UBC Wiki - User contributions [en]

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T23:56:58Z

HaileyNelson:

== Introduction/ background. ==

=== What is ''C. taxifolia?'' ===
[[File:Killer Algae (Caulerpa taxifolia).jpg|thumb|''Caulerpa taxifolia''|134x134px]]
''Caulerpa taxifolia (C. taxifolia)'' is an invasive strain of green macroalgae located in the Mediterranean. Sea<ref name=":2">{{Cite journal|last=Galil|first=B.S.|date=12 January 2007|title=Loss or gain? Invasive aliens and biodiversity in the Mediterranean Sea|url=https://doi.org/10.1016/j.marpolbul.2006.11.008|journal=Marine Pollution Bulletin|volume=55|pages=314-322|via=Elsevier Science Direct}}</ref>. The ''C. taxifolia'' strain was created in Australia; the goal for it was so it could be used in and survive aquarium environments.<ref name=":3">{{Cite journal|last=Meinesz|first=Alexandre|last2=Belsher|first2=Thomas|last3=Thibaut|first3=Thierry|last4=Antolic|first4=Boris|last5=Mustapha|first5=Karim Ben|last6=Boudouresque|first6=Charles--Francçois|last7=Chiaverini|first7=Danièle|last8=Cinelli|first8=Francesco|last9=et al.|date=June 2001|title=The Introduced Green Alga Caulerpa Taxifolia Continues to Spread in the Mediterranean|url=https://doi.org/10.1023/A:1014549500678|journal=Biological Invasions|volume=3|pages=201-210|via=Springer Nature Link}}</ref>. The strain was implemented into aquariums as decorations, as well as for their great nutrient export<ref name=":2" />. The ''C. taxifolia'' strain was later commercialized and expanded through trade, which is how it came to areas surrounding the Mediterranean Sea<ref name=":2" />.

=== How did it enter the ecosystem? ===
[[File:Monaco Europe Location.svg|thumb|Where Monaco is in respect to the Mediterranean Sea.|left|145x145px]]
''C. taxifolia'' accidentally entered the Mediterranean Sea through a water circuit from the Oceanographic Museum of Monaco, in Monaco<ref name=":5">{{Cite journal|last=Siguan|first=Maria A. R.|date=2002|title=Review of Non-Native Marine Plants in the Mediterranean Sea.|url=https://doi.org/10.1007/978-94-015-9956-6_31|journal=Invasive Aquatic Species of Europe. Distribution, Impacts and Management|volume=1|pages=291-310|via=Springer Nature Link}}</ref>. The process of the water circuit is when a pump moves water in an aquarium tank out and filters the water, in order for the tank to be cleaned, and then back into the tank.<ref name=":3" /><ref name=":4">{{Cite journal|last=de Blok|first=J.W.|date=September 1975|title=The Texel aquarium|url=https://doi.org/10.1016/0077-7579(75)90018-6|journal=Netherlands Journal of Sea Research|volume=9|pages=231-232|via=Elsevier}}</ref> When the water is being filtered, it filters out debris, uneaten food, and toxic compounds, which is how some ''C. taxifolia'' were able to escape through the water circuit and into the Mediterranean Sea<ref name=":5" /><ref name=":4" />.

=== What is the location? ===
When ''C. taxifolia'' entered the Mediterranean Sea, it spread quickly along the northwestern Mediterranean coastline<ref name=":13">{{Cite journal|last=Montefalcone|first=Monica|last2=Morri|first2=Carla|last3=Parravicini|first3=Valeriano|last4=Bianchi|first4=Carlo Nike|date=26 May 2015|title=A tale of two invaders: divergent spreading kinetics of the alien green algae Caulerpa taxifolia and Caulerpa cylindracea|url=https://doi.org/10.1007/s10530-015-0908-1|journal=Biological Invasions|volume=17|pages=2717-2728|via=Springer Nature Link}}</ref>. ''C. taxifolia'' was along the coast of Croatia, France, Italy, Monaco, Spain, Tunisia, and Turkey<ref name=":13" />. Although ''C. taxifolia'' is native to Southeast Asia, the Pacific Islands, and Australia, it thrives in tropical waters<ref name=":13" /><ref name=":14">{{Cite journal|last=Windarto|first=Seto|last2=Wijaya|first2=Yusuf Jati|last3=Putri|first3=Diwyacitta Antya|last4=Umam|first4=Ahmad Khoirul|date=September and October 2025|title=Green Gold of the Ocean: Unlocking the Potential of Caulerpa in Global Seaweed Markets – A Review|url=https://doi.org/10.21608/ejabf.2025.430429.6737|journal=Egyptian Journal of Aquatic Biology and Fisheries|volume=29(5)|pages=2673-2700|via=Egyptian Journal of Aquatic Biology and Fisheries}}</ref>. Part of the reason why ''C. taxifolia'' is native to those areas in the Indo-Pacific, is that ''C. taxifolia'' has more predators in those areas than in the Mediterranean Sea<ref name=":14" />.

== The problem: Invasive C. taxifolia outbreak. ==

=== What is the C. taxifolia outbreak? ===
[[File:CaulerpaTaxifolia.jpg|left|thumb|224x224px|Dense meadow of ''C. taxifolia'']]
Once ''C. taxifolia'' entered the Mediterranean Sea, it spread rapidly through vegetative propagation<ref name=":2" /><ref name=":14" />. Vegetative propagation is a form of asexual reproduction, where part of the thallus, which is a vegetative plant body, breaks apart into smaller fragments, and this allows ''C. taxifolia'' to colonize disturbed habitats quickly<ref name=":14" /><ref name=":18">{{Cite journal|last=Thomaz|first=Sidinei Magela|date=30 July 2025|title=Asexual reproduction of aquatic macrophytes via stem fragments: A review on determinants of plant fragmentation and propagule dispersal|url=https://doi.org/10.1007/s10750-025-05942-x|journal=Hydrobiologia|via=Springer Nature Link}}</ref>. Since ''C. taxifolia'' exhibits invasive behavior when in non-native ecosystems, it formed dense meadows that impacted native seagrass<ref name=":2" /><ref name=":14" />. Those dense meadows compete with the native seagrass ''Posidonia oceanica'' for light, space, and nutrients<ref name=":2" />. ''P. oceanica'' is an important species ecologically in the Mediterranean, and any changes in its density and quality would majorly impact food webs as they are a spawning ground and nursery<ref name=":2" />. The dense meadows ''C. taxifolia'' form an obstruction to fish that feed on benthic invertebrates<ref name=":2" />.

In areas where ''C. taxifolia'' invaded ''P. oceanica'' seagrass beds, the total species richness, density, and biomass of fish are much lower in the invaded seagrass beds than in the native ''P. oceanica'' seagrass beds<ref name=":2" />. ''C. taxifolia'' was mainly found in depths of 0 to 30 m and on rocky and sandy substrates and on dead mattes of ''P. oceanica''<ref name=":19">{{Cite journal|last=Mannino|first=Anna Maria|last2=Balistreri|first2=Paolo|date=13 November 2017|title=An updated overview of invasive Caulerpa taxa in Sicily and circumSicilian Islands, strategic zones within the NW Mediterranean Sea|url=https://doi.org/10.7320/FlMedit27.221|journal=Flora Mediterranea|volume=27|pages=221-240|via=Flora Mediterranea}}</ref>. ''C. taxifolia'' is able to survive in varying habitats, which enhances its invasive behavior when in non-native ecosystems, like the Mediterranean Sea<ref name=":14" /><ref name=":19" />.
[[File:Paracentrotus lividus profil.JPG|thumb|224x224px|Sea urchin (''Paracentrotus lividus'')]]
It is hard for native species in the Mediterranean to get rid of ''C. taxifolia,'' because ''C. taxifolia'' has toxic secondary metabolites<ref name=":20">{{Cite journal|last=Bourdouresque|first=Charles F.|last2=Meinesz|first2=Alexandre|last3=Ribera|first3=María A.|last4=Ballesteros|first4=Enric|date=1995|title=Spread of the green alga Caulerpa taxifolia (Caulerpales, Chlorophyta) in the Mediterranean: possible consequences of a major ecological event|url=http://hdl.handle.net/10261/28423|journal=Scientia Marina|volume=59|pages=21-29|via=Digital CSIC}}</ref>. Toxic secondary metabolites are enzymes that are used as a defense mechanism when a potential predator or grazer, like a sea urchin, ''Paracentrotus lividus,'' tries to attack the algae<ref name=":20" />. From the presence of the toxic secondary metabolites, predators tend to stay away from ''C. taxifolia'', as those that did prey upon the algae died a few months after<ref name=":20" />. A decline in sea urchin populations was detected in areas invaded by ''C. taxifolia''<ref name=":20" />. The spread of ''C. taxifolia'' negatively impacted the Mediterranean Sea, decreasing its biodiversity and limiting native organisms by competing for light, food, and nutrients<ref name=":2" /><ref name=":14" /><ref name=":18" /><ref name=":20" />.

