Title: Chemical Oceanography
1Chemical Oceanography
- Lecture 1 Primary Production
- Lecture 2 Marine Bio-geochemistry and
Sedimentation
2Lecture 9 Primary Production
- The Reactions of Life, Photosynthesis,
Respiration and Growth. - Phytoplankton The Plants of the Ocean
- Seasonal Plankton Blooms, Thermoclines and
Nutrient Cycling - Seeding the Open Ocean, IRONEX
- Chemosynthesis at Hydrothermal vents
3The Reactions of Life, Photosynthesis,
Respiration and Growth.
- In order to live, grow and reproduce all plants
and animals need energy, ultimately there are
there are only two sources of energy for life on
Earth - The Sun plants have evolved to be able to
capture and store the energy in sunlight by
photosynthesis - Geothermal Heat (residual heat from formation of
the Earth and from radioactive decay in the core)
can drive chemosynthesis
4Photosynthesis and Primary Production
- Biologically driven reactions that cycle carbon
dioxide, water and oxygen - CO2 H2O sunlight ? CH2O O2
- CH2O O2 ? CO2 H2O
- Many other elements are required, most
importantly Nitrate and Phosphate. These
nutrients limit growth in ocean and are found to
be absorbed in a very constant rate (Redfield
Ratio) - 106 CO2 16 HNO3 H3PO4 122 H2O sunlight ?
(CH2O)106(NH3)16(H3PO4) 138 O2
5Nutrients Limit Growth
- Typical CNP Composition of Ocean Water
- (Redfield Ratio 106 C 16 N 1 P)
- C 42400 mg/m3 / 106 400 units C
- N 480 mg/m3 / 16 30 units N
- P 50 mg/m3 / 1 50 units P
- There is ample C, but N and P will be quickly
exhausted. - There are many other nutrients and
micronutrients Ca (carbonate shells), Si (silica
shells), S, K, Na, Cl, Mg, Cr, Co, Cu, F, I, Fe,
Mn, Mo, Se, Zn, Ni, Sn, and V.
6World Primary Production
7Phytoplankton
- On land plants are the main primary producers
they need to complex bodies for support and to
collect light. e.g. forests, grassland etc. - In the oceans seaweeds and corals are similar,
e.g. kelp forests. but limited to coasts - In the open ocean there is no need for support
and the main primary producers and microscopic
plankton.
8Cyanobacteria (blue/green algae)
- Very simple single-celled prokaryotes, earliest
life form on earth. Contain chlorophyll to
collect light for photosynthesis, form filaments
and mats composed of long chains of cells -
9Organic tests Dinoflagellates
- Single celled eukaryotes, have a strong organic
cuticle, collect light using a red pigment,
blooms can produce poisonous red tides
10Silica tests Diatoms
- Single Cell Algae, Use silica to grow a
transparent frustules (diatoms)), collect light
in green chloroplasts (10 200 ?m)
11Silica tests Radiolaria
- Single Cell Algae, Use silica to grow a
transparent tests (radiolaria), collect light in
green chloroplasts (0.5 2 mm)
12Calcium carbonate Tests Foraminifera
- Use CaCO3 to grow tests. foraminifera farm
symbiotic dinoflagettes for food, also feed on
other plankton e.g. diatoms. (0.5 2mm)
13Calcium carbonate Tests Coccoliths
- Use CaCO3 to grow tests. Coccoliths are very
small but abundant Chalk! (30 ?m)
14Seasonal Plankton Blooms in Temperate Regions
15The Spring Bloom
- Increasing light levels and high nutrient levels
cause phytoplankton to grow
16Summer Zooplankton Bloom
- High light levels, but nutrients low, zooplankton
take over from phytoplankton
17The Autumn Bloom
- Winter mixing starting to break down Thermocline
mixing of nutrients into surface waters
18Total Annual Biomass Production
19IRONEX seeding the ocean
- The open oceans are areas of low primary
production - But light and (N, P) nutrients are available
- Essential micronutrients such as Fe thought to
limit plankton growth - IRONEX will adding Fe to the central Pacific
Ocean cause a bloom in Plankton? - Oct 1993 Fe(III)citrate and SF6 added to a patch
of surface water
20Chlorophyll Increase
21IRONEX and Global CO2
- Hoped that this experiment might provide a way to
cure global warming. - But A lot of Fe would be needed
- 99 of organic matter is recycled in upper ocean,
more in deep water - Cyanobacteria were stimulated, they have no hard
shell and do not sink well - Bloom was very short lived
- Not a practical solution
22Chemosynthesis at Black Smokers
- Hydrothermal vents discovered in 1977 by ALVIN
submersible - Geothermal heat causes seawater to circulates
through hot volcanic rocks at MORs - Fluids becomes very reducing as sulphide, Fe, Mn,
Cu, Au, etc. dissolves - When hot waters emerges back into the ocean at
vents the cold seawater causes sulphide
minerals to precipitate - Builds sulphide mineral chimneys
- Chemical energy is used by chemoautotrophic
bacteria
23Known Black Smoker locations
24Chemosynthesis
- Without light photosynthesis is not possible
- CO2 H2O sunlight ? CH2O O2
- But the bacteria found at black smokers can
extract energy from the reaction of hydrogen
sulphide from the vents and oxygen in the
seawater - CO2 H2O H2S O2 ? CH2O H2SO4
- Respiration can then proceed as normal
- CH2O O2 ? CO2 H2O
- This reaction is the basis for the food chain
- Most species have symbiotic bacteria in their
bodies - These chemoautotrophs are very ancient and some
think this environment could hold key to origin
of life
25Chemoautotrophic Bacteria
26Tube Worms
27Giant Calms
28Mussels
29Spider Crabs
30Fish
31Octopus