Sentinel Species - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 171

7.2.2.1.1 Microorganisms and Invertebrates

• The effects of Cd, Cu, and Zn were examined in numerous species of freshwater
microorganisms by taking as a reference parameter the dissolved exposure con-
centration of metals associated with IC 50 for photosynthesis (Takamura et al. 1989).
In Figure 7.5, these data are shown for three taxa, selecting only strains from envi-
ronments where the level of metal contamination was low, in order to eliminate
any interference by the presence of any acquired tolerance. Cyanophyceae (blue
green bacteria) are sensitive to the three metals, whereas Chlorophyceae (green
algae) tend to show less sensitivity. Within each of these taxa, the interspecific dif-
ferences of IC 50 can reach 1 (Cd, Zn) to 2 (Cu) orders of magnitude.
• Bielmyer et al. (2010) exposed three species of coral to dissolved copper (ranging
from 2 to 20 μg L -1 ) for 5 weeks: the western Atlantic species Acropora cervicor-
nis (a threatened species of staghorn coral), Montastraea faveolata (star coral), and
the Indo-Pacific species Pocillopora damicornis (cauliflower coral), each containing
different algal symbionts ( Symbiodinium A3, C1, or D1a). The three coral species
exhibited significantly different sensitivities to copper, with toxic effects occur-
ring in A. cervicornis and P. damicornis at copper concentrations as low as 4 μg L -1 .
Copper exposure affected zooxanthellar photosynthesis in A. cervicornis and P.

Cu

4
3
2
1
0
-1

Cyanophyceae Diatoms Chlorophyceae

Cd

2

1

0

-1

Cyanophyceae Diatoms Chlorophyceae

Zn

3

2
1
0
-1

Cyanophyceae Diatoms Chlorophyceae

FIGURE 7.5
Comparison of the inhibition of photosynthesis by metals in different taxa of microorganisms. Log IC 50 in μg L -1
(Cu) or mg L -1 (Cd, Zn). (After Takamura, N. et al., J. Appl. Phycol ., 1, 39-52, 1989.)