Jellyfish Experts Show Increased Blooms Are a Consequence
of Periodic Global Oscillations
Dec 31, 2012
(Dauphin Island, Alabama) – Blooms, or proliferations, of jellyfish can show a
substantial, visible impact on coastal populations – clogged nets for fishermen, stinging waters
for tourists, even choked cooling intake pipes for power plants. Recent media reports have
created a perception that the world's oceans are experiencing trending increases in jellyfish,
but a new international study suggests that there is no robust evidence for proof of a global
increase in jellyfish over the past two centuries.
The results of the study, led by Dr. Rob Condon, marine scientist at the Dauphin Island
Sea Lab (DISL) in Alabama, appear in the latest issue of Proceedings of the National Academy of
Science (PNAS manuscript # 2012-10920R). His co-authors are comprised of experts from the
Global Jellyfish Group, a consortium of approximately 30 researchers of gelatinous organisms,
climatology, oceanography, time-series analyses and socioeconomics from around the globe,
and include lead co-authors Dr. Carlos Duarte of the University of Western Australia’s Oceans
Institute and the Instituto Mediterráneo de Estudios Avanzados (IMEDEA) in Spain, Dr. Kylie Pitt
of Griffith University in Australia and Dr. Cathy Lucas of the University of Southampton in the
The Global Jellyfish Group conducted their work at the National Center for Ecological
Analysis and Synthesis (NCEAS), a cross-discipline ecological and data synthesis research center
affiliated with the University of California, Santa Barbara.
The key finding of the study shows global jellyfish populations undergo concurrent
oscillations with successive decadal periods of rise and fall, including a rising phase in the 1990s
and early 2000s that has contributed to the current perception of a global increase in jellyfish
abundance. The previous period of high jellyfish numbers during the 1970s went unnoticed
due to limited research on jellyfish at the time, less awareness of global-scale problems and a
lower capacity for information sharing (e.g., no internet).
While there has been no increase over the long-term, the authors detected a hint of a
slight increase in jellyfish since 1970, although this trend was countered by the observation that
there was no difference in the proportion of increasing vs. decreasing jellyfish populations over time. “Sustained monitoring is now required over the next decade to shed light with statistical
confidence whether the weak increasing linear trend in jellyfish populations after 1970 is an
actual shift in the baseline or part of a larger oscillation,” Condon said.
To date, media and scientific opinion for the current perception of a global increase in
jellyfish was evidenced by a few local and regional case studies. “Clearly, there are areas where
jellyfish have increased; the situation with the Giant Jellyfish in Japan and parts of the
Mediterranean are classic examples,” says Condon. “But there are also areas where jellyfish
numbers have remained stable, fluctuated over decadal periods, or actually decreased over
The group says that it is important to sample over appropriate spatial and time scales so
that trends are not misinterpreted and the correct message is communicated.
Increased speculation and discrepancies about current and future jellyfish blooms by
the media and in climate and science reports formed the motivation for the study. “There are
major consequences for getting the answer correct for tourism, fisheries and management
decisions as they relate to climate change and changing ocean environments,” Duarte said.
“The important aspect about our work is that we have provided the long-term baseline backed
with all data available to science, which will enable scientists to build on and eventually repeat
these analyses in a decade or two from now to determine whether there has been a real
increase in jellyfish.”
Condon added: “The realization that jellyfish synchronously rise and fall around the
world should now lead researchers to search for the long-term natural and climate drivers of
jellyfish populations, in addition to begin monitoring jellyfish in open ocean and Southern
Hemisphere regions that are underrepresented in our analyses”.
“The more we know, the better we can manage oceanic ecosystems or respond
accurately to future effects of climate change,” Duarte said.
Given the potential damage posed by jellyfish blooms to fisheries, tourism and other
human industries, the findings of the group foretell recurrent phases of rise and fall in jellyfish
populations that society should be prepared to face.
PNAS Article #2012-10920R: “Recurrent Jellyfish Blooms are a Consequence of Global
Oscillations" by Robert Condon et al.
Media enquiries should be directed to the contacts listed below. For media- or embargo-related
questions, please contact the PNAS News Office.
Dauphin Island Sea Lab
Dr. Rob Condon, Senior Marine Scientist, Dauphin Island Sea Lab, Alabama; tel: 251-654-3464;
University of Western Australia
Dr. Sally-Ann Jones, Media Liaison Public Affairs, The University of Western Australia, Australia;
tel: +61 8 6488 7975 or 0488 631 286; e-mail: email@example.com
National Center for Ecological Analysis and Synthesis, UCSB
Dr. George Foulsham, News Director, Office of Public Affairs & Communication, UC Santa
Barbara, CA; tel: 805-893-3071, email: firstname.lastname@example.org
Griffith University, Australia
Ms. Helen Wright, Senior Communications Officer, Griffith University, Australia; tel: +61 7 3735
4288; e-mail: Helen.email@example.com
University of Southampton, UK
Mr. Glenn Harris, Media Relations Officer, Communications, University of Southampton, UK; tel:
+44 (0)23 8059 3212; e-mail: G.Harris@soton.ac.uk