Caulerpa Taxifolia is a seaweed that has been altered by man, to look pretty in aquariums. The problem? If even a small branch is put into the ocean
it explodes into a massive growth that is almost impossible to kill. The only ways to kill it, that are known so far, are massive amounts of salt,
copper sulfate (which kills EVERYTHING), chlorine, and some predators.
The problem first began in the Monaco, when a small amount of Caulerpa Taxifolia got into the water. It was brought to the Oceanographic Museum, run
by Jaques Cousteau in 1982. In 1984, Alexandre Meinsez discovered a growth area under the windows of the museum, in the ocean, approximately 1 meter
square. By 1995, it had reached the Adriatic, by 1997, it had reached France, and Tunesia. Also in 1997, new growth areas were identified in
California off San Diego, Port Hacking, Lake Conjola, and Careel Bay in Australia.
Several predators of the plant have been discovered, but there have been problems with this method of control. They aren't able to eat the plant
fast enough, and in large enough amounts to destroy established growth areas, but are able to slow the spread somewhat.
The other method of destroying the plant involves using chemicals. Rock salt seems to work, however, it is needed in such large amounts that growth
areas that are established need more salt than can be found in most areas. Copper works well, but kills everything else as well. The US tried an
experiment with chlorine, where a growth area was covered with a special tarp, with a valve to pump in chlorine. This worked well, however it also
had the effect of killing everything else along with the taxifolia. The only other method is manual uprooting.
The spread of this plant is insidious, because it only needs a small part of a branch to begin to take over an area. Once it fully begins its growth,
it simply takes over an entire area and soon looks like an underwater forest. Once it has fully taken over an area a new ecological balance is
created, and the area is forced to adapt to the new growth.
Very little is currently being done to fight this problem. In fact not many people are even aware of the problem that is going on. Until, and unless
more is done then this plant can soon take over huge portions of the oceans, and decimate currrent species. The plant has been found everywhere from
deep cold regions, to shallow warm regions. Anywhere there is light, it will grow.
In the early 1980s, the curator of the tropical saltwater aquarium at the Wilhelmina Zoo in Stuttgart (FRG), noticed the exceptional properties
of a bright green, beautiful green alga, C.taxifolia, used as tank decoration in the presentation of multicolored tropical fish. It was captively bred
by the aquarium staff and exposed, for years, to chemicals and ultraviolet light. This exposure to abiotic stressors altered and switched on genes
that have not been previously present, expressed or active in wild type strains found across the Pacific. The genetically altered seaweed, in contrast
to other algae does not wither and grows with astounding vigor resisting cool water temperatures. Specialists quickly learned about these qualities,
and public aquaria around the globe acquired cuttings.
Prolific growth of Caulerpa along the Cote d’Azur (France), where the introduction was first reported, has been associated with urban
wastewater pollution (1.3Chisholm et al., 1997). It easily proliferates vegetatively via fragmentation aided by subsequent dispersal via anchors and
fishing nets (1.4Meinesz, 1992), or dumping ballast water across the oceans; in particular at harbors, marinas and other places where boats anchor
(1.6Boudouresque et al., 1995). Mid range spread of this species is easily achieved by currents, which transport fragments of it into new areas yet to
be colonized (1.3Chisholm et a., 1997). Apart from shipping vectors, long range dispersal of this alga was facilitated by the aquarium trade
(1.7Schaffelke et al., 2002). The fact that C.taxifolia possess a chemical defence mechanism (the alga produces repellent toxins) renders it
unpalatable to generalist herbivores in the N-W Mediterranean (1.8Paul, 2002), which facilitated this biological invasion. Thus, C.taxifolia is
upsetting the biocoenosis by invading and out-competing the indigenous flora while protecting itself against predation, thus threatening the
biological stability of the marine environment (1.9Pesando et al., 1996). Apart from a few serious attempts to eradicate this species (mainly in AUS
and USA), monitoring, mapping and public awareness programs are the only efforts made so far. It seems that control of the invasion was and still is
never a priority for most of the affected EU-countries. A shameful attitude that aids in the dispersal of this invasive strain.
The DNA fingerprints of C.taxifolia presented here support existing evidence for the descent of the Mediterranean C.taxifolia from an aquarium
strain. The introduction of C.taxifolia via the Oceanographic aquarium in Monaco is strongly supported on the basis of having identical internal
transcribed spacer (ITS) rDNA sequences (2.32Jousson et al., 1998). The phylogenetic analysis of these sequences show that the Mediterranean alga is
genetically identical to the strain cultivated in aquaria (see figure 2.h - left image). Interestingly, the aquarium strain differs from all tropical
populations of Caulerpa in lacking internal transcribed spacers (ITS) polymorphism, a fact that can be related to a prolonged confinement under
aquarium conditions.
Wiedenmann et al., (2.302001) compared samples from 11 locations in the Mediterranean Sea with 3 representatives from public aquaria. The
uniformity of hybridization patterns indicates that representative specimens from the Mediterranean and aquaria belong to the same clone. The slight
differences in hybridization patterns in C.taxifolia from Manly Harbour (Australia) suggest that it carries very similar chloroplast and mitochondria
traits. The Australian population of Manly Harbour/Moreton Bay is well suited for comparative studies of the role of C.taxifolia in a
non-Mediterranean ecosystem because of the close relationship to the aquarium strain.
The comparative results of C.taxifolia strains from aquaria, the Mediterranean Sea and from Manly Harbour (Australia) are shown in fig. 2.j in which
(CAC)5-hybridised Southern blots of total DNA after TaqI digestion (restriction patterns in ethidium-bromide stained agarose gels) have been
performed. In contrast, the control sample (left lanes 1-2) clearly distinguishes them from the aquarium strain (C.prolifera, C.taxifolia from
Martinique). The aquaria strains from Stuttgart and Enoshima reveal identical restriction patterns as samples from the Mediterranean Sea (Monaco, Krk,
Sicily, Mallorca, Elba 1-3, St.Cyprien 1-3). Only slight differences in the position of a single band (indicated by the circle) were detected between
the sample from Manly Harbour (lane 16) and the aquaria specimens.
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