Silica: an essential nutrient in wetland biogeochemistry

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.

Vegetation and proximity to the river control amorphous silica storage in a riparian wetland (Biebrza National Park, Poland)

“…624 E. Struyf et al: Silica storage in a riparian wetland for exported DSi (Bartoli, 1983;Farmer et al, 2005). More recently, a literature overview suggested that wetlands have the potential to exhibit a profound influence on terrestrial silica transport and storage (Struyf and Conley, 2009). Wetlands can modify nutrient fluxes along the aquatic continuum through transformation and storage.…”

Combining limnology and palaeolimnology to investigate recent regime shifts in a shallow, eutrophic lake

“…4b). Diatom productivity and abundance are often estimated from biogenic silica (BSi; Conley and Schelske 2001;Struyf and Conley 2009), and these concentrations are low throughout the zone (1.8-2.9 wt%; Fig. 5).…”

Landscape elements and river chemistry as affected by river regulation – a 3-D perspective

“…Moreover, grasses and sedges are known to contain significant amount of amorphous silica in their biomass (Saccone et al, 2007). In a recent study, Struyf and Conley (2009) have shown that especially these arctic wetlands are impressive storages of amorphous silica (ASi) that are either diatom frustules or phytoliths (Piperno, 1988). Initial analyses show that subarctic wetlands in Northern Sweden contain 1-5% of ASi by weight percent, which is an order of magnitude above the amount stored in temperate wetlands and confirm the capacity of subarctic wetlands to accumulate large amounts of ASi.…”

“…Thus, the soil/water contact time will obviously increase downstream. A long soil/water contact time increases also the potential for a build up of a ASi pool in the soils that is further enhanced by regular flooding events that in turn lead to an enhanced deposition of suspended soils, sediment associated phytoliths and diatoms (Struyf and Conley, 2009). In other words, these authors suggest that the wetland rich areas, such as the riparian zone, of arctic and boreal river systems has evolved to a massive Si storage since the last glaciation and act now as a significant source for DSi in these river systems.…”

“…This study aims to highlight such potential "hot spots" in catchments with regard to dissolved constituents, showing that alterations of a relatively small area can result in major changes in river chemistry if vital areas are affected. Estimates of the areas of land classes and the reduction in area of certain classes containing potential hot spots for river loading with DSi (Struyf and Conley, 2009), were derived from 2-dimensional GIS maps. Moreover, we developed a digital elevation model (DEM) for the area draped with land classes and soil depths which highlights that topography of various land classes is critical in determining water residence time in soils and biogeochemical fluxes (Laudon et al, 2007).…”