phytoremediation - Shaopeng LI

International Symposium for Biodiversity and Theoretical Ecology

May. 10th, 2011

Algal species richness enhancing the phytoremediation of cadmium pollution Shaopeng Li, Jintian Li, Jialiang Kuang, Hongnan Duan, Yi Zeng, Wensheng Shu* School of Life Sciences and State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, P. R. China

Contents

Background

Materials & methods

Results & discussion Conclusions

Phytoremediation With the ever-growing range of toxic chemicals (such as heavy metals) into the environment, phytoremediation that uses living plants to restore ecosystems affected by pollutants has become one of the most rapidly developing fields of restoration ecology.

Some algal species may be able to serve as phytoremediators.

Phytoremediation With the ever-growing toxic chemicals (such asofheavy metals) However, an importantrange factoroflimiting the effectiveness constructed into the environment, phytoremediation that uses living plants to restore ecosystems affected for bioremediation of contaminated sites their lowrapidly efficiency ecosystems by pollutants has become one ofisthe most developing fields of restoration ecology. and sustainability.

Some algal species may be able to serve as phytoremediators.

Biodiversity resistance ( Tilman & Downing 1994, Nature; Tilman 1996, Ecology ) ( Tilman et al. 2001, Science ) ( Mulder et al. 2001, PNAS )

temporal stability

productivity

( Tilman et al. 2006, Nature )

stability

biodiversity

invader

(Kennedy et al. 2002, Nature)

sequester pollutants recovery (Cardinale. 2011, Nature )

( van Ruijven & Berendse, 2010, J Ecol )

Biodiversity resistance ( Tilman & Downing 1994, Nature; Tilman 1996, Ecology ) ( Tilman et al. 2001, Science ) ( Mulder et al. 2001, PNAS )

temporal stability

productivity

( Tilman et al. 2006, Nature )

stability

biodiversity

invader

(Kennedy et al. 2002, Nature)

sequester pollutants recovery (Cardinale. 2011, Nature )

( van Ruijven & Berendse, 2010, J Ecol )

However, these blue-sky researches (biodiversity-ecosystem functioning) have not yet led to solve environmental problems (remediation of polluted environments).

……

…… resistance

efficiency

tolerance

productivity

Our hypothesis We can theoretically predict that:

Increasing the level of species richness may be a helpful strategy to increase the ecosystem function (productivity, remediation efficiency and resistance) of phytoremediation systems.

Focal species

Ankistrodesmus falcatus (Af)

Chlamydomonas eugametos (Ce)

Chlamydomonas moewusii (Cm)

Chlamydomonas reinhardtii (Cr)

Scenedesmus dimorphus (Sd)

Scenedesmus obliquus (So),

Scenedesmus quadricauda (Sq)

Selenastrum capricornutum (Sc)

Chlorella pyrenoidosa (Cp)

Staurastrum polymorphum (Sp)

Tolerant species, TS; TI > 100%

Sensitive species, SS; TI < 100%

Af (139%), Cm (371%), Cp (106%), Cr (145%)

Ce (28.3%), Sc (2.56%), Sd (25.1%), So (20.1%), Sq (10.2%), Sp (7.33%)

Experimental design No pollution (NP)

Moderate pollution ( 6 mg/L Cd2+, MP)

Serious pollution (12 mg/L Cd2 +, SP)

1

2

4

8

Algal species richness

This design yielded a total of 330 treatment replicates.

Sampling & analysis

Microscope (1000×)

Microcosms



Productivity measure complementarity effect & selection effect



Cadmium concentrations Cd removal effects & transgressive over-removal effects Optima 2100 PV, Perkin Elmer; Massachusetts, USA



Resistance measure community, functional group & individual population-level resistance

Biodersity & biomass relationship

-1

Biomass ( μg L )

400

NP

ns MP*** SP**

350 300 250 200

NP MP SP

150 100 0

2

4 6 Species richness

8

Fig. 1. Effect of different levels of cadmium (Cd) pollution on the relationship between algal species richness and community productivity

(Li et al., 2010; Journal of Applied Ecology )

-1

Complementarity effect ( μg L )

100

*

-1

Selection effect ( μg L )

Selection & complementarity effect

0 ***

-100 -200

**

NP MP SP

-300

*

-400 2

4

Species richness

8

500

**

NP MP SP

400

***

300 200 100

*** ***

*

***

0 2

4

8

Species richness

Fig. 2. Response of selection effect and complementarity effect to changes in algal species richness

(Li et al., 2010; Journal of Applied Ecology )

Biodiversity & pollutants removal Moderate pollution

5 4 3 2 1

Serious pollution

8

r = 0.30, P = 0.001

0

Cd removal ( μg/mL )

Cd removal ( μg/mL )

6

6 4 2 r = 0.58, P < 0.001

0 0

2

4

6

8

0

2

Species richness

4

6

8

Species richness

Fig. 3. Effects of algal species richness on Cd removal efficiency

 The horizontal line and the grey shaded area show means ± 95% confidence intervals for the monoculture of the most tolerant species Chlamydomonas moewusii (Cm), which achieved the highest Cd removal values of all the monocultures.

(Li et al., unpublished data)

Transgressive over-removal effects Moderate pollution

1.0

.5 0.0 -.5 r = 0.23, P = 0. 1

-1.0

Over-removal effect

Over-removal effect

1.0

Serious pollution

.5 0.0 -.5 r = 0.28, P = 0. 06

-1.0 0

2

4

6

8

0

Species richness

2

4

6

8

Species richness

Fig. 4. Effects of algal species richness on transgressive over-removal effects  Cd over-removal effects was defined as proportional deviation of Cd removal from the most tolerant one of their constituent species in monocultures.Transgressive over-removal occurs when a mixture Cd-removal more than any monoculture of the component species

(Li et al., unpublished data)

Biodiversity & resistance Moderate pollution

Serious pollution

2 1 0 -1 -2 -3

r = 0.31, P < 0.001

-4

Proportional resistance

Proportional resistance

3

2 0 -2 -4 -6 r = 0.29, P = 0.002

-8 0

2

4

6

8

0

2

Species richness

4

6

8

Species richness

Fig. 5. The relationship between algal species richness and the resistance to Cd pollution.  we determined proportional resistance (as the difference in logs of Cd-polluted and control biomass production) of microcosm ecosystems to Cd stress to measure community –level resistance.

(Li et al., unpublished data)

Functional group resistance Serious pollution 600

-1

Resistance ( μg L )

600

-1

Resistance ( μg L )

Moderate pollution 400 200 0 -200 -400 -600

400 200 0 -200 -400 -600

0

2

4

6

8

0

2

Species richness Dependent variable

4

6

8

Species richness Moderate Cd pollution r P value

Severe Cd pollution r P value

Cd-tolerant functional group resistance ( μg L-1 )

0.02

0.874

0.03

0.797

Cd-sensitive functional group resistance ( μg L-1 )

0.50