Tracking Change Beneath the Waves: A Baltic Sea Research Cruise

What is the main goal of this cruise, and what kinds of data are you collecting?
To study if there have been changes in southern Baltic Sea seabeds after cessation of bottom trawling in 2019. We repeated our surveys from 2019/20/23 in order to follow the changes in physical sediment properties, benthic macrofauna communities and ecosystem function (based on species trait analysis and estimates of sediment carbon storage).

To collect this data, what instruments are you using? 
We used a lot of different instruments, including: Van Veen grab and Gemini corer for sediment samples and a CTD for background environmental data.

What’s a typical day like onboard for the research team? 
They are long, we start at 08:00 and work until at least 20:00.

Sampling stations were 45-60 min from Simrishamn harbour. When we reached the sampling station the team had their individual tasks, some started to sieve out the macrofauna and preserved them in ethanol, meanwhile others did gemini casts to obtain sediment cores. We sliced the cores – some of these were immediately frozen, others were sieved to extract the macrofauna. During all this, it was vital to keep track of our exact positions, which core was taken at which position, and which container or bag contained which sample. 

We usually managed two sampling stations per day and continued processing the samples on the way back to the harbour. After a good night’s sleep, we were back on deck the next morning!

Did you encounter any surprising findings during the cruise?
The findings are yet to come; we have months of lab work before getting there. But I am excited!

Why is this research important, and how might it impact people and/or the planet?
There is a lack of knowledge about the impacts of bottom trawling disturbance on Baltic Sea seafloor ecology and ecosystem function. This information is essential in the effective planning of marine protected areas (MPAs), ecosystem-based fisheries management and the assessment of seafloor integrity and environmental status of benthic ecosystems that is necessary in the Marine Strategy Framework Directive (Descriptor 6: Seafloor Integrity). One particular ecosystem function that has received a lot of recent attention internationally is the role of seafloor sediments as carbon sinks; the debate about whether bottom trawling can decrease carbon storage has been much discussed during the last few years. Good quality data is needed to refine current estimates of carbon storage and remobilisation that are currently based mainly on calculations and modelling.

What’s one thing you wish more people understood about marine research?
That it’s not simple to collect samples and data and get quick answers and of course that it is great fun!

What’s the most challenging part of doing science at sea?
There are a lot of things that need to work for voyages going ahead as planned. For example, this cruise we had some challenges with electricity problems onboard, which resulted in a delayed start.  Long days with a lot of physical work onboard a rocking ship is also a challenge!

What has receiving the SWERVE funding and ship time meant for you? 
We would not have been able to collect this data at all without support from Swerve! This extra cruise is extremely valuable since it provides us with one more time point in our time series tracking seabed changes after the cessation of trawling. It is a unique opportunity to follow the impacts of such a fisheries closure in real time at this spatial scale – very few other studies of this type have been done in any ocean.

On top of this, it also gave a master’s student a fantastic opportunity to go to sea and collect samples that he will work with for his project!