write an effective conclusion to an essay about jellyfish after reading this article
Introduction
When distributed in reasonable numbers, native jellyfish play important ecological roles. But when jellyfish populations run wild, they may jam hundreds and perhaps even thousands of square miles with their pulsating, gelatinous bodies. In recent years, massive blooms of stinging jellyfish and jellyfish-like creatures have overrun some of the world's most important fisheries and tourist destinations—even transforming large swaths of them into veritable jellytoriums. The result: injuries (sometimes serious) to water enthusiasts and even occasional deaths. Jellyfish swarms have also damaged fisheries, fish farms, seabed mining operations, desalination plants and large ships. And proving that jellyfish can be political animals, knots of jellyfish have done the work of anti-nuclear activists: they have disabled nuclear power plants by clogging intake pipes. In short, since the 1980s, worldwide jellyfish blooms have caused hundreds of millions—or perhaps even billions—of dollars in losses. Worldwide reports of massive jellyfish blooms are triggering speculation that jellyfish swarms are increasing because of human activities. But are they? This report—which is guaranteed to make your skin crawl—explains the basics of jellyfish biology and what scientists have thus far discovered about the causes and future of jellyfish blooms.
Swarms
Why Swarms Form
A swarm is a dense, rapidly formed cluster of animals. Jellyfish swarms are a naturally occurring, world-wide phenomenon. Scientists believe that jellyfish swarms—even huge ones—have occurred for millions of years and would continue to occur in some locations even without environmental damage from people. For example, scientists have observed dense summer swarms of sea salps—a three-inch long, tube-shaped gelatinous creature—covering up to 38,600 square miles in the North Atlantic. Such swarms are believed to be natural occurrences that are not influenced by human activities. Scientists believe that gelatinous creatures swarm when ecological conditions align to favor their survival. These conditions include the concentration of predators and competitors, food availability, and currents as well as the temperature, salinity, and oxygen content of the water.
Damage from Large Swarms
Natural and unnatural swarms cause various types of problems by:
Discouraging tourism: Summer blooms of stinging jellyfish keep bathers out of the water in prime tourist destinations from Maryland to the Mediterranean. Various species of box jellyfish, which are among the world's most toxic creatures, regularly swarm in tropical waters around the world, including Hawaii and Australia.
Damaging fishing operations: Jellyfish have interfered with fishing operations in world-class fisheries, including the Gulf of Mexico, the Black Sea and the Bering Sea by:
busting fishing nets;
poisoning and crushing captured fish;
consuming fish eggs and young fish; and
clogging the engines of fishing boats.
Crippling industrial operations: Jellyfish have recently disrupted the operations of marine diamond mining facilities in Namibia, desalination plants in Iran and various large ships around the world by clogging intake pipes carrying sea water.
Jellyfish swarms have also forced a number of nuclear power plants around the world to interrupt output or temporarily shut down. In fact, enough jellyfish to fill 50 trucks clogged the intake pipes of a power plant in the Philippines in 1999, and thereby plunged 40 million people into darkness and started rumors of a coup d'état. (Such freak events prove that jellyfish can be political animals.)
Black Sea
EUROPE'S MOST POLLUTED OCEAN BECOMES THE WORLD'S JELLYFISH CAPITAL If the world had an official jellyfish capital, it would surely be the Black Sea—a huge inland sea located between Europe and Asia. Why? Because the Black Sea was transformed into a veritable jellytorium during the 1990s by an invasion of Mnemiopsis, a voracious, rapidly reproducing species of comb jelly. At its most jellified state during the late 1990s, the Black Sea harbored more than one billion tons of Mnemiopsis—which equals more than 10 times the weight of all fish caught throughout the world annually. In some parts of the Black Sea, each cubic meter of water— a space comparable to the interior of a large garbage bag—teemed with thousands of the golf ball-sized jellies. The domination of Mnemiopsis over the Black Sea started in 1982—probably when a U.S. ship jettisoned into this sea ballast water from the U.S., along with some hitchhiking Mnemiopsis. This comb jelly is a hardy ecological squatter that is rapidly spreading along the east coast of the U.S. but had previously never visited the Black Sea.
Nevertheless, the Black Sea, Europe's most polluted ocean, provided a particularly hospitable environment to the Mnemiopsis newcomer. Why? Because the Black Sea has no natural predators of Mnemiopsis and because its overfished waters offered Mnemiopsis only minimal competition from fish. Feasting on copious quantities of plankton and able to shed 8,000 eggs daily, Mnemiopsis reproduced with wild abandon.
Swarming from coast to coast, Mnemiopsis crowded out almost all fish in the Black Sea. The result: losses of hundreds of millions of dollars to the area's fishing and tourism industries. The tide only turned on Mnemiopsis in 1997, when another invading species of comb jelly, called Beroe, arrived in the Black Sea, probably also via ballast water from the U.S. Because Beroe eats Mnemiopsis, it has helped tame the Black Sea's Mnemiopsis monster.
Moreover, because Beroe eats nothing but Mnemiopsis and disappears as Mnemiopsis disappears, it has improved its adopted habitat without causing ecological problems—a rarity for an introduced species.
Nevertheless, Mnemiopsis remains a serious problem. Why? Because even though Mnemiopsis is controlled in the Black Sea through Beroe-assisted jellycide, it still greatly impacts area ecology. Additionally, Mnemiopsis has fanned out from the Black Sea via canals and ships to the Caspian, Azov and Mediterranean Seas. Also, additional waves of U.S.-based Mnemiopsis have recently invaded the North Sea and the Baltic Sea.
Just as it did in the Black Sea, Mnemiopsis has significantly reduced fish catches in many of these other huge seas. Indeed, Mnemiopsis has caused even more damage to fisheries in the Caspian Sea than it did in the Black Sea.
Some European nations have considered intentionally introducing Beroe into their Mnemiopsis-infested waters. But so far, they have refrained from doing so for fear of unintended ecological consequences from such introductions. Moreover, it is uncertain whether Mnemiopsis-infested waters besides the Black Sea meet Beroe's requirements for salinity, temperature and other environmental conditions.