and elsewhere in the university about the interesting work they do. And I may bump into my supervisors and glean valuable advise on how to study invasive species, food webs and ecosystem processes.