Iron & Manganese Depositing Cold-Seeps: A Lotic to Marine Ecosystem At Soda Bay, Alaska

Soda Bay Creek is a pristine low-temperature iron- and manganese-rich carbonate depositing ecosystem located in Southeast Alaska. It encompasses a lotic to marine watershed, which flows into Soda Bay Estuary, mixing with seawater from the Pacific Ocean in Tlevak Strait. Dissolved iron and manganese minerals from the groundwater are transported through fissures and cracks to the surface of the limestone bedrock and along geologic contacts, forming several cold springs and seeps along the banks of Soda Bay Creek and subsurface in Soda Bay. Iron- and manganese-rich carbonate mounds as tall as 3 meters have been observed, these are formed when fluids super-saturated in carbon dioxide and dissolved minerals come into contact with the oxygenated atmosphere.

Research integrates geochemistry, microscopy, oceanography and geomicrobiology to study the biogeochemical transformations of an unusual groundwater ecosystem. This study focuses on the following questions regarding the impact of these metalliferous seeps and their seasonal effects on the surrounding ecosystem:

(1) What are the abiotic vs. biotic processes affecting mineral formation?
(2) What chemolithotrophic microorganisms are dominant in these habitats?
(3) Are there unique metal oxidation products and/or unusual biogenic minerals formed?
(4) What are the effects of these high alkalinity seeps on the Soda Bay Seep ecosystem?