Figure 1.
Examples of morphological aberrations observed on valves for the four diatom species studied. Pinnularia mesolepta: (a) normal, (b) shape, (c) asymmetry, (d) asymmetry + shape, (e) raphe + stria (minor), (f) raphe + stria (major), Gomphonema truncatum: (g) normal, (h) normal, (i) shape, (j) raphe, (k) raphe + stria, (l) shape + stria, Nitzschia palea: (m) normal, (n) fibulae, (o) shape, (p) shape, (q) raphe canal, (r) raphe canal, (s) raphe canal, Mayamae atomus: (t) normal, (u) shape, (v) shape, and (w) shape. Scale bar: 10 µm.
Figure 1.
Examples of morphological aberrations observed on valves for the four diatom species studied. Pinnularia mesolepta: (a) normal, (b) shape, (c) asymmetry, (d) asymmetry + shape, (e) raphe + stria (minor), (f) raphe + stria (major), Gomphonema truncatum: (g) normal, (h) normal, (i) shape, (j) raphe, (k) raphe + stria, (l) shape + stria, Nitzschia palea: (m) normal, (n) fibulae, (o) shape, (p) shape, (q) raphe canal, (r) raphe canal, (s) raphe canal, Mayamae atomus: (t) normal, (u) shape, (v) shape, and (w) shape. Scale bar: 10 µm.
Figure 2.
Mean effective quantum yield (percentage of the control (Ctrl), ± standard error) as a function of Cd concentration for N. palea, P. mesolepta, M. atomus, and G. truncatum after 19 h of exposure to Cd (n = 3, * p < 0.05, ** p < 0.01, *** p < 0.001).
Figure 2.
Mean effective quantum yield (percentage of the control (Ctrl), ± standard error) as a function of Cd concentration for N. palea, P. mesolepta, M. atomus, and G. truncatum after 19 h of exposure to Cd (n = 3, * p < 0.05, ** p < 0.01, *** p < 0.001).
Figure 3.
Cadmium concentrations in growth medium (µg Cd/L ± standard error, n = 3) for each exposure time for the control and the Cd treatment (Cd100) in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures. White circles represent the control and black squares represent Cd treatment (Cd100). Detection and quantification limits were 0.06 and 0.35 µg Cd/L, respectively. Nominal concentrations were 0 and 100 µg Cd/L for the control and Cd100.
Figure 3.
Cadmium concentrations in growth medium (µg Cd/L ± standard error, n = 3) for each exposure time for the control and the Cd treatment (Cd100) in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures. White circles represent the control and black squares represent Cd treatment (Cd100). Detection and quantification limits were 0.06 and 0.35 µg Cd/L, respectively. Nominal concentrations were 0 and 100 µg Cd/L for the control and Cd100.
Figure 4.
Mean Chl-a concentration in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures (μg Chl-a/mL ± standard error) at each exposure time for the cadmium treatment and the control. Stars indicate statistical differences from the control (n = 3, ** p < 0.01, *** p < 0.001). Black squares represent Cd exposure media (Cd100) and white circles represent the control.
Figure 4.
Mean Chl-a concentration in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures (μg Chl-a/mL ± standard error) at each exposure time for the cadmium treatment and the control. Stars indicate statistical differences from the control (n = 3, ** p < 0.01, *** p < 0.001). Black squares represent Cd exposure media (Cd100) and white circles represent the control.
Figure 5.
Mean effective quantum yield (±standard error) at each exposure time for the cadmium treatment and the control in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures. Stars indicate statistical differences from the control (n = 3, * p < 0.05, ** p < 0.01, *** p < 0.001). Black bars represent Cd exposure media (Cd100) and white bars represent the control (Ctrl).
Figure 5.
Mean effective quantum yield (±standard error) at each exposure time for the cadmium treatment and the control in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures. Stars indicate statistical differences from the control (n = 3, * p < 0.05, ** p < 0.01, *** p < 0.001). Black bars represent Cd exposure media (Cd100) and white bars represent the control (Ctrl).
Figure 6.
Mayamaea atomus SEM images of normal and deformed valves. (a) External valve view, typical valve raphe apices not equally formed. (b) Internal valve view, typical valve formation. (c) Axial and central areas symmetric, selected areolae deformed linear-slits. (d) Typical valve with deformed terminal raphe end. (e) Broken raphe at the central area. (f) Double raphe formation on one side of the valve and asymmetry of the valve. Scale bars: (a,b,d,f) = 5 µm, (c,e): 2 µm.
Figure 6.
Mayamaea atomus SEM images of normal and deformed valves. (a) External valve view, typical valve raphe apices not equally formed. (b) Internal valve view, typical valve formation. (c) Axial and central areas symmetric, selected areolae deformed linear-slits. (d) Typical valve with deformed terminal raphe end. (e) Broken raphe at the central area. (f) Double raphe formation on one side of the valve and asymmetry of the valve. Scale bars: (a,b,d,f) = 5 µm, (c,e): 2 µm.
Figure 7.
Mean effective percentage of total deformities (±standard error) in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures after 21 days of the experiment for the control (Ctrl) and the Cd treatment (Cd100). The deformities affecting the shape of G. truncatum were not considered in the calculation of the percentage of total deformities. Stars indicate statistical differences from the control (n = 3, * p < 0.05, ** p < 0.01).
Figure 7.
Mean effective percentage of total deformities (±standard error) in (a) N. palea, (b) P. mesolepta, (c) M. atomus, and (d) G. truncatum cultures after 21 days of the experiment for the control (Ctrl) and the Cd treatment (Cd100). The deformities affecting the shape of G. truncatum were not considered in the calculation of the percentage of total deformities. Stars indicate statistical differences from the control (n = 3, * p < 0.05, ** p < 0.01).