== How does ''C. taxifolia'' impact marine ecosystems? ==
[[File:Rhizosphere.png|thumb|273x273px|Rhizosphere structure ]]
''C. taxifolia'' are able to stimulate nitrogen fixation in low-nutrient environments <ref name=":0">{{Cite journal|last=Chisholm|first=J. R. M|last2=Moulin|first2=P.|date=2003|title=Stimulation of Nitrogen Fixation in Refractory Organic Sediments by Caulerpa taxifolia (Chlorophyta)|url=https://www.jstor.org/stable/3096580|journal=Limnology and Oceanography}}</ref>. This occurs when ''C. taxifolia'' releases photosynthetic products (Ex, organic carbon) into the rhizosphere <ref name=":0" />. The rhizosphere is the zone around the root where microorganisms and processes important for growth and plant health are located <ref>{{Cite journal|last=Bakker|first=Peter A. H. M.|last2=Berendsen|first2=Roeland|last3=Doornbos|first3=Rogier F.|last4=Wintermans|first4=Paul C. A|last5=Pieterse|first5=Corné M|date=2013|title=The rhizosphere revisited: root microbiomics|url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3667247/|journal=Frontiers in Plant Science}}</ref>. This process mimics the behaviour of saltwater vascular plants <ref name=":0" />. The excreted organic carbon then stimulates fermenting bacteria<ref name=":0" />. This fermenting bacterial community breaks down the organic carbon into substrates that support sulphate-reducing bacteria <ref name=":0" />. This creates low-oxygen (anaerobic) conditions <ref name=":0" />. ''C. taxifolia'' caused nitrogen fixation rates to increase in sediment below the algae by a factor of 28 <ref name=":0" />. This nitrogen fixation enhances the decomposition of native seagrass <ref name=":0" />. The nitrogen fixation also increases nutrient availability and improves sediment conditions for ''C. taxifolia'' <ref name=":1">{{Cite journal|last=Renn,|first=Chloe|last2=Vadillo Gonzalez|first2=Sebastian|last3=Marzinelli|first3=Ezequiel M.|last4=Dafforn|first4=Katherine A.|date=2025|title=Propagule pressure and native macrophyte biomass mediate the success of an invasive alga: the role of below-ground microbial communities|url=https://doi.org/10.1007/s10530-025-03599-0|journal=Biological Invasions}}</ref>. This creates a positive feedback loop that allows for ''C. taxifolia'' to grow and spread quickly in poor sediment conditions, further enhancing the invasive species' success <ref name=":0" /><ref name=":1" />.

=== Measurable Ecosystem Changes to Primary Productivity: ===
The invasive ''Caulerpa taxifolia'' disrupts Mediterranean ecosystems through intense competition for light and space, notably reducing the summer productivity of sensitive species like ''Cystoseira barbata'' by 20-30%. By utilizing the allelopathic effects of Caulerpenyne, ''C. taxifolia'' suppresses competitors. This chemical interference is seasonally mediated, with toxicity peaking in summer, when caulerpenyne concentrations can reach ~9.6 µg/mL. Caulerpenyne also deters generalist herbivores such as sea urchins, reducing grazing pressure and allowing ''C. taxifolia'' to persist. Thus, primary productivity becomes increasingly concentrated within the invasive species.<ref name=":9">Boudouresque, C. F., & Verlaque, M. (1997). Ecology of Caulerpa taxifolia in the Mediterranean Sea. Marine Ecology Progress Series, 149, 279–289. <nowiki>https://www.int-res.com/articles/meps/149/m149p279.pdf</nowiki></ref>

Furthermore, exposure to invasive algal toxins forces native species into defensive physiological responses. For instance, the seagrass ''Posidonia oceanica'' exhibits a stress response when exposed to waterborne ''Caulerpa taxifolia'' toxins. To mitigate toxic exposure, the seagrass reallocates metabolic energy away from primary growth toward the synthesis of protective phenolic compounds and tannins. While these antioxidants protect tissues, the diversion of resources leads to diminished health and stunted growth. Over time, the chronic stress weakens the seagrass beds, reducing habitat complexity and negatively impacting the diverse communities that rely on these meadows for survival. <ref name=":9" />

=== Measurable Ecosystem Changes to Trophic strcuture: ===
The invasion of ''Caulerpa taxifolia'' triggers measurable shifts in ecosystem connectivity, fundamentally altering the base of the benthic food web. This disruption is best reflected in the declining density of sediment-dwelling meiofauna, which play a vital role in nutrient cycling and energy transfer. In intact ''Posidonia oceanica'' meadows, meiofaunal densities are reported to be up to ten times higher than in adjacent areas dominated by ''C. taxifolia''. This shift is driven in part by the algae’s dense growth, which traps organic matter and lowers oxygen availability, creating inhospitable conditions for infaunal communities.<ref name=":10">Cvitkovic, I., Despalatovic, M., Uljevic, A., Matijevic, S., Bogner, D., Lusic, J., & Travizi, A. (2017). Structure of epibiontic and sediment meiofauna in the area invaded by invasive alga caulerpa taxifolia. Marine Biology, 164(1), 1-15. <nowiki>https://doi.org/10.1007/s00227-016-3034-4</nowiki></ref>

In addition, the release of toxic compounds (such as caulerpenyne) selectively alters microbial assemblages by suppressing Gram-positive bacteria while promoting Gram-negative strains<ref name=":9" />. Thus, it effectively acts as a biological filter that reshapes microbial composition. These changes disrupt natural nutrient cycling processes and reinforce the persistence of ''C. taxifolia'', further degrading ecosystem structure. As a result, energy pathways become simplified and less efficient, weakening connections between trophic levels. This is reflected at larger scales through habitat homogenization and a documented 25–50% reduction in native algal diversity in invaded areas<ref name=":10" />.

== Negative human impacts/vulneraboele on the ''C. taxifolia'' outbreak? ==

=== Aquarium dumping (original source) ===

=== Boating (spreading & creating new colonies) ===

=== Eutrophication (exacerbate rapid expansion) ===

=== Rising sea temperatures (exacerbate rapid expansion) ===

== What organisms does it impact? ==
[[File:Screenshot 2026-04-09 at 8.16.32 PM.png|thumb|''P. oceanica in the Mediterranean Sea'']]

=== Native Seagrass ===
''C. taxifolia'' and ''P. oceanica'', a native seagrass to the Mediterranean, directly compete for both space and light <ref>{{Cite journal|last=Ceccherelli|first=Giulia|last2=Cinelli|first2=Francesco|date=1999|title=Effects of Posidonia oceanica canopy on Caulerpa taxifolia size in a north-western Mediterranean bay|url=https://www.sciencedirect.com/science/article/pii/S0022098199000441|journal=Journal of Experimental Marine Biology and Ecology}}</ref>. ''C. taxifolia'' produces a phytotoxin called caulerpenyne <ref name=":6">{{Cite journal|last=Oliva|first=Daniela|last2=Piro|first2=Amalia|last3=Carbone|first3=Marianna|last4=Mollo|first4=Ernesto|date=2024|title=Physiological and proteomic responses of Posidonia oceanica to phytotoxins of invasive Caulerpa species|url=https://www.sciencedirect.com/science/article/pii/S0098847224003459|journal=Environmental and Experimental Botany}}</ref>. This toxin can severely damage ''P. oceanica'' by inhibiting the growth of adult leaves and preventing new leaf formations <ref name=":6" />. The toxin can also damage growth tissues called meristems, which threaten the seagrass’s survival <ref name=":6" />. It disrupts ''P. oceanica''’s ability to photosynthesize and produce energy by reducing key proteins <ref name=":6" />. Caulerpeyne triggers ''P. oceanica''’s stress responses <ref name=":6" />. These responses include oxidative stress, which occurs when the seagrass produces excess reactive oxygen species (ROS) <ref name=":6" />. When under stress, ROS accumulate, causing cellular damage <ref name=":6" />. ''C. taxifolia'' also produces caulerpin, a secondary metabolite <ref name=":6" />. This metabolite had little to no effect on leaf growth or formation but still caused metabolic and cellular changes, including impacts on transport and photosynthesis <ref name=":6" />. It also induces a defensive response in the seagrass, but to a lesser degree than caulerpeyne <ref name=":6" />. As competition between the two organisms increases, seagrass leaf length and age decrease and the leaves show more damage <ref>{{Cite journal|last=Dumay|first=Olivier|last2=Fernandez|first2=Catherine|last3=Pergent|first3=Gérard|date=2002|title=Primary production and vegetative cycle in Posidonia oceanica when in competition with the green algae Caulerpa taxifolia and Caulerpa racemosa|url=https://www.proquest.com/docview/224128965/abstract/770D818CE0D14DE3PQ/1|journal=Marine Biological Association of the United Kingdom. Journal of the Marine Biological Association of the United Kingdom}}</ref>.
[[File:Screenshot 2026-04-09 at 8.23.58 PM.png|thumb|''Sabella spallanzanii,'' a species of marine polychaete worms]]

