On a global scale, jellyfish populations in coastal marine ecosystems exhibit increasing trends of abundance. High-density outbreaks may directly or indirectly negatively affect human economic and recreational activities, as well as public health through impacts on tourism, fisheries, industry and local wildlife.
For example, Rhopilema nomadica is a large, tropical invader jellyfish which arrived through the Suez Canal in the Mediterranean in the late 1970s and is now considered one of the 100 worst invading marine species because of its potential for population outbreaks. In 2010, a 200km long swarm formed off the coast of Israel, composed of more than 100 million jellyfish individuals, with a total biomass of 500,000 tons. The jellyfish consumed 5,000 tons of plankton (from small crustaceans - larval fish food - to fish eggs and larvae) every day, scraping clean the oligotrophic Levantine sea. Coastal trawling and purse-seine fishing were disrupted due to net clogging and inability to sort yield, one swarm forced the shutdown of a power plant after clogging the coolant water pipes and local municipalities reported a decrease in holiday-makers frequenting the beaches because of the public’s concern over the painful stings inflicted by the jellyfish. This jellyfish is slowly migrating westward into the Mediterranean and VECTORS scientists have reported the westernmost record - off the Maltese islands, suggesting that climate change is becoming conducive to the spread of species of warm water affinity, as another hallmark of the warming trend in the Mediterranean Sea. As predicted, this species has now entered the Western Mediterranean Sea, with an established population in the Gulf of Tunis.
The VECTORS finding of a new, conspicuous and out-breaking jellyfish species (Pelagia benovici, new to science) into the Gulf of Venice, has remarked the high susceptibility to bioinvasions of the Mediterranean Sea and the value of large-scale citizen science campaigns.
Also, increasing proliferation of artificial structures (ocean sprawl) associated to human activities on coastal zones (e.g. shipping, aquaculture, coastal defences, maritime tourism, coastal industries) are providing new habitats for the completion of life cycles of jellyfish species with benthic stages (i.e. living on the sea hard bottoms). VECTORS scientists assessed the impact of secondary hard substrated represented by wind farm pillars, on the occurrence and distribution of the moon jelly Aurelia aurita in the SW Baltic Sea. The study confirmed offshore wind farms have the potential to increase the abundance of jellyfish populations, expanding environmental issues on several sectors, mainly fishery, energy and tourism.
Conversely, with a positive perspective, the large amount of jellyfish biomass could be considered to be a valuable source of bioactive compounds beneficial for humans, including bioactive peptides, collagen and gelatine, oligosaccharides, fatty acids, enzymes, calcium, water-soluble minerals, and biopolymers. The various identified biological activities, including antioxidant activity, make them a potentially valuable material for food, cosmetic, and biomedical industries, such as has been proposed for seafood processing by-products.
VECTORS research has provided new tools to understand and predict potential changes to local marine environments in the event of non-indigenous jellyfish species invading new areas or native species periodically producing large outbreaks. By understanding the drivers of invasions local authorities can, where possible, administer preventative management through better informed policy and governance to at least minimise the impacts caused by the jellyfish presence. Where this is not possible, the research can help management bodies to identify the likely mechanisms and to forsee impacts of the invasion for the environment and socio-economy of the area. Through understanding these impacts there is an opportunity to adapt and / or mitigate the effects through awareness raising, adaptive governance and evolving practices. Furthermore, VECTORS has identified potential socio-economic benefits from jellyfish harvesting that could have far reaching implications for food, health and industry so that we no longer need to look on the number of increasing jellyfish as a management problem but also an opportunity.