Helgoland Marine Research

, Volume 58, Issue 3, pp 168–182 | Cite as

Polychaetes associated with the sciaphilic alga community in the northern Aegean Sea: spatial and temporal variability

Original Article

Abstract

Polychaete biodiversity has received little attention despite its importance in biomonitoring. This study describes polychaete diversity, and its spatial and temporal variability in infralittoral, hard substrate assemblages. Seven stations were chosen in the central area of the northern Aegean Sea. At each station, one to three depth levels were set (15, 30 and 40 m). Five replicates were collected by scuba diving with a quadrat sampler (400 cm2) from each station and depth level during summer for the spatial analysis, and seasonally for the study of temporal changes. Common biocoenotic methods were employed (estimation of numerical abundance, mean dominance, frequency, Margalef’s richness, Shannon-Weaver index and Pielou’s evenness). A total of 5,494 individuals, belonging to 79 species, were counted and classified. Diversity indices were always high. Clustering and multidimensional scaling techniques indicated a high heterogeneity of the stations, although these were all characterized by the sciaphilic alga community. A clear seasonal pattern was not detectable. Summer and autumn samples discriminate, while winter and spring form an even group. The abundance/biomass comparison indicated a dominance of k-strategy patterns, characteristic of stable communities.

Keywords

Polychaeta Infralittoral Aegean Sea Hard substrate Biodiversity 

Introduction

There is a growing interest in biodiversity, defined as the collection of genomes, species and ecosystems occurring in a geographical region (CBDMS 1995). The most fundamental meaning of this term is expressed at species level by the concept of species richness (Bianchi and Morri 2000). Species richness does not simply refer to the number of species, but includes species variety, i.e. composition, which is an important indicator of diversity across spatial scales (Costello 1998). According to the Convention of Biological Diversity definition, biodiversity concerns variability within species (individual/population level), between species (community level), and at the ecosystem level (functional level). The value of biodiversity as an indicator of environment health, and for the functioning of ecosystems, is now largely recognized (Gaston and Spicer 1996; Bianchi and Morri 2000).

Polychaetes are among the most frequent and species-rich taxa in marine benthic environments (Fauchald and Jumars 1979; Costello et al. 1996). Many authors have suggested a key role of polychaetes in biomonitoring studies (Reish 1978; Bellan 1980; Wenner 1988; Warwick 1986, 1993; Damianidis and Chintiroglou 2000). Before data from polychaete assemblages can be used to identify disturbances, as demanded by international directives and conventions, it is necessary to provide a database on the composition of natural assemblages (Pocklington and Wells 1992; Gaston and Spicer 1996; Ergen and Cinar 1997).

The distribution of polychaetes in hard-bottomed sites is commonly related to algal structure and zonation (Giangrande 1988; Somaschini 1988; Sardà 1991). However, the distribution of polychaetes depends on algal cover and epiphytes more than on the presence of particular macroalgal species (Abbiati et al. 1987; Sardà 1987; Giangrande 1988; Fraschetti et al. 2002). There is a large amount of literature on polychaetes in midlittoral and infralittoral zones of the western Mediterranean (Retiere and Richoux 1973; Cardell and Gili 1988; reviewed by Sardà 1991), yet much less information on the situation in the eastern Mediterranean (Nicolaidou et al. 1986; Bellan-Santini et al. 1994; Chintiroglou 1996; Ergen and Cinar 1997; Damianidis and Chintiroglou 2000).

According to Marinopoulos (1988), the infralittoral zone can be divided into three ecologically different belts. This study was restricted to the lowest belt (below 15 m), where the sciaphilic alga community occurs (Laubier 1966; Margalef 1984; Antoniadou et al. 2004). Its aim was to reveal the spatial and temporal variability of the polychaete fauna associated with the sciaphilic alga community.

Methods

Sampling sites

Seven coastal stations were selected in the northern part of the Aegean Sea (Fig. 1). These sites share some common physical characteristics, such as hard substrate down to a depth of 30–40 m and an inclination of more than 50° (for details see Antoniadou et al. 2004), which lead to the establishment of the sciaphilic alga community in the lower infralittoral zone (15–40 m). According to the vertical extension of the hard substrate, one to three depth levels (15, 30 and 40 m) were set at each station, covering the depth range of the local sciaphilic alga community. The main physical characteristics of the sampling sites are given in Table 1. For the spatial analysis, the sites were sampled during summer 1998 (stations 1–6) or summer 1999 (station 7). Station 3 was chosen for the temporal analysis (summer 1997 to summer 1998) due to its geomorphology protecting it from the N, NE and NW winds that usually occur in this area during winter.
Fig. 1

Map of the study area

Table 1

Physical and biotic characteristics of the sampling sites

Station

Slope (°)

Maximum depth (m)

Prevailing winds

Depth level (m)

Pilot algal species

1 Kakia Skala

90

65

N, NE, SE

15

Polysiphonia sp.

30

Polysiphonia sp., Lithophyllum sp.

40

Lithophyllum sp., Peyssonnelia sp.

2 Kelyfos

70

35

S, SW, SE, NW

15

Padina pavonica, Polysiphonia sp.

30

Womersleyella setacea, Padina pavonica

3 Porto Koufo

90

50

SW

15

Womersleyella setacea

30

Womersleyella setacea

40

Lithophyllum sp., Peyssonnelia sp.

