Автор неизвестен - Inter-annualdepth-dependent toxicity and bioaccumulation of cadmium in marine benthic protist communities - страница 7

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0±0.

10

1377І0.

16

901±0.

20

680±0.

15

0±0.

10

0±0.

00

 

72

0±0.

00

1139І0.

10

272±0.

25

119±0.

17

0±0.

00

0±0.

00

 

 

0±0.

00

646±0.

25

272±0.

11

357±0.

10

0±0.

00

0±0.

00

 

96

0±0.

00

561±0.

20

527±0.

25

425±0.

10

544±0.

18

0±0.

10

 

 

0±0.

10

918±0.

13

272±0.

20

833±0.

25

306±0.

19

0±0.

00

performed using protist densities during the treatment showed that the main effect was due to depth, followed by time. The effect of depth was greater in the fractions with cadmium, but less in the control.

Number of species.

In the 2002 assay, the total number of species was lower in the control (176) than in the treatments with cadmium (187). Hierarchical Conglomerate Analysis performed using the number of species showed that the dissimilarities between the depths corresponding to the control were noticeably lower that those corresponding to the cadmium treatments (Fig. 3).

18 15 12 9 6 3

T—' fl <NI(N fl ^

Q      Q      Q      QiH      H      H H

Fig. 3. Dendrogram of the Hierarchical Cluster Analysis obtained using the number of species during the treatment in 2002. The y-axis represents the metric distance (Manhattan distance). CT, control; CD, fractions with cadmium

In the 2004 assay, after 24 h there was a decrease in the number of species at all depths except 8 cm, where the drop was registered after 48 h. The diminutions were more pronounced than in the control. (Fig. 4).

Depth-related effects. In the 2002 assay, the highest number of species was recorded at the surface (87, 46.52%), and this number decreased with depth, so that the percentages at 8 and 12 cm were conspicuously low (14.44 and 13.37% respectively). The greatest variations occurred at 4 cm (F 2.96; p < 0.05), thus coinciding with the results relating to density (Multiple Comparison). In the 2004 assay, both in the control and in the fractions with cadmium, depth was also a significant factor influencing the number of species (F 19.24; p < 0.05).

Time-related effects. At the surface and at 12 cm depth there was a decrease in the number of species after 24 h, while at 4 cm a drop was observed after

0

48 h, and at 8 cm there was no reduction. A recovery in the number of species was observed after 72 h at 0 and 4 cm, and after 48 h at 12 cm.

Variation in the protist groups. In the 2002 assay, the drop in the number of species at the surface after 24 h was due mainly to diatoms, whereas

100

I 60 depth 0 cm

1

1 40

20 0

100 ec 60

1 40

20 0

100 ec 60

e

.E

I

S3

с

e

.E

I

40 20 0

100 ec 60

yp

40 20 0

depth 4 cm

depth 8 cm

depth 12 cm

24 48 72

time [hours]

SARC    I    I HFLA    CIL    □ DIN

96

Fig. 5. Percentages of the number of species from the different protist groups (AFLA, autotrophic flagellates; DIAT, diatoms; SARC, sarcodines; HFLA, heterotrophic flagellates; CIL, ciliates; DIN, dinoflagellates) during the treatment with cadmium at the different depths in the 2002 assay

0

AFLA

DIAT

at 12 cm this decrease was due to all groups except diatoms. The drop in the number of species at 4 cm after 48 h was due to all groups except sarcodines. The recovery in the number of species at the surface and at 4 cm after 72 h was due to all groups except dinoflagellates at the surface, and autotrophic flagellates at 4 cm. The recovery observed after 48 h at 12 cm was due to all groups except sarcodines and diatoms (Fig. 5). Multiple Comparison showed that after 24 h there was a significant difference between all the depth levels (F 3.74; p < 0.05), and that the same thing occurred after 72 h (F 3.13; p < 0.05). These results coincided with those found with respect to the density. In the 2004 assay the groups contributing most to the variance were different in the control and in the fractions with cadmium. The only exception was recorded at 0 cm depth, in which heterotrophic flagellates were the principal group. In the control, heterotrophic flagellates, autotrophic flagellates and dinoflagellates were the groups contributing most to the variance at 4, 8 and 12 cm depth, respectively. In the treatments with cadmium, at the same depths the groups contributing most were diatoms, dinoflagellates and ciliates.

Biomass. The effects on biomass were similar to those observed with regard to the density and number of species.

Principal Component Analysis of the protist biomass in the 2002 experiment showed that cadmium treatment and control samples belonged to two distinct groups (Fig. 6).

