Çetin Yağcılar, a lecturer and aquaculture engineer in the Department of Hydrobiology at Namık Kemal University, said brown and white jellyfish have found suitable conditions in the Marmara Sea, with their populations increasing rapidly over the past three years.
Populations of brown jellyfish, locally known as “compass jellyfish,” and white jellyfish, commonly called “moon jellyfish,” have increased in the Marmara Sea in recent years. The jellyfish are particularly common along the coasts of Tekirdağ, Istanbul, Çanakkale and Balıkesir, where they have gathered in some areas and caused difficulties for vacationers.
Yağcılar said the jellyfish arrived in the Marmara Sea about 10 to 15 years ago through ballast water taken on by ships to maintain their stability.
He said brown and white jellyfish found favorable conditions in the Marmara Sea and that their populations have increased rapidly over the past three years.
Yağcılar said rising sea temperatures are among the main factors driving the growth in jellyfish populations.
“Particularly in the Marmara Sea, the main factors behind the increase in brown and white jellyfish populations include rising sea temperatures due to climate change, the introduction of nutrients such as nitrogen and phosphate into the marine environment through domestic and industrial waste and a decline in predatory fish species that feed on jellyfish as a result of overfishing,” he said.
“This can disrupt the natural balance of the ecosystem, leading jellyfish to multiply and become dominant. Overfishing of certain predatory fish, particularly species such as mackerel, reduces their natural predators and facilitates the uncontrolled growth of these species,” he added.
Yağcılar said jellyfish encounters could cause panic among people in tourist areas of the Marmara region.
“From a human health perspective, contact with jellyfish can cause burning, redness and itching on the skin, as well as allergic reactions in some people. As a first response, the affected area should be rinsed with seawater, followed by a visit to the nearest health care facility,” he said.
Yağcılar emphasized the importance of taking measures to control the growing jellyfish population.
“Unfortunately, rising sea temperatures are not something within our control. Due to climate change, we are facing a global climate problem both regionally and worldwide,” he said.
He called for limiting the overfishing of predatory species such as mackerel and other fish. “If we avoid catching these fish in excessive numbers, especially before they reach the size at which they are typically targeted by fisheries, we can allow them to reach their reproductive period at least once,” he said.
“If we ensure this, these species will be able to reproduce more freely. They can consume organisms such as jellyfish, which may be considered harmful when they become overly abundant and help prevent these organisms from multiplying excessively in the environment,” he added.
Yağcılar also warned about the impact of domestic and industrial waste on the Marmara Sea. “When we discharge excessive amounts of domestic or industrial waste into this area, unfortunately, we have no way of removing it from the region,” he said.
He called for stronger wastewater treatment measures, particularly at industrial facilities.
“Factories should face greater pressure to properly treat domestic and industrial waste. Treatment facilities need to be strengthened to prevent high concentrations of nutrients such as nitrogen and phosphorus from entering the marine environment,” he said.
