Effects of Invasive Nature of the Phyllorhiza Punctata Jellyfish
Technical Briefing for NR 1114
Leah Worley
Introduction
The Phyllorhiza Punctata is a type of medusae jellyfish that can be identified by a bluish
exumbrella body and characterized by numerous white spots. This characteristic led to the
common name for the species, the white spotted jelly. The jellies use long oral arm clubs with
blue and white tips for feeding. (Larson 1990). In general, gelatinous species are known to be
extremely adaptive and have the ability to take up new habitats and increase their ranges in
existing ones (Verity 2011). In 2010, an estimated 10 million Phyllorhiza Punctata jellyfish
appeared in waters of the Gulf of Mexico (Bolton 2004). This non-native species had never
before been observed in the western tropics, as it originates in Australia and is found in other
tropical Pacific and Indo Pacific waters (Larson 1990). Over the past century, populations of the
jellyfish have expanded to include tropical and subtropical waters of all three major oceans
(Verity 2011). Outbreaks have also documented in the Mediterranean Sea (Boero 2009), in both
the western and central regions, but it is unknown how exactly these tropical jellyfish invaded
(Abed-Navandi 2007).
This seemingly global spread of the Phyllorhiza Punctata is of great interest to marine
scientists and attempts at tracking this translocation are being made. The question at hand is how
exactly these jellies have migrated so far from their native homes and what affects they produce
on the ecosystems and industries of their new habitats. Recorded booms of the Phyllorhiza
Punctata have generally disrupted ecosystems, altered food web structure, created competition
between species, and cost millions in damage to fishing industries (Verity 2011). I will be
investigating the invasive nature of the Phyllorhiza punctata jellyfish and its effects on native
ecosystems and fishing industry and evaluating the proposed solution of legal inspection of the
hulls of ships, as well as several other potential solutions.
Figure 1: Conceptual Model of Invasive Nature of the Phyllorhiza Punctata Jellyfish
Issues
The spread of Phyllorhiza punctata to non-native waters has had detrimental effects on
established aquatic ecosystems and the fishing industry. To begin with, the species ingests
massive quantities of zooplankton on a daily basis. Zooplankton clearances rates increase
linerally with medusa bell diameter within range of prey concentrations (Garcia 1993). Ingestion
rates vary as a function of zooplankton prey density and size specific abundance of jellyfish
populations (Garcia 1993). They also consume eggs and larvae of commercially important
species such as shrimp menhaden, anchovies, crabs and oysters. (Perry 2001). Phyllorhiza
punctata utilize two principles capture surfaces, one being their oral arm cylinder and the other
being the underside of the subumbrella surface (D’Ambra 2001). Prey is ingested by small
polyp-like mouthlets located at these surfaces. The jellyfish are usually surrounded by high
channel flows whilst swimming, so their body morphology is constructed to channel flows to the
capture surfaces (D’Ambra 2001). Swimming activity creates these flows, so the feeding process
for Phyllorhiza punctata is continuous. Because the jellies consume so much of the available
zooplankton, other fish and larvae have to compete for food. This leads to overall decline in
populations of fish and shellfish, which affects organisms higher up in the food chain that prey
on these species. In Europe, similar invasions have been observed and the final result was the
complete removal of a species from the food chain.
The spread of Phyllorhiza punctata has also been extremely harmful to commercial
fishing industries. As I mentioned before, the jellyfish ingest the eggs and larvae of
commercially important species. The jellies also get stuck in fishnets and clog them, sometimes
breaking the equipment in the process. This decreases boat intakes of targeted fish species and
profit for the fishermen. A predicted 10 million was lost in the shrimping industry following the
boom of jellyfish in the Gulf of Mexico in 2010 (Bolton 2004). High concentrations of the
species force fishermen to cease trawling activities and move to other areas (Perry 2001). Certain
productive areas may close to fishing activities if the population of the Phyllorhiza punctata get
out of hand. The fisherman have no choice but to attempt to find new areas in which they can
capture large quantities of their desired fish without disruption from the jellyfish. As can be seen,
the spread of Phyllorhiza punctata to non-native waters has negative effects on aquatic
ecosystems and their related fishing industries.
There are several key reasons as to why this problem exists. The first of these reasons is
the existence of oceanic currents. The appearance of the jelly in the Gulf Waters may have been
a result of transport on the Gulf Stream current in Eastern Florida or the Loop current in the Gulf
of Mexico, which joins with the Gulf Stream (Verity 2011). The Loop current flows clockwise
around the Gulf of Mexico and joins the Florida current to form the Gulf Stream east of Florida.
The Gulf Stream regularly enters shelf waters while spring and summer winds carry out
northward transport of costal water (Verity 2011). Currents are conducive to the transport of
water and water bound organisms and can carry both long distances. Warm temperatures and
high levels of salinity can also contribute to increased numbers of the jelly have been shown to
directly increase asexual reproduction (Verity 2011). This is why populations of Phyllorhiza
punctate have been seen to flourish in the spring and summer time. In terms of solutions, little
can be done to cease the transport of jellies in oceanic currents. The currents are naturally
occurring and the jellyfish will continue to be swept up and transported to non-native territory if
they happen to interact with the current. For these reasons, the existence of oceanic currents
contributes to the invasive spread of the Phyllorhiza punctata jellyfish.