4 Armenistis

50–60

35

NE

15

Womersleyella setacea, Padina pavonica

30

Womersleyella setacea

5 Vourvourou

55

18

N, SE

15

Pseudolithophyllum expansum, Gelidium pectinatum

6 Eleftheronissos

70

30

NE, SE, N, S

30

Lithothamnion sp., Polysiphonia sp.

7 N. Iraklitsa

65

35

NE, NW, SE

15

Cutleria multifida, Gelidium pectinatum

30

Cutleria multifida, Gelidium pectinatum

Physico-chemical factors

Measurements of the main abiotic factors (temperature, salinity, conductivity, dissolved O2 and pH) were carried out along the water column using a WTW salinity-conductivity-O2 meter and Lovibond Checkit (pH meter) micro-electronic equipment. Water clarity was determined using a Secchi disc. The inclination of the hard substratum was calculated using a clinometer; currents (speed and direction) were recorded using the autographic current meter Sensordata SD-4 in May 2000.

Data collection

Sampling was carried out by scuba diving using a quadrat sampler (Bellan-Santini 1969) covering a surface of 400 cm2 (Weinberg 1978; Karalis et al. 2003). Following Marinopoulos (1988), five replicates were collected at each depth level and site (see Table 1). A total of 75 and 65 samples were available for the study of spatial and seasonal variations, respectively. All samples were sieved (0.5 mm mesh size) and preserved in a 10% formalin solution. After sorting, all polychaetes were counted, weighted (wet weight) and identified to species level. Furthermore, the algae collected were identified, and the dominant species (in terms of percentage cover) were estimated.

Statistics

Common biocoenotic methods were employed to analyze the data (Hong 1982; Marinopoulos 1988; Antoniadou et al. 2004). Thus, the numerical abundance per square meter (A/m2), the mean dominance (mD), the frequency (F), and a variety of diversity indices (Margalef’s richness, Shannon-Weaver H’ and Pielou’s evenness J’ based on log2) were calculated.

In order to check the null hypothesis (no significant variations in polychaete abundance), a two-way mANOVA test was used to examine the effects of two different factors: depth, and space or time. A logarithmic transformation (logx+1) was used in order to normalize the variance of numerical abundance data in both cases (Zar 1984; Clarke and Green 1988).

The data obtained from each sampling site were analyzed using cluster and multidimensional scaling (MDS) techniques, based on the Bray-Curtis similarity and log-transformed numerical abundances, using the PRIMER package (Clarke and Warwick 1994). The significance of the multivariate results was assessed using the ANOSIM test. SIMPER analysis was applied in order to identify the percentage contribution of each species to the overall similarity within a site, and to the dissimilarity among sites (Clarke and Warwick 1994). Moreover, an abundance-biomass comparison (ABC curves) was performed for each site in order to detect any kind of disturbance in the examined assemblages (Warwick 1986). All the above techniques were employed in both the spatial and temporal analysis.

Results

Spatial variation

Abiotic factors

The main abiotic parameters showed slight variations in relation to depth and sampling site (Table 2). A detailed analysis is given by Antoniadou et al. (2004). Water currents follow the general pattern of cyclonic circulation in the northern Aegean Sea (Stergiou et al. 1997; Somarakis et al. 2002).
Table 2

Mean values of the main abiotic factors in the water column (0–40 m) for stations 1–7 (summer) and for seasons (station 3). T temperature, S salinity, C conductivity, WC water clarity, CV water current velocity, CD water current direction

Station

T (°C)

S (psu)

C (μS/cm)

O2 (mg/l)

pH

WC (m)

CV (cm/s)

CD

1

23.1

35.4

48.2

6.98

8.6

21

2.69

NE

2

23.1

35.3

48.1

7.42

8.2

22

1.93

N

3

21.6

36.1

49.0

7.22

8.2

20

1.80

SW

4

26.2

34.6

47.0

8.18

7.5

20

3.10

E

5

25.9

34.9

47.3

7.64

8.2

12

2.74

SE

6

23.1

34.8

47.5

7.73

8.1

21

11.40

N

7

25.7

33.2

45.5

7.75

8.7

18

1.58

NW

Seasons

Summer

21.6

36.1

49.0

7.22

8.2

20

Autumn

19.3

36.8

50.2

6.72

8.2

23

Winter

12.9

37.4

51.3

6.84

8.2

18

Spring

14.1

36.9

50.8

8.25

8.2

16

Community description

All sites can be classified to the sciaphilic alga community (Augier 1982; Pérès and Picard 1964; Bellan-Santini et al. 1994). However, according to the dominant algae, four facies could be distinguished:
  1. 1.

    A facies of the red alga Polysiphonia sp. or Womersleyella setacea;

     
  2. 2.

    A facies of the red alga Gelidium pectinatum and the brown alga Cutleria multifida;

     
  3. 3.

    A facies of the red algae Lithophyllum sp., Lithothamnion sp. and Peyssonnelia sp.; and

     
  4. 4.

    A facies with the mixed occurrence of the red algae Pseudolithophyllum expansum, Gelidium pectinatum, Lithophyllum sp. and Polysiphonia sp. (see Antoniadou et al. 2004).

