Lecture 19 Redox Environments in the Oceans

Multi-colored sediments!

What’s going on here???

Aerobic Respiration in Red Clay Sediments

Murray and Grundmanis, 1980

Denitrification and MnO2 reduction – Hemipelagic Sediments

Emerson et al

Guatemala Basin, North Pacific

Iron reduction – Hemipelagic Sediments

Emerson et al

East Pacific Rise – North Pacific

Sulfate ReductionMethane Production

Anaerobic Methane Consumption

Saanich Inlet, BCSediments

Kuivila and Murray (1990)

The Black Sea

Why is the Black Sea Interesting to Oceanographers?

1. The classic anoxic basin.Oxic layer over sulfidic layer.

2.Model for modern and ancient anoxic environments.

3. Well developed transitionor suboxic zone. Model forworld’s organic rich sediments.

4. Suboxic reactions easy to study here because of predictable depth locations.

5. An ideal location to study effect of climate forcing on ocean distributions.

The Bosporus Strait connects the Black Sea with the Marmara Seaand is the only source of (relatively warm) salty water.

Marmara Sea

Black Sea

Temperature and Salinity along the

Bosporus

• Some CIW advected into strait in upper half of interface

• T minimum in deep water erased over South Sill

Gregg et al (1999)

Bosporus Inflow and Entrainment of CIL

CIL(from NW Shelfin winter)

from Ozsoy et al.,(1993)

Bosporus Inflow

CIL/BI ≈ 4 for deep Black Seafrom 50m to 2000m

The Suboxic Zone: Oxygen – Sulfide Depth versus Density

Total depth = 2200m

0 100 200 300 400O x y g en (M )

17

16 .5

16

15 .5

15

14 .5

14

13 .5

Sig

ma

Th

eta

0 10 20 30 40 50H y d ro g en S u lf id e (M )

S t. 7 L eg 8 K n o rr 2 0 0 3O x y genH y d ro g en S u lfid e

0 1 2 3 4 5N O 3

- M

17

16 .5

16

15 .5

15

14 .5

14

13 .5

Sig

ma

Th

eta

0 5 10 15 20 25N H 4

+ M

0 0.0 2 0 .0 4 0 .0 6 0 .0 8 0 .1N O 2

- M

S t 7 L eg 8 K n o rr 2 0 0 3N itra teA m m o n iaN itr ite

Example of NO3-, NO2

- and NH4+ for R/V Knorr 2003

suboxic zone

CIL

Data suggests anammoxFirst seen during 1988 Expedition

Results from Knorr 1988 Cruise(w/ Pump Profiling System)

Oxygenated surface layer over a sulfide rich deep layerwith a suboxic zone at the interface

O2H2S

NO3

Suboxic Zone

NO2

Murray et al (1995)

Mn Fe

NH4 PO4