Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington What is Sea Salt? What are Sea Salts? • Water • Mostly what you already know • Salts – Sodium (Na+) ~ 31% of salts – Salinity = grams salts – Chloride (Cl-) ~ 55% of salts per kilogram sea water – Together NaCl ~86% of salts – Average = 35 g/kg = 3.5% • World ocean has 5 x 1015 (quadrillion) kg salts – Cover Earth 45 m deep

Garrison Fig. 7.4 p. 166 1 Garrison Fig. 7.4 p. 166 2

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington What are Sea Salts? What are Sea Salts? • Some other familiar dissolved chemicals • Big 6 account for 99.4% of all sea salts 2+ – Sulfate (SO4 ) ~ 3% of salts – Na + Cl = 86% 2+ – Magnesium (Mg ) ~ 1% of salts – SO4 + Mg + Ca + K = 13.4% – Calcium (Ca2+) ~0.4% of salts – Potassium (K+) ~0.4% of salts - – Bicarbonate (HCO3 ) ~0.15% of salts

Garrison Fig. 7.4 p. 166 Garrison Fig. 7.4 p. 166 3 4 Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Chemical Nature of Sea Salts Chemical Nature of Sea Salts Salts are molecules that break apart easily in Ionic molecules dissolve • • H (+) water solution easily in water O (-) – Atoms separate from each other – Water molecule H2O has – Form ions electrical polarity H (+) Garrison Fig. 7.3 p. 164 • Electrically charged atoms • Like a v-shaped bar magnet • Gain or lose one or more • Oxygen more negative electrons while in solution • Hydrogen more positive – NaCl ionizes to form: – Water molecules attract • Na+ (loses the electron) salt ions • Cl- (gains the electron) • Help pull Na & Cl ions apart – Only occurs with certain – O- attracted to Na+ – H+ attracted to Cl- 5 combinations of atoms Garrison Fig. 7.2 p. 164 6

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Salts in the Sea Why the Sea is Salt • Solubility affects fate of chemicals when • The real question: they enter the ocean – Why isn’t the sea much saltier than it is? – High solubility • Total mass of dissolved solids entering the • Accumulates at high concentrations in sea water oceans each year • Remains in the ocean a long time – 0.000005 of one percent (5*10-8) of the total mass – Low solubility of dissolved solids already in the oceans Low concentrations in sea water • • How long until the oceans would reach their • Leaves the ocean relatively sooner present salinity? – NaCl a very soluble salt “Only” 20 million years • But only a salt when it is solid – • Dissolves to yield two most abundant ions • But sediments indicate constant ocean salinity

7 • Remains in the oceans for millions of years 8 – Last 1.5 billion years Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Why the Sea is Salt Sources & Sinks • The real question: • Each type of ion has a different set of sources – Why isn’t the sea much saltier than it is? & sinks Garrison Fig. 7.5 p. 168 • Something is removing salts from the oceans – & different residence time based on its solubility – Ocean chemistry is at equilibrium – Inputs are equaled by outputs – Sources = Sinks • Sink= a removal location or process – Residence time = how long salt stays in ocean

Residence time in the oceans At equilibrium, sink = source 9 Source for salt X “Sink” for salt X 10

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Sources & Sinks Sources • Example: Na & Cl • Erosion of land, transport by rivers – Sodium + chloride sink = sediments – Sodium, Calcium, Sulfate, Bicarbonate – Cl source = volcanoes + rain, Na source = rivers • “Excess volatiles” – Ions delivered as gases rather than dissolved solids – Terrestrial volcanoes • Sulfate, Chloride • Carbon – Hydrothermal vents at rift valleys • Calcium • Potassium 11 12 Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Sinks Residence Time • Inorganic (non-biogenous) sediments • Residence time (years) = – Sodium, Calcium, Sulfate, Bicarbonate – Amount in ocean ÷ amount entering/leaving per year • Organic (biogenous) sediments • Long residence time – Calcium, carbonate – Large amount in ocean – Silicon – Very soluble • Evaporation • Short residence time – Sodium, Chloride – Small amount in • Hydrothermal ocean vents – Poorly soluble – Magnesium 13 – Sulfate 14

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Residence Time Residence Time • Residence time (years) = • Short residence – Amount in ocean ÷ amount entering/leaving per – Small amount in ocean year Chloride Sodium – Poorly soluble Silicon Manganese • Long residence Magnesium Potassium Aluminum Iron Sulfate Calcium • Sources – Large amount in 100,000,000 – Erosion & rivers 20,000 ocean • Sinks: sediments – Very soluble 75,000,000 15,000 – Silicon part of diatom – The Big 6 ions 50,000,000 skeletons 10,000

25,000,000 – Manganese in Mn 5,000 nodules 0 – Aluminum in clay 0 15 Residence Time (Years) 16 Residence Time (Years) Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Dissolved Gases Important Gases in the Ocean

• Also have sources & sinks • Nitrogen (N2) – Both inorganic (non-living ) & organic (living) – “Fixed” nitrogen (NO3, NO2, NH4) an essential – Inorganic: nutrient for photosynthesis • Gases from atmosphere dissolve in sea water – “Nitrogen fixing” bacteria convert N2 gas to fixed N • Main effect is on surface waters • Make it available for biological production Global density • • Oxygen (O2) circulation transports them – Generated by photosynthesis into deep water – Consumed by respiration & decay • Sinking of cold, • Carbon dioxide (CO2) salty water at polar latitudes – Generated by respiration & decay

