Lecture 22 - Ocean Biogeochemistry

Lecture 22 - Ocean Biogeochemistry - Lecture 15 Ocean Floor...

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Unformatted text preview: Lecture 15 Ocean Floor Lecture 22 Ocean Biogeochemistry Consensus among the participants was that higher CO 2 levels will generally be detrimental to calcifying organisms and that food web structures and biodiversity will likely change, but it is not clear how this might impact overall productivity and top level predators (e.g. fish). Coccolithophores Forams Corals calcite calcite aragonite Carbonate Compensation Depth CCD varies with Latitude CCD varies between Oceans North Pacific: 1000 m South Pacific: 2500 m Atlantic: 4000 m Calcite Compensation Depth Photosynthesis CO 2 + H 2 O CH 2 O + O 2 Respiration CH 2 O + O 2 CO 2 + H 2 O Carbon Dioxide Controls Calcite Dissolution and Precipitation CaCO 3 + CO 2 + H 2 O Ca 2+ + 2HCO 3- Dissolution of Biogenous Particles Carbonates Foraminifera (Calcite) less soluble Pteropods (Aragonite) more soluble Dissolution is highest in Deep Waters High pressure Low temperatures Low pH (high CO 2 ) Carbonate Compensation Depth (CCD) Carbonate Compensation Depth New Deep Waters have low CO 2 concentrations Old Deep Waters have high CO 2 concentrations Animal respiration Decomposer activities Pacific deep waters are older than Atlantic deep waters Global Thermohaline Circulation We find sediments containing calcite deep in sediment cores taken well below the CCD. Why? Carbonate Compensation Depth Deep-sea stratigraphy refers to the broad-scale layering of sediments that cover the basaltic crust. The stratigraphy of the deep sea is strongly influenced by sea-floor spreading. 4-2 Stratigraphy and Model of Pacific Basin Carbonate Compensation Depth & Greenhouse Effect? CO 2 in atmosphere, seawater & sediments are interrelated! Will increase in atmospheric CO 2 cause an increase in dissolved seawater CO 2 ? Consequences of a shallow CCD? Release into atmosphere of dissolved carbonate sediments? Calcite Compensation Depth Photosynthesis CO 2 + H 2 O CH 2 O + O 2 Respiration CH 2 O + O 2 CO 2 + H 2 O Carbon Dioxide Controls Calcite Dissolution and Precipitation CaCO 3 + CO 2 + H 2 O Ca 2+ + 2HCO 3- CO 2 changes in the last 300 yr 100 ppm Industrial Revolution Theory predicts that increasing CO 2 will warm the planet what do we see? 380 2003 379 ppm 2004 381 ppm 2005 383 ppm 2006 385 ppm 2050 473 ppm 2100 573 ppm Todays world pCO 2 : 280-380 ppmV High-CO 2 world pCO 2 : 580-720 ppmV Emiliania huxleyi Gephyrocapsa oceanica Calcidiscus leptoporus A summary of studies indicate that almost all calcifying species examined to date have shown reduced calcification rates at higher pCO 2 levels, but only a small fraction of the natural species have been tested. Warm water corals have primarily formed in aragonite saturation levels > 4, can survive at levels > 3.5, and generally stop growing < 3 Authigenic Sediments...
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This note was uploaded on 01/26/2012 for the course EAS 2600 taught by Professor Ingalls during the Fall '08 term at Georgia Institute of Technology.

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Lecture 22 - Ocean Biogeochemistry - Lecture 15 Ocean Floor...

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