Nadescha Zwerschke is a benthic ecologist with the British Antarctic Survey. She was recently shortlisted for Functional Ecology’s Haldane Prize for Early Career Researchers.

In this Insight, she talks about her shortlisted paper, Competition between co‐occurring invasive and native consumers switches between habitats

Oyster vs Oyster

In Europe, the native oyster is declining due to overfishing and habitat destruction, effectively extirpating it from intertidal areas and limiting small populations to subtidal habitats. To compensate for these losses, the Japanese oyster has been introduced into Europe as an aquaculture species. Unfortunately, the Japanese oyster has spread rapidly across mainland Europe, taking over entire coastlines and further spreading into colder regions, such as the UK, Ireland and Scandinavia. Since it was assumed that they reside in different habitats (native oyster – subtidal, Japanese oyster – intertidal), it was never thought that both species could, or would, compete with one another. Only the recent discovery of Japanese oysters in subtidal habitats – and historical anecdotes of the native oyster in the intertidal zone – have raised the question whether both species are indeed competing for the same resources, thus impeding the recovery of the native oyster.

Surprisingly angle on competition vs cooperation

When I started working on the two species, I was generally surprised that nobody had looked at potential interactions between them before as this was one of the major concerns of the oyster fishery. More specifically, we thoroughly expected the Japanese oyster to have a negative impact on the native oyster and wanted to gage the severity of this effect across a range of abiotic stress (represented by intertidal and subtidal habitat) and at differing substratum orientations (vertical and horizontal). We were intrigued to find that high abiotic stress actually negatively affects, what we assumed was the invaders more adept ability to compete. We were even more surprised that competitive interactions only occurred at the horizontal orientation, whilst at the vertical orientation the two species seemingly helped one another out.

The importance of context

Our paper reiterates the need to include environmental context into any meaningful ecological study and further highlights the importance of testing theories using a variety of variables in field experiments. Ecosystems are incredibly complex; governed by physical forces and interactions between species and we are still far from understanding the mechanisms underpinning them. In our paper we have shown that something as simple as the orientation of the substratum a species is attached to, can completely alter how it interacts with other species. As far as I know this has not been considered previously in marine systems and would never have been included in any model outputs simulating species interactions. We might never be able to fully understand how ecosystems function, yet in our quest to do so we have to strive to think outside the box and use a variety of approaches.

About The Author

What are you currently working on?

I am primarily interested in how species interactions affect community structure and ecosystem functions. I have now moved on from temperate shores and am currently working for the British Antarctic Survey, investigating how the physical disturbance of icebergs affects species interactions, within a polar nearshore benthic food-web. This is important, because the West Antarctic Peninsula is one of the most rapidly warming places on Earth, resulting in glacial retreat; generating an increasing number of icebergs, which scour shallow subtidal benthic systems and killing everything in their wake. We wish to determine how resilient this slow growing and otherwise pristine marine system is to this increased disturbance.

What is the best thing about being an ecologist?

I love being an ecologist, because the job is versatile, highly applied and never gets boring. One day you might be standing knee-deep in mud being hailed on, then the next day might be spent on a rocky shore in glorious sunshine. Presently I’m fortunate to get to experience diving in the pristine waters of Antarctica. But just as much as I enjoy the practical aspects of setting up experiments and collecting data, I love the analytical side of labwork and spending hours trying to get my statistical analysis to work in R (admittedly that is mostly Type-II fun)! The most rewarding aspect of my job, is following months of planning and fieldwork, everything comes together in the final write-up – which is generating brand-new insights into the way ecosystems work. These might not always be earth shattering, but will hopefully contribute to help human society better understand the incredible natural world we live in and redound to alleviating the threat that it is currently under.

You can read Nadescha’s shortlisted paper, along with the winning and other shortlisted papers here.