Trace Metals &

Phytoplankton

Gert Vlaming

24-01-2003

Contents

• Introduction

• Trace metals

• Importance of phytoplankton

• Conclusion

Gaia theory

Environment Life

Trace metals

Trace metals of importance

Fe3+

Mn2+

Co2+

Cu2+

Ni2+

Cd2+

Zn2+

Complexation field diagram

Whitfield, 1997

Recycled elements

• Low concentrations in the surface layer

• Enhanced concentrations in the deeper water

• Residence time: intermediate (103 – 105 yrs)

• Concentrations: 10-12 – 10-5 M

Element Atlantic -

Surface

Atlantic -

Deep

Pacific -

Surface

Pacific -

Deep

Fe 3+ 2.0 *10-9 7.0*10-9 0.2*10-9 2.0*10-9

Cu2+ 1.3*10-9 2.0*10-9 1.3*10-9 4.5*10-9

Ni2+ 2.0*10-9 7.0*10-9 2.0*10-9 10*10-9

Cd2+ 0.1*10-10 3.5*10-10 0.1*10-10 10*10-10

Zn2+ 1.5*10-10 1.6*10-9 1.5*10-10 8.2*10-9

Mn2+ 1.9*10-9 1.8*10-9 1.9*10-9 8.0*10-10

Co2+ 2.7*10-11 1.5*10-11 2.3*10-11 1.5*10-11

Concentrations

mol/l

Concentrations II

• Atlantic ocean receives a greater flux of windborne dust and atmospheric contaminants than the Pacific

• Accumulated elements released from the decaying particulate matter

• Mn and Co: adsorption onto particles

Biochemical functions

Fe • nitrogen fixation• transport of oxygen• protection

Zn • Food digestion

Ni • hydrolysis of urea

• reactions with H2

And many enzymatic reactions

Availability

• > 97% of the total metal in solution is held in strong organic complexes

• These complexes are not available for phytoplanktonic uptake

The essential trace metals have very low concentrations

Importance of life for trace metal concentrations

Fractionation

Broecker & Peng, 1982

Recycling ratio

flux circulating within the ecosystem flux circulating through the environment

R =

Cd 494

P 214

C 54

N 33

Cu 2.2

Zn 1.9

Fe 1.8

Mn 1.4

R R

Recycling ratio

Whitfield, 1997

Recycling ratio II

• The inability of phytoplankton to exercise absolute discrimination

• Phytoplankton are capable of actively regulating their internal economy

• For most essential trace metals the cells are at, or close to, their nutrient limitation levels

Adaptations

• Internal

• External

• Interspecific

• Collective

There’s a “chemical war” going on ...

Uptake

• Diffusion

• Transfer of complexes

• Capture

• Uptake by Michaelis-Menten kinetics

Organic complexation

• Cells release organic complexing agents

• Beneficial for Fe, Cu en Mn

• Enabling large pool of Fe to be maintained

• Maintaining concentrations below toxic levels

Conclusions

• Availability of trace metals is a significant factor regulating primary production

• Phytoplankton is strongly effecting the concentrations of trace metals

Questions

Additional

Evolution of life

• Prokaryotic life: 3.5 Ga

• Eukaryotic life: 1.5 Ga

• Multicellular life: 600 Ma

Possibly because:

Start of multicellular life

• Lowering of the alkalinity of the oceans

• The attainment of an appropriately low global mean temperature

• The maintenance of a critical level of dissolved oxygen in the sea

• The establishment of the required cocktail of available trace metals