17 18 – Consumed by photosynthesis

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oxygen & Carbon Dioxide Carbon Dioxide & Acidity

• Change with depth because of biological • CO2 part of the complex dissolved carbonate activity system – O2 maximum at • Key functions surface – Controls acidity & alkalinity of sea water • Light available for • Affects many other chemical & biological reactions photosynthesis – Source of skeletal material for numerous organisms • Consumes CO2 • Calcium carbonate CaCO3 – CO2 maximum deep • Calcareous plankton in water • Bottom-living shellfish: clams, crabs, etc. • Decomposition of Coral reefs sinking dead material • Multiple interchangeable forms of combined carbon • Consumes O2 – 19 20 Garrison Fig. 7.8 p. 172 Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Carbon Dioxide & Acidity Carbon Dioxide & Acidity • pH = negative log of hydrogen ion • pH always slightly concentration alkaline (>7) – Neutral = 7 • pH higher (more alkaline) – Acid = less than 7 at surface – Alkaline = more than 7 – Photosynthesis consumes • Average acidity CO2 of ocean ~8 • pH lower (less alkaline) at – Alkaline: range 7.8-8.3 bottom of lighted zone & in deep sea – Respiration generates CO2

– CaCO3 skeletons dissolve 21 Garrison Fig. 7.9 p. 172 22 Garrison Fig. 7.12 p. 174

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Carbon Dioxide in Sea Water Carbon Dioxide Buffering

- -2 • CO2 + water H2O gives carbonic acid H2CO3 • Proportions of CO2, H2CO3, HCO3 , CO3 , H + – H2CO3 splits shift to maintain constant pH - + • HCO3 & H – Reactions - – HCO3 splits proceed in -2 + • CO3 & H either • 5 C species direction in equilibrium • Add CO2 -2 + – Buffering – CO3 & H recombine – Proportions -2 shift to keep • Add CO3 pH constant – More H2CO3 23 24 splits Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Carbon Dioxide Buffering Conservative Constituents • Why does buffering of pH matter? • Some dissolved constituents of sea water are – Some biochemical reactions sensitive to pH biologically active & others are not – Major example: formation of calcium carbonate – Conservative constituents not biologically active CaCO3 skeletons • Maintain a constant ratio to total salinity • Calcareous plankton • Na, Cl, Mg, K, SO4 • Bottom-living shellfish: clams, crabs, etc. – Nonconservative constituents are biologically active • Coral reef • Ratio to total salinity varies depending on biological use • Ocean pH currently decreasing • Ca, CO2 system members, O2, nutrients – Increasing atmospheric CO2 • “Principle of Constant Proportions” – Mostly decreasing at surface – Can calculate concentration of one conservative ion

– More difficult to form CaCO3 skeletons from any other 25 26 • Measure salinity from Cl- alone (“Chlorinity”)

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Nutrients Marine Nutrients • Primary production = conversion of non-living • Marine photosynthesizers require same to living material nutrients as land plants – Photosynthesis conducted by plants, algae, – Also silicon for diatom skeletons bacteria • ~0.003 g/kg (~3000 micrograms/kg) – Chemosynthesis conducted by bacteria, archaea – N, P, Si the “macronutrients” • Marine photosynthesizers require same – Also “micronutrients” nutrients as land plants • Order of magnitude less abundant (~10 micrograms/kg) – Fertilizers: Nitrogen N, phosphorus P, potassium K • Iron, other trace metals, vitamins • Plenty of K in sea water (1 of the Big 6) • Supply of these nutrients limits primary – ~0.4 g/kg production under some conditions • N & P are present in very small amounts – Often depleted for photosynthesis at the surface 27 – ~0.00001 g/kg (~100-500 micrograms/kg, parts/billion) 28 Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Nutrient Cycles Nutrient Depletion • Garrison has very complex diagrams • 1 more critical factor for biological production – Nitrogen as an example – The oceans are layered Atmospheric nitrogen gas Atmospheric nitrogen gas

Terrestrial nutrients Terrestrial nutrients Sea surface Sea surface

Dissolved nitrogen gas Dissolved nitrogen gas

Erosion & river transport Plate Erosion & river transport Bacteria tectonics Bacteria Photosynthesis Photosynthesis Dissolved fixed nitrogen Algae Dissolved fixed nitrogen Algae Pycnocline

Wastes Animals Detritus Wastes Animals Detritus

29 Sediments 30 Sediments

Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 22 © 2006 University of Washington Nutrient Depletion Nutrient Depletion • Organic matter sinks to deep water & bottom • What processes return nutrients to surface? – Trapped below the pycnocline – Not pictured here: Upwelling & vertical mixing Atmospheric nitrogen gas Atmospheric nitrogen gas

Terrestrial nutrients Terrestrial nutrients Sea surface Sea surface

Dissolved nitrogen gas Dissolved nitrogen gas Erosion & river transport Erosion & river transport Bacteria Bacteria Photosynthesis Photosynthesis Dissolved fixed nitrogen Algae Pycnocline Dissolved fixed nitrogen Algae Pycnocline

Wastes Animals Detritus Wastes Animals Detritus

31 Sediments 32 Sediments