     
The main biocoenotic parameters are presented in Table 3. Overall, 4,361 individuals were counted, belonging to 79 species. Twenty-four species were the most dominant: only Syllis hyalina and Nereis rava were present at all sites.
Table 3

Polychaetes from the facies of the sciaphilic alga community (replicates of each depth level pooled). N number of individuals, S number of species, A (=N/m2) abundance, F frequency, d Margalef richness, H’ Shannon-Weaver index, J’ equitability index

Species

Station 1

Station 2

Station 4

Station 5

Station 6

Station 7

A

F

A

F

A

F

A

F

A

F

A

F

15 m

30 m

40 m

15 m

30 m

15 m

30 m

15 m

30 m

15 m

30 m

Laetmonice hystrix (Savignyi, 1820)

10

14

Harmothoe areolata (Grube, 1860)

5

7

5

10

Harmothoe ljungmani (Malmgren, 1867)

10

5

20

Harmothoe spinifera (Ehlers, 1864)

10

5

20

5

10

20

10

50

10

40

10

40

10

20

Chrysopetalum debile (Grube, 1855)

5

7

5

10

5

10

Euphrosine foliosa Audouin & Milne Edwards, 1833

Phyllodoce madeirensis (Langerhans, 1880)

5

10

Kefersteinia cirrata (Keferstein, 1862)

5

7

5

10

30

5

10

5

20

Syllidia armata Quatrefages, 1865

10

10

Pionosyllis lamelligera Saint-Joseph, 1856

5

7

5

10

5

20

Exogone naidina Orsted, 1845

30

10

5

35

5

10

Grubeosyllis limbata (Claparede, 1868)

15

14

15

20

Sphaerosyllis pirifera Claparede, 1868

95

105

10

74

30

50

60

20

40

10

40

15

5

40

Spermosyllis torulosa Claparede, 1864

5

5

14

Eusyllis blomstrandi Malmgren, 1867

10

7

5

10

Pterosyllis formosa Claparede, 1863

Haplosyllis spongicola (Grube, 1855)

10

10

14

5

10

30

10

5

20

20

80

10

20

15

5

40

Syllis amica Quatrefages, 1865

5

45

40

Syllis armillaris Muller, 1771

10

10

40

Syllis cornuta Rathke, 1843

35

35

20

54

55

50

55

95

80

10

40

15

15

40

Syllis gracilis Grube, 1840

5

10

10

10

30

Syllis hyalina Grube, 1863

170

170

50

80

40

25

80

160

70

100

60

80

45

60

30

55

70

Syllis krohnii Ehlers, 1864

10

20

5

10

Syllis prolifera Krohn, 1852

80

30

10

46

120

45

100

70

40

80

30

60

25

80

5

10

Syllis vittata Grube, 1840

30

5

40

Trypanosyllis coeliaca Claparede, 1868

57

10

20

10

35

50

5

20

10

10

30

Trypanosyllis zebra (Grube, 1860)

35

10

5

35

15

40

50

5

10

45

60

10

20

35

10

60

Xenosyllis scabra (Ehlers, 1864)

5

10

Nereis rava Ehlers, 1868

155

60

30

67

65

250

100

270

165

100

55

80

55

100

120

70

100

Nereis zonata Malmgren, 1867

20

5

5

27

40

85

70

55

25

40

30

80

10

20

10

25

50

Platynereis dumerilii (Audouin & Milne Edwards, 1833)

60

35

15

60

10

110

70

150

85

100

15

40

15

20

60

Nereididae Heteronereis stage

10

14

Glycera tesselata Grube, 1863

105

65

10

67

95

90

90

175

440

100

15

40

Glycinde nordmanni (Malmgren, 1865)

Goniada maculata Ortsed, 1843

Arabella iricolor (Montagu, 1804)

10

10

Dorvillea rubrovittata (Grube, 1855)

5

10

15

10

50

Eunice oerstedii Stimpson, 1854

35

40

5

10

10

40

Eunice torquata Quatrefages, 1865

10

14

15

30

Eunice vittata (Delle Chiaje, 1929)

110

95

25

80

40

30

15

180

60

10

40

30

40

70

Lysidice ninetta (Audouin & Milne Edwards,1833)

20

25

15

60

30

20

45

40

35

80

10

40

20

45

80

Marphysa fallax Marion & Bobretzky, 1875

5

7

15

20

Nematonereis unicornis (Grube, 1840)

15

15

14

15

50

70

20

5

30

15

40

Palola siciliensis (Grube, 1840)

5

10

20

10

Lumbrineris coccinea (Renier, 1804)

5

10

Scoletoma funchalensis (Kinberg, 1865)

10

14

5

15

30

50

40

10

10

Aponuphis bilineata (Baird, 1870)

5

7

Onuphis sp.

