Human impact on N, P, and Si cycle: an aquatic perspective

Didier BahoTarikul IslamMohammad Ashraful Haque MollahLorenz Meire

Applied ecosystem ecology

Introduction

Nitrogen

Phosphorus

Silica

Nutrient balance

Low deposit of N

N limiting

High deposit of N

P limiting

Nutrient balance60 % reduction in dissolved silica transport

DSi

Ecological Consequences

• Eutrophication:

Source: RMB Environmental Laboratories, 2007

Increasein level of N and P

Consequences of Eutrophication• Increase in Cyanobacteria bloom causing a

decline in the effective light regime.

• Depletion of O2 due to enhanced decomposition of organic matter

Source: Bellingham 2008

Cyanobacteria bloom Overwinter fish death caused by decrease O2 depletion

• Depletion of oxygen can increase the release of phosphorus sequested in the sediments

Source:http://www.elmhurst.edu/~chm/onlcourse/chm110/outlines/images/natcyles.GIF

Shift in Phytoplankton communities

• P limitation cause a shift towards nutrient poor phytoplankton

• Shift due to DSi reduction

Diatoms Dinoflagellates and Coccolithophore.

DSi

Biological Pump

Biological pump is primarily limited by the availability of light and nutrients, and not by carbon.

Impact on biological pump

• Decrease in DSi shifts diatoms communities which affect carbon sequestration, consequently soft pump rate decreased

• DSi demand is met up by two process

– In open ocean>by upwelling

– In coastal water> by river input

a. Preventive process:

• Reduction of N and P flux before

water discharge (eg. ↓ P in detergent)

• Environment friendly agricultural methods

• Treatment of Sewage before discharge in catchement

Management options

b. Curative process:

• Biomanipulation: Introduction of Piscivores and improvement the trophic cascades

＋

Conclusion

N:P:Si

Ratio

Thank you for your attention!

References