Table 2 Total number of species (N ₀) and number of species observed in one site and not in the other (s), and average (±SE) of species richness, species diversity (H), evenness, total abundance, abundance without mussels, biomass, biomass without mussels, and abundances of dominant species in Limfjorden (n = 25 for each site) and the Oosterschelde (reference site n = 8; mussel site n = 10)

N₀ (s)

19 (10)

23 (14)

27 (13)

54 (40)

Species richness

5.42 ± 0.27

6.04 ± 0.48

ns

6.0 ± 1.9

15.3 ± 1.8

<0.01

Diversity (H)

0.90 ± 0.05

0.80 ± 0.06

ns

1.17 ± 0.29

1.7 ± 0.1

ns

Evenness

0.54 ± 0.02

0.50 ± 0.05

ns

0.79 ± 0.03

0.60 ± 0.01

<0.05

Total abundance (ind. m⁻²)

2,589 ± 201

4,972 ± 782

ns

392 ± 134

1,194 ± 233

<0.05

Abundance without mussels (ind. m⁻²)

2,586 ± 202

1,061 ± 140

<0.01

392 ± 134

565 ± 143

ns

Biomass (g AFDW m⁻²)

40.8 ± 15.2

309 ± 59

<0.01

4.1 ± 2.4

602 ± 136

<0.01

Biomass without mussels (g AFDW m⁻²)

40.8 ± 15.2

9.0 ± 1.25

<0.05

4.1 ± 2.4

22.3 ± 14.9

ns

Heteromastus filiformis (ind. m⁻²)

1,941 ± 180

130 ± 88

<0.01

11 ± 11

7 ± 4

ns

Scoloplos armiger (ind. m⁻²)

138 ± 21

0

<0.01

110 ± 32

10 ± 4

<0.05

Pectinaria koreni (ind. m⁻²)

231 ± 34

424 ± 56

ns

–

–

–

Nephtys cirrosa (ind. m⁻²)

–

–

–

84 ± 30

5 ± 4

<0.05

Magelona papilicornis

–

–

–

21 ± 6.5

0

<0.01

Nereis sp. (ind. m⁻²)

0

78 ± 17

<0.01

0

16 ± 4

<0.05

Harmothoe impar/imbracata (ind. m⁻²)

0

65 ± 17

<0.01

0

94 ± 19

<0.01

Capitella capitata (ind. m⁻²)

0

38 ± 22

<0.05

3 ± 3

74 ± 48

<0.05

Syllidia armata (ind. m⁻²)

0

51 ± 19

<0.01

–

–

–

Polydora sp. (ind. m⁻²)

0

38 ± 15

<0.01

0

9 ± 4

<0.05

Oligochaeta (ind. m⁻²)

26 ± 14

24 ± 9

ns

0

112 ± 78

<0.01

Ensis sp. (g AFDW m⁻²)

28.4 ± 15.5

0

<0.05

0.03 ± 0.01

0

ns