Laonice cirrata (Sars, 1851)

Polydora caeca (Orsted, 1843)

40

10

Dodecaceria concharum Orsted, 1843

5

10

Capitella capitata (Fabricius, 1780)

15

10

Heteromastus filiformis (Claparede, 1864)

15

30

Euclymene oerstedii (Claparede, 1836)

5

7

Polyopthalmus pictus (Dujardin, 1839)

5

7

75

40

10

40

Sclerocheilus minutus Grube, 1863

5

10

Amphitrite variabilis (Risso, 1826)

10

5

14

5

10

5

10

30

Theostoma oerstedi (Claparede, 1864)

Polycirrus aurianticus Grube, 1860

5

10

Terebella lapidaria Linneaus, 1767

5

10

5

10

Terebellides stroemi Sars, 1835

5

7

Amphiglena mediterranea (Leyding, 1851)

70

15

40

105

50

80

50

20

70

5

20

20

5

50

Branchiomma bombyx (Dalyell, 1853)

10

5

5

27

5

10

30

5

5

20

Sabella fabricii Kroyer, 1856

10

20

Sabella pavonina Savignyi, 1820

10

7

Jasmineira candela (Grube, 1863)

5

10

20

20

Janita fimbriata (Delle Chiaje, 1822)

10

14

5

10

Ficopomatus enigmaticus (Fauvel, 1923)

5

20

Hydroides pseudouncinata Zibrowius, 1968

5

10

5

20

5

10

Placostegus crystallinus Zibrowius, 1968

10

20

Pomatoceros triqueter (Linnaeus, 1865)

5

20

40

15

30

60

Serpula concharum Langerhans, 1880

5

7

15

10

5

20

20

35

50

Serpula vermicularis Linnaeus, 1767

10

7

10

10

Vermiliopsis infundibulum (Gmelin, 1788)

5

10

5

14

35

40

25

50

50

35

100

30

40

45

25

80

Vermiliopsis labiata (Costa, 1861)

5

7

5

10

5

10

Protula sp.

5

10

5

10

5

10

Spirorbidae

9,380

910

90

725

40

Polygordiidae

5

10

15

20

S

26

29

21

27

36

23

24

18

18

26

28

N

217

143

54

2,010

250

394

262

83

57

105

101

A

1,085

715

270

10,050

2,160

1,970

1,310

415

285

525

505

d

4.64

5.64

5.01

5.11

6.33

3.68

4.13

3.85

4.21

5.37

5.85

H

3.87

4.04

4.01

3.81

4.39

3.21

3.28

3.81

3.74

4.18

4.21

J

0.82

0.83

0.92

0.81

0.85

0.71

0.71

0.91

0.90

0.89

0.87

Abundance of polychaete fauna

Concerning the spatial distribution, mANOVA showed that both depth and site had a significant effect (F=15.94, P=0.001 and F=13.30 P=0.001, respectively). The Fisher PLSD test indicated that differences exist between the three depth levels (15, 30 and 40 m) and between stations 2 and 4 on the one hand, and the rest of the stations on the other. Stations 2 and 4 are discriminated mainly due to the presence of high numbers of spirorbids. The decrease in polychaete abundance with depth is probably related to the algal vertical zonation: filamentous algae dominate in shallow waters, and encrusting algae in deep.

Composition and diversity of polychaete fauna

The spatial fluctuation of the diversity indices and of the total number of individuals (N) and species (S) at each depth level is shown in Fig. 2. Richness values (D) ranged from 3.80 to 6.60, H’ values from 3.28 to 4.35 and J’ values from 0.72 to 0.91. These indices are a function of the number of species and individuals: high N and low S values result in low diversity indices. Spirorbids were excluded from the above calculation. They occurred at high numbers at stations 2 (15 and 30 m) and 4 (15 m), reaching abundances of 9,380, 910 and 725 individuals/m2, respectively, thus altering the diversity values.
Fig. 2

Biocoenotic parameters (above) and diversity indices (below) for each depth level (15, 30, 40 m) and stations in summer. d Margalef richness, H’ Shannon-Weaver index, J’ Pielou’s evenness, S number of species, N number of individuals

Affinity analysis

The affinity of the samples (station, depth) is given in Fig. 3. Both analyses (cluster and non-metric MDS) indicate a separation of the samples into four main groups at about 55% similarity degree. The stress value for the two-dimensional MDS configuration is 0.16. The one-way ANOSIM test gave global R=0.87, at a significance level of P<0.1, indicating a good discrimination between the four basic groups. Further examination in order to localize the differences among the groups by means of a pairwise test did not reveal any significant variation in R values, yet did show higher similarities between groups A and B, and between C and D.
Fig. 3

Affinity of summer samples from different sites (stations 1–7) and depths (15, 30, 40 m). Results of cluster (above) and MDS (below) analysis based on Bray-Curtis similarity index

SIMPER analysis identified 6–9 (13–19) species as responsible for 60% (90%) of the average similarity of groups, and 16–20 (38–46) species as responsible for 60% (90%) of the average dissimilarity of groups (Table 4).
Table 4

Percentage contribution of species to 60% similarity (S) within groups and /or dissimilarity (DS) among groups, according to the spatial multivariate analysis