0.6 A.

■-і----------------------------------------1—^ і і

-0.16 0.04 0.24 0.44 0.64

Fig. 6. Principal Component Analysis performed with the biomass values during the 2002 treatment; x-axis, first principal component; y-axis, second principal component; CT, control; CD, fractions with cadmium

Depth- and time-related effects. In the 2002 assay, at the surface and at 12 cm, a biomass diminution was observed after 24 h, while at 4 cm and, to a lesser extent, at 8 cm, this effect was observed after 48 h (Table 5). A recovery of biomass was recorded after 48 h at the surface and at 12 cm, and after 72 h at 4 cm and 8 cm. After 24 h, at the surface all the protist groups decreased noticeably in biomass, and the same occurred at 12 cm with the exception of diatoms. At 4 cm, all groups dropped in biomass with the exception of sarcodines after 48 h. At 8 cm, after 48 h, there was a slight diminution due mainly to heterotrophic flagellates. The recovery of biomass at the surface was due to diatoms, sarcodines and dinoflagellates, whereas at 12 cm, it was due to all groups except diatoms. The recovery of biomass at 4 and 8 cm was due to all groups except autotrophic flagellates.

In the 2004 assay (Table 6), there was a noticeable diminution of the biomass after 24 h, which continued until 48 h at the depths of 0, 4 and 8 cm. At 12 cm a slight recovery was recorded after 48 h, which lasted until 72 h, at which time a recovery was observed at the other depths. In the control, biomass at 4 and 8 cm decreased, though to a lesser extent than in the treatment with cadmium, while in the surface and 12 cm there was a rise in biomass during the first phases of the assay. In the control, a significant difference was observed between the total protist biomass at the different

depths (F 5.88; p <0.05).

Component Variance Analysis showed that the surface level of the sediment presented the maximum contribution in biomass with respect to the variation in time and depth, both in the control and in the cadmium treatments.

Dominant protist groups.

2002 assay. Effects due to cadmium exposure. In the treatments with cadmium in the 2002 assay, heterotrophic flagellates were the dominant group (31.09-60.50% of the protist density). They were dominant in 12 (60%) of the 20 fractions of the assay (4 depths+ 5 stages). The second group were ciliates (46.55-52.94% of the protist density), which were dominant in 3 (15%) of the 20 fractions of the assay. Autotrophic flagellates (73.95-100%) were dominant in two (15%), as were dinoflagellates (34.95­36.10%) (15%). Sarcodines were the last group (30.80%), dominant in one fraction (5%) (Table 7). In the control in the 2002 assay, there were two dominant groups: heterotrophic flagellates and sarcodines, which were dominant in 6 fractions (30%). The third group were dinoflagellates (15%). The fourth group were diatoms (10%), and the last group were au­totrophic flagellates, dominant in one fraction (5%) (Table 7). In comparison with the cadmium treatments, sarcodines were dominant in the control,

Table 5. Mean biomass values [mgC m 3] of the protist groups during the 2002 assay

Mean ± standard deviation (above, treatments with cadmium; below, control)

Depth Hours Autotrophic Heterotrophic Dino-

Sarcodines

Diatoms

Ciliates

[cm]

 

flagellates

flagellates

flagellates

 

 

 

 

0

4.198±57

535±05

1.272±05

18.923±52

31.605±50

4.131±51

 

 

1.609±55

11.475±52

2.245±54

4.550±50

8.265±51

2.842±50

 

24

104±56

127±44

258±27

1.792±56

00±00

911±49

 

 

90±10

83±05

326±45

2.889±10

3.876±52

00±00

0

48

00±00

219±11

1.825±52

3.803±57

297±05

46±05

 

 

00±00

351±29

00±00

15.490±55

2.726±16

00±00

 

72

685±05

503±05

109±05

20.283±50

1.012±51

3.401±57

 

 

00±00

170±44

00±00

1.702±05

413±05

00±00

 

96

58±05

67±05

140±10

37.757±34

1.505±56

3.053±28

 

 

00±00

103±

2.524±

2.620±

146±

00±00

 

0

448±51

3.658±10

00±00

00±00

4.457±50

00±00

 

 

00±00

1.521±50

1.103±50

12.534±52

771±50

99±05

 

24

578±50

672±05

00±00

196±50

1.738±50

117±52

 

 

195±53

870±52

289±50

7.854±53

5.427±52

00±00

4

48

00±00

45±05

177±50

1.065±50

892±51

00±00

 

 

00±00

08±02

1.814±52

4.478±56

1.497±51

4.553±51

 

72

00±00

218±50

00±00

1.869±53

1.341±53

49±05

 

 

26±05

44±05

47±05

1.401±50

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