=== Macrofauna ===
''C.taxifolia'' provide a significant amount of detritus <ref name=":7">{{Cite journal|last=Taylor|first=Sl|last2=Bishop|first2=Mj|last3=Kelaher|first3=Bp|last4=Glasb|first4=Tm|date=2010|title=Impacts of detritus from the invasive alga Caulerpa taxifolia on a soft sediment community|url=http://www.int-res.com/abstracts/meps/v420/p73-81/|journal=Marine Ecology Progress Series}}</ref>. This detritus negatively affects invertebrates, as it lowers the abundance and reduces biodiversity <ref name=":7" />. Caulerpenyne, a phototoxin mentioned above, can be toxic or stressful for many invertebrates <ref name=":6" /> <ref name=":7" />. Since invertebrates are unable to consume ''C. taxifolia'', many species die or move to different areas with a more abundant food source <ref name=":7" />. As seen above, ''C. taxifolia'' stimulate nitrogen fixation <ref name=":0" />. This nitrogen fixation, causes anaerobic sediment condition <ref name=":0" />. These low oxygen conditions make it hard for organisms to survive <ref name=":6" /><ref name=":7" />. ''C. taxifolia'' also change the habitat. Accumulated detritus can physically alter the sediment by making it more compact or unstable <ref name=":7" />. Macrofauna rely on seagrass like ''P. oceanica'' for shelter, so when ''P. oceanica'' is outcompeted by the algae, macrofauna lose their habitat and are more vulnerable to predation <ref>{{Cite journal|last=Cvitkovic|first=Ivan|last2=Despalatovic|first2=Marija|last3=Uljevic|first3=Ante|last4=Matijevic|first4=Slavica|last5=Bogner|first5=Danijela|date=2017|title=Structure of epibiontic and sediment meiofauna in the area invaded by invasive alga Caulerpa taxifolia|url=https://www.proquest.com/docview/1844241953/abstract/94F108D3EB2641EEPQ/1|journal=Marine Biology}}</ref>.

=== Native Fish ===
The spread of ''Caulerpa taxifolia'' directly alters fish communities by restructuring benthic habitats in ways that reduce feeding efficiency and increase energetic stress. Its dense mats of stolons and rhizomes form tightly interwoven networks that physically limit access to prey, particularly for benthic foragers. As a result, fish must adjust their behaviour in response to this constrained environment. <ref name=":11">Longepierre, S., Robert, A., Levi, F., & Francour, P. (2005). How an invasive alga species (caulerpa taxifolia) induces changes in foraging strategies of the benthivorous fish mullus surmuletus in coastal mediterranean ecosystems. Biodiversity & Conservation, 14(2), 365-376. <nowiki>https://doi.org/10.1007/s10531-004-5356-7</nowiki></ref>
[[File:Mullus surmuletus, Bouches-du-Rhône, Provence-Alpes-Côte d'Azur, FR imported from iNaturalist photo 277193780.jpg|thumb|''Mullus surmuletus'']]
Studies on the striped red mullet (''Mullus surmuletus'') provide clear evidence of this shift, showing that individuals in ''C. taxifolia'' habitats travel shorter distances, make more frequent feeding attempts, and spend significantly more time searching for food compared to those in ''Posidonia oceanica'' seagrass meadows. Despite this increased effort, feeding success is reduced, indicating a decline in overall foraging efficiency. This is further reflected in population structure, where large individuals comprise only about 1.19% of fish in ''C. taxifolia'' beds, compared to approximately 27.8% in seagrass habitats, suggesting that limited resource access constrains growth and survival. As prey becomes less accessible, intraspecific competition intensifies, forcing individuals to expend more energy for diminishing returns. These changes not only impact individual fitness, disrupt broader energy transfer, and contributing to a simplified and less productive food web.<ref name=":11" />
[[File:Scorpaenidae sp. No id. (29887533328).jpg|thumb|''Scorpaena porcus'']]
A second study conducted in France further highlights how ''Caulerpa taxifolia'' can impact fish at a physiological level. Research on the Mediterranean scorpionfish (''Scorpaena porcus'') found that exposure to the alga alters the fish’s Cytochrome P450 system, a group of liver enzymes responsible for detoxification and hormone regulation. This disruption was evident in the way the fish processed progesterone, where one key metabolite decreased by 25% while another increased significantly, indicating a substantial shift in internal biochemical pathways. Notably, these effects occurred even when fish did not ingest the alga, as simply inhabiting the same water was sufficient to trigger changes. <ref name=":12">Uchimura, M., Sandeaux, R., & Larroque, C. (1999). The enzymatic detoxifying system of a native mediterranean scorpio fish is affected by caulerpa taxifolia in its environment. Journal of Agricultural and Food Chemistry, 47(4), 1754-1759. <nowiki>https://pubs.acs.org/doi/10.1021/jf9808650</nowiki></ref>

This demonstrates that ''C. taxifolia'' exerts influence through waterborne chemical exposure, extending its impact beyond direct trophic interactions. As a result, impaired enzyme function may reduce the fish’s ability to properly break down toxins, increasing the likelihood of toxin accumulation within tissues. This not only compromises individual health but also raises broader ecological and human concerns, as these accumulated toxins may transfer through the food web and potentially affect higher-level consumers (such as ''H. sapiens''). <ref name=":12" />

== Are their unique characteristics of ''C. taxifolia'' that make it vulnerable? ==
Even though ''C. taxifolia'' has shown that it can outcompete and thrive in the Mediterranean, there are characteristics that make it vulnerable. An example of this is that ''C. taxifolia'' reproduce asexually <ref name=":8">{{Cite journal|last=Žuljević|first=Ante|last2=Antolić|first2=Boris|date=2000|title=Synchronous release of male gametes of Caulerpa taxifolia (Caulerpales, Chlorophyta) in the Mediterranean Sea|url=https://doi.org/10.2216/i0031-8884-39-2-157.1|journal=Phycologia}}</ref>. The main mode of dispersion that ''C. taxifolia'' use is vegetative dispersion <ref name=":8" />. A key mechanism to this is fragmentation <ref name=":8" />. Fragmentation is the process where the algae splits into parts and reattaches to new substrates, growing into clone of the original algae <ref name=":8" /><ref>{{Cite web|date=2026|title=Fragmentation - Definition and Examples - Biology Online Dictionary|url=https://www.biologyonline.com/dictionary/fragmentation|url-status=live|website=Biology Articles, Tutorials & Dictionary Online}}</ref>. This process can occur due to factors such as wave action, anchors, or other disturbances <ref name=":8" />. ''C. taxifolia'' release their gametes synchronously <ref name=":8" />. This release occurs in short coordinated windows, typically in the early morning <ref name=":8" />. However, these releases are highly dependent light conditions <ref name=":8" />. If there is low light intensity, the release time will be prolonged <ref name=":8" />. It was also found that during these releases, only male gametes were produced <ref name=":8" />. This eliminates any chance of sexual reproduction <ref name=":8" />. Since all gametes are identical to each other, there is no genetic diversity <ref name=":8" />. Even though ''C. taxifolia'' are able to thrive in the current conditions, if the conditions change unfavourably, they are unable to adapt <ref name=":8" />.

== Where are we today? ==
The spatial extent of ''C. taxifolia'' peaked around 1994, then steadily declined from the early 2000s onward, and now remains at relatively low densities. However, this decline does not indicate recovery. At its peak, ''C. taxifolia'' covered thousands of hectares, fundamentally reshaping habitats. These changes disrupted food availability and ecosystem structure, and their effects continue even as the algae itself has receded. As a result, the system has not fully recovered and may, in fact, be more vulnerable to further invasions. This aligns with the invasion meltdown hypothesis, which suggests that one invasive species can facilitate the success of others.