Species

A

B

C

D

A:B

A:C

A:D

B:C

B:D

C:D

S=59.9

S=63.2

S=56.9

S=67.7

DS=48.1

DS=53.6

DS=54.5

DS=49.4

DS=51.7

DS=48.1

Harmothoe ljungmani

2.24

3.03

Harmothoe spinifera

1.87

Grubeosyllis limbata

2.23

3.50

2.83

Exogone naidina

3.36

4.09

3.75

Sphaerosyllis pirifera

6.70

8.35

3.19

2.40

2.25

4.48

4.15

Haplosyllis spongicola

Syllis amica

2.06

2.20

1.90

Syllis cornuta

5.87

5.61

2.65

3.26

Syllis gracilis

2.75

3.73

Syllis hyalina

6.20

10.87

16.81

7.87

1.85

Syllis prolifera

7.83

6.01

9.25

2.02

3.00

5.04

4.04

4.08

Syllis vittata

2.04

2.22

1.89

Trypanosyllis coeliaca

1.88

Trypanosyllis zebra

2.54

2.06

3.12

Nereis rava

9.68

9.94

10.95

3.91

3.85

4.66

3.47

3.60

Nereis zonata

7.29

3.49

3.40

2.18

2.00

Platynereis dumerilii

4.58

5.61

3.07

4.61

2.68

4.21

2.23

2.68

Glycera tesselata

9.45

10.90

4.88

6.61

6.16

7.96

4.03

Eunice vittata

8.53

7.87

3.63

2.29

2.14

5.51

4.02

Palola siciliensis

2.70

Lysidice ninetta

9.54

6.51

2.40

2.33

1.94

2.73

2.45

Nematonereis unicornis

2.15

3.45

3.64

2.31

Dorvillea rubrovittata

2.58

3.11

4.21

Scoletoma funchalensis

2.04

3.80

2.38

1.85

Polyopthalmus pictus

2.25

2.56

2.01

Polydora caeca

2.30

2.78

3.77

Amphitrite variabilis

2.66

2.59

Amphiglena mediterranea

7.83

6.40

1.84

5.18

3.12

4.69

2.35

2.70

Branchiomma bombyx

2.26

3.34

Serpula concharum

6.51

3.01

3.51

5.66

Pomatoceros triqueter

5.61

2.11

3.70

4.73

Vermiliopsis infundibulum

7.98

7.25

2.33

2.16

1.88

2.28

2.02

2.15

Spirorbidae

16.12

13.42

14.59

12.41

The ABC curves (Fig. 4) show that, for most sites, the biomass curve was above that of abundance. Accordingly, the k-dominance pattern was produced. For station 2, however, the situation was reverse, and for station 4 the two curves coincide. This is due to the extremely high number of spirorbids, species with very small body size and thus negligible biomass.
Fig. 4

ABC curves for stations 1–7 (summer)

Temporal variation

Abiotic factors

The seasonal pattern of the main abiotic parameters is summarized in Table 2. A seasonal thermocline was detected at about 20 m depth (end of July), while salinity and conductivity gained lower values during summer.

Community description

The main biocoenotic parameters are presented at Table 5. Overall 1,133 individuals were counted, belonging to 66 species. 24 species, largely the same as those reported in the spatial survey, were dominant in the seasonal samples. Syllis hyalina, Sphaerosyllis pirifera, Glycera tesselata and Vermiliopsis infundibulum were dominant in all seasons.
Table 5

Polychaetes from seasonal samples of the sciaphilic alga community at station 3 (replicates of each depth level pooled). N number of individuals, S number of species, A (=N/m2) abundance, F frequency, d Margalef richness, H’ Shannon-Weaver index, J’ equitability index, 30 m* sampling in July 1998

Species

Summer 1997

Autumn 1997

Winter 1998

Spring 1998

A

F

A

F

A

F

A

F

15 m

30 m

30 m*

40 m

15 m

30 m

40 m

15 m

30 m

40 m

15 m

30 m

40 m

Laetmonice hystrix (Savigny, 1820)

5

7

Harmothoe areolata (Grube, 1860)

5

7

5

7

5

10

20

Harmothoe ljungmani (Malmgren, 1867)

5

5

14

5

7

5

7

Harmothoe spinifera (Ehlers, 1864)

5

5

5

7

5

5

14

5

5

14

Scalisetosus fragilis (Claparede, 1868)

5

7

Pholoe minuta (Fabricius, 1780)

5

7

Chrysopetalum debile (Grube, 1855)

5

7

5

7

Euphrosine foliosa Audouin & MilneEdwards, 1833

5

5

5

7

Phyllodoce madeirensis (Langerhans, 1880)

5

5

10

5

15

27

5

7

Kefersteinia cirrata (Keferstein, 1862)

5

5

10

20

14

5

15

27

Syllidia armata Quatrefages, 1865

5

7

5

7

Pionosyllis lamelligera Saint-Joseph, 1856

5

5

5

15

5

7

5

7

5

5

5

20

Exogone naidina Orsted, 1845

55

10

25

45

5

7

5

7

Grubeosyllis limbata (Claparede, 1868)

45

35

10

45

5

7

Sphaerosyllis pirifera Claparede, 1868

130

50

55

20

90

15

65

10

54

35

30

46

25

65

54

Eusyllis blomstrandi Malmgren, 1867

20

10

5

5

30

5

7

Pterosyllis formosa Claparede, 1863

5

5

Haplosyllis spongicola (Grube, 1855)

5

5

10

15

5

7

10

5

15

34

5

10

5

20

Syllis amica Quatrefages, 1865

5

5

14

Syllis armillaris Muller, 1771

20

14

5

7

Syllis cirropunctata Michel, 1909

5

7

Syllis cornuta Rathke, 1843

35

5

25

20

55

15

10

5

34

25

5

5

40

Syllis hyalina Grube, 1843

120

95

65

105

80

30

25

40

10

30

25

46

95

50

5

54

Syllis krohnii Ehlers, 1864

5

5

5

7

5

7

Syllis prolifera Krohn, 1852

65

10

15

15

45

15

15

27

25

10

5

34

20

25

5

46

Trypanosyllis coeliaca Claparede, 1868

10

10

20

5

20

10

15

20

5

20

27

Trypanosyllis zebra (Grube, 1860)

