There is a belief that the proliferation of jellyfish in waters around the world is increasing globally and that this increase could be related to global warming or activities related to human action such as fisheries, coastal construction or eutrophication.
In this context, the Mar Menor represents a unique opportunity to determine whether or not these factors are affecting the massive appearance of these animals and if we are heading towards what has been called a ‘gelatinous ocean’, and at the same time to know their interactions with other organisms such as ichthyoplankton and ultimately its effects on fishing.
According to Alfredo Fernández Alías, FPI researcher at the Seneca Foundation in the Ecology and Management of Coastal Marine Ecosystems group at the University of Murcia, “it must be taken into account that, although it is generally considered that the waters of the Mar Menor are warm (and thus they are during the summer) there is more than 20ºC difference between the summer maximum and the winter minimum. In addition, the salty lagoon is home to important fisheries, such as shrimp or sea bream, it has numerous ports on its coastline and we have witnessed the effects of eutrophication on its waters in recent years. All this makes it a model ecosystem to analyze the effect that climate change can have on jellyfish populations worldwide.
On the other hand, although there are certain discrepancies among scientists about whether or not these proliferations are increasing, there is consensus that they cause interference and annoyance for humans, either through bites to bathers, hindering fishing activities or even blocking power stations. power plants that use seawater pumping systems for cooling. “We believe that a greater understanding of the functioning of these beings will allow us to anticipate their proliferations in the future and improve local management to reduce these negative interactions,” says Fernández Alías.
The researcher is immersed in the project ‘Population dynamics and ecological role of three species of the Scyphozoa class during a eutrophication process’, which is part of a monitoring system of the Mar Menor that aims to improve the knowledge that is possessed on the operation of the lagoon, as well as its ecological status. “The idea is to know the biology and population dynamics of jellyfish species and their role in controlling the food web and the state of eutrophication. For this, a network of sampling points was developed, distributed throughout the Mar Menor lagoon and its communications with the Mediterranean, where information is collected in situ on physical variables, such as temperature and salinity, and biological variables, such as abundance. of jellyfish and chlorophyll concentration, in addition to collecting samples for chemical and biological analysis upon arrival at the laboratory, “he says.
The work is possible thanks to the financing of the Seneca Foundation, through its program of pre-doctoral contracts FPI, while the monitoring system is financed through the regional government, through the General Directorate of Mar Menor. Likewise, the group also participates in projects in the RIS3Mur calls and in European projects of the Biodiversa or Life calls.
Within the framework of the monitoring system, the study carried out as part of Alfredo Fernández’s doctoral thesis aims to determine what factor or factors are those that promote the massive development of jellyfish species that inhabit the waters of the Mar Menor, and the role that these develop later in the regulation of the lagoon trophic network. That is, on the one hand, it is intended to build a predictive model of the abundance of jellyfish in the ecosystem with the parameters that are collected in the various sampling points and that facilitate the development of similar methodologies that can be applied in other affected ecosystems. by jellyfish. On the other hand, we want to study if these species reduce the turbidity of the waters through their consumption of planktonic organisms such as diatoms or copepods, if there is competition between the different species of jellyfish or of these with the species of fishing interest of the region.
“Currently –explains the researcher– we have a time series that we continue to reinforce month by month thanks to the continuous and prolonged effort over time. The greatest stumbling block that will arise in the future is possibly the interannual variability traditionally shown by populations. To give an example, last year the fried egg jellyfish (‘Cotylorhiza tuberculata’), which by the way is not native to the Mar Menor but entered by dredging the Estacio channel to make it navigable, barely made an appearance after a few summers in those that formed true swarms and populations of more than forty million individuals. A priori, there are not excessive very important differences between the years of massive proliferation and those of absence. But now we hope to be able to increase the resolution on a small, medium and large scale by studying a wide period of time with data collections closely spaced in time, so that we limit both specific events and large temporal fluctuations ».
So far they have been able to determine how the species behaved in 1997, a moment that they consider a base level or pre-eutrophication, where a temporal and spatial separation was appreciated in the Mar Menor that allowed a continuous action to regulate the trophic network. These results serve as a reference for studying the effect of the accumulated impacts over the last two decades in which the Mar Menor has shown intermittent rupture episodes. Although the project is mainly developed by the UMU, eventually collaborations are made with other groups such as the CNR of Venice (Italy) and with the University of Klaipeda (Lithuania) for hydrodynamic and food web modeling, respectively.