Alien Species of the Week: Nomad Jellyfish

Rhopilema Nomadica (Nomad jellyfish)

Originally from the Indo-Pacific, the Nomad jellyfish first made its appearance in the Mediterranean in the 70s via the Suez Canal, while the first mass appearance was registered in 1995 in Mersin Bay, off the coast of Turkey (Öztürk and İşinibilir 2010). 

The large presence of this invasive species in the Mediterranean is a cause of concern for the local populations (due to the particularly bad stings), and also for the tourist industry in the affected areas, such as the Israeli coast. The Rhopilema Nomadica affects fishing as well, as it gets entangled in fishing nets and  also eats fish larvae, causing a decrease in the fish stock (Galil 2007).

Nomad Jellyfish (Rhopilema Nomadica)

Due to its rapid spread, the Rhopilema Nomadica is included in the list of the 100 worst invasive species in Europe within the Delivering Alien Invasive Species Inventories for Europe (DAISIE). Its diffusion is diminishing plankton resources and is being detrimental to fishing, tourism and coastal installations. Seasonal variations in water temperature regimes could help fight the annual occurrence of the nomadic jellyfish, whose presence has been further recorder in 2004 in Malta and the Sicily Channel ( Deidun et al. 2011). 

The discovery of R. Nomadica in Maltese waters is another alarming indication of the increasing warming of the Mediterranean Sea as a result of climate change. Among the proposed preventative measures is a salinity barrier in the Suez Canal in order to reduce the number of Red Sea aliens in the Mediterranean.

Will R. Nomadica spread as north as the Ionian Sea and further north along the Italian coasts?

Watch this very short video below to see for yourself how jellyfish are threatening Israeli Power Plants: It's quite astonishing!!

More on the spread of the nomad jellyfish in the Mediterranean:

An alien jellyfish Rhopilema nomadica and its impacts to the Eastern Mediterranean part of Turkey

Alien Species in the Mediterranean Sea

Mosquitoes on the Move as Climate Changes

As already hinted from my previous post, I will be looking at mosquitoes!

Most of us, have at least once in our lives been bitten by one or more mosquitoes. We all know that mosquito bites are itchy and are rather uncomfortable when trying to sleep. Although, the effects of these bites are unpleasant, we never expect these bites to cause us any serious harm or severe illness in Europe. However, scientists have warned that the number of harmful diseased mosquitoes spreading across the European continent is on the rise bringing new public health surprises!

Asian Tiger Mosquito
(Aedes albopictus)

In Europe, the Asian Tiger mosquito (Aedes albopictus) is an invasive species that has the potential to transmit infectious diseases such as dengue and chikungunya fever. The mosquito is native to the tropical and sub-tropical areas of Southeast Asia (Caminade et al.2012). 

However, over the last couple of decades, owing to increasing international travel and the global transport of goods, the Asian Tiger mosquito has invaded many countries around the world and has been ranked as one of the “World’s Worst” invaders by the  Global Invasive Species Database. 

These mosquitoes have the ability to out compete and completely eradicate other species with similar breeding habitats, as they lay drought-resistant eggs (Benedict et al. 2007). This is what makes this invasive species so dangerous!

As well as many other incidents, the Asian tiger mosquito was responsible for the outbreak of Chikungunya fever that occurred in the Italian province of Ravenna, summer 2007 (Enserink 2007). More than 200 people were infected with the disease (ECDC 2007). Scientists have investigated these recent outbreaks and have related them to the wetter and warmer climate patterns over central Europe (Gould et al. 2010). 

The map below shows the known distribution of the Asian tiger mosquito in 2011.

Known distribution of A. albopictus based on field observations from the ECDC/VBORNET
project (December 2011)

So what impact will our warming climate have on the spread of infectious disease carrying mosquitoes?

Through the use of regional climate model scenarios for the future and high-resolution observations, scientists from the University of Liverpool have investigated the suitability of Europe for A. albopictus by using both recent and future climate conditions (Caminade et al. 2012). The results showed that during the 1960-80s, northern coasts of Spain, Italy and southern France were climatically suitable areas for the establishment of these mosquitoes. The main finding of the study showed that over the last two decades climate conditions have become more suitable for the mosquitoes over central northwestern Europe and the Balkans, whilst they have become less suitable in southern Spain and areas around the Mediterranean basin (Caminade et al. 2012). 

Future trends show a similar pattern with climate suitability for mosquitoes increasing over northern Europe (including southern UK) as winters become warmer and wetter. In contrast, conditions appear to become more unsuitable over southern European countries such as Spain and Portugal, as more droughts are predicted in these areas in the future (see figure below).  

 http://171.66.127.193/content/9/75/2708.full.pdf+html. The left column depicts the mean suit- ability based on the ensemble mean of all RCM-driven projections for 2030–2050. The right column shows the future changes (2030–2050) with respect to the 1990–2009 climatology.

 

Several other studies modelling and mapping the distribution and survival of Asian tiger mosquitoes across Europe, such as those carried out by Fischer et al. (2011) and Medlock et al. (2006), show similar distribution trends across Europe. Large areas of western and central Europe that are inappropriate for the species today are projected to change during the 21st century towards a climate that can support the survival of the species.

Thus, climate change is affecting the distribution of mosquito populations and thus the spread of infectious diseases across Europe. It is clear that in the future, unintended anthropogenic introduction can be expected as a constant source of insecurity. European health officials must be prepared and ready to tackle future epidemics of vectorborne and waterborne infectious diseases.

Climate change will have enormous implications for human health in the future.

Further Reading:
Is Climate Change Aiding the Spread of Disease?

Sorry!

I just wanted to excuse myself for my lack of blog posts over the last week and a half. Having caught the dreaded flu over a week ago, I have only just recovered! However, being ill has inspired one of my next blog posts-here's a clue...

Snake Plague

Having received my new issue of Geographical today, I read a short article that stirred my interest. The article was about the dramatic increase in spider population on the Pacific island of Guam. What was fascinating was that the single accidental introduction of the brown tree snake 60 years ago, managed to wipe out 12 species of native bird. As a result, the island lost almost all its insect-eating birds allowing spider populations to thrive (Rogers et al. 2012).

Brown tree snake

I don't know about you, but I find it astonishing how a few snakes can eliminate almost an entire islands indigenous bird population in such a short space of time?

I suppose, Guam can be described as a text book example of what alien invasive species can inflict on an ecosystem. When the snakes were first introduced to Guam, the indigenous birds did not fear snakes and there were no predators to maintain the snake population. The island was a snake "paradise".

I delved further into the snake situation and discovered that there are an estimated 3,000 brown tree snakes per square mile on the 30 mile long island (National Geographic 2012).

A new research paper published in PLOS ONE (an open access paper, yay!) is one of the first papers to examine the impact of bird loss on the scale of an entire forests. Biologists from the University of Washington, Rice University and the University of Guam, lead by Haldre Rogers,  compared the density of spiders webs on Guam with the density of webs on the nearby Marianas Islands. They discovered that Guam has 40 times more spiders than any of the surrounding islands! Such astonishing results highlight how previous, small-scale studies underestimated the impact of bird loss on spider density as demonstrated by Guam- a large-scale natural experiment.

           Map of the Mariana Islands

(All forest birds are functionally extinct on the island of Guam, whereas relatively healthy bird populations remain on three nearby islands of Saipan, Tinian and Rota.)

 

 

 

It seems unbelievable that the effect of one invasive species can change the way in which biologists study and understand alien species interaction with ecosystems.  

So if you have arachnophobia I would not recommend a holiday to Guam!