15

5

5

15

10

5

25

46

20

20

15

5

20

Ceratonereis costae (Grube, 1840)

5

7

Nereis rava Ehlers, 1868

100

5

30

35

5

35

46

35

40

20

54

55

15

40

Nereis zonata Malmgren, 1867

10

5

5

15

10

15

27

5

10

10

34

5

7

Platynereis dumerilii (Audoin & Milne Edwards, 1833)

20

30

35

55

30

15

54

15

40

34

5

7

Nereididae Heteronereis stage

15

10

Glycera tesselata Grube, 1863

115

110

65

40

85

5

70

30

67

60

55

40

67

45

80

60

Glycinde nordmanni (Malmgren, 1865)

5

5

Goniada maculata Orsted, 1843

5

5

5

7

Arabella iricolor (Montagu, 1804)

Dorvillea rubrovittata (Grube, 1855)

5

5

Eunice oerstedii Stimpson, 1854

5

5

5

7

15

5

27

15

5

20

Eunice torquata Quatrefages, 1865

10

7

5

7

Eunice vittata (Delle Chiaje, 1929)

20

65

30

5

50

35

10

27

65

5

35

40

20

25

5

40

Lysidice ninetta (Audoin & Milne Edwards, 1833)

30

15

35

40

5

5

14

15

20

5

34

35

20

5

54

Nematonereis unicornis (Grube, 1840)

5

5

10

5

5

14

5

7

10

7

Lumbrineris coccinea (Renier, 1804)

5

5

Scoletoma funchalensis (Kinberg, 1865)

35

15

5

35

20

10

10

34

35

10

5

40

10

15

10

46

Onuphis sp.

5

5

5

7

Laonice cirrata (Sars, 1851)

5

5

Polydora caeca (Orsted, 1843)

5

7

Polyopthalmus pictus (Dujardin, 1839)

5

5

14

5

5

14

Pherusa sp.

5

7

5

7

Amphitrite variabilis (Risso, 1826)

10

10

10

5

30

45

10

20

Theostoma oerstedi (Claparede, 1864)

5

5

Polycirrus aurianticus Grube, 1860

5

7

Terebellides stroemi Sars, 1835

25

15

5

7

Amphiglena mediterranea (Leyding, 1851)

120

35

20

15

65

10

15

20

40

5

15

46

40

10

5

40

Branchiomma bombyx (Dalyell, 1853)

15

25

15

35

15

14

Sabella pavonina Savignyi, 1820

5

5

5

7

10

7

Hydroides pseudouncinata Zibrowius, 1968

10

14

Placostegus crystallinus Zibrowius, 1968

5

5

14

5

7

Pomatoceros lamarckii (Quatrefages, 1865)

5

7

Pomatoceros triqueter (Linnaeus, 1865)

30

10

30

5

7

5

5

14

25

5

20

Jasmineira candela (Grube, 1863)

5

5

5

7

5

7

Janita fimbriata (DelleChiaje, 1822)

5

5

15

20

5

7

Serpula concharum Langerhans, 1880

5

15

15

5

7

25

5

27

Serpula vermicularis Linnaeus, 1767

5

5

5

7

20

14

15

14

Vermiliopsis infundibulum (Gmelin, 1788)

65

10

15

15

50

15

10

15

34

15

5

20

34

45

25

5

54

Protula sp.

5

5

5

10

20

S

37

27

19

21

18

18

27

29

19

23

21

29

16

N

233

122

80

68

49

62

63

103

56

66

93

88

19

A

1,165

610

400

340

260

320

330

530

285

350

510

465

100

d

6.61

5.41

4.1

4.74

4.37

4.12

6.28

6.04

4.47

5.25

4.41

6.25

5.1

H

4.36

4.01

3.73

3.59

3.64

3.46

4.41

4.29

3.72

4.15

3.82

4.12

3.73

J

0.84

0.84

0.88

0.82

0.87

0.83

0.93

0.88

0.87

0.92

0.87

0.85

0.97

Abundance of polychaete fauna

Only depth had a significant effect (mANOVA: F=6.58, P=0.002). The Fisher PLSD procedure revealed that this effect was restricted to 40 m versus 15 and 30 m. No direct seasonal effect on polychaete abundance was detectable (F=2.30, P=0.06).

Composition and diversity of polychaete fauna

The temporal fluctuation of the diversity indices, the total number of individuals (N) and the number of species (S) at each depth level is shown in Fig. 5. Richness values (D) ranged from 3.91 to 6.48, H’ values from 3.45 to 4.41, and evenness values (J’) from 0.80 to 0.97. In general, diversity indices varied among seasons.
Fig. 5

Biocoenotic parameters (above) and diversity indices (below) over an annual cycle at station 3 (15, 30, 40 m depth). S summer, A autumn, W winter, Sp spring, d Margalef richness, H’ Shannon-Weaver index, J’ Pielou’s evenness, S number of species, N number of individuals

Affinity analysis

The seasonal discrimination of samples is given in Fig. 6. Five groups (A–E) can be distinguished at about 50% similarity level. The stress value for the two-dimensional configuration is 0.12, indicating a good ordination (Clarke and Warwick 1994). The ANOSIM test confirms the results of the discriminative techniques (R=0.88, P<0.1). The pairwise test showed that the variations were significant in all cases (R ranging from 0.75 to 1).
Fig. 6

