Scientists investigating the effects of ocean acidification, microplastic and lanthanum on marine organisms observed color changes in shellfish, immune system issues in some species, a decrease in cell counts and a fall in reproduction. Amid this trend, fish stocks have been gradually decreasing in the Black Sea and the quantity of fish stock does not meet the desired needs, an expert said while drawing attention to the importance of sustainable fishing.

Istanbul University's Faculty of Science, Department of Biology and General Biology Department faculty members professor Murat Belivermis and professor Önder Kılıç examined the effects of ocean acidification, microplastic and lanthanum, which they refer to as the "triple stress factor," on marine life in Turkish waters and human consumption within the scope of the project titled "Biological Effects of Stress Factors in the Marine Environment" initiated 10 years ago.

Belivermiş and Kılıç observe the effects of these factors by exposing the creatures they collect from the sea to stress factors in the marine environment they have created in their laboratory at the university, including mollusks, shrimp and sea urchins as they play a key role in the ecosystem.

Stating that they are currently working on a sea urchin species they collected from the Gulf of Saros, Belivermiş said, "These species live in the Marmara Sea and the North Aegean. It will generate important data and will serve us with many solutions for the future," he said.

Acidification

Acidification in oceans has become a global issue and affects the seas around Türkiye. The reason behind ocean acidification is also increasing carbon dioxide emissions that cause the pH to drop in the sea, and organisms with a calcium carbonate skeleton are particularly affected by it. Living things spend their energy dealing with this acidification, reproduce less and their immune systems are affected, Belivermiş explained.

"Adopting a holistic approach, we have seen whitening in oyster species. In fact in previous studies, we saw reductions in the hemolymph cells of mussels due to acidification. This suggests a problem with the immune system, resulting in weakening or color changes in the shells."

Kılıç noted that if ocean acidification seriously affects the lives of these species, it will lead to a decrease in the population, and this decrease will also transpire as a decrease in the human food supply.

Microplastics

Microplastics are a pollutant that is not easy to dissolve and passes into living things through respiration or as food.

Citing an example of mussels, Belivermiş said: "The mussels filter the microplastic, and consume it as if they are eating microalgae. The microplastic enters the digestive system, resulting in less energy and adversely affects reproduction."

Lanthanum

The third stress factor on marine organisms is an element that has been little studied and its use is increasing: lanthanum. The use of this element in industries is increasing and thereby negatively affecting the eco-system, Belivermiş said.

Regarding the risk of stress factors of all three to the food chain, Kılıç said: "These may be transported through the food chain to humans. Lanthanum and microplastics are seen in the food chain, but acidification only has an effect on the organism, such as a chemical element or accumulation."

Black Sea

Karadeniz Technical University (KTU) Marine Sciences and Technology Institute Director Cemal Dinçer said that pelagic fish and fish stocks are decreasing gradually in the Black Sea. While bonito fishing was relatively good at the beginning of the season, it tapered off later, Dinçer said, drawing attention to the importance of sustainable fishing.

Expressing concerns that the fish stocks in the Black Sea are gradually decreasing, Dinçer said: "When we look at the legal statistics of aquaculture in the last two years, it is a fact that the fishing production has decreased, but the aquaculture production has increased in the last few years. We should increase farming if the natural stocks continue to decrease."

Since seasonal fish varieties have a short shelf life, unfortunately, fishermen freeze some stock for later. The abundance of stock can cause the prices to fall and also leads to overfishing during the season. "We should catch and consume these fish homogeneously throughout the expected season," Dinçer emphasized.