Nutrients & Tracers Nutrients & Tracers OPHYLL

The food chain is not a nice thing: Big animals eat little animals Little animals eat plants What do plants eat?

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)

Which is not a major ion? A) Sodium (Na + ) B) Potassium (K + ) C) Chloride (Cl - ) D) Silicon (Si) E) Sulfate (SO 4 2- ) Question

Which is not a major ion? A) Sodium (Na + ) B) Potassium (K + ) C) Chloride (Cl - ) D) Silicon (Si) E) Sulfate (SO 4 2- ) Major ions are Cl -, Na +, SO 4 2-, Mg 2+, Ca 2+, K + Question

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

Phytoplankton are microscopic plants are the basis of the marine food web they photosynthesize Phyto = plant, plankton = wandering (Greek)

Phytoplankton grow by ‘eating’ dissolved chemicals Essential nutrients: for soft tissue Carbonas Bicarbonate ionHCO 3 - Nitrogen as Nitrate as Ammonium NO 3 - NH 4 + Phosphorou s as PhosphatePO 4 3-

Phytoplankton grow by ‘eating’ dissolved chemicals Micronutrients: used in very small amounts Magnesiumused in chlorophyll Ironused in photosynthesis Seleniumused in enzymes etc Mistaken identity? Cadmiummistaken for PO 4 3- Bariummistaken for Si

Skeleton building chemicals Phytoplankton grow by ‘eating’ dissolved chemicals Calcium (Ca 2+ ) Silica (SiO 2 )

Nutrient sources CarbonCO 2 in atmosphere Nitrogen Atmospheric N 2 can not be used Needs to be “fixed” into NO 3 - or NH 4 + Most fixed in-situ Some from rain and rivers PhosphorousRain and rivers Iron Dust from the continents carried by wind

Photic zone Energy from light gets stored in organic (carbon containing) compounds

Some nutrients (like PO 4 3- and SiO 2 ) have long residence time, but 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 Question

Some nutrients (like PO 4 3- and SiO 2 ) have long residence time, but 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 Question

Station ALOHA Hawaii Ocean Time- series

Vertical distribution of major ions

HOT profiles Depth [m] NO 3 [  M/kg] 0123 PO 4 [  M/kg]

Sections Pacific (P16) Atlantic (A16)

Pacific Ocean Eq60 o S55 o N km Nitrate Phosphate

Atlantic Ocean Eq50 o S60 o N 0 0 6km Nitrate Phosphate

Limiting nutrient Nitrate and phosphorous low in upper ~140 m Depth [m] 0 NO 3 [  M/kg] PO 4 [  M/kg] 12 At HOT Nitrate goes to zero - Limiting nutrient

Why 140m? (Varies from place to place) Depth [m] Photosynthetically available radiation (PAR) Below about 100 m, there is no light left in the ocean. The deeper ocean is totally black.

Why 140m? (Varies from place to place) Photosynthes is only possible to ~ 1% light level Depth [m] Photosynthetically available radiation (PAR) Below about 100 m, there is no light left in the ocean. The deeper ocean is totally black.

Likely iron (Fe) limitation In some places neither NO 3 - nor PO 4 3- go to zero Annual mean surface Nitrate

Dust carries iron Husar et al., 1997 SeaWiFS

Iron fertilization These patches of chlorophyll were created by adding iron to the Southern Ocean Iron was the limiting nutrient in this case Irod et al., 2005

How much dust do you think is deposited on the surface of the ocean each year? A) 10 tons B) 300 tons C) 5,000 tons D) 10 million tons E) more Question

How much dust do you think is deposited on the surface of the ocean each year? A) 10 tons B) 300 tons C) 5,000 tons D) 10 million tons E) more 358 million tons Question

Recycling soft tissue Organisms can almost completely remove NO 3 - and PO 4 3- from the surface ocean How are nutrients restored so life can continue?

Recycling soft tissue Organisms can almost completely remove NO 3 - and PO 4 3- from the surface ocean

How much biological material (organic C) do you think is produced in the surface ocean each year? A) 1 thousand tons B) 50 thousand tons C) 1 million tons D) 1 billion tons E) 50 billion tons Question

How much biological material (organic C) do you think is produced in the surface ocean each year? A) 1 thousand tons B) 50 thousand tons C) 1 million tons D) 1 billion tons E) 50 billion tons 50 billion tons = 50x10 12 kg Question

Not eaten - not an energy source Slowly dissolve (mainly at seabed) Some buried in sediments Paleo-recorders of ocean chemistry Recycling skeletons Depth [m] 0 SiO 2 [  M/kg]

HOT Depth [m] NO 3 [  M/kg] PO 4 [  M/kg]SiO 2 [  M/kg]

Silicate sections Pacific Atlantic Color scales are not the same

Chemicals as tracers Tritium ( 3 H) from H-bomb tests

3 H in North Atlantic and 2 TU contours plotted Input of Tritium into ocean peaked in

3 H in Indian Ocean Eq 60 o S pord.ucsd.edu/whp_atlas/indian/i08i09/sections/ 0 6.5km

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 140m deep. Limiting nutrient is an essential nutrient, that if missing, prevents growth. Non-conservative elements make good tracers of ocean currents. Some key ideas