== Ineffective and effective solutions ==
Fortunately, since 2006, the killer algae ''C. taxifolia'' has been successfully eradicated with minimal coverage at all spread locations<ref name=":13" />. After years of efficient eradication methods and natural degradation, the invasive algae is no longer an ecological issue <ref name=":15">{{Cite web|last=Ivesa|first=Jeklin|date=2006|title=Vegetation patterns and spontaneous regression of Caulerpa taxifolia|url=https://doi.org/10.1016/j.aquabot.2006.06.009|url-status=live|pages=324-330}}</ref>. The boom and bust phenomena in the Mediterranean and global solutions involving legal, chemical, and physical actions effectively combated the invasion<ref name=":17" />
[[File:1-s2.0-S0304377006001069-gr1.jpg|left|thumb|379x379px|Area covered by reappearance of ''C. taxifolia'' at 4 sites in Malinska. E represents the time of eradication.]]

=== Local Solutions ===
After recognition in Malinska, a coastal town in Croatia, suction pumps were tested at 4 different sites in the Mediterranean in 1996 and 1997. However, eradication was only successful if the patch was small. All 4 sites needed re-pumping shortly after due to the algae’s quick and aggressive reappearance. The reappearance at 4 different sites displayed different colonization patterns and area covered, as supported by Figure 7 <ref name=":15" />.

After 2001, Figure 7. Shows ''C. taxifolia'' covers were not found at any sites if not sparsely distributed. The spontaneous decline of the algae after repopulation supports the assumption that ''C. taxifolia'' experienced a natural solution of the boom and bust phenomena in the Mediterranean, especially when water temperatures were cooler during Winter months, which made them more susceptible to death.

It is important to note that these conflicting patterns of recolonization cannot confidently conclude the ecological cause of regression of ''C. taxifolia'' at these sites. Thus, although the local solution was not as effective as expected, the possibility of boom and bust naturally eradicated the algae along the coast of Croatia.

In other areas of across the Mediterranean, eradication methods like biocontrol and dredging were largely unsuccessful due to the algae's uncontrolled spread. Efforts have only mitigated algae growth but did not completely eradicate coverage. Today, there is still a reduced amount of coverage in areas of the Mediterranean including the coast of Italy, France, and Spain<ref>{{Cite journal|last=R.G.|first=Creese|date=June 2004|title=Control Techniques for Caulerpa taxifolia|url=https://www.dcceew.gov.au/sites/default/files/documents/caulerpa-taxifolia6.pdf|journal=NSW Fisheries|volume=64|pages=59-76}}</ref>.

=== Global Solutions ===

==== Legal ====
At the first infestations of ''C. taxifolia'' in the waters surrounding Europe, Australia, and eventually the US, many countries took immediate legal action in managing and mitigating the spread of the algae. (Schaffelke). After the algae spread to the waters in Southern California, the U.S. government listed ''C. taxifolia'' on the U.S. Federal Noxious Weed List in 1999. Due to the 15 year history of the killer algae dispersal starting from the Mediterranean, the aquarium strain of ''C. taxifolia'' was banned in sales and possession<ref>United States Department of Agriculture (2007). Federal Noxious Weed List. December 10, 2010. <nowiki>https://www.aphis.usda.gov/sites/default/files/weedlist.pdf</nowiki></ref>. The US Animal and Plant Health Inspection Service maintains a list of federal noxious weeds including aquatic, parasitic, and terrestrial plants that are prohibited because of their damage to native ecosystems, agriculture, and trade. Other countries like Spain, France, and Australia implemented the same policies of prohibited sale, possession, and transport of ''C. taxifolia''<ref>Schaffelke, Britta. Capi Digital Library. (2008, March). ''Caulepra taxifolia (killer algae).'' [Datasheet]. CAPI Compendium. <nowiki>https://doi.org/10.1079/cabicompendium.2929</nowiki></ref>.

==== Chemical ====
[[File:Eradication.png|thumb|590x590px|List of globally tested eradication methods. Red boxes are Southern California and Australia eradication methods that saw complete success.]]
Since the spread of ''C. taxifolia'' dominating Southern California, there have been numerous scientifically planned attempts to eradicate the algae. Chemical methods were worked on small infestations first with minimal ecological impacts<ref name=":17" />. Once success has been achieved, they can then carry out these procedures to eradicate ''C. taxifolia'' in a large scale way. In Southern California, covering and sealing of Polyvinylchloride tarps and injecting liquid chlorine at a 12% stock solution underneath the tarp has seen complete success<ref name=":17">Walters, L. (2009). Ecology and management of the invasive marine macroalga caulerpa taxifolia. ''Management of invasive weeds'', 287-318. <nowiki>https://doi.org/10.1007/978-1-4020-9202-2_15</nowiki> </ref>. To be considered “eradicated” no trace of ''C. taxifolia'' should be present at the initial site; however this is complicated to confirm due to water turbidity and epiphytism<ref name=":17" />. In California, after 2 years of monitoring closely with no observed ''C. taxifolia'', it was successfully eradicated in July 2006.

The invasive algae’s spread in Southern Australia raised immediate concern because of its great ability to outcompete native species. A chemical method that worked for Australia was applying coarse sea salt of 99.5% NaCl specifically in the cooler months. The most successful dosage was 50kg/m^2<ref name=":16">Glasby, T. M., Creese, R. G., & Gibson, P. T. (2005). Experimental use of salt to control the invasive marine alga ''Caulerpa taxifolia'' in New South Wales, Australia. ''Biological Conservation, 122(4)'', 573-580. <nowiki>https://doi.org/10.1016/j.biocon.2004.09.012</nowiki> </ref>. The salt killed the algae within a few hours via osmotic shock and cell lysis while unharming native flora and fauna<ref name=":16" />. Taking advantage of ''C. taxifolia''’s extreme sensitivity to salt conditions effectively decreased their population while native species like ''Z. capricorni'' in South Australia can adapt and recover to the salinity change<ref name=":16" />.

=== Spreading Awareness ===
Since algae can rapidly transcend into national waters, the problem is considered global, requiring global action. For efficiency of reducing this spread, rapid response plans along with immediate funding must be adequate in coastal regions around the world. If marine invasions could be treated to the same extent as natural disasters like tornados, fires, floods, then rapid response should be achievable. To deal with future invasions, researchers suggested preparing biological experts, ownership of waterways, past eradication strategies, and funding<ref>Anderson, L. W. J. (2005). California's reaction to ''Caulerpa taxifolia'': A model for invasive species rapid response. ''Biological Invasions, 7(6''), 1003-1016. <nowiki>https://doi.org/10.1007/s10530-004-3123-z</nowiki> </ref>.

== References ==
<references />

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T05:56:12Z

HaileyNelson: /* Photoautotrophs */

== Introduction/ background. ==

=== What is ''C. taxifolia?'' ===
''Caulerpa taxifolia (C. taxifolia)'' is an invasive strain of green macroalgae located in the Mediterranean. Sea<ref name=":2">{{Cite journal|last=Galil|first=B.S.|date=12 January 2007|title=Loss or gain? Invasive aliens and biodiversity in the Mediterranean Sea|url=https://doi.org/10.1016/j.marpolbul.2006.11.008|journal=Marine Pollution Bulletin|volume=55|pages=314-322|via=Elsevier Science Direct}}</ref>. The ''C. taxifolia'' strain was created in Australia; the goal for it was so it could be used in and survive aquarium environments.<ref name=":3">{{Cite journal|last=Meinesz|first=Alexandre|last2=Belsher|first2=Thomas|last3=Thibaut|first3=Thierry|last4=Antolic|first4=Boris|last5=Mustapha|first5=Karim Ben|last6=Boudouresque|first6=Charles--Francçois|last7=Chiaverini|first7=Danièle|last8=Cinelli|first8=Francesco|last9=et al.|date=June 2001|title=The Introduced Green Alga Caulerpa Taxifolia Continues to Spread in the Mediterranean|url=https://doi.org/10.1023/A:1014549500678|journal=Biological Invasions|volume=3|pages=201-210|via=Springer Nature Link}}</ref>. The strain was implemented into aquariums as decorations, as well as for their great nutrient export<ref name=":2" />. The ''C. taxifolia'' strain was later commercialized and expanded through trade, which is how it came to areas surrounding the Mediterranean Sea<ref name=":2" />.

