Marine Geologist Raina Hristova: Bulgarian Scientists Study Climate Change Impact on Ocean Floor

During the 32nd Bulgarian Antarctic Expedition, the Bulgarian scientists will study the impact of climate change on the ocean floor, marine geologist Assoc. Prof. Raina Hristova from the Institute of Oceanology at the Bulgarian Academy of Sciences said in an interview for BTA. Hristova, who is part of the expedition,  explained that this is an integrated project with the participation of experts in three fields that was launched during the 31st Bulgarian Antarctic Expedition. 

Hristova is working on a project for integrated research of sediment, biota and waters in the marine ecosystem of the Bulgarian Antarctic base’s littoral zone. The project combines biological, geological, and oceanographic research over a two-year period starting from 2023.

She explained that on their previous visits, the scientists worked on land, so the territorial waters have not been studied systematically. “Our project is the first of its kind, and my task is to study the seafloor sediments,” she noted. These sediments are very complex systems and a key component of the ocean ecosystem, but the integrated approach will allow for more global conclusions on the state of the environment. In her words, the practice is for the scientists working in different fields to go out in a boat and collect samples simultaneously from areas outlined in advance. 

The seafloor sediments Hristova works with can provide data on the speed of contemporary sedimentation, which she believes is affected by climate change. In her words, everything there happens before their eyes: huge blocks of ice fall from a glacier and settle on the seafloor. The quick melting of a glacier causes rivers that too have an impact and add to the seafloor sediments.

The sediments Hristova studies can also be explained as contemporary marine silts that formed in the Holocene – the epoch when humans appeared. “We live in that epoch, its range is around 11,000 years, so being studied are the most contemporary geological formations that are yet to become rock samples,” she explained. These contemporary silts can also be reviewed as a trap that will allow the scientists to determine whether there is anthropogenic pollution in this part of the planet. 

The samples taken are subjected to complex analyses at the University of Sofia and the Institute of Oceanology. The first samples have been tested for heavy metals. If the results are positive, the scientists will know whether humans are responsible for their presence. The samples are tested for arsenic, copper, chrome, mercury, lead as well as for strategically important metals, such as selenium and molybdenum. The third focus in the studies are the so-called rock-forming elements. 

“When we came back from our first trip [to Livingston Island], during the previous expedition, these analyses were started but progress is slow,” Hristova noted. That is because the samples need to dry naturally, and not in laboratory conditions, which takes a lot of time. At the end of the integrated project, when the results from all samples are taken into view, a proto-ecological model will be made of the sediments in the bay.

During the 31st Bulgarian Antarctic Expedition, the working areas of the Bulgarian scientists were mostly along the coast at a working depth of 5-6 to 29-30 metres. The samples were taken by hand with the help of a device that was lowered to the seafloor. For the current expedition, the scientists hope to work at greater depths; to that end, a more special device will be used – a gravity tube – with the logistics assistance of the crew of the Bulgarian naval research ship Sv. Sv. Kiril I Metodii.

Asked if something managed to surprise her in the previous expedition, Hristova said through a smile that she has sufficient experience as a marine geologist but in the Black Sea, not on Livingston Island in Antarctica. “Everything there is different, extreme, unfamiliar; you feel as though you are an astronaut, because you row and touch materials that no one has ever touched. That is both intoxicating and responsible and makes you want to study more and more,” she told BTA.

The participants in the Bulgarian expedition strive to leave as little an imprint of their activity and presence in Antarctica as possible. According to her, a human imprint on the seafloor there could be found. Humans have been everywhere and, unfortunately, there are many fields in live that produce unreasonable amounts of waste, she argued.

On this expedition, the scientists plan to step on Smith Island, which is terra incognita. One of the tasks will be to map the sea floor, Hristova told BTA.