Affinity of seasonal samples from different depths at station 3. Results of cluster (above) and MDS (below) analysis based on Bray-Curtis similarity index

SIMPER analysis identified 5–7 (10–17) species as responsible for 60% (90%) of the average similarity of groups, and 12–20 (22–38) species as responsible for 60% (90%) of the average dissimilarity of groups (Table 6).
Table 6

Percentage contribution of species to 60% similarity (S) within groups and/or dissimilarity (DS) among groups, according to the temporal multivariate analysis

Species

C

E

A:B

A:C

A:D

A:E

B:C

B:D

B:E

C:D

C:E

D:E

S=51.5

S=58.9

DS=71.4

DS=57.8

DS=67.7

DS=67.8

DS=57.8

DS=53

DS=57.1

DS=54.5

DS=50.2

DS=49.9

Harmothoe spinifera

2.21

Phyllodoce madeirensis

6.02

4.97

2.47

4.54

3.00

2.96

Syllidia armata

5.40

3.04

6.08

3.93

2.37

Grubeosyllis limbata

2.54

2.21

2.70

2.93

Exogone naidina

Haplosyllis spongicola

2.41

2.61

Syllis amica

10.34

3.69

6.68

6.27

7.54

4.24

3.24

5.34

4.73

3.22

Syllis armillaris

3.25

Syllis cirropunctata

5.40

5.12

6.08

4.33

Syllis cornuta

2.21

Syllis hyalina

3.97

3.74

5.35

Syllis krohni

11.46

3.69

4.12

5.67

6.29

3.01

2.60

4.50

6.26

3.02

Trypanosyllis coeliaca

6.98

2.86

3.37

5.24

4.45

Trypanosyllis zebra

4.66

4.97

2.98

4.41

4.46

3.07

Pionosyllis lamelligera

3.25

2.16

2.47

Nereis rava

2.21

2.62

Nereis zonata

6.98

5.22

9.41

4.80

3.03

2.79

3.89

3.60

3.76

Ceratonereis costae

3.51

2.33

2.81

2.55

Platynereis dumerilii

8.54

4.66

5.15

5.24

2.23

4.46

2.36

Heteronereis stage Nereididae

15.12

6.41

8.11

2.64

4.15

2.95

5.47

7.63

Goniada maculata

17.08

13

6.53

11.59

3.14

8.94

7.21

7.68

Eunice vittata

3.69

3.50

2.91

Nematonereis unicornis

6.04

3.39

2.62

2.85

2.81

3.52

5.78

Lumbrineris coccinea

16.16

6.47

6.50

3.18

3.12

4.15

2.26

8.44

2.45

6.34

Polydora caeca

2.84

2.64

Polycirrus aurianticus

2.33

2.21

2.62

2.10

Terebellides stroemi

2.48

2.13

2.44

2.85

Amphiglena mediterranea

3.14

2.62

Branchiomma bombyx

10.77

6.92

3.25

3.42

4.41

4.15

4.95

Sabella pavonina

2.57

2.84

Serpula concharum

3.14

2.62

Serpula vermicularis

3.25

2.62

2.81

2.64

Placostegus crystallinus

3.69

3.14

3.50

2.87

2.81

Pomatoceros lamarckii

3.14

2.80

2.62

2.38

2.81

2.94

Vermiliopsis infundibulum

4.66

6.27

4.54

3.58

4.55

3.78

3.78

Hydroides pseudouncinata

2.35

2.35

The ABC curves for different seasons show biomass curves being always above those of abundance (Fig. 7). Therefore, the k-strategy pattern dominated throughout the year.
Fig. 7

ABC curves for different seasons (station 3). S summer, A autumn, W winter, Sp spring

Discussion

According to Pérès and Picard (1964), the Mediterranean infralittoral zone comprises two distinct communities: the photophilic alga community (at the upper level) and the sciaphilic alga community (at the lower level, often mentioned as precoralligenous and coralligenous). These two communities share some common characteristics: they both depend on the presence of different algal forms (Bellan-Santini et al. 1994) and are influenced by the hydrodynamism and light (Hong 1982; Marinopoulos 1988).

