Sulfide as a soil phytotoxin—a review

Abstract

In wetland soils and underwater sediments of marine, brackish and freshwater systems, the strong phytotoxin sulfide may accumulate as a result of microbial reduction of sulfate during anaerobiosis, its level depending on prevailing edaphic conditions. In this review, we compare an extensive body of literature on phytotoxic effects of this reduced sulfur compound in different ecosystem types, and review the effects of sulfide at multiple ecosystem levels: the ecophysiological functioning of individual plants, plant-microbe associations, and community effects including competition and facilitation interactions. Recent publications on multi-species interactions in the rhizosphere show even more complex mechanisms explaining sulfide resistance. It is concluded that sulfide is a potent phytotoxin, profoundly affecting plant fitness and ecosystem functioning in the full range of wetland types including coastal systems, and at several levels. Traditional toxicity testing including hydroponic approaches generally neglect rhizospheric effects, which makes it difficult to extrapolate results to real ecosystem processes. To explain the differential effects of sulfide at the different organizational levels, profound knowledge about the biogeochemical, plant physiological and ecological rhizosphere processes is vital. This information is even more important, as anthropogenic inputs of sulfur into freshwater ecosystems and organic loads into freshwater and marine systems are still much higher than natural levels, and are steeply increasing in Asia. In addition, higher temperatures as a result of global climate change may lead to higher sulfide production rates in shallow waters.

Toxic effects of increased sediment nutrient and organic matter loading on the seagrass Zostera noltii

“…Sulfide is known to be very toxic to seagrasses (Calleja et al, 2007;Koch and Erskine, 2001;Lamers et al, 2013;Marba et al, 2006;Terrados et al, 1999) and Van der Heide et al (2012) showed a negative effect on Zostera noltii biomass production at porewater sulfide levels <200 mol L -1 . We found similar threshold values in our field experiment and also found that patch expansion was entirely blocked by sulfide concentrations >1000 mol L -1 .…”

“…Sulfide is a strongly phytotoxic compound, as it blocks the activity of cytochrome oxidase and other metal containing enzymes (Lamers et al, 2013). It is formed in anaerobic sediments rich in organic matter, where sulfate is used as an alternative terminal electron acceptor during the microbial breakdown of organic matter (Gray and Elliott, 2009;Holmer and Nielsen, 1997).…”

Marine Phytophthora species can hamper conservation and restoration of vegetated coastal ecosystems

“…Sulfide was measured according to the method described in Govers et al [36]. We measured porewater sulfide concentrations since this indicates sediment anoxia (sulfide is only produced in anoxic conditions), and sulfide is toxic to most eukaryotic life, including marine plants [40] and perhaps also oomycetes, potentially affecting seed survival and infection by Phytophthora and Halophytophthora species.…”

Iron clad wetlands: Soil iron‐sulfur buffering determines coastal wetland response to salt water incursion

“…Sea water incursion increases salinity but also alters sulfate concentrations by orders of magnitude as fullstrength seawater has 10-1000X more sulfate than freshwaters [Lamers et al, 2013]. Sulfate reduction to sulfide, via microbial respiration, follows nitrate and iron reduction as the next most thermodynamically favorable reaction to microbes [Stumm and Morgan, 1996].…”