=== How did it enter the ecosystem? ===
[[File:Monaco Europe Location.svg|thumb|Where Monaco is in respect to the Mediterranean Sea.]]
''C. taxifolia'' accidentally entered the Mediterranean Sea through a water circuit from the Oceanographic Museum of Monaco, in Monaco<ref name=":5">{{Cite journal|last=Siguan|first=Maria A. R.|date=2002|title=Review of Non-Native Marine Plants in the Mediterranean Sea.|url=https://doi.org/10.1007/978-94-015-9956-6_31|journal=Invasive Aquatic Species of Europe. Distribution, Impacts and Management|volume=1|pages=291-310|via=Springer Nature Link}}</ref>. The process of the water circuit is when a pump moves water in an aquarium tank out and filters the water, in order for the tank to be cleaned, and then back into the tank.<ref name=":3" /><ref name=":4">{{Cite journal|last=de Blok|first=J.W.|date=September 1975|title=The Texel aquarium|url=https://doi.org/10.1016/0077-7579(75)90018-6|journal=Netherlands Journal of Sea Research|volume=9|pages=231-232|via=Elsevier}}</ref> When the water is being filtered, it filters out debris, uneaten food, and toxic compounds, which is how some ''C. taxifolia'' were able to escape through the water circuit and into the Mediterranean Sea<ref name=":5" /><ref name=":4" />.

=== What is the location? '''(A'''dd native species and where that is at) ===

== The problem: Invasive C. taxifolia outbreak. Molly ==

=== Describe what the C. taxifolia outbreak ===
add mat formats for native and invasive

== How does ''C. taxifolia'' impact marine ecosystems? ==
[[File:Rhizosphere.png|thumb|273x273px|Rhizosphere structure ]]
''C. taxifolia'' are able to stimulate nitrogen fixation in low-nutrient environments <ref name=":0">{{Cite journal|last=Chisholm|first=J. R. M|last2=Moulin|first2=P.|date=2003|title=Stimulation of Nitrogen Fixation in Refractory Organic Sediments by Caulerpa taxifolia (Chlorophyta)|url=https://www.jstor.org/stable/3096580|journal=Limnology and Oceanography}}</ref>. This occurs when ''C. taxifolia'' releases photosynthetic products (Ex, organic carbon) into the rhizosphere <ref name=":0" />. The rhizosphere is the zone around the root where microorganisms and processes important for growth and plant health are located <ref>{{Cite journal|last=Bakker|first=Peter A. H. M.|last2=Berendsen|first2=Roeland|last3=Doornbos|first3=Rogier F.|last4=Wintermans|first4=Paul C. A|last5=Pieterse|first5=Corné M|date=2013|title=The rhizosphere revisited: root microbiomics|url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3667247/|journal=Frontiers in Plant Science}}</ref>. This process mimics the behaviour of saltwater vascular plants <ref name=":0" />. The excreted organic carbon then stimulates fermenting bacteria<ref name=":0" />. This fermenting bacterial community breaks down the organic carbon into substrates that support sulphate-reducing bacteria <ref name=":0" />. This creates low-oxygen (anaerobic) conditions <ref name=":0" />. ''C. taxifolia'' caused nitrogen fixation rates to increase in sediment below the algae by a factor of 28 <ref name=":0" />. This nitrogen fixation enhances the decomposition of native seagrass <ref name=":0" />. The nitrogen fixation also increases nutrient availability and improves sediment conditions for ''C. taxifolia'' <ref name=":1">{{Cite journal|last=Renn,|first=Chloe|last2=Vadillo Gonzalez|first2=Sebastian|last3=Marzinelli|first3=Ezequiel M.|last4=Dafforn|first4=Katherine A.|date=2025|title=Propagule pressure and native macrophyte biomass mediate the success of an invasive alga: the role of below-ground microbial communities|url=https://doi.org/10.1007/s10530-025-03599-0|journal=Biological Invasions}}</ref>. This creates a positive feedback loop that allows for ''C. taxifolia'' to grow and spread quickly in poor sediment conditions, further enhancing the invasive species' success <ref name=":0" /><ref name=":1" />.

=== Measurable Ecosystem Changes to Primary Productivity: ===
The invasive ''Caulerpa taxifolia'' disrupts Mediterranean ecosystems through intense competition for light and space, notably reducing the summer productivity of sensitive species like ''Cystoseira barbata'' by 20-30%. By utilizing the allelopathic effects of Caulerpenyne, ''C. taxifolia'' suppresses competitors. This chemical interference is seasonally mediated, with toxicity peaking in summer, when caulerpenyne concentrations can reach ~9.6 µg/mL. Caulerpenyne also deters generalist herbivores such as sea urchins, reducing grazing pressure and allowing ''C. taxifolia'' to persist. Thus, primary productivity becomes increasingly concentrated within the invasive species.<ref name=":9">Boudouresque, C. F., & Verlaque, M. (1997). Ecology of Caulerpa taxifolia in the Mediterranean Sea. Marine Ecology Progress Series, 149, 279–289. <nowiki>https://www.int-res.com/articles/meps/149/m149p279.pdf</nowiki></ref>

Furthermore, exposure to invasive algal toxins forces native species into defensive physiological responses. For instance, the seagrass ''Posidonia oceanica'' exhibits a stress response when exposed to waterborne ''Caulerpa taxifolia'' toxins. To mitigate toxic exposure, the seagrass reallocates metabolic energy away from primary growth toward the synthesis of protective phenolic compounds and tannins. While these antioxidants protect tissues, the diversion of resources leads to diminished health and stunted growth. Over time, the chronic stress weakens the seagrass beds, reducing habitat complexity and negatively impacting the diverse communities that rely on these meadows for survival. <ref name=":9" />

=== Measurable Ecosystem Changes to Trophic strcuture: ===
The invasion of ''Caulerpa taxifolia'' triggers measurable shifts in ecosystem connectivity, fundamentally altering the base of the benthic food web. This disruption is best reflected in the declining density of sediment-dwelling meiofauna, which play a vital role in nutrient cycling and energy transfer. In intact ''Posidonia oceanica'' meadows, meiofaunal densities are reported to be up to ten times higher than in adjacent areas dominated by ''C. taxifolia''. This shift is driven in part by the algae’s dense growth, which traps organic matter and lowers oxygen availability, creating inhospitable conditions for infaunal communities.<ref name=":10">Cvitkovic, I., Despalatovic, M., Uljevic, A., Matijevic, S., Bogner, D., Lusic, J., & Travizi, A. (2017). Structure of epibiontic and sediment meiofauna in the area invaded by invasive alga caulerpa taxifolia. Marine Biology, 164(1), 1-15. <nowiki>https://doi.org/10.1007/s00227-016-3034-4</nowiki></ref>

In addition, the release of toxic compounds (such as caulerpenyne) selectively alters microbial assemblages by suppressing Gram-positive bacteria while promoting Gram-negative strains<ref name=":9" />. Thus, it effectively acts as a biological filter that reshapes microbial composition. These changes disrupt natural nutrient cycling processes and reinforce the persistence of ''C. taxifolia'', further degrading ecosystem structure. As a result, energy pathways become simplified and less efficient, weakening connections between trophic levels. This is reflected at larger scales through habitat homogenization and a documented 25–50% reduction in native algal diversity in invaded areas<ref name=":10" />.

== Negative human impacts/vulneraboele on the ''C. taxifolia'' outbreak? (Kaiya) ==

=== Aquarium dumping (original source) ===

=== Boating (spreading & creating new colonies) ===

=== Eutrophication (exacerbate rapid expansion) ===

=== Rising sea temperatures (exacerbate rapid expansion) ===

== What organisms does it impact? ==
[[File:Screenshot 2026-04-09 at 8.16.32 PM.png|thumb|''P. oceanica in the Mediterranean Sea'']]

