Alien species on SyltSeaweeds

Maria Redeker, Carolin Barz, Olga Kolychalow

Native Phaeophycea (brown alga)

Fucus vesiculosushttp://www.arkive.org/species/ARK/plants_and_algae/Fucus_vesiculosus/

Alien Algae on Sylt

Gracilaria vermiculophyllaSince 2002 in Wadden Sea

Sargassum muticumSince 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

http://www.welt-atlas.de/datenbank/karten/karte-1-227.gif

a. Oyster bed

b. Former military area

c. Boulders

d. Oyster farm

Methods

• Measuring length of thalli

• Determine attachment type

Length of macroalgae

Median 25%-75% Range without outliers

FucusGracilaria

Sargassum

Species

-50

0

50

100

150

200

250

300

350

Leng

th

Length of F. vesiculosus relating to attachment type

Median 25%-75% Range without outliersbrick oyster mussel stone

Substrate

5

10

15

20

25

30

35

40

45

50

55

Leng

th [c

m]

Length of G. vermiculophylla relating to attachment type

Median 25%-75% Range without outliers Outlier

stonerazor clam

musselrotten

oyster

Substrate

20

40

60

80

100

120

140

160

180

Leng

th [c

m]

Length of S. muticum relating to attachment type

Median 25%-75% Range without outliers

stoneoyster

slipper limpetmussel

Substrate

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

Leng

th [c

m]

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!!