Algae: An overview of

Invasive Species

Annie Shin

BOT 437

Invasive Species: Consequences and Implications of their Proliferation

When considering invasive species, it is important to view these incursions within the context of more generic environmental or health emergencies4.

There is neither an adequate awareness of the costs, nor are systems in place to react to disruptions caused by problematic invasive species, particularly in the marine and freshwater environments4

Non-indigenous species (NIS) have an ability to negatively affect the ecosystem they arrive in. The consequences often are due to ecological interactions through e.g. competition for resources, including place to settle and spawning grounds, grazing or predation, trophic cascading effects, or filling up empty niches. However, many NIS can also have a severe impact by changing the habitat itself, physically or chemically, directly or indirectly7

Human Contribution

Historically, humans have transferred species for food and agricultural purposes. The speed at which the transfer of species happen has increased drastically1.

The most likely vectors of transport are through ship fouling and/or ballast water because many of these nonindigenous algae were first collected in or around harbors and gradually dispersed to neighboring areas2. As well as intentional/unintentional release of aquaria water

SUCCESS!!!

The success of these nonindigenous algae may be the result of a variety of factors including chemical or physical defense from herbivory and diverse physiological characteristics that lead to rapid growth rates2.

Non-indigenous species, termed ecosystem engineers, have been considered keystone species for ecosystems7.

Ecosystem Engineers: Non-indigenous Algae Species affect ecosystems in many ways7

Changing light conditions:

the large canopies and high densities of the introduced brown alga Sargassum muticum have been implicated in having a negative effect on native species by reducing the light conditions for them,especially in the subtidal and lower intertidal zones7.

Sargassum muticum is a native of the Sea of Japan but now occupies most areas of North America’s Pacific Coast and Europe’s Atlantic Coast. Figure 2. Percent cover of Sargassum muticum at different

depth intervals in the central part of Limfjorden (reference area 4, cf. fig. 1). DENMARK8.

A sentiment for sediment: Substrate Modifiers

The invasive red algae A. preissii and W. setacea, introduced in the Mediterranean, have been found to accumulate sediments in the mats affecting the ability of fauna beneath to collect deposited particles

Trapping particles has been extensively studied for salt marsh species. Species of the genus Spartina alterniflora, introduced on the American Pacific coast, Europe and China, result in dense stands.

A negative impact is the transformation of beaches to marshes, while a positive effect is that more rooted plants can grow there and seedlings of other species can emerge and survive due to the reduction of physical disturbances.

Allelopathy and Toxin Production

The introduced calcareous red algal crust, Lithophyllum yessoense , was first recorded in the Thau lagoon, southern France, in 1994, probably being brought by Japanese oysters

Potential future implications for European ecosystems because of L. yessoense could follow the current model in Asia; many areas are covered and very few seaweeds can recolonize this substratum, from providing much shelter, to a very simple one, which can have adverse, indirect influences on other organisms.

L. yessoense has several allelopathic substances, which inhibit settlement and germination of various other Asiatic red, brown and green seaweeds. Among those tested were also species having been introduced in Europe, such as the red algae G. turuturu and Lomentaria hakodatensis, the brown alga U. pinnatifida and the green alga Ulva pertusa

Another example: C. taxifolia, Produces secondary metabolites by causing chlorosis and necrosis7

Fragmentation

Fragments as small as 1 mm can regrow to full size plants in laboratory based studies for many siphonous taxa6

Abilities to fragment readily disperse widely prior to recruitment and successfully attach in short periods are the obvious hallmarks of weedy invasive species that bloom frequently having serious negative ecological impacts on native plant communities6 (e.g. Caulerpa taxifolia).

Caulerpa taxifolia, “Killer Algae”

Caulerpa taxifolia is an invasive alga that is causing serious environmental problems in the Mediterranean Sea3.

In the 15 years since its discovery off Monaco, the invasive green algae, Caulerpa taxifolia, has come to cover 97% of available surfaces between Toulon and Genes (France, Monaco and Italy) has already been spread to the Adriatic Sea, and is projected to eventually spread over most of the Mediterranean5.

The invasive strain of Caulerpa in the Mediterranean Sea smothers other algal species, seagrasses and sessile invertebrate communities3.

Small infestations found in Agua Hedionda Lagoon in Carlsbad near San Diego and Huntington Beach near Los Angeles, took six years to eradicate at a cost of more than $7 million

References1. Leppakoski, E., S. Gollasch, and S. Olenin. Invasive aquatic species of Europe:

distribution, impacts, and management. New York: Springer, 20022. Smith, J. E., C. L. Hunter, and C. M. Smith. 2002. Distribution and Reproductive

Characteristics of Nonindigenous and Invasive Marine Algae in the Hawaiian Islands. Pacific Science. 56(3): 299-315

3. "CISR: Caulerpa." CISR: The Center for Invasive Species Research. 20 May 2009 <http://cisr.ucr.edu/caulerpa_taxifolia.html>.

4. Anderson, L. W. J. California’s reaction to Caulerpa taxifolia: a model for invasive species rapid response. 2005. biological Invasions. 7: 1003-1016

5. Bax, N., A. Williamson, M. Aguero, E. Gonzalez, W. Geeves. 2003. Marine invasive alien species: a threat to global biodiversity. Marine Policy. 27: 313-323

6. Smith, C. M., and L. J. Walters. 1999. Fragmentation as a Strategy for Caulerpa Species: Fates of Fragments and Implications for Management of an Invasive Weed. Marine Ecology, 20(3-4): 307-319

7. Wallentinus, I., and C. D. Nyberg. 2007. Introduced marine organisms as habitat modifiers. Marine Pollution Bulletin, 55: 323-332

8. "Invasion of Sargassum muticum." 21 May 2009 <http://users.cybercity.dk/~dko10792/poster2.htm>.