site.btaMarine Biologist: Aquatic Biodiversity Is in Dire Need of More Attention and Action to Protect It 

Aquatic biodiversity is in desperate need of more attention and action for its conservation, says marine biologist Tihomir Stefanov, an associate professor at the National Museum of Natural History in Sofia. He is about to join the 32nd Bulgarian expedition to Antarctica, where he will continue his work on studying the impact of melting glaciers on the species. Stefanov's work focuses on the impact of this process on fish feeding, reproduction and movement.

He talked to BTA in a section of the National Museum of Natural History dedicated to Antarctic biodiversity.

“Clearly, the glacial melt is accelerating. The site we have chosen for our studies is a closed bay, at the bottom of which there is a large glacier,” Stefanov explained. It's like a small closed laboratory and from what we see there we can predict the processes that will be triggered by an accelerated global glacier melt, he added.

The flow of fresh glacial water is dramatically changing the habitat of marine fish. It changes not only the salinity of water but also its transparency. This leads to changes in the amount of photosynthesizing algae, hence oxygen. Any change of this kind in conditions also affects fish life, the scientist explained.

The upcoming voyage to Antarctica will be Stefanov's third.

He has also been on an expedition to Greenland, where he joined a team of scientists studying the impact of glacial melt on fish there.

Looking deeper into Antarctic water

“I've always wanted to study the fish in the Southern Ocean. It's a very interesting group of endemic fish. These are species that are only found around Antarctica. And it's a real challenge to do research on very highly adapted organisms such as the fish there,” said Stefanov.

He is attracted by the mystery of Antarctica's fish and their high adaptability to their environment. Stefanov spoke with excitement about the Antarctic Convergence, the marine belt around Antarctica, where cold Antarctic waters meet the warmer waters of the sub-Antarctic. He says it is the boundary that isolates the southernmost part of the Southern Ocean and the fish that inhabit it develop additional adaptations that make them to stand out in the world's ocean ichthyofauna.

“The fish in the Southern Ocean are mainly of the so-called nototheniid fishes. They have additional adaptations for life in cold waters. They develop glycoprotein molecules in their bodies that prevent their body fluids from freezing at water temperatures below zero degrees, as is often found in Antarctica,” the scientist explained.

Stefanov showed the ice fish to Bulgarians for the first time in 2021. The specimen was on display at the National Museum of Natural History and can still be seen today.

Icefish are another interesting group that have developed unique adaptation mechanisms for life in Antarctic conditions. Their blood is white as it contains no haemoglobin. Because of the low water temperatures, the solubility of oxygen is very high and it reaches the body's tissues and cells by simple diffusion, without the help of a mediator molecule, the Stefanov said.

In scientific work, optimal conditions for conducting research are very important. That is why Stefanov is pleased that the Bulgarian research base on Livingston Island has a functioning laboratory and a prepared logistics team to help the scientists. A brand new laboratory is also under construction.

Field work involves catching fish, setting nets, going to different parts of the Southern Bay of the island. Samples are also being taken for genetic and isotopic studies, said Stefanov.

Antarctica plans

Stefanov and another marine biologist, Lyubomir Kenderov from the Faculty of Biology of Sofia University, are planning this year to dive for the underwater research. “As we dive, we expect to get a very good idea of the diversity of species,” he said.

It will be particularly interesting for the nutritional analysis for fish, Stefanov added. He believes that once the fish species in the area are known, the bottom invertebrates that the fish potentially feed on can be studied in detail.

The Bulgarian scientists have found that Antarctic fish inhabit different depths in the Southern Bay. An interesting detail they have found is that there is a pattern of larger fish inhabiting the shallower depths, with smaller species appearing as depth increases. They have identified seven different species of fish in the Southern Bay.

“We have done a lot of research on the food spectrum of two fish species, Notothenia coriiceps and Notothenia rossii,” Stefanov said. And he noted that he has gained a very good insight into what exactly these fish feed on.

“What we need to research more this season is the differences in the feeding strategies of different species in areas of active melt and freshwater inflow with those in the open sea,” said Stefanov.

Climate change and human activity 

Looking at Antarctica, one can predict how far climate change might go, Stefanov says. “If the process of glacial meltwater deepens considerably, the level of the world's oceans will rise, but this won’t be the only effect to be felt,” he warned.

The additional "inflow" of cold fresh water will lead to a change in ocean currents, and this will bring about a dramatic climate change over a short period of time in certain areas, the biologist said.

Stefanov is also preoccupied with the human impact on the Earth's aquatic life. “I strongly hope that people will become increasingly aware of the impact they are having and of the need to take measures to reduce it,” he said.

He uses as an example the fate of sturgeon fish in the Danube and the Black Sea. “The last remaining sturgeon breeding habitats are shared between Bulgaria and Romania in the lower reaches of the Danube. These are large fish that take long to mature sexually. They don’t breed every year. Overfishing for the valuable sturgeon roe could easily wipe out a population of this species. This, together with the construction of the Iron Gates dam, which blocks the migration route of sturgeon, has led to a dramatic reduction in the population.

“We see the last specimens that breed, which are on the verge of extinction and therefore urgent measures are needed for their conservation,” Stefanov further said.

Stefanov hopes to pass on to the younger generations his enthusiasm to work for the protection of aquatic creates through his works with PhD students and assistants at the museum.

Every year he also participates in research on fish in Bulgaria. One of the projects in which he is currently involved in for breeding and resettlement of Balkan trout.

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During the 32nd Bulgarian expedition to Antarctica, which started on November 8, 2023, the Bulgarian News Agency (BTA) is publishing interviews with Antarctic researchers. The Bulgaria-Antarctica BTA's Log again provides coverage of the voyage of the Sv. Sv. Kiril i Metodii to Antarctica and back and its stay there, as it did during the 31st expedition between December 27, 2022 and May 2, 2023. Back then, only BTA had a correspondent, Daily News Editor Konstantin Karagyozov, who covered the 127-day expedition with text, video and photos during the entire voyage (including across the Atlantic in both directions) and throughout the stay in Antarctica. In June 2023, BTA published in Bulgarian and in English an issue of its LIK magazine "To Antarctica and Back under the Bulgarian Flag" dedicated to the historic expedition.

Again, all of BTA's information on the Bulgarian scientific research in Antarctica and the support provided by the Bulgarian naval research vessel, as well as on the other activities at the Bulgarian Antarctic Base, will be available to all media outlets in Bulgarian and in English on BTA's website in the Bulgaria - Antarctica: BTA's Log section.

BTA has a National Press Club on board the ship and is planning to open a National Press Club at the Bulgarian Antarctic Base on Livingston Island.