The jellyfish that will survive the worst of climate change | Science

Mediterranean, in 80 years. The temperature of the sea water reaches 30 degrees, the pH is at a pH of 7.7. It’s the worst-case scenario predicted by the Intergovernmental Panel on Climate Change (IPCC, a scientific advisory body of the United Nations). Many species do not survive the new environment, but one does: jellyfish Cotylorhiza tuberculata, one of the most common species in this sea. A team from the Institute of Marine Sciences of Andalusia (ICMAN, associated with CSIC, Spain’s official scientific research agency), provided samples of this type for such conditions and analyzed their adaptability. Angelica Enrique Navarro, lead author of the experiment, Published in the magazine PLUS ONE, explains that “the high tolerance to environmental changes exhibited by the polyps of this jellyfish will allow the species to acclimatize gradually over the long term, adapting to the expected temperatures and acidification conditions.”

The effect will not be just the unusual spread of these jellyfish, a circumstance that has already become familiar. The problem is that it will change the ecosystem. Jamila Javidpour, a professor of biology at the University of Southern Denmark, considers that it is expected that “when we see an increase in jellyfish, we will also see a shift in the numbers of predators, especially in areas where the numbers of common prey can be compromised due to the presence of a changing environment.” Javidpur is the author of a study focused on jellyfish and published in the journal Plankton Research Journal.

Episodes of these jellyfish proliferation and generalization in worst climate change scenarios were related to factors such as disproportionate exploitation of fishing and excessive presence of inorganic nutrients from human activities, as well as changes in sea temperature and acidity. These conditions affect all species, but the study showed it Cotylorhiza tuberculata It is more tolerant and shows greater adaptability, which, according to the Spanish researcher, can lead to its expansion as a more opportunistic species.

“These jellyfish are among the most resistant types of jellyfish,” explains Enrique Navarro. “They have inhabited the oceans for 500 million years and have adapted to countless changes since then. Without competition from other marine animals, they could become dominant and alter the ecosystem.”

For this ability, they developed two basic skills. The first is that they alternate between sexual and asexual reproduction. In the latter, they generate millimeter polyps fixed to the marine substrate and produced, by budding (protrusion or yolk from the parent individual), genetically identical clones, which give rise to small jellyfish called ephiras. “If conditions are good, they multiply exponentially,” the expert adds.

The second primary ability of these marine invertebrates is their symbiosis with microalgae known as zooxanthellae. These, in exchange for the jellyfish’s protection against predators, mitigate the negative effects of UV rays and low pH for their own survival.

The expert notes that other studies point to a third species’ ability to survive: a molecular thermostat that indicates the best temperature conditions for breeding.

Experience

In this study, Enrique Navarro’s team provided samples of Cotylorhiza tuberculata To three scenarios: one with the average normal temperature of the current Mediterranean winter (18°C), the other 24°, and the worst that will happen in the year 2100, when the water temperature reaches 30°, to maintain the current climate. directions of change.

Various acidity scenarios have been added to the water for these conditions. “Most of the studies on jellyfish,” the researcher explains, “considered only temperature consequences, and we wanted to see the synergistic effect of the two variables.”

Enrique Navarro summarizes the results: “They indicate that the asexual reproduction of jellyfish remains the same, and in some cases, with temperatures of 30 degrees with acidification expected in the year 2100, it was even higher.” Ultimately only “heating and acidification affected the transition from polyps to jellyfish and the formation of aphids, resulting in abnormalities and displaying their survival.” But in most cases, they were able to withstand extreme conditions.

The study allows for a more accurate understanding of the phenomenon of the spread of jellyfish and their biological response to climatic conditions, in addition to helping to establish themselves in these communities as biological indicators of the environmental conditions of the sea and allowing the development of measures.

The impact of jellyfish reproduction is immediate and direct, and not just in the fragile balance of the marine ecosystem. As summarized by Gerhard Herndel, Professor in the Department of Functional and Evolutionary Ecology at the University of Vienna, “The large jellyfish breeding impedes coastal power delivery and desalination plants, interferes with ship operations and causes damage to the tourism, fishing, and aquaculture industries.” Herndel believes that it is important to “completely understand the role and impact of these episodes on the marine ecosystem”.

One of these studies co-authored and came out in Frontiers in Microbiology, analyzes what happens when this surplus of jellyfish dies, which is an increasingly common occurrence. According to the study, at the end of their life cycle they also generate “a rapid growth of a few strains of opportunistic marine bacteria, which in turn will provide food for other marine animals in the water column.” It concludes: “There are many species of jellyfish and other gelatinous organisms whose spread can cause temporary changes in the food web, and not all ecosystems in which they occur are similar and cannot tolerate the same strains of bacteria.”