=== Native Seagrass ===
C. taxifolia and P. oceanica, a native seagrass to the Mediterranean, directly compete for both space and light <ref>{{Cite journal|last=Ceccherelli|first=Giulia|last2=Cinelli|first2=Francesco|date=1999|title=Effects of Posidonia oceanica canopy on Caulerpa taxifolia size in a north-western Mediterranean bay|url=https://www.sciencedirect.com/science/article/pii/S0022098199000441|journal=Journal of Experimental Marine Biology and Ecology}}</ref>. ''C. taxifolia'' produces a phytotoxin called caulerpenyne <ref name=":6">{{Cite journal|last=Oliva|first=Daniela|last2=Piro|first2=Amalia|last3=Carbone|first3=Marianna|last4=Mollo|first4=Ernesto|date=2024|title=Physiological and proteomic responses of Posidonia oceanica to phytotoxins of invasive Caulerpa species|url=https://www.sciencedirect.com/science/article/pii/S0098847224003459|journal=Environmental and Experimental Botany}}</ref>. This toxin can severely damage ''P. oceanica'' by inhibiting the growth of adult leaves and preventing new leaf formations <ref name=":6" />. The toxin can also damage growth tissues called meristems, which threaten the seagrass’s survival <ref name=":6" />. It disrupts ''P. oceanica''’s ability to photosynthesize and produce energy by reducing key proteins <ref name=":6" />. Caulerpeyne triggers ''P. oceanica''’s stress responses <ref name=":6" />. These responses include oxidative stress, which occurs when the seagrass produces excess reactive oxygen species (ROS) <ref name=":6" />. When under stress, ROS accumulate, causing cellular damage <ref name=":6" />. ''C. taxifolia'' also produces caulerpin, a secondary metabolite <ref name=":6" />. This metabolite had little to no effect on leaf growth or formation but still caused metabolic and cellular changes, including impacts on transport and photosynthesis <ref name=":6" />. It also induces a defensive response in the seagrass, but to a lesser degree than caulerpeyne <ref name=":6" />. As competition between the two organisms increases, seagrass leaf length and age decrease and the leaves show more damage <ref>{{Cite journal|last=Dumay|first=Olivier|last2=Fernandez|first2=Catherine|last3=Pergent|first3=Gérard|date=2002|title=Primary production and vegetative cycle in Posidonia oceanica when in competition with the green algae Caulerpa taxifolia and Caulerpa racemosa|url=https://www.proquest.com/docview/224128965/abstract/770D818CE0D14DE3PQ/1|journal=Marine Biological Association of the United Kingdom. Journal of the Marine Biological Association of the United Kingdom}}</ref>.
[[File:Screenshot 2026-04-09 at 8.23.58 PM.png|thumb|''Sabella spallanzanii,'' a species of marine polychaete worms]]

=== Macrofauna ===
''C.taxifolia'' provide a significant amount of detritus <ref name=":7">{{Cite journal|last=Taylor|first=Sl|last2=Bishop|first2=Mj|last3=Kelaher|first3=Bp|last4=Glasb|first4=Tm|date=2010|title=Impacts of detritus from the invasive alga Caulerpa taxifolia on a soft sediment community|url=http://www.int-res.com/abstracts/meps/v420/p73-81/|journal=Marine Ecology Progress Series}}</ref>. This detritus negatively affects invertebrates, as it lowers the abundance and reduces biodiversity <ref name=":7" />. Caulerpenyne, a phototoxin mentioned above, can be toxic or stressful for many invertebrates <ref name=":6" /> <ref name=":7" />. Since invertebrates are unable to consume ''C. taxifolia'', many species die or move to different areas with a more abundant food source <ref name=":7" />. As seen above, ''C. taxifolia'' stimulate nitrogen fixation <ref name=":0" />. This nitrogen fixation, causes anaerobic sediment condition <ref name=":0" />. These low oxygen conditions make it hard for organisms to survive <ref name=":6" /><ref name=":7" />. ''C. taxifolia'' also change the habitat. Accumulated detritus can physically alter the sediment by making it more compact or unstable <ref name=":7" />. Macofauna rely on seagrass like ''P. oceanic'' for shelter, so when ''P. oceanica'' is outcompeted by the algae, macrofauna lose their habitat and are more vulnerable to predation <ref>{{Cite journal|last=Cvitkovic|first=Ivan|last2=Despalatovic|first2=Marija|last3=Uljevic|first3=Ante|last4=Matijevic|first4=Slavica|last5=Bogner|first5=Danijela|date=2017|title=Structure of epibiontic and sediment meiofauna in the area invaded by invasive alga Caulerpa taxifolia|url=https://www.proquest.com/docview/1844241953/abstract/94F108D3EB2641EEPQ/1|journal=Marine Biology}}</ref>.

=== Native Fish ===
The spread of ''Caulerpa taxifolia'' directly alters fish communities by restructuring benthic habitats in ways that reduce feeding efficiency and increase energetic stress. Its dense mats of stolons and rhizomes form tightly interwoven networks that physically limit access to prey, particularly for benthic foragers. As a result, fish must adjust their behaviour in response to this constrained environment. <ref name=":11">Longepierre, S., Robert, A., Levi, F., & Francour, P. (2005). How an invasive alga species (caulerpa taxifolia) induces changes in foraging strategies of the benthivorous fish mullus surmuletus in coastal mediterranean ecosystems. Biodiversity & Conservation, 14(2), 365-376. <nowiki>https://doi.org/10.1007/s10531-004-5356-7</nowiki></ref>

Studies on the striped red mullet (''Mullus surmuletus'') provide clear evidence of this shift, showing that individuals in ''C. taxifolia'' habitats travel shorter distances, make more frequent feeding attempts, and spend significantly more time searching for food compared to those in ''Posidonia oceanica'' seagrass meadows. Despite this increased effort, feeding success is reduced, indicating a decline in overall foraging efficiency. This is further reflected in population structure, where large individuals comprise only about 1.19% of fish in ''C. taxifolia'' beds, compared to approximately 27.8% in seagrass habitats, suggesting that limited resource access constrains growth and survival. As prey becomes less accessible, intraspecific competition intensifies, forcing individuals to expend more energy for diminishing returns. These changes not only impact individual fitness, disrupt broader energy transfer, and contributing to a simplified and less productive food web.<ref name=":11" />

A second study conducted in France further highlights how ''Caulerpa taxifolia'' can impact fish at a physiological level. Research on the Mediterranean scorpionfish (''Scorpaena porcus'') found that exposure to the alga alters the fish’s Cytochrome P450 system, a group of liver enzymes responsible for detoxification and hormone regulation. This disruption was evident in the way the fish processed progesterone, where one key metabolite decreased by 25% while another increased significantly, indicating a substantial shift in internal biochemical pathways. Notably, these effects occurred even when fish did not ingest the alga, as simply inhabiting the same water was sufficient to trigger changes. <ref name=":12">Uchimura, M., Sandeaux, R., & Larroque, C. (1999). The enzymatic detoxifying system of a native mediterranean scorpio fish is affected by caulerpa taxifolia in its environment. Journal of Agricultural and Food Chemistry, 47(4), 1754-1759. <nowiki>https://pubs.acs.org/doi/10.1021/jf9808650</nowiki></ref>

This demonstrates that ''C. taxifolia'' exerts influence through waterborne chemical exposure, extending its impact beyond direct trophic interactions. As a result, impaired enzyme function may reduce the fish’s ability to properly break down toxins, increasing the likelihood of toxin accumulation within tissues. This not only compromises individual health but also raises broader ecological and human concerns, as these accumulated toxins may transfer through the food web and potentially affect higher-level consumers (such as ''H. sapains''). <ref name=":12" />

== Are their unique characteristics of ''C. taxifolia'' that make it vulnerable? ==
Even though ''C. taxifolia'' has shown that it can outcompete and thrive in the mediterranean, there are characteristics that make it vulnerable. An example of this is that ''C. taxifolia'' reproduce asexually <ref name=":8">{{Cite journal|last=Žuljević|first=Ante|last2=Antolić|first2=Boris|date=2000|title=Synchronous release of male gametes of Caulerpa taxifolia (Caulerpales, Chlorophyta) in the Mediterranean Sea|url=https://doi.org/10.2216/i0031-8884-39-2-157.1|journal=Phycologia}}</ref>. The main mode of dispersion that C. taxifolia use is vegetative dispersion <ref name=":8" />. A key mechanism to this is fragmentation <ref name=":8" />. Fragmentation is the process where the algae splits into parts and reattaches to new substrates, growing into clone of the original algae <ref name=":8" /><ref>{{Cite web|date=2026|title=Fragmentation - Definition and Examples - Biology Online Dictionary|url=https://www.biologyonline.com/dictionary/fragmentation|url-status=live|website=Biology Articles, Tutorials & Dictionary Online}}</ref>. This process can occur due to factors such as wave action, anchors, or other disturbances <ref name=":8" />. C.taxifolia release their gametes synchronously <ref name=":8" />. This release occurs in short coordinated windows, typically in the early morning <ref name=":8" />. However, these releases are highly dependent light conditions <ref name=":8" />. If there is low light intensity, the release time will be prolonged <ref name=":8" />. It was also found that during these releases, only male gametes were produced <ref name=":8" />. This eliminates any chance of sexual reproduction <ref name=":8" />. Since all gametes are identical to each other, there is no genetic diversity <ref name=":8" />. Even though C. taxifolia are able to thrive in the current conditions, if the conditions change unfavourably, they are unable to adapt <ref name=":8" />.

