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Chemical Oceanography

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Essential micronutrients such as Fe thought to limit plankton growth. IRONEX: will adding Fe to the central Pacific Ocean cause a bloom in Plankton? ... – PowerPoint PPT presentation

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Title: Chemical Oceanography


1
Chemical Oceanography
  • Lecture 1 Primary Production
  • Lecture 2 Marine Bio-geochemistry and
    Sedimentation

2
Lecture 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

3
The 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

4
Photosynthesis 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

5
Nutrients 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.

6
World Primary Production
7
Phytoplankton
  • 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.

8
Cyanobacteria (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

9
Organic tests Dinoflagellates
  • Single celled eukaryotes, have a strong organic
    cuticle, collect light using a red pigment,
    blooms can produce poisonous red tides

10
Silica tests Diatoms
  • Single Cell Algae, Use silica to grow a
    transparent frustules (diatoms)), collect light
    in green chloroplasts (10 200 ?m)

11
Silica tests Radiolaria
  • Single Cell Algae, Use silica to grow a
    transparent tests (radiolaria), collect light in
    green chloroplasts (0.5 2 mm)

12
Calcium 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)

13
Calcium carbonate Tests Coccoliths
  • Use CaCO3 to grow tests. Coccoliths are very
    small but abundant Chalk! (30 ?m)

14
Seasonal Plankton Blooms in Temperate Regions

15
The Spring Bloom
  • Increasing light levels and high nutrient levels
    cause phytoplankton to grow


16
Summer Zooplankton Bloom
  • High light levels, but nutrients low, zooplankton
    take over from phytoplankton

17
The Autumn Bloom
  • Winter mixing starting to break down Thermocline
    mixing of nutrients into surface waters

18
Total Annual Biomass Production
19
IRONEX 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

20
Chlorophyll Increase
21
IRONEX 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

22
Chemosynthesis 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

23
Known Black Smoker locations
24
Chemosynthesis
  • 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

25
Chemoautotrophic Bacteria
26
Tube Worms
27
Giant Calms
28
Mussels
29
Spider Crabs
30
Fish
31
Octopus
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