The Great Jellyfish Invasion Pollution, Overfishing and Dead Zones Have Created Prime Conditions for Jellyfish

jellyfishJellyfish, a prominent feature of ancient oceans, have weathered multiple mass extinctions and date back at least 500 million years. Their populations were kept in check by fish, which eat small jellyfish and compete for jellyfish food such as zooplankton. But in recent years, jellyfish have made a major comeback, one that threatens to upset the balance of the oceans.Research suggests that the gelatinous creatures may be benefiting from the very things responsible for the oceans’ decline: namely, pollution, overfishing (particularly of predator fish) and rising carbon dioxide (CO2) emissions. As CO2 increases in the atmosphere it dissolves into the ocean as carbonic acid, triggering acidity levels in the ocean to rise. A 2010 report by the United Nations Environment Programme (UNEP) linked ocean acidification, which affects fish, but not jellyfish, to “increased jellyfish numbers and changes in fish abundance.

Another catalyst may be the increasing spans of ocean falling victim to eutrophication caused by agricultural fertilizer runoff and sewage from increased coastal development. Eutrophication generates low-oxygen “dead zones,” notably the 6,765 square miles reported in the Gulf of Mexico last year, which are uninhabitable for fish and other marine life. Jellyfish, on the other hand, have modest oxygen requirements that allow them to thrive in these predator-free, algae-choked expanses. Thicker masses of floating jellyfish will consume large volumes of fish eggs and larvae, preventing fish populations from rebounding. Once jellyfish take over a stressed ecosystem, they may continue to dominate it indefinitely, sending it into what Lucas Brotz of the University of British Columbia Fisheries Center refers to as a “jellyfish spiral.”

“The continued intensification of seasonal hypoxia in the Gulf of Mexico may forecast further increases in jellyfish abundance and distribution,” Brotz wrote in one 2000 reportJellyfish invasions have been incurring costs for industries far and wide, including fisheries in the Mediterranean, the Sea of Japan, the Black Sea and the Gulf of Mexico. This is in part because fishing nets become clogged or ruined from entangled jellyfish tentacles, driving up costs for labor or gear replacement and reducing catch numbers needed to meet quotas.

jellyfish © Thinkstock

Vacationers are also finding their fun in the sun clouded by the ever-growing presence of jellyfish swarms. In the popular tourist spot of Cocoa Beach, Florida, exhausted lifeguards treated nearly 2,000 beachgoers for jellyfish stings in one week this past summer. Benadryl cream, which is used to neutralize stings, along with vinegar, was sold out in local convenience stores and pharmacies

“It was by far the most jellyfish we have ever seen; you couldn’t even walk down the beach without being stung,” Jeff Scabarozi, ocean lifeguard chief in Brevard County, Florida, told The New York Times. “People came out screaming and hollering that they had been stung. We haven’t seen these jellyfish ever. We had to Google it.”

jellyfish © ThinkstockAnd power plants in Scotland, Japan and Israel were shut down last year as blankets of jellyfish flooded their cooling systems and blocked their filters, leaving surrounding communities without power. Numerous aquaculture farm pens have also suffered raids as extra fish feed and fish waste produce the eutrophic conditions so enticing to jellyfish. In 2007, Northern Ireland’s only salmon farm was wiped out by mauve stinger jellyfish, which are normally found in Mediterranean waters, leaving more than 100,000 fish dead and $1.5 million in losses.A group of researchers including Brotz, William “Monty” Graham of the University of South Alabama, Mary Beth Decker of Yale University, Steven Haddock of the Monterey Bay Aquarium’s Research Institute and others are currently collaborating at the University of California’s National Center for Ecological Analysis and Synthesis ( for the project “Global Expansion of Jellyfish Blooms: Magnitude, Causes and Consequences.”Citing the need for a “composite understanding of the extent of the problem” the group formed to achieve four main objectives over the next two years: to examine the global expansion of jellyfish blooms and explore possible drivers for this expansion; to examine the effects of jellyfish blooms on the ecosystem, addressing in particular carbon cycling and food webs; to identify current and future consequences of jellyfish blooms for tourism, industry and fisheries; and to notify the public at large of the project results. The last scheduled week-long set of meetings will be held in February.

“I would suggest that the primary goal of the group has already been accomplished,” Brotz says, referring to collaboration between jellyfish re-searchers. “While there have been numerous recent advances in our understanding of jellyfish, we still know relatively little about these enigmatic creatures, and it is high time that research and knowledge catches up with their apparent population explosions.”

Animal Rights National Conference 2018