Silica: an essential nutrient in wetland biogeochemistry
01 Mar 2009-Frontiers in Ecology and the Environment (Ecological Society of America)-Vol. 7, Iss: 2, pp 88-94
TL;DR: In this article, the authors show that wetland ecosystems may be as important for Si transport and processing as they are for other important biogeochemical cycles, such as nitrogen and phosphorus cycling.
Abstract: Recent research has emphasized the importance of terrestrial ecosystems in the global biogeochemical cycle of silica (Si). The production, retention, and dissolution of amorphous silica of biological origin in soils and vegetation effectively control terrestrial Si fluxes. However, surprisingly little is known about the role of wetlands in these processes. Wetlands are known hotspots for both nitrogen and phosphorus cycling, and there have been countless studies and numerous reviews on these nutrients worldwide. By bringing together previously scattered results, we show that wetland ecosystems may be as important for Si transport and processing as they are for other important biogeochemical cycles. Yet, the range of studied systems is small and incomplete. This constitutes a serious gap in our understanding of both coastal eutrophication and climate change, issues that are strongly linked to Si biogeochemistry. Ecosystem scientists and wetland biogeochemists around the world need to begin addressing these issues.
Citations
More filters
TL;DR: Salinization, a widespread threat to the structure and ecological functioning of inland and coastal wetlands, is currently occurring at an unprecedented rate and geographic scale as discussed by the authors, and the causes of salinization are diverse and include alterations to freshwater flows, land-clearance, irrigation, disposal of wastewater effluent, sea level rise, storm surges, and applications of de-icing salts.
Abstract: Salinization, a widespread threat to the structure and ecological functioning of inland and coastal wetlands, is currently occurring at an unprecedented rate and geographic scale. The causes of salinization are diverse and include alterations to freshwater flows, land-clearance, irrigation, disposal of wastewater effluent, sea level rise, storm surges, and applications of de-icing salts. Climate change and anthropogenic modifications to the hydrologic cycle are expected to further increase the extent and severity of wetland salinization. Salinization alters the fundamental physicochemical nature of the soil-water environment, increasing ionic concentrations and altering chemical equilibria and mineral solubility. Increased concentrations of solutes, especially sulfate, alter the biogeochemical cycling of major elements including carbon, nitrogen, phosphorus, sulfur, iron, and silica. The effects of salinization on wetland biogeochemistry typically include decreased inorganic nitrogen removal (with implica...
566 citations
TL;DR: An ecological perspective to research outcomes from diverse disciplines is provided, showing that silicon is an important element in plant ecology that is worthy of greater attention.
246 citations
TL;DR: In this paper, the authors identify relevant geochemical tracers of Si pathways within the soil-plant system to obtain a better understanding of the origin of DSi exported towards rivers.
Abstract: . Silicon (Si) released as H4SiO4 by weathering of Si-containing solid phases is partly recycled through vegetation before its land-to-rivers transfer. By accumulating in terrestrial plants to a similar extent as some major macronutrients (0.1–10% Si dry weight), Si becomes largely mobile in the soil-plant system. Litter-fall leads to a substantial reactive biogenic silica pool in soil, which contributes to the release of dissolved Si (DSi) in soil solution. Understanding the biogeochemical cycle of silicon in surface environments and the DSi export from soils into rivers is crucial given that the marine primary bio-productivity depends on the availability of H4SiO4 for phytoplankton that requires Si. Continental fluxes of DSi seem to be deeply influenced by climate (temperature and runoff) as well as soil-vegetation systems. Therefore, continental areas can be characterized by various abilities to transfer DSi from soil-plant systems towards rivers. Here we pay special attention to those processes taking place in soil-plant systems and controlling the Si transfer towards rivers. We aim at identifying relevant geochemical tracers of Si pathways within the soil-plant system to obtain a better understanding of the origin of DSi exported towards rivers. In this review, we compare different soil-plant systems (weathering-unlimited and weathering-limited environments) and the variations of the geochemical tracers (Ge/Si ratios and δ30Si) in DSi outputs. We recommend the use of biogeochemical tracers in combination with Si mass-balances and detailed physico-chemical characterization of soil-plant systems to allow better insight in the sources and fate of Si in these biogeochemical systems.
244 citations
Cites background from "Silica: an essential nutrient in we..."
