Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences. Issue 3 (6th March 2016)

• Record Type: Journal Article
• Authors: Moffett, Kevan B.; Gorelick, Steven M.
• Is Part Of: Water resources research. Volume 52:Issue 3(2016:Mar.)
• Page Start: 1729
• Page End: 1745
• Publication Date: 2016-03-06
• Subjects: salt marsh -- pore water -- geochemistry -- self‐organization -- vegetation zonation -- feedback; Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2015WR017406
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone‐specific pore water geochemistry, this could complement known physical mechanisms of marsh self‐organization. A high‐resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root‐induced oxidation and nutrient (P) depletion, surface and creek‐bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh‐estuary solute exchange and ecology. Key Points: Pore water geochemistry relates to species‐specific plant water use and aeration Sediment texture variations are a secondary influence on pore water patterns Pore water seepage was 41% of ebb solute export overall, and up to 87% for Ni