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56 Wirkung von Habitatsstrukturen auf die Benthoszönose
Tab. 4.19: Macrozoobenthos recorded in 2000, 2001 and 2002 and grouped by TWINSPAN. Their
mean relative frequency (+ = 1-4, 1 = 5-9, 2 =10-29, 3 = 30-99, 4 ≥ 100 individuals m -2 )
at each sample group (Fig. 4.8) and Spearman rho of significant correlations (p ≤ 0.05)
with percentage soil texture class are given. Grey: main distribution. Mean abundance
in all samples with standard error.
species
transect groupings Spearman rho ind.m -2
I II III IV V silt sand gravel ± std. err.
Gomphus flavipes 1 + 1 + 1.8 ± 0.4
Galba truncatula + + + -0.1 0.7 ± 0.3
Pisidium spec. 2 1 + 3.9 ± 0.9
Caenis spec. + + -0.1 0.1 ± 0.1
Corbicula fluminea + 0.2 0.1 ± 0.1
Pisidium henslowanum 3 2 1 + -0.1 0.3 18.7 ± 2.7
Pisidium moitessierianum + + 1 0.1 2.6 ± 0.7
Anodonta anatina + 0.1 ± 0.1
Baetis spec. + 0.1 ± 0.1
Caenis horaria + 0.1 ± 0.1
Cordylophora caspia + -0.1 -0.3 -0.1
Hydra spec. + -0.1 -0.2 -0.1 0.1 ± 0.1
Physella acuta + -0.1 0.1 ± 0.1
Chelicorophium curvispinum + 3 1 2 + -0.3 -0.4 -0.2 9.3 ± 1.4
Jaera sarsi + 1 + -0.2 -0.3 -0.2 1.5 ± 0.5
Dreissena polymorpha + + + -0.2 -0.4 -0.2 0.2 ± 0.1
Gammarus tigrinus 2 3 4 1 2 -0.1 0.1 28.2 ± 6.9
Potamopyrgus antipodarum 1 + 1 + 1 -0.1 -0.1 2.6 ± 0.5
Caenis luctuosa +
Dikerogammarus villosus + 3 1 4 1 -0.3 -0.4 -0.2 14.8 ± 2.4
Pisidium supinum 1 + 2 3 -0.1 0.1 0.2 7.6 ± 1.1
number of sample groups 34 43 35 17 33 162
number of taxa 13 16 11 10 7 21
mean abundance [ind.m -2 ] 92.6
Another differentiation of the TWINSPAN-groups was caused by the gradual abundance
of certain stenotopic species within group I, II and III. At study site 2 (group I) the mean
abundance of G. flavipes and P. henslowanum was much higher than in study site 1 (group
II). It was lowest in group III, including the highest proportion of traditional inclined
groynes of both sites. G. tigrinus shows in the same group-gradient a rising abundance.
In group IV, a shallow-water transect group with a high portion of gravel, mainly
originated from sample group b at study site 2, many species were found which normally
occurred on hard substrata of the groynes. Especially C. curvispinum, G. tigrinus,
D. villosus and Pisidium supinum were recorded with a high abundance.
Inter-annual differentiation between the groups was given by variability in populations
or the immigration of new species into the study sites within timeframe of the investigations
like Jaera sarsi (Janiridae, Isopoda) or Corbicula fluminea (Corbiculidae, Bivalvia),
with an absence in the year 2000 (group V).