...topsoil, litterfall being the most important Si flux from vegetation to soil (Sommer et al., 2006; Blecker et al., 2006; Struyf and Conley, 2009; Cornelis et al., 2010c; Struyf et al., 2010)....
[...]
...It is well known that aquatic macrophytes and wetland species can contain significant amounts of Si (Struyf and Conley, 2009; Struyf et al., 2009)....
[...]
TL;DR: Investigation of biogenic silica, cellulose and lignin content of 16 aquatic/wetland species along the Biebrza river in Poland in June 2006 and 2007 concludes that macrophytes have an overlooked but potentially vast storage capacity for Si.
Abstract: *Although silica (Si) is not an essential element for plant growth in the classical sense, evidence points towards its functionality for a better resistance against (a)biotic stress. Recently, it was shown that wetland vegetation has a considerable impact on silica biogeochemistry. However, detailed information on Si uptake in aquatic macrophytes is lacking. *We investigated the biogenic silica (BSi), cellulose and lignin content of 16 aquatic/wetland species along the Biebrza river (Poland) in June 2006 and 2007. The BSi data were correlated with cellulose and lignin concentrations. *Our results show that macrophytes contain significant amounts of BSi: between 2 and 28 mg BSi g(-1). This is in the same order of magnitude as wetland species (especially grasses). Significant antagonistic correlations were found between lignin, cellulose and BSi content. Interestingly, observed patterns were opposite for wetland macrophytes and true aquatic macrophytes. *We conclude that macrophytes have an overlooked but potentially vast storage capacity for Si. Study of their role as temporal silica sinks along the land-ocean continuum is needed. This will further understanding of the role of ecosystems on land ocean transport of this essential nutrient.
194 citations
Cites background or result from "Silica: an essential nutrient in we..."
...Wetland grasses are well known for their capacity to accumulate BSi (Struyf & Conley, 2009)....
[...]
...More and more evidence points towards strong control of silica biogeochemistry by plant communities (Derry et al., 2005; Struyf & Conley, 2009)....
[...]
...This is comparable with the values found for several Poaceae and Cyperaceae (Lanning & Eleuterius, 1983; Hodson et al., 2005; Struyf & Conley, 2009)....
[...]
TL;DR: It is demonstrated that across plant families and stress types, Si increases dry weight, assimilation rate and chlorophyll biosynthesis and alleviates oxidative damage in stressed plants, and Meta-analyses showed consistent alleviation by Si of oxidative damage caused by a range of abiotic stresses across diverse species.
Abstract: 1. Hundreds of single species studies have demonstrated the facility of silicon (Si) to alleviate diverse abiotic stresses in plants. Understanding of the mechanisms of Si-mediated stress alleviation is progressing, and several reviews have brought information together. A quantitative assessment of the alleviative capacity of Si, however, which could elucidate plant Si function more broadly, was lacking.
2. We combined the results of 145 experiments, predominantly on agricultural species, in a meta-analysis to statistically assess the responses of stressed plants to Si supply across multiple plant families and abiotic stresses. We interrogated our database to determine whether stressed plants increased in dry mass and net assimilation rate, oxidative stress markers were reduced, antioxidant responses were increased and whether element uptake showed consistent changes when supplied with Si.
3. We demonstrated that across plant families and stress types, Si increases dry weight, assimilation rate and chlorophyll biosynthesis and alleviates oxidative damage in stressed plants. In general, results indicated that plant family (as a proxy for accumulator type) and stress type had significant explanatory power for variation in responses. The consistent reduction in oxidative damage was not mirrored by consistent increases in antioxidant production, indicative of the several different stress alleviation mechanisms in which Si is involved. Silicon addition increased K in shoots, decreased As and Cd in roots and Na and Cd in shoots. Silicon addition did not affect Al, Ca or Mn concentration in shoots and roots of stressed plants. Plants had significantly lower concentrations of Si accumulated in shoots but not in roots when stressed.
4. Meta-analyses showed consistent alleviation by Si of oxidative damage caused by a range of abiotic stresses across diverse species. Our findings indicate that Si is likely to be a useful fertilizer for many crops facing a spectrum of abiotic stresses. Similarities in responses across families provide strong support for a role of Si in the alleviation of abiotic stress in natural systems, where it has barely been explored. We suggest this role may become more important under a changing climate and more experiments using non-agricultural species are now needed.
182 citations
Cites background from "Silica: an essential nutrient in we..."
