Marine Chemistry and Biological Oceanography

海洋化學與生物海洋

Biology starts with chemistry

• Biological processes – the levels of elements and compounds

• Abundance of biota and tropic relationship – chemical parameters, salinity, dissolved oxygen and nutrient

Global water cycle

turnover time

• The ocean has a turnover time of about 37,000 years with respect to river inflow. This is how long it would take to fill the ocean if it were totally dry.

• Turnover times are defined as the mass in the reservoir divided by the input or removal rate. By comparison the average residence time of water in the atmosphere with respect to evaporation from the oceans and continents is only about 10 days.

Scope of Chemical Oceanography: Fundamental Questions

• - What are the chemical controls on biological production and food web structure of the ocean? In some ocean areas iron limits phytoplankton growth.

• Martin (1991) conducted experiments where he added iron to samples and showed that adding iron stimulated growth rate and also stimulated diatom production.

• Martin (1991) conducted experiments where he added iron to samples and showed that adding iron stimulated growth rate and also stimulated diatom production.

- In what ways do biological processes control the distributions of chemicals in the ocean?

• Photosynthesis and respiration control the distribution of many elements in seawater.

Compositions of sea water

• 0.45 m filter

• Passed –

• Can not pass –

• Humic acid, protein and amino acid, polysaccharide, pigments, inorganic colloids (iron hydroxide)

salinity

• Total amount of salts in water

Bioavailability

• Can be utilized by cells - membrane• related to dissolved materials and particulate ma

terials

• Most particulate materials can not be efficiently utilized by phytoplankton and algae

• 理由 : large size of particulate materials – can not pass through cell membrane or via the channel

Speciation and global hydrological cycle

7 days

3550 days

Global hydrological cycle

Time-dependent events

Dissolved gases

• Oxygen: dissolved oxygen (DO)

• Surface, temperature, biological utilization and emission

• 2.0-10 mg/L intertidal regions

• Vertical distribution: 50 m no variation

• Photosynthesis (+O2)

• Respiration (-O2)

Primary productivity

CO2 cycle

• CO2 (gas) ↔ CO2 (dissolved)• H2O + CO2 ↔ H2CO3

• H2CO3 ↔ H+ + HCO3-

• HCO3- ↔ H+ + CO3

2-

• Ca2+ + CO32- ↔ CaCO3 (solid)

• 表示法 : alkalinity (A) – the number of moles of hydrogen ion required to convert all anions of weak acids to their unionized form in 1 kg of water

pH and CO2

CO2 cycle

C cycle

Nutrient

• Phosphorus (P)• Nitrogen (N)• Co-variation of N and P• Refield atomic ratio: C:N:P=106:16:1 (1934, 1

963)• N:P ratio > 30:1 P limitation• N:P ratio < 10:1 N limitation

• Silicon

Spatial variations

Temporal variations

Organic carbon

• Dissolved organic carbon DOC

• Particular organic carbon POC• POC in photic zone is recycled by micro-organisms.