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 MnO 2 reduction – Hemipelagic Sediments Emerson et al Guatemala Basin, North Pacific

Iron reduction – Hemipelagic Sediments Emerson et al East Pacific Rise – North Pacific

Sulfate Reduction Methane Production Anaerobic Methane Consumption Saanich Inlet, BC Sediments 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 transition or suboxic zone. Model for world’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 Sea and 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 Shelf in winter) from Ozsoy et al.,(1993) Bosporus Inflow CIL/BI ≈ 4 for deep Black Sea from 50m to 2000m

The Suboxic Zone: Oxygen – Sulfide Depth versus Density Total depth = 2200m

Example of NO 3 -, NO 2 - and NH 4 + 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 layer with a suboxic zone at the interface O2O2 H2SH2S NO 3 Suboxic Zone NO 2 Murray et al (1995)

Mn Fe NH 4 PO 4