Logo Universitat Bremen
Page path:

IC7_II

Range expansion mechanisms in invasive seaweeds

The research of the project will mainly focus on the large brown seaweed Undaria pinnatifida which is commonly known as Wakame. It can grown up to 3 meters in length and is considered as a canopy forming species. As such U. pinnatifida is capable of altering local physical conditions and forming habitat for associated organisms. Beside its ecological meaning U. pinnatifida also bears a high economical importance as it is eaten and cultivated as a food product. The seaweed is native to the Northwestern Pacific, along the coast of Japan, Korea and China.
For aquaculture reasons U. pinnatifida got intentionally introduced in some countries and during the last it became invasive in many parts of the world. Today it can be found in Europe, Australia, New Zealand, North America and along the coast of Argentina. Important vectors for the spread of U. pinnatifida are the accidental import with other aquatic organisms, hull fouling and transport of the microscopic life stages within the ballast water tanks of big ships.
The introduction of U. pinnatifida implicates ecological consequences for concerned coasts. Studies on invaded shores reported a reduction in native kelp cover, changes in community composition and habitat structure as well as lowered spatial heterogeneity. Additionally, U. pinnatifida developed to be a fouling problem in ports and on aqua cultural structures.
U. pinnatifida also invaded the two key regions of the INTERCOAST research group, the North Atlantic and New Zealand coasts:
  • U. pinnatifida arrived in Europe in 1971 with imported oysters from Japan on the French Mediterranean coast. Farmers started to culture the kelp on the coast of Brittany as they believed the water would be too cold for its reproduction. Since then U. pinnatifida spread along the Atlantic shore, south to Spain and as far North as the Dutch sea inlet the Oosterschelde.
  • The introduction to New Zealand most likely happened by international shippings from Japan. U. pinnatifida was first discovered in 1987 in Wellington harbour and can now be found all along the coast of New Zealand. The distribution, however, is mainly restricted to ports and marinas where the seaweed grows on artificial substrates such as seawalls or pontoons.
As its distribution demonstrates U. pinnatifida is able to grow on a wide range of latitudes and temperatures. The overarching aim of the project will therefore be to identify characteristics of invasive seaweeds that facilitate the invasion into new habitats.
The possibility to conduct the study on the coasts of the North Atlantic and New Zealand offers an excellent opportunity to study and compare the latitudinal distribution and adaptation mechanisms of the seaweed in both regions.

Main research questions and aspect for the project will be:
  1. Which physiological mechanisms allow the large temperature range of U. pinnatifida
  2. Which role does the delayed development of the gametophytes play for the invasion potential? As this trait might play a major role for future expansion of the species physiological adaptations and limits of performance of the resting life stage will be investigated.
  3. Which coasts will it be able to invade in the coming decades?
  4. Once an invasive species arrived in a new environment it needs to establish to the local community. Competition with native canopy forming seaweeds is a crucial factor for the invasion success. Competition abilities of spores of U. pinnatifida will be tested in laboratory experiments. Using fluorescent labeling techniques spore development can also be observed in the field.
  5. Do invasive species exhibit common „key features“? This question might be answered by comparing characteristics of U. pinnatifida to other invasive and non-invasive kelp species.
A first experimental phase (March – May 2013) will investigate the delayed development in U. pinnatifida gametophytes (Research question 2.). The study will be done in the laboratories of the University of Bremen on cultured material. The infrastructure to rear seaweed gametophytes in the culture rooms has already been established and a culture of gametophytes of U. pinnatifida was started on the 27th of November 2012. The gametophytes were isolated in China and Japan at different years (1972, 1983, 1996, 2002).

Members

Proponents:Prof. Dr. Kai BischofUniversity of Bremen
:Prof. Dr. Conrad PilditchUniversity of Waikato
PhD Candidate:Merle BollenUniversity of Bremen

Publications

N / A

Miscellaneous

N / A