The appearance of jellyfish of the Cotylorhiza tuberculat variety —better known as fried egg jellyfish— in the Mar Menor is due to a greater transparency of the water, which favors both their reproduction and a greater presence of this species, according to reports. of the General Directorate of Fisheries and the University of Murcia.
The latter can already be consulted on the ‘CanalMarMenor’ website and it mentions that “the installation of ‘anti-medusa’ nets is counterproductive and should be considered “with extreme caution, being, in general, inadvisable”, according to sources from the Community in a press release.
Jellyfish populations in the Mar Menor are not something new, since since the mid-1990s their presence has been constant, and during some periods, pronounced. In 2016 they disappeared or were found at low levels as a result of the darkening of the water column that prevented light from reaching the seabed and caused the death of the jellyfish.
This situation has lasted in recent years until in 2021 “a timid recovery” of the populations began to be detected, more evident during 2022 and which this year is once again at levels as high as those prior to the eutrophic processes of 2016 , as specified by the same sources.
The lagoon has always had a winter species called Aurelia aurita, known by fishermen as ‘bad water’, which closes its cycle at the beginning of summer, so its presence during the summer season is very low or practically non-existent from the first days of July, depending on the water temperature.
The second most common jellyfish in the lagoon is Cotylorhiza tuberculata, colloquially known as the fried egg due to its appearance. This jellyfish reaches very high densities during the months of July and August, has a life cycle of between 2 and 6 months and is not stinging. This species has mechanisms that cause its multiplication to not totally depend on the availability of nutrients (phytoplankton and zooplankton) in the water.
Other jellyfish present in the lagoon are the Rhizostoma pulmo, which has a stinging nature, and the Phyllorhiza punctata, which recently appeared and is morphologically similar to the Rhizostoma pulmo, but with a dotted bell. They have been detected and follow-up is being done to assess their situation.
On the other hand, the spokesman for the Scientific Committee of the Mar Menor, Emilio María Dolores, referred to the area of ??whitish water located around the mouth of El Albujón. He has said of it that “it is not a new image and it is due to the continuous resuspension of insoluble particulate material that has reached that area as a result of runoff and leachate. This area is usually the one with the highest concentration of nutrients. The dimension and shape of the patch depends on the currents and prevailing winds”.
The spokesman added that “the current nutrient levels fall within the parameters set by the regulations, except in two stations in front of the Albujón boulevard, and the amount of water that has entered has been significantly less than in 2022, although still excessive”.
“In short, this summer, and except for episodes that negatively affect Cotylorhiza tuberculata such as thermal stress and/or darkening of the water column, the populations of this non-stinging species will be high, allowing better control of the trophic chain of the lagoon and will contribute to a greater transparency of the waters”, summarized the spokesman for the Scientific Committee of the Mar Menor.
Regarding the state of the Mar Menor, the Ministry of the Environment, Mar Menor, Universities and Research reports on the evolution of the physical-chemical parameters that allow us to know the state of the ecosystem. Thus, the levels of chlorophyll and transparency improve, while they are maintained in the rest, with respect to 2022.
In this way, from the measurements carried out on June 21, an average oxygen level of 6.23 micrograms per liter is revealed, chlorophyll stands at 0.52 micrograms per liter, the temperature is 27.44 degrees Celsius, salinity at 42.36 and turbidity at 1.05 FTU.
“If we compare the parameters with those registered in previous years, we find the best salinity data since 2019, oxygen values ??similar to the previous ones and chlorophyll at low levels as in 2021 and 2022, significantly lower than the values 2019 and 2020”, explained Emilio María Dolores, “so we can conclude that the Mar Menor maintains the level of stability that it has been showing in recent months”.
“We continue to monitor the evolution of the state of the Mar Menor permanently and at all points in the ecosystem, especially now with the increase in temperatures, which is the factor that worries us the most, like every summer,” the Committee spokesman concluded.
