Table 1 Monthly variation of total plant biomass (gDW.m ⁻² ) and amphipod abundance and values of Shannon-Wiener ( H ′) and evenness indexes ( J ′)

Macroalgae and seagrass

Ulva lactuca

4

7

5.15

2.11

3

3

8

10.73

60

66.10

68.60

30

Cladophora sp.

0

0

7

2

3

3.73

0

0

8

11

0

0

Gracilariopsis longissima

1

4

0

3

14

20

27

30

20.10

11.01

8

9.08

Gracilaria bursa-pastoris

1

4

0

4

15

20

30.18

32

23

11.10

8.01

9

Cymodocea nodosa

38

38.48

30

12

8

7

8

8

16.2

17

17

37.08

Monthly total biomass

44

61.48

41.15

23.11

44

53.73

73.18

80.73

127.12

116.21

96.7

85.16

Amphipods

Gammarus aequicauda (Martynov, 1931)

99

199

87

111

128

132

320

165

172

116

41

233

1,803

49.80

1

49.80

De

Gammarus insensibilis Stock, 1966

89

19

38

113

92

11

89

12

18

13

6

94

594

16.40

1

16.40

De

Gammarella fucicola (Laech, 1814)

15

49

32

18

34

87

81

325

8.97

0.66

5.92

He

Elasmopus rapax Costa, 1853

9

1

5

15

0.41

0.25

0.10

S

Monocorophium acherusicum (Costa, 1853)

7

3

1

4

15

0.41

0.33

0.13

Ds

Ericthonius difformis (Milne-Edwards, 1830)

21

20

28

67

11

48

8

14

8

32

29

286

7.90

0.91

7.18

Ds

Cymadusa filosa Savigny, 1816

13

19

12

6

15

5

14

153

159

84

480

13.26

0.66

8.75

He

Microdeutopus gryllotalpa Costa, 1853

5

10

1

9

9

34

0.94

0.41

0.38

He

Dexamine spinosa (Montagu, 1813)

11

10

4

42

67

1.85

0.33

0.61

De

Caprella sp. (Laech, 1814)

1

1

0.02

0.08

0.00

O

N

238

262

165

297

246

220

488

257

221

399

322

505

3,620

100

H′

2.19

1.53

1.70

1.54

1.37

1.05

1.74

1.74

1.03

1.92

1.68

1.98

J′

0.78

0.54

0.85

0.97

0.68

0.45

0.58

0.62

0.4

0.74

0.72

0.76