Rise of the Jellyfish

Pink Jellyfish

On the Rise

While several marine organisms are on the decline, jellyfish populations are rapidly growing.  Jellyfish are found in every ocean in the world, and they are an indicator species.  According to Lisa-Ann Gershwin, the author of Stung! On Jellyfish Blooms and the Future of the Ocean, an abundance of jellyfish is a sign that the environment is out of balance.  When jellies flourish in an area, something is seriously wrong and trouble usually follows their arrival.  Recent blooms of jellyfish have been recorded in the Mediterranean, the Gulf of Mexico, the Black and Caspian Seas, the Northeast US coast, and in Far East Coastal waters.  Some in the scientific community remain skeptical of these population changes, but there are areas that are clearly experiencing an increase in jellyfish.  Some areas have also experienced a decrease or fluctuation in population size over decadal periods.     

Swarm of Jellyfish

            Several factors contribute to the increase of jellyfish populations including overfishing, pollution, climate change, and ocean acidification.  All of these factors create the perfect environment the jellies need to thrive.  Jellies are able to flourish in low oxygen environments that would suffocate other marine organisms.  They also have several methods of reproduction, which increases their population size quickly: hermaphroditism, cloning, external fertilization, and self-fertilization.  Their polyps settle in layers on hard surfaces and then detach when conditions are right.  The polyp stage can live indefinitely by cloning.  A polyp colony started in 1935 in a lab in West Virginia is still alive and growing today.  Also, jellies have long lifespans.  They can actually “de-grow.”  They are able to reduce their size while their bodies remain proportionate.  When food is abundant they are able to begin growing again.  

             One factor that is contributing to the boom of jellies is overfishing.  For example, at one time, anchovies were abundant in the Black Sea and off the coast of Africa.  Overfishing of anchovies, which compete with jellies for food, has led to an abundance of food for the jellies which then take over.  

             Another factor in the jellyfish population boom is pollution.  Trash and garbage polluting the ocean kills many jellyfish predators, such as sea turtles.  Man-made objects within the ocean, such as piers and boat hulls, provide perfect nursery sites for jelly polyps.  Another form of pollution affecting jelly populations is nutrient run-off, which leads to eutrophication zones.  These zones are areas that are oxygen depleted and provide a great area for jellies to thrive.

            Climate change, the warming of the oceans, is extending jellyfish ranges.  Warm water also contains less oxygen, which the jellies like.  Also, another impact to consider if ocean acidification.  Because jellies don’t have hard parts, they aren’t affected as much by acidification.

Impact

            Jellyfish consume a huge amount of food and will pretty much eat anything.  They have very efficient metabolisms and can put the energy they ingest toward growth.  One species (a comb jelly), Mnemiopsis, will gorge and continue to kill and collect prey even though it's no longer hungry.  A study showed that this species killed 30% of the copepod population that was available to it each day.    They continue to kill until nothing is left.

                  Jellies can have a large impact on important organisms within an ecosystem and can reduce biodiversity.  Mnemiopsis invaded the Black Sea via seawater ballasts and took over by the 1980’s.  Anchovies and sturgeon began to disappear in this area due to competition with the jellies for food.  The Mnemiopsis jellies made up 95% of the Black Sea’s biomass. 

Hope?

            A possible solution to the abundance of jellyfish: eat them.  Jellyfish have been part of the human diet for a long time in China.  In recent years the global jellyfish harvest has risen to 321,000 tons, and the harvested jellies are mainly consumed in China and Japan. 

            So much damage has occurred within the oceans that we aren’t sure what the future holds for them.  As said by author Lisa-Ann Gershwin, we must “adapt.”

Giant Nomura's Jellyfish

Resources

Jellyfish: On the Rise or Not?

Rise of jellyfish reveals sickness of world's oceans.

They're taking over!