...The benefits of Si 456 accumulation in wetland environments have been studied in terms of increased ability to resist water currents 457 and allow roots to better penetrate mud (Ernst, Vis & Piccoli 1995; Struyf & Conley 2008, not included in the 458 meta-analysis)....
[...]
References
More filters
TL;DR: For example, the accumulation of biogenic silica in estuarine deposits removes a maximum of 8 × 1014g SiO2/yr or 10% of the dissolved silica input to the oceans as mentioned in this paper.
1,128 citations
TL;DR: Information on the phylogenetic variation in shoot Si concentration may provide useful palaeoecological and archaeological information, and inform studies of the biogeochemical cycling of Si and those of the molecular genetics of Si uptake and transport in plants.
871 citations
TL;DR: In this paper, the authors present long-term data sets of water and nutrient discharge from the River Danube to the Black Sea, revealing a reduction in the dissolved silicate load of the river by about two-thirds since dam constructions in the early 1970s.
Abstract: Rivers contribute significantly to the pollution and eutrophication that have caused drastic changes to the ecosystem of the Black Sea1–3. Although damming is known to affect riverborne nutrient loads, and thus riverine ecosystems, evidence for significant effects in open coastal waters is sparse4–6. Here we present long-term data sets of water and nutrient discharge from the River Danube to the Black Sea. These data reveal a reduction in the dissolved silicate load of the river by about two-thirds since dam constructions in the early 1970s. A concomitant decrease in wintertime dissolved silicate concentrations by more than 60% was observed in central Black Sea surface waters. The consequent changes in silicon to nitrogen ratio of the Black Sea nutrient load appear to be larger than those caused by eutrophication alone, and seem to be responsible for dramatic shifts in phytoplankton species composition from diatoms (siliceous) to coccolithophores and flagellates (non-siliceous). Our results strongly suggest that the damming of the Danube has been instrumental in causing the observed changes in Black Sea surface waters3,7–9, and that the large number of dams in operation around the world today could similarly affect the food web structure and biogeochemical cycling in coastal seas.
700 citations
TL;DR: Arguments are presented that silicon is often the controlling nutrient in altering a diatom to a flagellate community and examples of such alterations are presented for oceanic, estuarine and inland water bodies.
Abstract: Diatom phytoplankton populations are the usual food for zooplankton and filter feeding fishes and contribute in a direct way to the large fishable populations in coastal zones. Flagellates, on the other hand, are frequently poor foods for most grazers and can lead to undesirable eutrophication effects. Arguments are presented that silicon is often the controlling nutrient in altering a diatom to a flagellate community. The alteration is governed by the relative magnitudes of the natural fluxes of the nutrients nitrogen, phosphorus and silicon to the receiving water body and the recycled fluxes of nitrogen and phosphorus from zooplankton grazing and phytoplankton respiration and decomposition. Examples of such alterations are presented for oceanic, estuarine and inland water bodies.
534 citations
TL;DR: The terrestrial biogeochemical Si cycle is of great interest because of its impact on global CO2 concentrations through the combined processes of weathering of silicate minerals and transfer of CO2 from the atmosphere to the lithosphere as discussed by the authors.
Abstract: [1] Most research on the global Si cycle has focused nearly exclusively on weathering or the oceanic Si cycle and has not explored the complexity of the terrestrial biogeochemical cycle. The global biogeochemical Si cycle is of great interest because of its impact on global CO2 concentrations through the combined processes of weathering of silicate minerals and transfer of CO2 from the atmosphere to the lithosphere. A sizable pool of Si is contained as accumulations of amorphous silica, or biogenic silica (BSi), in living tissues of growing plants, known as phytoliths, and, after decomposition of organic material, as remains in the soil. The annual fixation of phytolith silica ranges from 60–200 Tmol yr−1 and rivals that fixed in the oceanic biogeochemical cycle (240 Tmol yr−1). Internal recycling of the phytolith pool is intense with riverine fluxes of dissolved silicate to the oceans buffered by the terrestrial biogeochemical Si cycle, challenging the ability of weathering models to predict rates of weathering and consequently, changes in global climate. Consideration must be given to the influence of the terrestrial BSi pool on variations in the global biogeochemical Si cycle over geologic time and the influence man has had on modifying both the terrestrial and aquatic biogeochemical cycles.
497 citations