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PLANTS AND LIFE PROCESSES  
Aquatic life: selection under extreme conditions

Fluctuating ponds: Confin

 

Only a few meters in depth, ponds Confin are strongly influenced by weather fluctuations.

Ponds Confin

1 - Ponds Confin full

Evaporation holes

2 - Ponds Confin empty

 

Evaporation holes are subjected to strong fluctuations (temperature, radiation, pH and solute concentration). Solar radiation forces organisms to develop strategies to overcome photo inhibition and other damages.

Input parameters are

  • global irradiance (heat influx, evaporation)
  • water influx (rain , snow), water-efflux (both contain solutes)
  • wind (mixing, heat efflux, evaporation)

Response parameters are

  • oxygen production / consumption
  • pH
  • biomass
  • conductivity

3 - Data on parameters influenced by fluctuating weather conditions at ponds Confin in August 1993

 

Effects of rain introduced nutrients

On August 10th a rain event introduced nutrients (ammonium, nitrate and phosphate). After one week phosphate concentration dropped under the detection limit and biomass built up.

 

Nutrient and phosphate level fluctuations due to rainfall

4 - Nutrient and phosphate level fluctuations due to rainfall

Changes in biomass after a rainfall event on August 10
   

no. of organisms (in thousand/ml)
   

Aug. 4

  

Aug. 11

 

Aug. 18

Cyanophytes:

Pseudoanab. sp.

210

>

8

<

28

Chlorophytes:

Chlamydomonas sp.

21

>

8

<

28
 

Scenedesmus ecornis

15

>

4

<

12
 

S. ecornis 2-celled

319

>

30

<

60
 

S. sp. 1-celled

4375

>

656

<

6800

others

  

12

<

30

>

8

spacer

 spacer

Total

  

4952

>

736

<

6936

 

Conclusions

  • Alpine ponds are exposed to strong temperature, pH and light fluctuations.
  • Rain events introduce nutrients and stimulate biological activity (PSI) for about one day.
  • The sampling date might not at all be representative of the processes in the pond.
  • The time resolution of the sampling must coincide with the time resolution of changing activities.

sampling of ponds

5 - Sampling of ponds

 

 

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29 August 2011
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