Another reason for the invasive spread of the Phyllorhiza punctata jellyfish is the
transportation of the polyp stages of the species on the hulls of boats. The polyp stage of jellyfish
is small stalk with upward facing tentacles attached to a mouth (Bolton 2004). This stage can
survive for years by constantly feeding. The next stage is a free swimming adult called an
ephyrae, followed by the mature medusa stage (Abed-Navandi 2006). Often, polyp stages are
sessile and can attach to the undersides of ships and other vessels. The polyp stage can be
transported globally via ships, barges and offshore drilling platforms (Bayha 2009). This stage is
extremely small in size, making it crytic and hard to study. Bayha and his colleagues developed a
method of testing using a Polymerase Chain Reaction (PCR) assay which utilized Taqman
probes that run polyp DNA extracted from boat hulls, dock pilings, oil rigs and settling plates
(Bayha 2009). The DNA anneals during the PCR reaction and fluorescence is emitted at the
same level as template copy number of the DNA if the target species is present (Bayha 2009).
The probes were successful in identifying the polyps of target species, reacting to as few as 50
copies of template DNA. This discovery and supporting qualitative data could lead to the
screening of incoming ships to the Gulf of Mexico and the continued study of the first two life
stages of the Phyllorhiza punctata. It may also lead to the better overall understanding of
population distribution and boom dynamics of the species. The inspection of ships, especially
those that travel through international waters, is what I consider to be the best solution available
to the invasive spread of jellyfish. As of right now, there is no legislation that requires ships to be
inspected for polyp stages, even though it would greatly decrease the amount of jellyfish in nonnative territory. I believe it is crucial that such legislation is proposed and passed. This may
require more public attention to be drawn to the issue and funding to be gathered. An
organization devoted solely to passing such as bill should be formed and should attempt to put
such a bill through Congress. The amount of community effort, awareness and funding necessary
to this happening serve as downsides to the solution proposed.
The “Hub and Spoke” Model for biological invader translocation can be applied to the
spread of Phyllorhiza punctata through the polyp stages. New invasions occur along dispersal
corridors for established hub populations to spoke populations (Bolton 2004). These invasions
are induced when interrelated factors facilitate invasion success (Bolton 2004). Examples of
these factors include changes in the donor regions, new donor regions, changes in recipient
regions, and invasion windows. This model can be used to explain how the Phyllorhiza punctata
population has spread and how we can continue to track their movement. To summarize, a major
reason for the invasive spread of the jellies is the transportation of the polyp stages of the species
on the hulls of boats, which can be explained using the “Hub and Spoke” Model.
The final and most significant reason for the continued invasive spread of the Phyllorhiza
punctata is that we do not know enough about the species to effectively prevent it from
occurring. Cnidarians, which is the phylum classification of Phyllorhiza punctata, are a poorly
studied taxonomic group and it is difficult to conclude whether the species is invasive or cryptic
(Haddad 2006). While cnidarians have a history of invading tropical or subtropical
environments, there is little direct evidence of translocation routes, source population and
translocation mechanisms (Bolton 2004). There are a modest number of invasive jellyfish
species documented while the actual rate of invasion remains much higher due to the cryptic
nature of the species (Bayha 2009). Also, most bio invasion studies tend to focus on the mature
medusa stage of jellyfish instead of the polyp stage, despite its clear role in invasive spread
(Bayha 2009). The solution I propose is the continued study of the species via reports, field tests
and observation to estimate populations and generate new ideas for preventative methods. Such
studies should focus on the polyp stages of the jelly rather than the medusa stage. A consequence
to this may be that such tests and studies are costly. Several methods have already been
discovered to effectively study these populations. Because populations cannot be observed from
satellites, diving expeditions and submersibles are preferred methods of direct observations
(Boero 2009). However, these require intense observation efforts that make large scale
evaluations difficult. Jellyfish can be observed from boats and docks that regularly record
appearance data. Another method is the citizen science initiative, which was launched by the
Mediterranean Commission to study Phyllorhiza punctata populations off on the coast of Italy.
(Boero 2009). There was widespread distribution of posters with images of the invasive jellyfish
species and media coverage for the event. Tourists, beach authorities and Coast Guards provided
hundreds of records of invasive jellies, often with pictures, that were assembled in a database.
(Boero 2009). With these methods, it is essential that were continue to study and propose
preventative solutions towards the invasive spread of the Phyllorhiza punctate jellyfish
Conclusion
In this briefing, I summarized invasive nature of the Phyllorhiza punctata jellyfish and its
effects on native ecosystems and fishing industry and evaluated the proposed solution of legal
inspection of the hulls of ships, as well as several other potential solutions. The Phyllorhiza
punctata, native to Pacific and Indo- Pacific waters, has increasingly appeared in western tropic
waters and has been sighted in all three major oceans. There are three key reasons for the
continuation of this problem. The first of these is the existence of currents that allow the jellies to
be transported from one area to another. The Loop and Gulf Stream currents are the main
perpetrators in this respect and little can be done to stop the natural migration of waters, along
with organisms within these waters. The second reason is the transport of the polyp stages of the
jellyfish on the hulls of ships. Legislation could be passed that requires inspection of such ships
and could serve as a central solution to invasive spread. The last reason for this problem is the
fact that little is known about the Phyllorhiza punctata and its patterns of population spread. To
combat this, researchers must continue to study both the polyp and medusa stages of the jellyfish
and come up with preventative solutions to the problem. The invasive spread of the Phyllorhiza
punctata must gain more attention in the public view because it is a problem that is not going to
go away on its own. The species continues to spread and is observed in more and more nonnative territories with each passing year. The jellyfish fundamentally disrupts ecosystems and
fishing industries and its affects are already being felt on the human population. To ensure that
economic damage does not continue to occur, we must act on solutions proposed in this briefing
and work together to propose even more resolutions to the issue.
References
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