Looking underneath an invasive macroalgae:
Benthic assemblages associated to Mastocarpus stellatus in human-made structures
Luis Giménez, Katharina Reichert, Karin Boos, Lars Gutow
Biologische Anstalt Helgoland, Alfred Wegener Institute for Polar and Marine Research, 27498 Helgoland - Germany
What are the potential roles of M. stellatus in the benthic community ?
Species abundance
Potential effects of M. stellatus after its incidental introduction to Helgoland in the 1980s
AWI
Study site:
Helgoland, German Bight, (North Sea)
Sessile species: habitat partitioning Mobile species: positive covariation
-40 -30 -20 -10 0 10 20 30 40
PCO-I (65.2%)
-1.0 -0.5 0.0 0.5 1.0
-30 -20 -10 0 10 20 30
PCO-II (11.0%)
-1.0 -0.5 0.0 0.5 1.0
Mobile
L. obtusata C. maenas
L. vincta
H. nilsoni I. granulosa
J. albifrons
Increasing M. stellatus cover
-30 -20 -10 0 10 20 30
PCO-I (41.6%)
-1.0 -0.5 0.0 0.5 1.0
-20 -10 0 10 20
PCO-II (24.6%)
-1.0 -0.5 0.0 0.5 1.0
Sessile
E. pilosa
Ulva lactuca F. hispida
Barnacles
Haemescharia hennedyi
Increasing M. stellatus cover
Cutting M. stellatus stands and looking underneath
Barnacles
Sampling:
Harbor wall: 3 samples at random in 10 occasions (June-August)
Methods
P. lenormandii
18 cm
Barnacles
M. stellatus
Community structure
Lack of strong negative effect on barnacles: no competitive exclusion
Positive effect on settlement and recruitment of shore crab C.
maenas and mussel M. edulis
Positive effects on guilds of peracarid crustaceans and gastropods (shelter and food)
M. edulis
H. n ilso
nii L. ma
r./obt.
L. vin cta
R. p
arva S. p
lanorbis
I. granulosa J. a
lbifrons M. e
dulis C. ma
enas L. litto
rea
total number of individuals
0 1000 2000 3000 4000 5000 6000
mobile invertebrates
P. lenorman dii
H. rubra
H. hennedyi Ectoca
rpales
U. lactuca
C. rupestris
C. rubrum C. seri
cea
mean cover (%)
0 5 10 15 20
25 algae
barnacles F. hi
spida
D. pumila J. pa
genstecher i
E. pilo sa
L. fle xuo
sa
mean cover (%)
0 20 40 60 80 100
sessile invertebrates
Jun Jul Aug Sep
mean cover (%)
0 1 2 3 4 5
Haemescharia hennedyi Ulva lactuca
Jun Jul Aug Sep
mean cover (%)
0 10 60 70 80 90 100
barnacles
Flustrellidra hispida Electra pilosa
Jun Jul Aug Sep
mean abundance
0 5 10 15 20 25 30 35
Carcinus maenas Idotea granulosa Jaera albifrons
Jun Jul Aug Sep
mean abundance
0 100 200 300 400 500
Littorina mariae/obtusata Lacuna vincta
Hyale nilsonii
