For a few Days Now, the Seville Aquarium Has been Exhibiting the Black Sea Jellyfish (Maeotias Marginata) in its Facilities
The jellyfish, which was first detected as an invasive species in North America in 1968 in the estuaries of rivers flowing into Chesapeake Bay, is difficult to find as it is seasonal and only lives in brackish water, which has an intermediate salinity between freshwater and seawater.
Its presence was confirmed during the protocol and systematic sampling carried out by the Marine Biology Laboratory of the University of Seville to monitor marine species in the estuary, during the period from June to October.
It is not known for certain how this species arrived in the Guadalquivir River. Experts think it may have arrived in the polyp phase or another resistant phase attached to the hull of a vessel or in a ballast water tank of a ship. After adapting to the conditions of the estuary, it has formed the first colonies of polyps, from which, seasonally, the jellyfish that appear in the samples are generated.
The Maeotias marginata, also known as the brackish water hydromedusa, has a bell diameter of up to 5.5 cm, a hemispherical shape, and is opaque white with a reddish tint near the bell.
Research at the aquarium
The importance of studying this organism lies in the fact that, as it adapts to the new environment, it can create ecological imbalances, competing with native species and reducing their natural populations, and in more critical cases, displacing them and even causing them to disappear.
The discovery and capture of these small hydrozoans provides university researchers with the possibility of measuring the influence of this invasive species on other species in the Guadalquivir. However, to do this, it is necessary to conduct different studies in the laboratories of the research area, and this is where the great challenge for the experts at the Seville Aquarium appears: finding the optimal conditions for maintenance, and even reproduction of this species, in order to study it in depth.
Currently, the staff of the Aquarium’s Conservation Department is testing various protocols (different tanks to house them and modifications in water circulation, salinity, temperature, and feeding) in order to keep them alive for as long as possible and attempt to close their life cycle. This way, they will be able to understand the factors that facilitate or hinder their propagation and thus be able to study possible measures to control their population in the Guadalquivir estuary, should the researchers at the Marine Biology Laboratory of the University of Seville deem it appropriate.
Their exhibition is also interesting as it is a unique and exclusive opportunity to observe these jellyfish up close and in ideal conditions to appreciate all their beauty.