Nutrients & iclicker Question Which is not a major ion? A) Sodium (Na + ) B) Potassium (K + ) C) Chloride (Cl - ) D) Silicon (Si) E) Sulfate (SO 4

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1 Nutrients & Tracers Non-conservative element: short residence time removed efficiently by biological or chemical processes Nutrients: used by living organisms Carbon, Nitrogen, Phosphorous, Iron, silicate, and others iclicker Question Which is not a major ion? A) Sodium (Na + ) B) Potassium (K + ) C) Chloride (Cl - ) D) Silicon (Si) E) Sulfate (SO 4 2-)

2 Plants combine CO 2 and a variety of other nutrients (their food) with energy from light to make organic modules (our food). CO 2 + H 2 O CH 2 O + O 2 (Biomass, carbohydrates, etc) Phytoplankton grow by eating dissolved chemicals Essential nutrients: for soft tissue Carbon as Bicarbonate ion HCO3 - Nitrogen as Nitrate as Ammonium NO 3 - NH 4 + Phosphorous as Phosphate PO4 3-

3 Phytoplankton grow by eating dissolved chemicals Micronutrients: used in very small amounts Magnesium used in chlorophyll Iron used in photosynthesis Selenium used in enzymes etc Mistaken identity? Cadmium mistaken for PO4 3- Barium mistaken for Si Phytoplankton grow by eating dissolved chemicals Skeleton building chemicals Calcium (Ca 2+ ) Silica (SiO 2) Nutrient sources Carbon Nitrogen Phosphorous Iron CO2 in atmosphere Atmospheric N2 can not be used Needs to be fixed into NO3 - or NH4 + Most fixed in-situ Some from rain and rivers Rain and rivers Dust from the continents carried by wind

4 Photosynthesis occurs in Photic zone Fe SiO 2 HCO 3 - NO 3 - PO 4 3- light No light Fe SiO 2 HCO 3 - NO 3 - PO 4 3- photosynthesis Organic matter created Organic matter eaten Sediments Energy from light gets stored in organic (carbon containing) compounds Hawaii Ocean Time-series Station ALOHA Vertical distribution of major ions Salinity [g/kg] Ratio between major ions

5 iclicker Question Some nutrients (like PO 4 3- and SiO 2) are biologically active. Photosynthesis can only occur near the surface, where there is light. Therefore, nutrients will be: A) Depleted with depth B) Depleted at the surface C) Unchanged with depth HOT profiles: Biological nutrients NO 3 [µm/kg] PO 4 [µm/kg] Sections Hawaii Pacific (P16) Atlantic (A16)

6 < > < < < 1 > < Pacific Ocean Nitrate 6.km Phosphate 6.km 6 o S Eq o N Atlantic Ocean Nitrate 6km Phosphate 6km o S Eq 6 o N Limiting nutrient Nitrate and phosphorous low in upper ~14 m NO 3 [µm/kg] 1 2 PO 4 [µm/kg] At HOT Nitrate goes to zero - Limiting nutrient

7 iclicker Question What determines the depth to which nitrate and phosphate are completely (or nearly completely) removed from the surface waters of the ocean? A) Light penetration B) Temperature C) Salinity D) Pressure Why 14m? (Varies from place to place) Below about 1 m, there is no light left in the ocean. The deeper ocean is totally black Photosynthesis only possible to ~ 1% light level Photosynthetically available radiation (PAR) In some places neither NO 3 - nor PO 4 3- go to zero Likely iron (Fe) limitation Annual mean surface Nitrate

8 Dust carries iron SeaWiFS Husar et al., 1997 Iron fertilization Dust carries iron These patches of chlorophyll were created by adding iron to the Southern Ocean Irod et al., 2 Iron was the limiting nutrient in this case Recycling soft tissue light No light 9 units 7-9 units 1 units of primary production 1 units sink out of photic zone 1-3 units reach the seafloor <1 unit preserved in sediments

9 iclicker Question How much biological material (organic C) do you think is produced in the surface ocean each year? A) thousand tons B) million tons C) million tons D) billion tons E) billion tons Recycling skeletons Not eaten - not an energy source Slowly dissolve (mainly at seabed) Some buried in sediments Paleo-recorders of ocean chemistry SiO 2 [µm/kg] HOT NO 3 [µm/kg] PO 4 [µm/kg] SiO 2 [µm/kg]

10 Silicate sections Pacific Atlantic Color scales are not the same Chemicals as tracers Tritium ( 3 H) from H-bomb tests H [TU] Year 3H in North Atlantic Latitude ( o N) Latitude ( o N) 1 and 2 TU contours plotted Input of Tritium into ocean peaked in

11 Aluminum m high Concentration 3 low Some key ideas Non-conservative elements have short residence times compared to the ocean stirring time. Many are used in biological processes. Nutrients are used by living organisms. Silicon or calcium used for shells. Photosynthesis can only occur where there is light. Most of the ocean is dark. Around Hawaii the Photic zone is about 14m deep. Limiting nutrient is an essential nutrient, that if missing, prevents growth. Non-conservative elements make good tracers of ocean currents.