Seabed in Gulf of Trieste like a book of environmental, tectonic change

The department has been doing extensive research of marine sediments in the Gulf of Trieste for the last few years, including by using geophysical methods to indirectly determine the geological structure of the seabed.

The Gulf of Trieste, which was land only little more than 10,000 years ago, harbours "crucial information about local and global environmental changes caused by astronomical and tectonic factors, and of additional pressure from anthropogenic influences".

Another reason the gulf is interesting is because the sea is not very deep and because weather conditions are relatively calm, allowing core sampling, the process of obtaining sediment cores from the seabed. So far little such research has been conducted.

Initially, the geology department used geophysical methods, which indirectly offer an insight into the geological structure of the seabed, but recently they realised this was not enough and that they need samples of the seabed to determine exactly what has been going on.

Cores offer a very good insight into sediment changes caused by climate change and humans

To obtain seabed samples, they opted for core sampling using a piston sampler. According to professor at the faculty, Andrej Šmuc, with this method the sampler - a plastic pipe - is pushed into the seabed before being pulled out of the sea filled with intact sediments.

This is rather hard work, as hand-lifted weights are used to push the sampler into the seabed. But "then we are rewarded with cores, which help us reconstruct events in this area in the last 10,000 to 15,000 years".

By reconstructing the dynamics of sedimentation, researchers will obtain information about the changes in rainfall patterns during the Holocene climate change and about the time frame and severity of tectonic events in the region. The results will also reveal where, when and why humans have become a geological factor.

"Our project focuses on the research of changes in the last 10,000 years, since this area has been covered by sea, and the cores will give us a very good insight into how the sediments have been changing because of climate change and the human influence," says Ana Novak, who works at the Geological Survey Of Slovenia and the geology department of the Faculty of Natural Sciences and Engineering in Ljubljana.

Impact of humans noticeable in the last metres of sediments

According to Novak, the impact of humans is expected to be seen in the last few meters of sediment. "Typically, the sediment in the Gulf of Trieste show very nicely when mercury smelting in Idrija was active. Particles containing mercury came to the gulf with the Soča river and were deposited in the seabed."

"We also expect other signs of human impact. All over the world we can see traces of radioactive particles that were created in nuclear explosions. We might be able to see that too. From more recent human activity, we expect to find microplastic in our sediments as well," said Novak.

First continuous overview over Holocene sediments

A lot of research has been conducted in the upper part of the sediment, while the project, dubbed Record of Environmental Change and Human Impact in Holocene Sediments, Gulf of Trieste, is to provide a continuous overview over the entire period of the last 10,000 years.

"The sea has not always been in the Gulf of Trieste; the last time it rose here was about 10,000 years ago," says Novak, adding that during the last ice age the sea level was about 120 metres lower and land started somewhere between Italy's Pescara and Croatia's Šibenik.

The northern Adriatic area was a plain of the river Po and its tributaries. The traces of their currents can still be seen in the seabed with the right equipment.

About the project

The project Record of Environmental Change and Human Impact in Holocene Sediments, Gulf of Trieste is financed by the Slovenian Research Agency and is running between 1 July 2019 and 30 June 2022.

The project group includes a multidisciplinary international team led by the Faculty of Natural Sciences and Engineering, and also the Jožef Štefan Institute, the company Sirio, the Marine Biology Station Piran of the National Biology Institute as well as the Italian OGS institute, the Croatian Geology Institute and the French University Savoie Mont Blanc.