Thousands of Jellyfish are pulled together by ocean currents into huge groups known as "blooms". The formation of blooms differs in each season and it is a complicated process which depends on factors such as the availability of nutrients, sufficient concentrations of oxygen, temperature, sunshine and the presence of prey. Apart from ocean currents congregating the jellyfish together, blooms can also be a result of a particularly high population of jellyfish occurring in the year. Many jellyfish are usually part of large blooms that can have as many as 100,000 jellyfish. Jellyfish blooms have increased tremendously over the years. 

Data collected on changing jellyfish populations around the world are low in number. Scientists are unable access quantitative data on present populations as well as on jellyfish populations in previous years. Scientists currently deliberate on the increasing jellyfish numbers without any previous data to base their research on. 

A study by the University of Washington suggests that the increasing numbers in blooms can be caused by the effect humans have on marine life. In certain locations, jellyfish have replaced the ecological role of many creatures that have been reducing in numbers due to extensive fishing in the area. Since jellyfish and fish feed on similar prey, jellyfish are likely to replace the fish if they are removed. The University states that they lack the necessary data to fully prove this hypothesis. Other human activities known to be possible causes of the largely increasing jellyfish blooms include pollution, climate change due to increased global warming as well as the presence of gas and oil rigs in the ocean. 

Certain populations of jellyfish that have increased over the last few years have been species that have traveled from other parts of the world to a different region. For example, the Caspian Sea, the Black Sea, the Baltic Sea and the coasts of Egypt, Israel and the Gulf of Mexico all consist of newly arrived foreign jellyfish. The blooms of these species increase dramatically due to the absence of predators to feed on them and suppress their growth. These blooms are not due to environmental problems and the impact of humans. 

Jellyfish blooms are likely to increase in size because of eutrophication, high concentrations of nutrients entering the water such as by agricultural means. Such an environment with a high saturation of nutrients offers extra nourishment to organisms which the jellyfish feed on. Eutrpphication results in the decrease of oxygen levels in the water and this too enables jellyfish to thrive as they favor this environment. 

Researchers discovered that jellyfish located on the coast of Namibia have a higher biomass than the fish in the area. This research was a quantitative analysis of the area after huge numbers of jellyfish emerged in the region after years of over fishing. 

Massive jellyfish blooms are dangerous because they have caused severe injuries to humans who dive in the ocean. Some of these injuries have had fatal results. They have also damaged fish farms, marine mines, plants, fisheries and ships. It has been suggested by many scientists and researchers that these jellyfish swarms have been responsible for millions of dollars worth of damage to many fishing and tourism industries around the world. 
Normen FAdel
Author of the article
writer and blogger, founder of jellyfish .

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