Alien_species_on_Sylt

							Alien species on Sylt
     Seaweeds




          Maria Redeker, Carolin Barz, Olga Kolychalow
Native Phaeophycea (brown alga)




   http://www.arkive.org/species/ARK/plants_and_algae/Fucus_vesiculosus/
                                                Fucus vesiculosus
                                   Alien Algae on Sylt




       Gracilaria vermiculophylla                                          Sargassum muticum
          Since 2002 in Wadden Sea                                             Since 1993 on Sylt
http://www.algaebase.org/search/species/detail/?species_id=4417   http://www.issg.org/database/species/ecology.asp?si=727&fr=1&sts=sss
                     Aims
• Do the species differ in length?
• Does any species prefer any specific attachment
  type?
• Does the length of the alga depend on the
  attachment type?
• Is there any competition between native and non-
  native species?
• Does the length reflect any habitat provision?
• May the non-native species have any effect on
  biodiversity?
                           Study sites
                                                       a. Oyster bed
                                                       b. Former military
                                                          area
                                                       c. Boulders
                                                       d. Oyster farm




http://www.welt-atlas.de/datenbank/karten/karte-1-227.gif
                Methods
• Measuring length
  of thalli




• Determine
  attachment type
               Length of macroalgae
         350


         300


         250


         200
Length




         150


         100


         50


          0


         -50                                     Median
                Fucus                Sargassum
                                                 25%-75%
                        Gracilaria
                                                 Range w ithout outliers
                        Species
Length of F. vesiculosus relating
      to attachment type
              55


              50


              45


              40


              35
Length [cm]




              30


              25


              20


              15


              10

                                                     Median
              5                                      25%-75%
                   brick   oyster   mussel   stone
                                                     Range w ithout outliers
                              Substrate
        Length of G. vermiculophylla
         relating to attachment type
              180


              160


              140


              120
Length [cm]




              100


              80


              60


              40

                                                                  Median
              20                                                  25%-75%
                    stone             mussel             oyster
                                                                  Range w ithout outliers
                            razor clam          rotten
                                                                  Outlier
                                    Substrate
Length of S. muticum relating to
       attachment type
               340
               320
               300
               280
               260
               240
               220
 Length [cm]




               200
               180
               160
               140
               120
               100
               80
               60
               40                                               Median
                     stone            slipper limpet
                                                                25%-75%
                             oyster                    mussel
                                                                Range w ithout outliers
                                Substrate
                  Results
• No obvious dependence of length and
  attachment type
• Attachment type does not influence growth
• Not possible to state if species prefer any
  specific attachment type
               Discussion
• Notably longer thalli and complexity of
  structure of both invasive species may
  imply a larger surface, i.e. habitat
• S. muticum supports twice as many species
  (local) as F.vesiculosus
• S. muticum provides habitat for species
  which otherwise would be rare or absent
  (e.g. several species of red algae)
               Discussion
• No competition between S. muticum and F.
  vesiculosus as they occur at different water
  levels
• G. vermiculophylla and F. vesiculosus occur
  in the same spots
              Conclusions
• Up to now no replacement of native species
  recorded in SE Wadden Sea
• Seem to have positive effects on habitat
  formation and biodiversity
• As non-native algae species are expected to
  increase in abundance, this might affect
  competitive ability of native species
              Conclusions
• Species have the potential to alter the
  ecology of Wadden Sea
• Attempts to eradicate S. muticum likely to
  fail
• Due to insufficient knowledge it is not
  possible to predict the future effects
• More research is needed !!!!!!
Thank you for your attention!!