Nemopilema nomurai, commonly known as Nomura’s jellyfish, is a large marine organism. Its massive size and periodic population explosions are a subject of ongoing study and concern.
Identifying Characteristics
Nomura’s jellyfish is gigantic, with its bell often reaching up to 2 meters (6 feet 7 inches) in diameter. These massive creatures can weigh as much as 200 kilograms (440 pounds), making them dense for jellyfish. The bell typically presents as cream or yellowish in color, with a distinct domed and gelatinous appearance.
The internal orange digestive system and tentacles are often visible through the translucent bell. Nemopilema nomurai possesses a mantle-like structure that supports eight stubby oral arms, rather than traditional long, singular tentacles.
Natural Habitat and Range
Nomura’s jellyfish primarily inhabits the waters of the Northwest Pacific Ocean, including the East China Sea, the Yellow Sea, and the Sea of Japan. The Yellow Sea serves as a primary breeding ground, maintaining populations year-round.
Ocean currents, particularly the Tsushima Current, play a significant role in their distribution. This warm current flows north along China’s coast and then between Korea and Japan, transporting larval and adult jellyfish. Changes in water salinity during June and July can also push young medusae out to sea, where they are carried by these currents into new areas.
Ecological and Economic Consequences
Massive blooms of Nomura’s jellyfish have substantial ecological and economic impacts. Ecologically, these blooms can significantly deplete zooplankton populations, a primary food source for many marine species. This competition for food can affect fish populations, and in dense aggregations, the jellyfish can contribute to localized oxygen depletion in the water.
Economic consequences are particularly severe for fishing industries. Fishermen often contend with nets clogged and damaged by the volume and weight of these jellyfish. When caught alongside fish, the jellyfish can crush, slime, or sting the fish, causing mass mortality or reducing their market value by as much as 70%. This leads to significant financial losses for fisheries, with some villages experiencing economic instability.
In addition to ecological and economic damage, Nemopilema nomurai stings can also affect humans. A sting from this jellyfish can cause intense pain, burning, redness, and blisters. In severe cases, systemic reactions can occur, and fatalities have been reported. The increasing frequency of these large blooms since 2002, compared to historical occurrences, raises concern for marine ecosystems and human activities.