Bellan (1964, 1969) studied the photophilic alga community and found 128 species of Polychaeta which were classified, according to their ecological preferences, to 11 discrete “stocks”. Cardell and Gili (1988) studied the facies of Lithophyllum tortuosum and recorded 71 species. They concluded that this assemblage is very homogeneous, both spatially and temporally. However, Sphaerosyllis pirifera and Platynereis dumerilii showed an increase in numerical abundance in summer. Most species were common in the hard substrate stock (Bellan 1969), and especially within the photophilic alga community: some species were characteristic of the concretioned substrate (Laubier 1966; Sardà 1991). Fraschetti et al. (2002) studied the facies of Cystoseira amentacea and found 59 species of Polychaeta, most of which were common species among sublittoral photophilic algae (Sardà 1991). The same authors did not find any noticeable seasonal changes, with the exception of the large numbers of Platynereis dumerilii in summer. Chintiroglou (1996) reported 87 species associated with Cladocora caespitosa colonies at 5–18 m depth, and Damianidis and Chintiroglou (2000) recognized 48 species associated with Mytilus galloprovincialis assemblages in the upper infralittoral zone. Sardà (1991), in a study of hard substrate communities from 1 to 40 m depth, found 220 species and discriminated five distinct communities: the Lithophyllum lichenoides (with the lowest diversity), the shallow photophilic, the deeper photophilic, the Posidonia oceanica rhizomes and the infralittoral sciaphilous community. The contributions of the different ecological stocks (Bellan 1969) to these communities change according to habitat complexity. In our study, we found 79 species of polychaetes in the sciaphilic alga community (15–40 m), while Marinopoulos (1988) found 36 (21 common) at similar depths. Most of these species are members of the photophilic alga community, but there is also a significant contribution of cryptic, hard substrate, soft substrate and coralligenous (concretioned substrate) species. It seems that polychaetes have a large ecological tolerance and that their occurrence is largely dependent on substrate availability and complexity (Bellan 1964, 1969; Hong 1982). We found clear spatial differences in polychaete distribution, while temporal differences were less apparent. The spatial distribution of polychaetes largely corresponds with the occurrence of different algal facies. We have noted a high affinity between stations 1 and 3 at all depth levels. This could be expected, since these two sites share some common characteristics such as the high inclination (~90°) and large bathymetrical extension of the rocky substrate. Station 7 is separated, probably due to abiotic parameters (low salinity). Its relatively moderate inclination sets station 7 near to stations 5 and 6, while the sharpest slope ranks stations 2 and 4 closer to stations 1 and 3. The depth level of 40 m (stations 1 and 3) shows high affinity with stations 5 and 6, as it hosts a fairly low number of polychaete species and individuals. SIMPER analysis showed that both the similarities within groups and the dissimilarities between groups were the result of small contributions of a large number of species, indicating a diverse community with a highly complex structure (Dahl and Dahl 2002). This heterogeneity may result from the presence of several algal species of different architecture (Chemello and Milazzo 2002). Fan-shaped structures and filamentous forms dominate group A, filamentous forms group B, encrusting forms group C, and filamentous bush-like encrusting forms group D. Many authors have stated that polychaetes are not related to specific algal species, but to specific algal architectures (Naim and Amoureux 1982; Sardà 1988; Gambi et al. 1995; Fraschetti et al. 2002). Groups A and B are characterized by high diversity and abundance in comparison to groups C and D. It should be noted that the high abundance in group A is mainly due to the presence of high numbers of spirorbids attached to the thalli of Padina pavonica. Spirorbids are capable of settling immediately after release from parental tubes and are typically multiannual in the sense of Fauchald (1983), living in unstable environments. They probably perish when the thalli of Padina pavonica decay after mid-September (Diapoulis and Koussouris 1988). Spirorbids strongly influence the discrimination of group A, the ABC analysis and the diversity indices. Another difference was found in the polychaete fauna associated with the two filamentous Rhodomelacea, Womersleyella setacea and Polysiphonia sp. An abundant and diversified polychaete is associated only with the former. Womersleyella setacea is an introduced and probably invasive species (Boudouresque and Verlaque 2002) which has spread over the Mediterranean (Verlaque 1989; Airoldi et al. 1995) and the northern Aegean Sea (Athanassiadis 1997). It forms paucispecific populations with increasing turf development. These turfs trap sediment, forming a stratum that prevents the development of other algal species on the rocky substrate (Piazzi and Cinelli 2000). However, the entrapped sediment increases the complexity of the system, offering suitable microhabitats for the settlement of many soft-sediment polychaete species.

The study of temporal changes in polychaete distribution revealed that summer is distinct from the other three seasons. Winter and spring form an even group, while autumn branches out according to depth. This is the case for the upper depth levels (15 and 30 m), where Womersleyella setacea dominated throughout the year. This species is capable of continuous vegetative reproduction (Athanassiadis 1997), creating a very stable and homogenous habitat which may contribute to the lack of seasonality. The image is much more complicated at the 40-mdepth level, where the dominant algae were represented by various species of Corallinacea and Peyssonneliacea. Here, summer samples were similar to winter ones, while autumn and spring samples discriminated.

According to the relevant literature, there is no distinct seasonality in the lower infralittoral zone, in contrast to the upper one (Hong 1982; Marinopoulos 1988). However, a discrimination of summer is frequently observed (Damianidis and Chintiroglou 2000) and may be due mainly to the massive recruitment of a few species, e.g. Platynereis dumerilii (Cardell and Gili 1988; Fraschetti et al. 2002). In our study, the bathymetric distribution of polychaetes changed with season, while the species inventory at the stations remained unchanged throughout the year. Marinopoulos (1988) also found seasonal changes in the abundance of polychaetes at different depths, with the same species (Syllis hyalina, Syllis prolifera, Syllis vittata, Platynereis dumerilii and Sphaerosyllis pirifera) being abundant at low depth during summer and in deeper waters during winter. It seems that the seasonality of the sciaphilic alga community is mainly achieved by a vertical rearrangement of the abundances of different polychaete species.

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Copyright information

© Springer-Verlag and AWI 2004

Authors and Affiliations

  1. 1.School of Biology, Department of ZoologyAristotle UniversityThessalonikiGreece
  2. 2.Zoological LaboratoryUniversity of AthensAthensGreece

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