CHANGES OF PROTOZOA POPULATIONS IN AN ARID

SOIL TRANSITING FROM WET TO DRY SEASON

Salvador Rodríguez ZaragozaMicrobiology Lab. UBIPRO,

FES Iztacala, UNAM

Global Warming Effects• The concentration of

greenhouse gases in the Atmosphere have been stabilized in 2000, however, thermal expansion will continue by the end of the 21st

century (Meehl et al, 2005)

• Due to Oceanic Thermal Inertia, the global temperature would increase more than 1°C in the following years (Wigley 2005)

• Increment of soil’s evapotranspiration

• Reduction of water income to soils

• Reduction of quantity and quality of plant exudatesdue to excessive stress

What’s the importance of soil protozoa?

• Temperature affects evapotranspiration, which affects soil water content and this affects soil’s organic matter decomposition.

• However this is just part of the story, because SOM decomposition is also affected by mineralogy, porosity, chemical composition of roots and litter, and macro and microfaunal activity

Plant productivity

Light, Water, CO2 and Temperature

Aboveground

Below ground

Soil NutrientsRoot exudes

Mycorrhiza and Bacteria

Microbial Predators

As predator’s wastes

Consumers

SugarsAmino Acids

Mites, nematodes,earthworms, AND Protozoa

Species Diversity of Soil Protozoa

Ciliates 400 species (Couteux y Darbyshire, 1997)! 35 to 200 microns

Flagellates 260 species (Foisner, 1991)! <5 (nanoflagelados) to 50 microns

Naked Amoebae 60 species (Couteux y Darbyshire, 1997) 140 at Villa del Carbón, Mex. (Rodríguez-Zaragoza 2000) 90 in the Negev Desert (Rodríguez-Zaragoza et al., 2005) and 59 in Tehuacan, Mex. (Rodríguez-Zaragoza et al., 2005) 2 microns (nanoamoebae?) to 2 mm

Species Identification of all of these groups is very difficult

Flagellates and Amoebae are scarcely studied (there are many species to describe)

Alternative: Morphological groups of soil protozoa are easier to study than species

Ciliates Flagelates

Amoebae

1

2

3

4

41

It is easier to follow up the population changes of the protozoan groups than trying to trace population changes of all the species at once

Question: Does the population of all the soil protozoan groups follow the same tendency during the shift from wet to dry season?

Hypothesis: Amoebae populations will remain high longer (as long as food lasts) since they need no water film for swimming

Temperature

BA

C D E

Precipitation

Porosity

0 20 40 60 80

1

2

3

4

5

6

Sam

plin

g Si

tes

%

Water Holding Capacity, Real and Apparent density

0 2 4 6 8

1

2

3

4

5

6

Ssam

plin

g Si

tes

g/cm3

DRDACC

pH

6 7 8 9

123

456

Sam

plin

g S

ites

values

Conductivity

0 50 100 150 200 250

1

2

3

4

5

6

Sam

plin

g Si

tes

moh

Microbial Nitrogen

0 0.2 0.4 0.6

123456

Sam

plin

g Si

tes

g/kg

Microbial Carbon

0 5 10 15

123456

Sam

plin

g Si

tes

g/kg

Organic Matter

0 2 4 6 8

1

2

3

4

5

6

Sam

plin

g Si

tes

%

Ciliates

0

1

2

3

4

A-00 M-00 J-00 A-00 N-00 J-01 F-01 M-01 A-01 M-01 J-01 j-01 jb-01 A-01 S-01

Month

Log

A B C D E

Nanoflagellates

0

1

2

3

4

5

A-00 M-00 J-00 A-00 N-00 J-01 F-01 M-01 A-01 M-01 J-01 j-01 jb-01 A-01 S-01

Month

Log

A B C D E

Flagellates

0

1

2

3

4

A-00 M-00 J-00 A-00 N-00 J-01 F-01 M-01 A-01 M-01 J-01 j-01 jb-01 A-01 S-01

Month

Log

A B C D E

Amoebae Type 3

0

1

2

3

4

M1 M2 M3 M4 M7 M9 M10 M11 M12 M13 M14 M15 M16 M17 Mx

Month

Log

A B C D E

Amoebae Type 1

0

1

2

3

4

5

A-00 M-00 J-00 A-00 N-00 J-01 F-01 M-01 A-01 M-01 J-01 j-01 jb-01 A-01 S-01

Month

Log

A B C D E

Amoebae Type 4

01234

A-00 M-00 J-00 A-00 N-00 J-01 F-01 M-01 A-01 M-01 J-01 j-01 jb-01 A-01 S-01

Month

Log

A B C D E

Amoebae Type 2

0

1

2

3

4

A-00 M-00 J-00 A-00 N-00 J-01 F-01 M-01 A-01 M-01 J-01 j-01 jb-01 A-01 S-01

Month

Log

A B C D E

The morphological groups of Protozoa had the same population dynamic across the different “environmental layers” of temperature-precipitation, which means the system is stabilized for such conditions along the gradient

However, stabilized doesn’t mean stress-free and the temporal environmental variation may have the effect of diminishing trophicdiversity, represented here by the reduction of type 3 amoebae (that feed mostly on bacteria) and the barely existence of type 4 amoebae (which feed on algae as well)

Amoebae types 1 and 3 follow the same dynamic than the other groups of protozoa. However, the variation observed in amoebae types 2 and 4 would have been masked if counting amoebae as one single group

There is an increased concern about conservation programs for several species of plants, especially cacti, for which many studies are under way taking in account only temperature and precipitation as the main factors for planning and designing areas for conservation

Should Microorganisms be also taken in consideration for planning?

Distribution of Echinocactus platyacanthus f. grandis atpresent (Davila et al 2004)

Distribution of Echinocactus platyacanthus f. Grandis in 100 years (scenario +2° C, -10% mm) (Davila et al 2004)

Distribution of Mammillaria sphacelata at present (Davila et al 2004)

Distribution of Mammillaria sphacelata in 100 years(scenario +2° C, -10% mm) (Davila et al 2004)

Distribution of Cephalocereus columna-trajani at present (Davila et al 2004)

Potential distribution of Cephalocereus columna-trajaniin 100 years (scenario +2° C, -10% mm) (Davila et al

2004)

After all, Microorganisms are also part of the plants’ “environment”

© American Society for Microiology 1995

THANK YOU VERY MUCH!!!