Sources of nutrients to the surface mixed layer of the ocean

Transcription

1 Sources of nutrients to the surface mixed layer of the ocean What are nutrients anyway? (to a chemist that is.) Where do they come from? Preformed (recycled, delivered from elsewhere) Biosynthesized Nutrient distributions in the ocean and water column.

2 Sources of nutrients to the surface mixed layer of the ocean Chemical component of density in the mixed layer of the ocean

3 Physical elements of the vertical profile

4 Salinity affects density. Salt constituents are heavier than H 2 O Temperature also affects density Colder water is heavier Saltier water is heavier Lets have a look at this. So colder saltier water sinks and this affects.. circulation To see how important it is

5 Wind drives the surface currents, but density drives the deep currents The Gulf stream delivers warm salty water to the North Atlantic. Where Arctic winds chill them.. What happens to the density?

6 The waters that sink in the N. Atlantic drive the global thermohaline circulation

7 Lets come back to salt

8 What is in the ocean anyway? They are one of several different categories of solids dissolved in ocean water. The 3 main constituents in sea water Conservative Bio-intermediate Bio-limiting (nutrients)

9 The major constituents of seawater. are salt! Na + 55% Cl - 30% Mg +2 4% SO % Ca+ 1% Other 3% The composition of these major salts in the ocean are invariant These are the elements that are measured in salinity These are the conservative constituents of seawater

10 The major constituents of seawater Na + Cl - Mg +2 SO -2 4 The only way to affect their concentrations is via evaporation or precipitation These are the conservative constituents of seawater

11 The conservative constituents of seawater. Na + 55% Cl - 30% Mg +2 4% SO % Ca+ 1% Other 3% The composition of these major salts in the ocean are invariant These are the elements that are measured in salinity

12 What are nutrients anyway? They are the non-conservative constituents in sea water Conservative Bio-intermediate Bio-limiting = nutrients

13 Bio-intermediate constituents Elements: Ca= Calcium, about ½ % less abundant than in deep water C= carbon, 15% less than in deep water Sr= strontium, Cu= copper, Se= selenium, Ba= barium, about 70% less abundant than in deep water Ra= radium (probably not needed but incorporated by accident ) Compounds: Carbonate (carbon as carbonate) = CO 3 Bio-intermediate components have variable distributions but rarely do their concentrations go to zero

14 Biolimiting constituents (a.k.a. nutrients) Nitrate (NO 3- ) Does not limit growth of bluegreen algae (cyanobacteria) they fix nitrogen. Phosphate (HPO 4= ) the ultimate limiting nutrient for plant growth Silicate (H 2 SiO 4 ) Limits the growth of diatoms Zinc (Zn ++ ) Cadimum (Cd ++ ) Iron (Fe ++ ) Germanium (H 4 GeO 4 ) These are almost totally depleted in surface water where most of the biology goes on: so much so their availability (or lack of it) controls growth.

15 Vertical distributions of chemical constituents in seawater Libes, 1992 The terms conservative and non conservative reflect the extent to which the concentration of a constituent is affected by chemical or biological processes in seawater in relation to it s overall concentration in seawater..

16 Vertical distribution of nutrients Phosphate 10-6 mol/liter nitrate 10-6 mol/liter silicate 10-6 mol/liter Libes, 1992 Note the slightly different shapes this has both to do with use and formation of the different nutrients

17 The biological pump and nutrients The biological pump moves nutrients from the surface ocean to the deep water masses

18 The balance between light and nutrients controls growth and is governed by the physics (light, mixing, stratification)

19 Physical and chemical vertical profiles

20 The biological pump and nutrients The biological pump moves nutrients from the surface ocean to the deep water masses: The chemists version These nutrients are returned to the surface mixed layer with winter mixing and upwelling

21 The biological pump and nutrients The vertical distribution of nutrients from the is controlled by this delivery of nutrient from the surface ocean to the deep waters Nutrients and organic matter aren t lost they are remineralized

22 Vertical distributions relative to physical properties Vertical distributions of physical properties and nutrients in the ocean over the full depth of the ocean. They are very similar from place to place. Libes, 1992

23 Differences between the oceans in vertical profiles of nutrients The deep Pacific has more nutrients than the Atlantic a.k.a. horizontal differences in nutrient profiles. Libes, 1992

24 The conveyor belt circulation

25 Control on global distribution of nutrients Water downwells: Low nutrients High O 2 N,P N,P N,P N,P N,P Nutrients in deep water become enriched with increasing age N,P N,P N,P N,P N,P N,P N,P N,P N,P N,P N,P N,P Sediments have extensive remineralization

26 The conveyor belt circulation

27 Differences between the oceans in vertical profiles of nutrients The deep Pacific has more nutrients than the Atlantic because the waters there have accumulated more nutrients through time Libes, 1992

28 Distribution of nutrients in the deep ocean Broecker and Peng, 1982

29 These areas are the most productive because nutrients are readily available but there is primary productivity everywhere in the surface ocean Coastal Upwelling zones in the world ocean Mann and Lazire

30 Annual Stratification sequence Recycling of nutrients at it s peak

31 New versus regenerated production Lalli and Parsons Note: the biggest arrow is upwelled NO 3

32 Some of the nutrients and organic matter are buried and removed from the system. The biological pump and burial