Jellyfish are among the oldest creatures on earth and one of the most venomous marine animals for humans.
Jellyfish have specialized stinging cells with which they inject their prey with poison within microseconds.
Some Jelly fish like the sea wasp (box jellyfish, which occurs in Australia), have up to 60 tentacles of
several meters in length armed with hundreds of thousands of stinging cells. 98% of the body of a Jellyfish
is water. They swim using a form of jet propulsion reaching a speed of 10km/h. Jelly fish has very advance
surviving skills that may compete with human evolution. In the article “ Jellyfish are taking over the seas,
and it might be too late to stop them,” Gwynn Guilford on explains how and why Jellyfish overgrowing
population is consequence of our misuse of our natural environment. The Jelly fish few predators such
sea turtles, salmon, mackerel and albatross are increasingly scarce. As Jellyfish compete with smaller fish
for the same food, and also eat those fishes’ eggs, they can collapse entire fish populations. Jelly fish, can
put away 10 times its body weight in food in a single day, even though it needs to eat only 16% of its body
weight to grow.
Not only Jelly fish may have gamed evolution but also Humans are helping them to reproduce. Jelly fish
are world-class proliferators reproducing by creating little bundles of clones (Polyps) that attach to hard
surfaces waiting for their opportunity to be released as small jellyfish. While they’re waiting, polyps clone
themselves, creating more bundles of future baby jellyfish. One reason jellyfish blooms are so disastrous
and is almost impossible to get rid of is the capability of exponential reproduction by some species, as well
as cells release through post-mortem decomposition, which somehow find each other again to form a whole
new polyp (as in Benjamin Button jellyfish). A few centuries ago, the hard surfaces available for polyps to
cling included mainly seabed rocks and oyster shells; those polyps that couldn’t find such surfaces couldn’t
clone. The proliferation of modern human structures provides surfaces to which polyps can cling to as
their new oyster shell. Piers, drilling platforms, plastic cigarette packets, offshore wind turbines, and boats
enable Jellyfish ability to bloom in such incredibly rapid fashion and shocking numbers.
The intricate lattice of ocean life has kept jellyfish in check. In written human history, jellyfish blooms
have never before infested the seas until now. Thanks to overfishing, pollution and other factors jellyfish
populations are exploding into superabundances and exploiting these changes in ways that we could never
have imagined. Overfishing of, say, salmon removes one of the jellyfish’s few predators. Jellyfish also
wreak havoc on the food chain when they’re introduced to new ecosystems, usually via ballast water that
shipping tankers take on and release as a counterbalance to cargo. Other contributors to the jellyfish
boom are the “dead zones” created by what scientists call “eutrophication.” That’s when farming pesticides
and sewage pumped into rivers meet the ocean. This affects phytoplankton, the tiny aquatic plants that
are the dinner buffet for vast numbers of sea creatures. Normally phytoplankton live on nutrients from
chemicals the seabed releases. But their populations explode when doped up on nitrogen and phosphorous,
forming algal blooms like the one in Qingdao, China, each summer. The whole food chain starts chowing
down, creating more excrement and more dead creatures. Those float to the bottom, stripping the water of
oxygen. Since most creatures can’t survive in areas with little oxygen, their numbers fall. As jellyfish need
very little oxygen to survive their colonies expand. The best example comes from China, where pollution
from the Yangtze River in western China has formed huge dead zones in the East China and Yellow Seas
(paywall). Scientists think dead zones are behind the surge in Nomura jellyfish in Japan.