OCEAN101 - Ch. 6: Seawater Chemistry

Name 5 of the conservative ions other than sodium and chloride found in seawater.

1) Sulfate (SO4 2-) 7.7 2) Magnesium (Mg 2+) 3.68 3) Calcium (Ca 2+) 1.17 4) Potassium (K +) 1.10 5) Bicarbonate (HCO3 -) 0.40

Define major constituents.

11 ions that make up 99.99% of salts dissolved in seawater.

Explain what makes the sea salty.

Because the salt is there already. The sea is salty because river runoff washes salt into the sea, & it remains at roughly the same salinity because of geochemical recycling, which also keeps the relative amounts of the different salts constant.

Which dissolved gases in seawater are biologically active?

Carbon dioxide & Oxygen - both considered to be non-conservative.

What sorts of organic compounds are found in seawater?

Components include lipids, carbohydrates, proteins, vitamins, & hormones.

Define conservative ions.

Conservative Constituent. Component or property of seawater whose value changes only as a result of mixing, diffusion, and advection and not as a result of biological or chemical processes; Ex. Salinity.

Describe the idea behind the proposed "Geritol Fix".

Could fertilizing the World Ocean with Fe dust reverse effects of global warming? Biological oceanographers found open ocean regions of High Nutrients, Low Chlorophyll concentrations. - Some HNLC areas due to low dissolved Fe - However, adding dissolved Fe salts very temporary & only helps part of phytoplankton

Define euphotic zone.

Depth of water column where there is sufficient sunlight for growth of photosynthetic organisms. Euphotic mean "well lit" in Greek.

Define nutrients.

In the ocean, any one of a number of inorganic or organic compounds or ions used primarily in the nutrition of primary producers: nitrogen and phosphorus compounds are examples.

Explain the concern raised by ocean acidification.

Increase in atm. CO2 => increase in dissolved CO2 in ocean -> lower pH in surface waters -> more difficult for organisms that use calcium carbonate in shells.

What are two indicators in the ocean for determining that a trace element is biologically essential?

Indicator for biological activity is element's depth profile. Near surface depletion characteristic. Spring reduction in near surface concentration with a fall increase also characteristic.

What did John Joly do?

John Joly - salts in the ocean come from small amounts of dissolved salts in river runoff. In 1899 he estimated age of the World Ocean from flow rates of different rivers & dissolved salt concentrations in each => ~90 million years.

Define residence time.

Length of time required for a complete replacement of substance present, dependent upon element & ionic state. Mean time that a substance remains in a given area before being replaced. Calculated by dividing the amount of a substance by its rate of addition or subtraction.

Name the 3 major nutrients in seawater and 2 trace elements found there.

Major: 1) Nitrogen (as NO3 -), 2) Phosphorus (as PO43-), 3) Silicon (as SiO44-) Trace: 1) Iron (Fe) 2) Zinc (Zn) Other: 1) Molybdenum (Mo) 2) Nickel (Ni) 3) Vanadium (V) 4) Selenium (Se)

What is an important biological implication of this rule?

Many saline & brackish water lakes have nearly no life at all, except when they have a similar salt composition to that of seawater. However, there are many species in World Ocean => Marine organisms have adapted to a relative constancy of different ions.

Define phytoplankton.

Microscopic floating plant-like organisms. Microscopic algal and photosynthetic forms of plankton.

How salty is the ocean off the Pacific Northwest?

Off Pacific NW 32-33 ppt

On average, how much salt is present in seawater?

On average ~35 gms per kilogram of seawater with a range of between 33 & 37 g/kg, or parts per thousand (ppt) for most of the ocean.

How do organic compounds get into seawater?

Present due to excretion & "leakage" from living organisms, as well as decomposition of dead ones. ≥ 50% of primary production "leaked" as dissolved organic matter (DOM) - basis of microbial loop.

What are the residence times for some conservative cations?

Residence Times in Millions of Years: Na- 210 Mg- 22 K- 11 Ca- 1

What made John Joly underestimate the age?

Salt deposits not included, some are enormous. Salt is recycled (unknown by Joly). Salt can be incorporated into clay minerals (also unknown).

Where is the sea saltier than normal, or much more dilute than typical?

Salty: In certain enclosed areas, can be as high as 40 gms (Red Sea) or as low as 7 (Baltic Sea). Dilute: Near coastlines generally lower than in open ocean.

What are the 2 most common ions dissolved in seawater?

The most common two ions in seawater are Na+ & Cl-. Comprise > 85.6 % of total salts in World Ocean.

Explain the Principle (or Rule) of Constant Proportions.

The percentage of each of the major ions is always the same, no matter the absolute concentration.

How do the residence times of nutrients differ from those of conservative ions?

The residence times of nutrients differ from those of conservative ions in that the residence times of nutrients is in thousands of years, while the residence times of conservative ions is in millions of years.

What is (are) the source(s) of sea salt?

These salts come from either runoff with ionic weathering products dissolved in it, or hydrothermal vent chemicals.

Define salinity.

Total quantity of dissolved salt. Measure of dissolved salts in seawater. Formally defined as the total amount of dissolved solids in seawater in parts per thousand (ppt).

Define anoxic.

Waters here can lose all oxygen, or become anoxic, due to bacterial action. Deficient in oxygen.