Table 1.
Mean EC25 (µg/L, confidence intervals α5%) effect on quantum yield of PSII for N. palea, P. mesolepta, M. atomus, and G. truncatum after 19 h of exposure to Cd (n = 3).
Table 1.
Mean EC25 (µg/L, confidence intervals α5%) effect on quantum yield of PSII for N. palea, P. mesolepta, M. atomus, and G. truncatum after 19 h of exposure to Cd (n = 3).
| EC25 (µg/L); α5% |
---|
N. palea | 1179 (1015, 1349) |
P. mesolepta | 9 (3, 23) |
M. atomus | 2394 (1890, 2896) |
G. truncatum | 606 (348, 926) |
Table 2.
Mean cadmium bioaccumulation levels in the diatoms (ng Cd/mg Chl-a ± standard error) at the different sampling times for Cd100 treatment. Detection (d.l.) and quantification (q.l.) limits were 0.09 and 0.56 µg Cd/L, respectively (after digestion in the solution of nitric acid and hydrogen peroxide). Cd concentrations for control treatment were below the detection limit at all sampling times and are not presented.
Table 2.
Mean cadmium bioaccumulation levels in the diatoms (ng Cd/mg Chl-a ± standard error) at the different sampling times for Cd100 treatment. Detection (d.l.) and quantification (q.l.) limits were 0.09 and 0.56 µg Cd/L, respectively (after digestion in the solution of nitric acid and hydrogen peroxide). Cd concentrations for control treatment were below the detection limit at all sampling times and are not presented.
| Cadmium Bioaccumulation for Cd100 Treatment (ng Cd/mg Chl-a) |
---|
T0 | T7 | T14 | T21 |
---|
N. palea | <q.l. | 25.9 ± 3.1 | 5.29 ± 0.92 | 8.74 ± 0.77 |
P. mesolepta | <q.l. | <d.l. | <d.l. | 12.36 ± 0.87 |
M. atomus | <q.l. | <q.l. | 201 ± 32 | 73 ± 14 |
G. truncatum | <q.l. | <d.l. | <d.l. | <d.l. |
Table 3.
Deformities observed on the four diatom species (N. palea, P. mesolepta, M. atomus, and G. truncatum) after 21 days of the experiment for the control (Ctrl) and the Cd treatment (Cd100). Microscopic observations were conducted on triplicate samples (labeled R1 to R3). The number of valves counted for each sample is indicated between brackets. Early-morphogenesis *, mid-morphogenesis **, late-morphogeneis ***, mixed ****.
Table 3.
Deformities observed on the four diatom species (N. palea, P. mesolepta, M. atomus, and G. truncatum) after 21 days of the experiment for the control (Ctrl) and the Cd treatment (Cd100). Microscopic observations were conducted on triplicate samples (labeled R1 to R3). The number of valves counted for each sample is indicated between brackets. Early-morphogenesis *, mid-morphogenesis **, late-morphogeneis ***, mixed ****.
Species/Type of Deformity | Ctrl | Cd100 |
---|
Ctrl-R1 | Ctrl-R2 | Ctrl-R3 | Cd100-R1 | Cd100-R2 | Cd100-R3 |
---|
Nitzchia palea |
Shape *** | 2 | 2 | 2 | 2 | 4 | 5 |
minor deviation of the raphe canal * | 3 | 2 | 6 | 6 | 12 | 1 |
moderate deviation of the raphe canal * | 2 | | 2 | 4 | 3 | 9 |
major deviation of the raphe canal * | | 1 | | 5 | | |
fibule/canal interruption * | 1 | | 2 | 2 | 2 | |
irregular fibulae * | 4 | 5 | 4 | 4 | 3 | 6 |
irregula striation pattern ** | 1 | 1 | | 3 | 1 | 1 |
mixed (deviation of the raphe canal + shape) **** | | | | 1 | 1 | 1 |
(valves counted) | (401) | (406) | (403) | (401) | (405) | (400) |
Pinnularia mesolepta |
Shape *** | 3 | 1 | 5 | 1 | 2 | 2 |
striation pattern ** | 3 | | 7 | 7 | 13 | 8 |
wide central area or lack of central area * | 1 | | 2 | 1 | 3 | |
Asymmetry * | | | | 4 | | 2 |
Raphe * | | 3 | 1 | 8 | 3 | 4 |
raphe and stria *,** | 2 | 3 | 4 | 8 | 6 | 3 |
mixed (shape/asymetry + raphe + stria) **** | | 1 | | 5 | 5 | 2 |
(valves counted) | (400) | (407) | (406) | (244) | (238) | (273) |
Mayamaea atomus |
Shape *** | 1 | 2 | 1 | 1 | 1 | |
striation pattern ** | 6 | 1 | 2 | 3 | 1 | |
raphe + stria *,** | 2 | 4 | | | 3 | 4 |
raphe * | 9 | 9 | 18 | 27 | 16 | 24 |
mixed (shape + raphe + stria) **** | 3 | 1 | | | | 1 |
(valves counted) | (159) | (159) | (164) | (148) | (182) | (153) |
Gomphonema truncatum |
Shape *** | 15 | 13 | 25 | 5 | 9 | 4 |
striation pattern ** | 22 | 21 | 17 | 12 | 13 | 5 |
Raphe * | 10 | 2 | 7 | 7 | 11 | 7 |
mixed (shape + raphe + stria) **** | 24 | 18 | 14 | 16 | 21 | 12 |
(valves counted) | (401) | (400) | (401) | (229) | (243) | (189) |