Paul Julian II, PhD

Ecologist, Wetland Biogeochemist, Data-scientist, lover of Rstats.

Publication Summary - Pryite

Written on September 1, 2017

Originally this blog post was originally posted on Aquatic Thoughts….

Quick Summary: Julian P, Chambers R, Russell T (2017) Iron and Pyritization in Wetland Soils of the Florida Coastal Everglades. Estuaries and Coasts 40:822–831.

Pyrite formation is a major wetland process broadly controlled by oxidation-reduction (redox) conditions, the availability of reaction iron (Fe) and free sulfide (\(S^{2-}\)). Generally, soil pyrite forms where sulfate reduction and associated fermentation reactions occur during anaerobic decomposition of organic matter. Much of the studies related to Fe-sulfur (S) interactions have been focused on marine/brackish waters or acidic lakes and acid mine tailing ponds. However, within the Everglades ecosystem S has been a topic of intense research related to the involvement in sulfate reducing bacteria in the mercury cycle.

In short: This paper evaluated the formation of pyrite along a freshwater-to-marine gradient within the Everglades ecosystem along Shark River Slough, Taylor Slough, the Panhandle region of Everglades National Park and Florida Bay. Each region of has different limiting factors that regulated pyrite formation along these flow paths. Regulators include limited Fe, \(S^{2-}\), organic matter and interaction with calcium minerals.

Why it’s important to science: This paper evaluates Fe dynamics and its interaction with S and other compounds within a large peat accreting wetland. More notably this study focuses on a region with carbonate-rich, biogenic soils considered to be anemic (low iron) relative to the Fe-rich terrigenous soils of most temperate wetland ecosystems. Iron availability for pyrite formation can significantly influence soil biogeochemistry and ecology.

Why it’s important: While typically considered trivial, iron plays an important role in the biogeochemical cycling in the Everglades system. The dynamics of Fe and S are exemplified across an ecosystem gradient from freshwater-to-marine each with unique characteristics, forcing factors and biological conditions. Iron-S dynamics are vitally important to biological integrity of the ecosystem due to the hypothesized role of Fe availability in mangrove recruitment, reducing sulfide exposure to plants, the potential link of Fe-S in mercury cycling and suspected role of regulating nutrient availability (as observed in other systems).

Future work: Future work related to Fe-S dynamics within the Everglades ecosystem include nutrient-pyrite interaction, pyrite as an early warning sign of sea-level rise, and the role of ecosystem productivity relative to pyrite formation (figures below).

Generalized ecosystem productivity gradient with the Florida Coastal Everglades.

Generalized degree of pyritization along ecosystem gradients. Degree of pyrtization is an indicator of pyrite formation (0=not likely, 1=Pyrite is present).