‘Cotylorhiza tuberculata’: The jellyfish that will survive the worst conditions of climate change | Science


A specimen of 'Cotylorhiza tuberculata', a species of jellyfish common in the Mediterranean and on which the adaptation to changes experiment has been carried out.
A specimen of ‘Cotylorhiza tuberculata’, a species of jellyfish common in the Mediterranean and on which the adaptation to changes experiment has been carried out.

Mediterranean in 80 years. Sea water reaches a temperature of 30 degrees and the acidity is at a pH of 7.7. It is the worst scenario foreseen in the Intergovernmental Panel on Climate Change (IPCC). Many species do not survive the new environment, but one does: the jellyfish Cotylorhiza tuberculata, one of the most common in this sea. A team from the Andalusian Institute of Marine Sciences (ICMAN-CSIC), of the Higher Council for Scientific Research (CSIC), has subjected these specimens to these conditions and has analyzed their adaptability. Angélica Enrique-Navarro, lead author of the experiment, published in PLOS ONE, explains: “The high tolerance to environmental changes evidenced by the polyps of this jellyfish will allow the species to carry out gradual long-term acclimatization, adapting to the expected temperature and acidification conditions.”

The effect will not only be an extraordinary proliferation of these jellyfish, a circumstance that has become common. The problem is that it will alter the ecosystem. Jamileh Javidpour, Professor of Biology at Syddansk Universitet (University of Southern Denmark), clarifies: “As we see an increase in jellyfish, I suspect that we will also see a change in predator populations, especially in areas where abundances of Common prey could be endangered by a changing environment ”. Javidpour is the author of research focused on jellyfish and published in Journal of Plankton Research.

These episodes of jellyfish proliferation and their generalization in the worst scenarios of climate change have been related to factors such as the disproportionate exploitation of fishing and the excessive presence of inorganic nutrients from human activities, in addition to the alteration of the sea temperature and its acidity. These circumstances affect all species, but research has shown that the Cotylorhiza tuberculata it is more tolerant and shows more adaptability, which is why, according to the Spanish researcher, it could lead to its expansion as a more opportunistic species.

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Enrique-Navarro explains that “these jellyfish are among the most resistant”: “They have been inhabiting the oceans for 500 million years and have adapted to many changes since then. If they lose the competition of other marine fauna they could become predominant and alter the ecosystem ”.

For that capacity they have developed two key skills. The first is that they alternate sexual and asexual reproduction. In the latter, they generate small millimeter polyps that are anchored to the marine substrate and generate, by budding (prominences or buds of the parent individual) genetically identical clones that give rise to small jellyfish called Ephrae. The researcher explains that, “the high tolerance to environmental changes evidenced by the polyps of this jellyfish allows the species to carry out a gradual long-term acclimatization, adapting to the conditions of temperature and acidification”. “If the conditions are good,” adds the researcher, “they reproduce exponentially.”

The second fundamental ability of these marine invertebrates is their symbiosis with microalgae known as zooxanthellae. These, in exchange for the protection that the jellyfish provide against predators, modulates the negative effects of the drop in pH on their survival and the incidence of ultraviolet rays.

There are other studies, according to the researcher, that add one more capacity for the survival of the species: a molecular chronometer that indicates the best temperature conditions to procreate.

The experiment

To carry out the investigation, Enrique-Navarro’s team submitted the specimens of Cotylorhiza tuberculata to three scenarios: one with the average normal temperature of the current winter in the Mediterranean (18 degrees), another with 24 degrees and the worst, which will occur in 2100, when the water temperature will reach 30 degrees if conditions are maintained of climate change.

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To these conditions they added different acidity scenarios in the water. “Most of the studies that have been done in jellyfish”, explains the researcher, “only took into account the consequences of temperature and we wanted to see what was the synergistic effect of the two variables.”

Enrique-Navarro summarizes the results: “They indicate that the asexual reproduction of the jellyfish remains the same and that, in some cases, with temperatures of 30 degrees and with the acidification forecast in 2100, it was even higher.” Only occasionally, the warming and acidification affected the transition phase from polyp to jellyfish and the formation of ephrae, generating malformations and compromising their survival “. But in most cases, they were able to withstand the harsh conditions.

The study allows a more precise understanding of jellyfish proliferation phenomena and their biological response to climatic conditions, in addition to helping to fixate on these communities as biological indicators of the environmental conditions of the sea and to establish measurements.

The impact of the proliferation of jellyfish is immediate and direct and not only in the fragile balance of the marine ecosystem. As summarized by Gerhard Herndl, professor at the Department of Functional and Evolutionary Ecology at the University of Vienna, “large jellyfish blooms block the pipelines of coastal power plants and desalination plants, interfere with ship operations and cause damage to industries. of tourism, fishing and aquaculture ”. Herndl considers it important to “fully understand the role and impact of these events on the marine ecosystem.”

One of these studies, co-authored by Herndl and published in Frontiers in Microbiology, it affects what happens when that excess of jellyfish, increasingly common, dies. According to the research, when they finish their life cycle, they also generate a “rapid growth of only a few strains of opportunistic bacteria from seawater which, in turn, will provide food for other marine animals in the water column”. And he concludes: “There are many species of jellyfish and other gelatinous organisms whose proliferations can cause temporary changes in the food web and not all ecosystems where they occur are the same nor can they support the same strains of bacteria.”

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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