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3. Episodic events quickly to environmental changes by increasing feeding,

growth and reproduction under optimal conditions
(Richardson et al., 2009; Boero, 2013). Beyond their
seasonal changes, some sporadic bloom events may
Since the mid-1970s, large-scale episodic events such
as disease epidemics, mass mortalities and biological also be associated with increased temperatures. High
population blooms have been occurring in marine en- abundances of gelatinous species in the mediterranean
vironments with increasing frequency, intensity, variety Sea have been associated with variations in water
and range (Harvel et al., 1999; Hayes, 2001). There is mass and high salinity as well as warm temperatures.
some evidence that climatic anomalies are the underly- Changes in the flow of rivers due to dams and other
ing (direct or indirect) cause of many of these events constructions can change the salinity of coastal waters,
attracting jellyfish to coastal areas. Moreover, the
(Harvel et al., 1999, 2002). Episodic weather events release of predation pressure on jellyfish, following the
such as storms change freshwater flows and the export reduction in the populations of their main predators due
of nutrients to coastal waters, and also affect the salinity to fishing, is also likely to be playing a significant role in
of coastal ecosystems. Temperature anomalies, even of the more frequent occurrence of jellyfish blooms.
short duration, can also trigger population explosions Blooms in the Mediterranean usually involve the jellyfish
of species such as jellyfish, toxic blooms of phytoplank-
ton, blooms of harmful benthic algae, mucilaginous Pelagia noctiluca, Cotylorhiza tuberculata, Rhizostoma
pulmo, Rhopilema nomadica (a non-native species) and
blooms, and pathogens causing mass mortalities of the common jellyfish Aurelia aurita, as well as cteno-
marine organisms and/or serious harm to tourism and
coastal industries. phore species such as Mnemiopsis leidyi and Beroe
ovata.
INDICATOR PROPOSED MONITORING PROCEDURE
In order to track these types of episodic events, sev-
Presence of species blooms eral monitoring approaches involving public partici-
pation have been developed in certain countries and
at Mediterranean level. The CIESM JellyWatch Pro-
Jellyfish blooms gramme is one of these. It was set up to gather time
3
baseline data on the frequency, extent and persistence
Climate change may be contributing to the increasing of jellyfish outbreaks across the Mediterranean Sea.
frequency and intensity of jellyfish blooms around the
world. Jellyfish are opportunistic organisms, responding 3. http://www.ciesm.org/marine/programs/jellywatch.htm

Blooms of jellyfish like Pelagia noctiluca are
becoming more common in the Mediterranean. Photo: C. Suárez, OCEANA

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