Evaluation of the Effects of Various Chemicals on Discharge of and Pain Caused by Jellyfish Nematocysts

Portuguese Man-of-War (Physalia physalis).

http://images.nationalgeographic.com/wpf/media-live/photos/000/006/cache/man-of-war_620_600x450.jpg

This study evaluated the effect of well-known remedies on the discharge of nematocysts in three species of Cnidarians: the sea nettle (Chrysaora quinquecirrha), sea wasp (Chiropsalmus quadrumanus) and the Portuguese man-of-war (Physalia physalis).  The remedies tested include acetic acid, ammonia, meat tenderizer, baking soda, and urea.  These remedies were evaluated to determine whether they stimulated or inhibited nematocyst discharge and if they brought relief to testers who were exposed to jellyfish tentacles.  It was found that many of the remedies did not relieve the pain and it actually stimulated nematocyst discharge.  However, immediate relief was experienced with lidocaine, a common anesthetic.  Exposure of the tentacle to lidocaine prevented nematocyst discharge when preceding exposure to acetic acid, ethanol, ammonia or bromelain.  Based on these observations, it is possible that lidocaine blocks the sodium and/or calcium channels of the nematocysts, preventing discharge.  The nematocysts of organisms in Phylum Cnidaria are hollow tubules in a saline solution containing neurotoxins.  Typical symptoms of jellyfish stings include pain, localized areas of swelling, redness and bleeding.  Used for defense, both mechanical and chemical stimuli cause nematocysts to be discharged.  With an increase in the number of envenomations in coastal beaches around the world, this study aimed to answer the question if traditionally used methods have effect on nematocyst discharge or if they dampened the pain associated with being stung.

Specimens were collected in coastal waters and tentacles were clipped and transferred to seawater.  These tentacle pieces were added to wells containing 1mL of seawater and examined under a light microscope.  To determine whether the chemical remedies had an effect on the nematocysts, 100µL of each chemical was added and observations were noted.  In a separate experiment, lidocaine was first added to the wells and then after one minute, each chemical was added in separate well plates.  A camera was attached to the light microscope to capture nematocyst discharging, and discharged nematocysts were counted.

During the human skin exposures, sea nettle and sea wasp tentacles were used.  Two of the authors exposed their inner arm to the tentacles over a period of 20 days with only one treatment per day.  Observations of skin redness before and after the addition of chemicals were made by outside observers.  Notes were taken of the stinging sensation as well. 

It was determined that chemicals traditionally used to treat jellyfish stings were found to stimulate nematocyst discharge and provided little or no relief from the pain and stinging sensation.  Lidocaine appears to provide relief by acting as an anesthetic and by preventing further nematocyst discharge.  Although blocking the pain, it did not prevent redness on the skin.  Also, when first applying lidocaine, then acetic acid or ammonia, the nematocyst discharge was prevented.  Overall, the best treatment option for jellyfish stings appear to be with the anesthetic lidocaine, as it blocks sodium ion channels in nerves that sense pain.            

Reference:

Birsa, L. M., Verity, P. G., & Lee, R. F. (2010). Evaluation of the effects of various chemicals on discharge of and pain caused by jellyfish nematocysts. Comparative Biochemistry and Physiology:Toxicology and Pharmacology, 151, 426-430.

 

 

 

Massive Jellyfish Swarms

Many Fisheries and tourist destinations are becoming cluttered with these Cnidarians. Areas that have been hit hard by these swarms include Hawaii, the Gulf of Mexico, the east coast of the U.S., the Bering Sea, the Mediterranean Sea, Australia, the Black Sea, the Sea of Japan, the North Sea, and Namibia.

Some of these swarms cover hundreds of square miles. Many water enthusiasts have been injured and a few have died. These swarms have also wreaked havoc on fisheries, fish farms, marine mines, desalination plants, ships, and nuclear power plants. It is estimated that jellyfish swarms have cost fishing and tourism industries hundreds of millions of dollars since the 1980s.

Some swarms consists of jellyfish the size of refrigerators such as the ones found in the Sea of Japan and other swarms off the coasts of Australia consists of jellyfish the size of peanuts. The cause of these swarms is unknown but it is hypothesized that they are human caused. Pollution, climate change, introductions of non-native organisms, overfishing, and the presence of artificial structures, such as oil and gas rigs have all been put to blame. Whether or not it was one of these or a combination has yet to be determined.

The article can be found at http://www.macroevolution.net/jellyfish-swarms.html