Can microbes save our salt marshes?

What impact does climate change have on salt marshes? What role do microbes, plants and animals such as shrimps play in this? If microbial ecologist Joana Falcao Salles knew, she would also know which recovery strategies to apply to protect the salt marshes. Her research project ‘Salt marshes: crucial for coastal protection and migratory birds’ is one of four research projects for which the University of Groningen’s Ubbo Emmius Fund hopes to receive support in the coming few years from its alumni and other friends of the university. For more information about the projects, please go to www.rugsteunt.nl , or watch the video at the end of this article .

‘A single tablespoon of soil contains more microbes than there are people on earth’, explains Professor Joana Falcao Salles. ‘Microorganisms are hugely important for biodiversity on earth. They produce nutrients for plants and animals, but they also determine how quickly flora and fauna are able to adapt to changing circumstances, for example in salt marsh areas.’ Salt marshes are a vitally important habitat for birds and plants, while they also play an essential role in coastal protection, for example by reducing the effects of soil subsidence. As each high tide brings an extra layer of silt with it, the salt marshes grow with the rising sea level. Plants such as sea couch and marsh samphire slow the sea water, allowing the silt to sink and preventing it from being washed away.

Sea level

This has long been how it works, and still is, but what will happen to the salt marshes when this balance is disturbed? For example, if conditions become wetter, or drier? If climate change continues and the sea level becomes too high? Plants and animals will need to adapt, and Falcao Salles explains the crucial role that microbes play in this, and that this is why she wants to explore the interaction between marsh samphire, the shrimp-like beach flea and microbes in particular, both in drought conditions and higher sea levels. What impacts do they have on one another? How do marsh samphire, beach fleas and microbes respond to the changing circumstances, in unison and alone? What is the impact of an increase in sea level on the soil structure? After all, if the plants die, the salt marsh will wash away, unless – of course – they manage to adapt. The role of soil bacteria in adapting to the different situations will be investigated in tests in the laboratory. This will involve keeping beach fleas and marsh samphire either underwater or completely dry for several weeks, in 48 pots with a diameter of about 20 centimetres. One hypothesis is that microbe activity will change in the different situations. Falcao Salles is interested in what this means for its interaction with the marsh samphire and the beach fleas. The experiment will take two months to complete, and the data analysis another four to six months.

Catastrophic

Falcao Salles: ‘Let us assume that certain essential functions of the microbes change if they are kept under water. They may then be unable to produce sufficient nutrients for the plants, with the effect that these die and the salt marshes are permanently lost. This would be catastrophic, as birds would no longer have a place to rest and breed. The salt marshes would also no longer function as coastal protection.’ As far as the beach fleas are concerned; they dig tunnels in the soil and transport oxygen deep beneath the surface. A continued high sea level would result in less oxygen in the soil, which could kill the beach fleas and plants. Falcao Salles: ‘We hope that we can find microbes that will help the plants and sea fleas to better withstand longer periods of drought or higher sea levels. If we do, we can use this knowledge to develop recovery strategies.’

This article has been taken from our alumni magazine Broerstraat 5. Text: Karin de Mik.