What is marsh acidification? Groundwater in coastal saltwater wetlands is called interstitial water and is anoxic (without oxygen) because it is characterized and dominated by anaerobic bacteria. Such bacteria use organics and sulfides to meet their energy and respiratory requirements, not oxygen, and cannot actually survive in the presence of oxygen. The bacterial respiratory process results in the release of hydrogen sulfide, which then forms sulfuric acid and iron sulfides. It also activates copper and arsenic, so they can be released during periods of tidal exchange or falling tides, or in the case of back basin mangrove systems, or those with paludal basins (large depressions), buildup on the marsh surface in acidified pools or lakes. Marsh acidifications have occurred many times around the globe, from the Carolina trunk marshes to Southeast Asian shrimp ponds. Such acidifications can also result from runoff from land-clearing of high sulfide, high-iron soils, and cause dramatic sea grass losses when this runoff reaches estuaries (Australia). In the United States, mangroves in Southeast Florida are being lost in the interior areas of swamps due to unreported causes. In the northern lagoon, sea grass collapse has accompanied super bloom conditions in the overlying water columns. These have initiated primarily along coastal marshes, where a clam farmer also reported dramatic clam losses accompanied by highly sulfidic sediments that suddenly showed up. Are these possibly related, and if so, how? Marsh acidification can be especially pernicious for the mangroves within the swamp affected, but release of high sulfide levels, in the form of sulfuric acid and activated iron, would also contribute to super blooms of iron-limited phytoplankton, and if severe enough, to negative impacts on sea grass. Since marsh elevations arent accreting (rising), then even small increases of water level, in the order of inches, can cause marsh acidification problems for the estuary.
Posted on: Wed, 03 Dec 2014 10:59:38 +0000
Trending Topics
Recently Viewed Topics
© 2015