== Where are we today? ==
The spatial extent of ''C. taxifolia'' peaked around 1994, then steadily declined from the early 2000s onward, and now remains at relatively low densities. However, this decline does not indicate recovery. At its peak, ''C. taxifolia'' covered thousands of hectares, fundamentally reshaping habitats. These changes disrupted food availability and ecosystem structure, and their effects continue even as the algea itself has receded. As a result, the system has not fully recovered and may, in fact, be more vulnerable to further invasions. This aligns with the invasion meltdown hypothesis, which suggests that one invasive species can facilitate the success of others.

== Positive human impacts and solutions? (winnie) ==

=== Local Solutions ===

=== Global Solutions ===

=== Spreading Awareness ===

== References ==
<references />

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:28:42Z

HaileyNelson: /* What organisms does it impact? */

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:27:36Z

HaileyNelson: /* What organisms does it impact? */

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:26:41Z

HaileyNelson: /* What organisms does it impact? */

File:Screenshot 2026-04-09 at 8.23.58 PM.png

2026-04-10T03:25:36Z

HaileyNelson: Uploaded a work by {{Unknown|author}} from https://en.wikipedia.org/wiki/Sabella_spallanzanii with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Polychate worm}}
|date=2025-07-16
|source=https://en.wikipedia.org/wiki/Sabella_spallanzanii
|author={{Unknown|author}}
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-sa-4.0}}

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:20:55Z

HaileyNelson: /* What organisms does it impact? */

File:Screenshot 2026-04-09 at 8.16.32 PM.png

2026-04-10T03:19:05Z

HaileyNelson: Uploaded a work by {{Unknown|author}} from https://en.wikipedia.org/wiki/Posidonia_oceanica with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=P. oceanica}}
|date=2026-04-04
|source=https://en.wikipedia.org/wiki/Posidonia_oceanica
|author={{Unknown|author}}
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-sa-4.0}}

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:16:08Z

HaileyNelson: /* How and why does it impact the identified ecosystems? */

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:13:49Z

HaileyNelson: /* Are their unique characteristics of C. taxifolia that make it vulnerable? */

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:10:08Z

HaileyNelson:

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T03:01:32Z

HaileyNelson:

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-10T02:48:55Z

HaileyNelson:

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T22:33:30Z

HaileyNelson: /* What organisms does it impact? (hailey) */

== Introduction/ background. Molly ==

=== What is C. taxifolia ===

=== how did it enter the ecosystem ===

=== what is the location. '''(A'''dd native species and where that is at) ===

== The problem: Invasive C. taxifolia outbreak. Molly ==

=== Describe what the C. taxifolia outbreak ===
add mat formats for native and invasive

== How does ''C. taxifolia'' impact marine ecosystems? ==

=== How and why does it impact the identified ecosystems? ===
[[File:Rhizosphere.png|thumb|273x273px]]
''C. taxifolia'' are able to stimulate nitrogen fixation in low-nutrient environments <ref name=":0">{{Cite journal|last=Chisholm, Moulin|first=J. R. M, P.|date=2003|title=Stimulation of Nitrogen Fixation in Refractory Organic Sediments by Caulerpa taxifolia (Chlorophyta)|url=https://www.jstor.org/stable/3096580|journal=Limnology and Oceanography}}</ref>. This occurs when ''C. taxifolia'' releases photosynthetic products (Ex, organic carbon) into the rhizosphere <ref name=":0" />. The rhizosphere is the zone around the root where microorganisms and processes important for growth and plant health are located <ref>{{Cite journal|last=Bakker, Berendsen, Doornbos, Wintermans, Pieterse|first=Peter A. H. M., Roeland, Rogier F., Paul C. A, Corné M|date=2013|title=The rhizosphere revisited: root microbiomics|url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3667247/|journal=Frontiers in Plant Science}}</ref>. This process mimics the behaviour of saltwater vascular plants <ref name=":0" />. The excreted organic carbon then stimulates fermenting bacteria<ref name=":0" />. This fermenting bacterial community breaks down the organic carbon into substrates that support sulphate-reducing bacteria <ref name=":0" />. This creates low-oxygen (anaerobic) conditions <ref name=":0" />. ''C. taxifolia'' caused nitrogen fixation rates to increase in sediment below the algae by a factor of 28 <ref name=":0" />. This nitrogen fixation enhances the decomposition of native seagrass <ref name=":0" />. The nitrogen fixation also increases nutrient availability and improves sediment conditions for ''C. taxifolia'' <ref name=":1">{{Cite journal|last=Renn, Vadillo Gonzalez, Marzinelli, Dafforn|first=Chloe, Sebastian, Ezequiel M., Katherine A.|date=2025|title=Propagule pressure and native macrophyte biomass mediate the success of an invasive alga: the role of below-ground microbial communities|url=https://doi.org/10.1007/s10530-025-03599-0|journal=Biological Invasions}}</ref>. This creates a positive feedback loop that allows for ''C. taxifolia'' to grow and spread quickly in poor sediment conditions, further enhancing the invasive species' success <ref name=":0" /><ref name=":1" />.

=== What are the measurable ecosystem changes that have occurred? (victoria) ===

== Negative human impacts/vulneraboele on the ''C. taxifolia'' outbreak? (Kaiya) ==

=== Aquarium dumping (original source) ===

=== Boating (spreading & creating new colonies) ===

=== Eutrophication (exacerbate rapid expansion) ===

=== Rising sea temperatures (exacerbate rapid expansion) ===

== What organisms does it impact? ==
C. taxifolia and P. oceanica, a native seagrass to the Mediterranean, directly compete for both space and light (Ceccherelli & Cinelli, 1999). ''C. taxifolia'' produces a phytotoxin called caulerpenyne (olivia). This toxin can severely damage ''P. oceanica'' by inhibiting the growth of adult leaves and preventing new leaf formations (Olivia). The toxin can also damage growth tissues called meristems, which threaten the seagrass’s survival (olivia). It disrupts ''P. oceanica''’s ability to photosynthesize and produce energy by reducing key proteins (olivia). Caulerpeyne triggers ''P. oceanica''’s stress responses (olivia). These responses include oxidative stress, which occurs when the seagrass produces excess reactive oxygen species (ROS) (Olivia). When under stress, ROS accumulate, causing cellular damage (Olivia). ''C. taxifolia'' also produces caulerpin, a secondary metabolite (olivia). This metabolite had little to no effect on leaf growth or formation but still caused metabolic and cellular changes, including impacts on transport and photosynthesis (olivia). It also induces a defensive response in the seagrass, but to a lesser degree than caulerpeyne (olivia). As competition between the two organisms increases, seagrass leaf length and age decrease and the leaves show more damage (Dumay).

''C.taxifolia'' provide a significant amount of detritus (Taylor). This detritus negatively affects invertebrates, as it lowers the abundance and reduces biodiversity (Taylor). Caulerpenyne, a phototoxin mentioned above, can be toxic or stressful for many invertebrates (Olivia and Taylor). Since invertebrates are unable to consume ''C. taxifolia'', many species die or move to different areas with a more abundant food source (Taylor). As seen above, ''C. taxifolia'' stimulate nitrogen fixation (1). This nitrogen fixation, causes anaerobic sediment condition (1). These low oxygen conditions make it hard for organisms to survive (Taylor+olivia). ''C. taxifolia'' also change the habitat. Accumulated detritus can physically alter the sediment by making it more compact or unstable (Taylor). Macofauna rely on seagrass like ''P. oceanic'' for shelter, so when ''P. oceanica'' is outcompeted by the algae, macrofauna lose their habitat and are more vulnerable to predation (Cvitkovi).

