MARINE NUISANCES – A tide of jelly

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Ask somebody to name you something that lives in the sea and the chances are that they will reply with a type of shark or fish species. This is because to us, humans, fish have always been an important food source and access to this source has meant that many of the world’s largest cities are coastal. With this in mind, one must accept that as global populations have grown, the pressure we have exerted on this resource has increased in many parts of the world, beyond what it can supply.

Commercial fishing is but one part of the story. The coastal zones are the most productive regions of the ocean. Unfortunately, they are also the parts which are under the most pressure from habitat changes by humans. Commercial shipping, for example, has dramatically changed the hydrology, diversity of species and the respective populations within the bay of Gibraltar and as this pressure has increased, the environment has deteriorated.

For the most part, it is important to recognise the positive impacts these developments have had to our economy and also to our standard of living. However, the full extent of the cost that is paid is often forgotten, if recognised at all; the health of the environment tends to come second.

The last decade has seen large influxes of Schyphozoans, the true jellyfish, and one species in particular, Pelagia Noctiluca, the mauve stinger, has plagued our coastline. As their name suggests, Pelagia is from the Greek pelagos, which means ocean, nocti for night and luca for light; ocean night lights. True to their name, they glow in the dark if you shine UV light on them. These jelly fish tend to move in large groups and their sting is particularly painful, as many of us can attest to. Scientists have recognised this as a growing problem and one researcher, Professor Josep-Maria Gili, from the Institute of Marine Sciences in Barcelona, is quoted as saying “It is a growing problem in the Mediterranean, as it is in the rest of the world”. So why is this?

Climate change is the universally accepted answer for any problem for which we have no immediate solution. It’s easy! No-one has a quick fix for it and so we all just have to accept it. And we do!

In fact, warming sea temperature caused by climate change is driving a change in ecological pressures on marine organisms. This environmental change is favouring the plankton and jellyfish species over the traditional fish dominated ecosystems and here is why. Quick changes in water temperature, from cold to warm, is one of the stimuli which generates jellyfish blooms. The greater the change in temperature, the larger the blooms tend to be. Traditionally, in fish dominated ecosystems, the young jellyfish are a food source for juvenile fish. However, as these jellyfish blooms are larger than normal, the juvenile fish are being overwhelmed and predator is turned into prey. This change in ecosystem dynamic means less fish and, crucially, more jellyfish!

Now, add the human component of over-fishing and habitat changes to coastal regions to a backdrop of warming oceans, and a worrying picture begins to emerge, especially if you are a fish.

So what can we do to contribute positively to this situation? Gibraltar’s contribution to global CO2 emissions is negligible and consequently any green power initiatives, although laudable, have a miniscule impact on the world’s total output.

With respect to fishing, Gibraltar has already introduced fishing licences, landing quotas, minimum size catch guides and even listed certain endangered species from being caught at all. These are all important steps in preventing the exploitation aspects, provided we all adhere to the guidelines. Again though, Gibraltar’s coastline is very small and our contributions alone will not be sufficient to stem the jelly tide.

Finally, habitat impact is something we can positively contribute to. A small coastline means that any development along it has a proportionally greater environmental impact – we need to play this to our advantage. Analysing how we use our coastline, the impacts that these activities are having on species abundances and diversity are crucial as part of an ongoing monitoring programme. Promoting larger marine protected areas to include zones of fish nurseries will help to balance the environment against the jellyfish. Once implemented, we would be in a good position to help other countries follow suit and place Gibraltar at the centre of global marine environmental management.

Looking forward, our summers are likely to bring larger and more frequent blooms of jellyfish. This is something we are probably going to have to live with. But there are some practical solutions to avoid getting stung:

Some oily sun protection creams are reported to prevent the mauve jellyfish from stinging humans. The oil prevents the stinging cells from activating and hence stinging us. You might want to be careful before applying and swimming into a large mauve bloom though.

A better solution are the swimmers wetsuits. These are thinner and less intrusive than the surfing or diving alternatives. Let’s face it, they are more like a 1930’s bathing costume, and provide full protection to the areas it covers. Jellyfish cannot sting through neoprene. They are cheap and widely available. Watch your face, hands and feet though.

If you do get stung then try and avoid the temptation to swipe away the sting as you will only increase the affected area. The tentacles tend to stick to our skin after stinging and should be removed by picking them off carefully.

But, as Dory famously said in Finding Nemo, if you do happen to see “Squishy” then “Just keep swimming, just keep swimming” calmly back to shore.

words | Lewis Stagnetto, The Nautilus Project