Jellyfish season comes early due to high temperatures

sea ​​jellyfish

Beaches saw a significant increase in visitors over the weekend due to rising temperatures. The coasts were not only full of bathers, but also full of jellyfish. And it is that, the Jellyfish season is brought forward with rising temperatures.

In this article we are going to tell you why the jellyfish season is coming forward with the increase in temperatures and what its consequences are.

jellyfish season


In the sandy area of ​​the Bay of Roses, located on the picturesque Costa Brava, a large number of these creatures can be found, a direct consequence of the impact that the coastal area has suffered. Scorching heat and prolonged drought are the underlying factors contributing to these events.

Experts warn that the appearance of phenomena such as drought and high temperatures is contributing to a higher prevalence of important populations of Jellyfish in recreational swimming areas.

According to local media, Josep Maria Gili, researcher at the Institute of Marine Sciences, has highlighted that the decrease in rainfall negatively impacts the quality of coastal water, causing a resemblance to the open sea and consequently creating a favorable environment for the presence of these organisms.

The particular type of jellyfish being analyzed is identified as Pelagia noctiluca. These jellyfish are distinguished by their transparent appearance, adorned with lilac or magenta spots, and their slender, elongated tentacles. Its natural habitat is typically found in large bodies of water. As Gili states, these jellyfish are responsible for a significant majority, between 60% and 70% of bites in the Playa, earning them the reputation of being the most potent in terms of their bite.

While these particular species can be seen during the summer months, their reproductive activities occur predominantly in the spring. Gili highlights that rising temperatures and drought, both consequences of climate change, will result in a greater prevalence of encounters with jellyfish in coastal areas.

Is the jellyfish considered a threat?

large number of jellyfish

The scyphozoan jellyfish, known by various names such as luminescent jellyfish, sea carnation or aquamala, is widely recognized as a true jellyfish. Its vibrant shade is easily identifiable as a striking pinkish purple shade.

The umbrella, called the upper structure, has a slightly flattened hemispherical shape that is adorned with elongated and rounded lobes. These lobes have the potential to reach a diameter of 20 cm. Additionally, the perimeter of the umbrella is decorated with 16 lobes located on the periphery.

In an alternating pattern, there are a total of 8 sensory organs and 8 marginal tentacles. In addition, four elongated and resistant oral tentacles extend from the mouth. In addition, this jellyfish has 16 marginal tentacles that often exceed its own length, extending over 2 meters when fully extended.

Warts adorn the surface of the jellyfish's umbrella, oral arms, and tentacles, composed of cnidocysts, which are stinging cells that define this particular species of jellyfish.

Why do jellyfish appear?

jellyfish on the beach

With the arrival of summer we can anticipate pleasant weather and the presence of jellyfish in the waters of Spain. These creatures have specific times of the year when they are most abundant, and this is closely related to temperature fluctuations. Although it may seem that there is an increase in jellyfish compared to previous years, experts advise considering several factors before drawing conclusions.

Mario Roche, curator of fish and invertebrates at the Oceanogràfic, explains that the lengthening of the season in which jellyfish can be found It is due to the increase in temperatures throughout the planet, especially in water.

As the number of warmer months of the year increases, there is a corresponding increase in jellyfish sightings. As a result, some swimmers claim that there is now a greater abundance of jellyfish compared to previous years. Roche points out that in 2023 the water temperature in the Mediterranean reached between 29 and almost 30 degrees.

During the spring, summer and even autumn seasons, when the weather is warmer, there is a notable increase in the presence of jellyfish along the coastline. This fact is directly related to the increase in ocean temperatures, as it prolongs the time these marine creatures spend in the water.

Life cycle and presence of predators

Regarding the regions of Spain with the highest concentration of jellyfish, the Oceanographic fish curator confirms that the Mediterranean coast is usually the area with the largest population of these creatures. This is probably due to the higher temperatures in the Mediterranean Sea compared to the Cantabrian area. However, It is important to note that jellyfish exist in the Cantabrian area, although in potentially smaller quantities.

According to Roche, the notable increase in jellyfish on the coast is due to their life cycle, which involves alternating different phases. These phases include a polyp stage that resembles a miniature coral or anemone, as well as the more prominent jellyfish phase commonly seen off the coast.

The expert highlights that due to the fluctuation between phases, the polyp responds to the increase in temperature by transforming into a jellyfish. As a result, these jellyfish are now observable along the coast for extended periods throughout the year.

However, Roche does not rule out the possibility that there has been an increase in jellyfish populations due to a decrease in their natural predators, such as certain types of fish. An example is the tuna or sunfish, a large and highly visible creature commonly found in the Mediterranean that feeds mainly on jellyfish.

The reduction of natural predators is clearly a contributing factor to the increase in jellyfish populations. Additionally, the increased abundance of organic matter in the water creates a favorable feeding environment for these marine creatures, leading to further growth in their numbers.

Favorable conditions for jellyfish proliferation, such as temperature and food availability, have been advantageous. On the contrary, There has been a decline in the population of natural predators, which has resulted in increased numbers of jellyfish populations during the spring and summer seasons.

I hope that with this information you can learn more about why the jellyfish season is coming forward with the increase in temperatures.

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