== Are their unique characteristics of ''C. taxifolia'' that make it vulnerable? (Hailey) ==

== What is the extent of the problem? (kaiay +Victoria ) ==

=== Outbreak status throughout time ===

=== What is the prognosis for the future if we continue on our current trajectory? ===

== Positive human impacts and solutions? (winnie) ==

=== Local Solutions ===

=== Global Solutions ===

=== Spreading Awareness ===

== References ==
<references />

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T22:31:20Z

HaileyNelson:

== Introduction/ background. Molly ==

=== What is C. taxifolia ===

=== how did it enter the ecosystem ===

=== what is the location. '''(A'''dd native species and where that is at) ===

== The problem: Invasive C. taxifolia outbreak. Molly ==

=== Describe what the C. taxifolia outbreak ===
add mat formats for native and invasive

== How does ''C. taxifolia'' impact marine ecosystems? ==

=== How and why does it impact the identified ecosystems? ===
[[File:Rhizosphere.png|thumb|273x273px]]
''C. taxifolia'' are able to stimulate nitrogen fixation in low-nutrient environments <ref name=":0">{{Cite journal|last=Chisholm, Moulin|first=J. R. M, P.|date=2003|title=Stimulation of Nitrogen Fixation in Refractory Organic Sediments by Caulerpa taxifolia (Chlorophyta)|url=https://www.jstor.org/stable/3096580|journal=Limnology and Oceanography}}</ref>. This occurs when ''C. taxifolia'' releases photosynthetic products (Ex, organic carbon) into the rhizosphere <ref name=":0" />. The rhizosphere is the zone around the root where microorganisms and processes important for growth and plant health are located <ref>{{Cite journal|last=Bakker, Berendsen, Doornbos, Wintermans, Pieterse|first=Peter A. H. M., Roeland, Rogier F., Paul C. A, Corné M|date=2013|title=The rhizosphere revisited: root microbiomics|url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3667247/|journal=Frontiers in Plant Science}}</ref>. This process mimics the behaviour of saltwater vascular plants <ref name=":0" />. The excreted organic carbon then stimulates fermenting bacteria<ref name=":0" />. This fermenting bacterial community breaks down the organic carbon into substrates that support sulphate-reducing bacteria <ref name=":0" />. This creates low-oxygen (anaerobic) conditions <ref name=":0" />. ''C. taxifolia'' caused nitrogen fixation rates to increase in sediment below the algae by a factor of 28 <ref name=":0" />. This nitrogen fixation enhances the decomposition of native seagrass <ref name=":0" />. The nitrogen fixation also increases nutrient availability and improves sediment conditions for ''C. taxifolia'' <ref name=":1">{{Cite journal|last=Renn, Vadillo Gonzalez, Marzinelli, Dafforn|first=Chloe, Sebastian, Ezequiel M., Katherine A.|date=2025|title=Propagule pressure and native macrophyte biomass mediate the success of an invasive alga: the role of below-ground microbial communities|url=https://doi.org/10.1007/s10530-025-03599-0|journal=Biological Invasions}}</ref>. This creates a positive feedback loop that allows for ''C. taxifolia'' to grow and spread quickly in poor sediment conditions, further enhancing the invasive species' success <ref name=":0" /><ref name=":1" />.

=== What are the measurable ecosystem changes that have occurred? (victoria) ===

== Negative human impacts/vulneraboele on the ''C. taxifolia'' outbreak? (Kaiya) ==

=== Aquarium dumping (original source) ===

=== Boating (spreading & creating new colonies) ===

=== Eutrophication (exacerbate rapid expansion) ===

=== Rising sea temperatures (exacerbate rapid expansion) ===

== What organisms does it impact? (hailey) ==
C. taxifolia and P. oceanica, a native seagrass to the Mediterranean, directly compete for both space and light (Ceccherelli & Cinelli, 1999). ''C. taxifolia'' produces a phytotoxin called caulerpenyne (olivia). This toxin can severely damage ''P. oceanica'' by inhibiting the growth of adult leaves and preventing new leaf formations (Olivia). The toxin can also damage growth tissues called meristems, which threaten the seagrass’s survival (olivia). It disrupts ''P. oceanica''’s ability to photosynthesize and produce energy by reducing key proteins (olivia). Caulerpeyne triggers ''P. oceanica''’s stress responses (olivia). These responses include oxidative stress, which occurs when the seagrass produces excess reactive oxygen species (ROS) (Olivia). When under stress, ROS accumulate, causing cellular damage (Olivia). ''C. taxifolia'' also produces caulerpin, a secondary metabolite (olivia). This metabolite had little to no effect on leaf growth or formation but still caused metabolic and cellular changes, including impacts on transport and photosynthesis (olivia). It also induces a defensive response in the seagrass, but to a lesser degree than caulerpeyne (olivia). As competition between the two organisms increases, seagrass leaf length and age decrease and the leaves show more damage (Dumay).

''C.taxifolia'' provide a significant amount of detritus (Taylor). This detritus negatively affects invertebrates, as it lowers the abundance and reduces biodiversity (Taylor). Caulerpenyne, a phototoxin mentioned above, can be toxic or stressful for many invertebrates (Olivia and Taylor). Since invertebrates are unable to consume ''C. taxifolia'', many species die or move to different areas with a more abundant food source (Taylor). As seen above, ''C. taxifolia'' stimulate nitrogen fixation (1). This nitrogen fixation, causes anaerobic sediment condition (1). These low oxygen conditions make it hard for organisms to survive (Taylor+olivia). ''C. taxifolia'' also change the habitat. Accumulated detritus can physically alter the sediment by making it more compact or unstable (Taylor). Macofauna rely on seagrass like ''P. oceanic'' for shelter, so when ''P. oceanica'' is outcompeted by the algae, macrofauna lose their habitat and are more vulnerable to predation (Cvitkovi).

== Are their unique characteristics of ''C. taxifolia'' that make it vulnerable? (Hailey) ==

== What is the extent of the problem? (kaiay +Victoria ) ==

=== Outbreak status throughout time ===

=== What is the prognosis for the future if we continue on our current trajectory? ===

== Positive human impacts and solutions? (winnie) ==

=== Local Solutions ===

=== Global Solutions ===

=== Spreading Awareness ===

== References ==
<references />

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T19:11:24Z

HaileyNelson:

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T18:56:57Z

HaileyNelson: /* How and why does it impact the identified ecosystems? (hailey) */

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T18:52:27Z

HaileyNelson:

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T18:47:33Z

HaileyNelson:

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-09T18:45:33Z

HaileyNelson: Nitrogen fixation

File:Rhizosphere.png

2026-04-09T18:43:51Z

HaileyNelson: Uploaded a work by John R. M. Chisholm, Pascale Moulin from https://www.jstor.org/stable/3096580 with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Figure __. Rhizosphere structure}}
|date=2003-03-01
|source=https://www.jstor.org/stable/3096580
|author=John R. M. Chisholm, Pascale Moulin
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-sa-4.0}}

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-08T00:10:23Z

HaileyNelson: j

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-04-08T00:09:12Z

HaileyNelson: h

Course:EOSC270/2026/Killer Algae in the Mediterranean

2026-03-17T22:55:08Z

HaileyNelson: HaileyNelson moved page Course:EOSC270/2026/Killer Algae in the Mediterranean to Course:EOSC270/2023/Killer Algae in the Mediterranean: Misspelled title

#REDIRECT [[Course:EOSC270/2023/Killer Algae in the Mediterranean]]

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-03-17T22:55:08Z

HaileyNelson: HaileyNelson moved page Course:EOSC270/2026/Killer Algae in the Mediterranean to Course:EOSC270/2023/Killer Algae in the Mediterranean: Misspelled title

== What is the problem? (Molly) ==

·    Clearly identify what the problem is

·    What human actions cause the problem?

·    Where does the problem occur?

·    How pervasive is the problem?

== How does this problem impact marine ecosystems? (Hailey) ==
·    How and why does it impact the identified ecosystems?

·    Are their unique characteristics of this habitat that make it vulnerable?

·    What organisms does it impact?

·    How and why does it impact this organism/s?

·    Are their unique characteristics of this organism/s that make it vulnerable?

== What is the extent of the problem? (Kaiya, Victoria) ==
·    What are the measurable ecosystem changes that have occurred?

·    What is the present status compared to the past?

·    What is the prognosis for the future if we continue on our current trajectory?

== Given the impact, what are the solutions? (Winnie) ==
·    What are the local solutions, if any?

·    What are the global solutions, if any?

== References ==
<references />

Course:EOSC270/2023/EOSC270/2026/Killer Algae in the Mediterranean

2026-03-17T22:52:26Z

HaileyNelson: HaileyNelson moved page Course:EOSC270/2023/EOSC270/2026/Killer Algae in the Mediterranean to Course:EOSC270/2026/Killer Algae in the Mediterranean: Misspelled title

#REDIRECT [[Course:EOSC270/2026/Killer Algae in the Mediterranean]]

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-03-17T22:52:26Z

HaileyNelson: HaileyNelson moved page Course:EOSC270/2023/EOSC270/2026/Killer Algae in the Mediterranean to Course:EOSC270/2026/Killer Algae in the Mediterranean: Misspelled title

Course:EOSC270/2023/Killer Algae in the Mediterranean

2026-03-12T00:48:10Z

HaileyNelson: Created page with "== What is the problem? (Molly) == · Clearly identify what the problem is · What human actions cause the problem? · Where does the problem occur? · How pervasive is the problem? == How does this problem impact marine ecosystems? (Hailey) == · How and why does it impact the identified ecosystems? · Are their unique characteristics of this habitat that make it vulnerable? · What organisms does it impact?..."