Jellyfish blooms and impacts on marine ecosystems – The term ‘jellyfish bloom’ refers to a phenomenon in which there is a rapid and massive increase in the population of jellyfish in a given marine area.
This phenomenon can be caused by a combination of environmental factors such as:
- Increased water temperatures: higher temperatures favour the reproduction and growth of jellyfish.
- Eutrophication: an excess of nutrients in the water, often due to agricultural or urban pollution, which increases the availability of food for jellyfish.
- Decline in natural predators: overfishing of predator species such as turtles and predatory fish reduces pressure on jellyfish populations, allowing them to thrive.
- Changes to ecosystems: environmental changes and habitat destruction can create favourable conditions for jellyfish.
Impacts of jellyfish blooms on marine ecosystems and human activities
Interference with fisheries
Jellyfish blooms can have a devastating impact on commercial and artisanal fisheries. Jellyfish, in large numbers, can compete with fish for food and, in some cases, directly prey on fish larvae. This can lead to a decrease in fish populations and, consequently, reduced catches for fishermen. In addition, jellyfish can fill fishing nets, making them heavy and difficult to manoeuvre, damaging them or rendering them unusable.
Damage to fishing nets
When jellyfish accumulate in fishing nets, they can cause significant physical damage. The weight of the trapped jellyfish can tear the nets, and jellyfish mucus can stick to the meshes, making it difficult to clean and maintain the equipment. This increases operating costs for fishermen, who must repair or replace damaged nets and spend more time on maintenance.
Obstruction of water intakes
Jellyfish can clog the water intakes of power plants and desalination plants, compromising the operation of this critical infrastructure. Water intakes used for cooling power plants can be blocked by jellyfish masses, causing overheating and potential failure. Desalination plants, which supply drinking water from marine resources, can also be compromised, reducing efficiency and increasing operating costs.
Problems for tourism
Jellyfish blooms also pose a significant problem for tourism, particularly at seaside resorts. The presence of large quantities of jellyfish can discourage tourists from swimming and water sports, reducing tourist influx and damaging the local economy. Jellyfish stings can cause pain and, in some cases, severe allergic reactions, increasing the risk to swimmers and requiring more frequent medical interventions.
Significant cases
A significant case occurred in 2007 in Japan, where a massive bloom of Nomura jellyfish (Nemopilema nomurai) caused serious problems for the country’s fisheries. The jellyfish, with a diameter of over two metres and a weight that can exceed 200 kg, damaged fishing nets and drastically reduced fish catches.
Solutions and mitigation
Various solutions have been proposed to mitigate the impact of jellyfish blooms. These include the installation of jellyfish barriers, the use of monitoring technologies to predict and manage blooms, and the promotion of jellyfish consumption as a food source. Some countries are also experimenting with methods to remove jellyfish from the water, using specially equipped boats.
Jellyfish blooms pose a growing threat to marine ecosystems and human activities. It is essential to develop and implement effective strategies to manage and mitigate these phenomena, thereby protecting the local economy and preserving the health of marine ecosystems.
Jellyfish blooms and impacts on marine ecosystems
