title: Recurrent jellyfish blooms are a consequence of global oscillations.
abstract: A perceived recent increase in global jellyfish abundance has been portrayed as a symptom of degraded oceans. This perception is based primarily on a few case studies and anecdotal evidence, but a formal analysis of global temporal trends in jellyfish populations has been missing. Here, we analyze all available long-term datasets on changes in jellyfish abundance across multiple coastal stations, using linear and logistic mixed models and effect-size analysis to show that there is no robust evidence for a global increase in jellyfish. Although there has been a small linear increase in jellyfish since the 1970s, this trend was unsubstantiated by effect-size analysis that showed no difference in the proportion of increasing vs. decreasing jellyfish populations over all time periods examined. Rather, the strongest nonrandom trend indicated jellyfish populations undergo larger, worldwide oscillations with an approximate 20-y periodicity, including a rising phase during the 1990s that contributed to the perception of a global increase in jellyfish abundance. Sustained monitoring is required over the next decade to elucidate with statistical confidence whether the weak increasing linear trend in jellyfish after 1970 is an actual shift in the baseline or part of an oscillation. Irrespective of the nature of increase, given the potential damage posed by jellyfish blooms to fisheries, tourism, and other human industries, our findings foretell recurrent phases of rise and fall in jellyfish populations that society should be prepared to face.
authors.affiliation: Dauphin Island Sea Laboratory, Marine Environmental Sciences Consortium, Dauphin Island, AL 36528, USA. rcondon@disl.org
authors.forename: Robert H
authors.initials: RH
authors.lastname: Condon
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Duarte
authors.forename: Kylie A
authors.initials: KA
authors.lastname: Pitt
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Robinson
authors.forename: Cathy H
authors.initials: CH
authors.lastname: Lucas
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Sutherland
authors.forename: Hermes W
authors.initials: HW
authors.lastname: Mianzan
authors.forename: Molly
authors.initials: M
authors.lastname: Bogeberg
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Purcell
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Decker
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Uye
authors.forename: Laurence P
authors.initials: LP
authors.lastname: Madin
authors.forename: Richard D
authors.initials: RD
authors.lastname: Brodeur
authors.forename: Steven H D
authors.initials: SH
authors.lastname: Haddock
authors.forename: Alenka
authors.initials: A
authors.lastname: Malej
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Parry
authors.forename: Elena
authors.initials: E
authors.lastname: Eriksen
authors.forename: Javier
authors.initials: J
authors.lastname: Quiñones
authors.forename: Marcelo
authors.initials: M
authors.lastname: Acha
authors.forename: Michel
authors.initials: M
authors.lastname: Harvey
authors.forename: James M
authors.initials: JM
authors.lastname: Arthur
authors.forename: William M
authors.initials: WM
authors.lastname: Graham
mesh_terms: D000818:Animals; D057231:Climate Change; D003063:Cnidaria / Q000254:growth & development; D037302:Ctenophora / Q000254:growth & development; D016208:Databases, Factual; D055669:Ecological and Environmental Phenomena; D017753:Ecosystem; D006801:Humans; D010507:Periodicity; D011157:Population Dynamics; D037401:Scyphozoa / Q000254:growth & development*; D013997:Time Factors; D014561:Urochordata / Q000254:growth & development; D015048:Zooplankton / Q000254:growth & development