Effects of seasonal dynamics in a Zostera noltii meadow on phosphorus and iron cycles in a tidal mudflat (Arcachon Bay, France)

Abstract

A study was conducted in Arcachon Bay, France, to determine the effect of seasonal dynamics in a Zostera noltii meadow on P and Fe cycles in the superficial sediments of a tidal mudflat. The redox-sensitive Fe particulate pool and associated P in the root zone showed a seasonal variation following the growth and decay of Z. noltii biomass, with a maximum content during the growth period. In comparison, the bare sediments did not show significant seasonal changes. A dissolved inorganic phosphorus (DIP) uptake was measured from the water column to the sediment in vegetated sediments, whereas a net DIP efflux was observed in the unvegetated sediments. During the growth period, the formation of an iron oxihydroxide-rich zone occurred and acted as a trap for dissolved phosphorus, constituting a reserve of available P for eelgrass growth. At the periphery of the rhizosphere, a strong reduction of the sediment occurred during the growth phase, probably due to increasing organic matter inputs via the roots. The iron oxihydroxide dissolution releases Fe(II) and the recently bound phosphorus to the pore water, making it available for assimilation by the eelgrass roots for growth metabolism. Fe(II) is re-oxidized to solid Fe(III) forms depleted in P into the root zone, or re-precipitated below as sulphur forms. The highest P uptake occurs by this process, and the seasonal variations in redox-sensitive P stock are sufficient to support the annual Z. noltii P requirement. During the decline period, as the P plant demand and the oxic layer thickness drop, the unused released DIP pool supplies large amounts of DIP to the pore water and water column. KEY WORDS: Nutrient · Eelgrass growth · Intertidal zone · Lagoon · Early diagenesisResale or republication not permitted without written consent of the publisher

Sulfide as a soil phytotoxin—a review

“…Many flooded or waterlogged plants show radial oxygen loss (ROL) from their roots, and the level and pattern of ROL is determined by photosynthetic rate, root architecture and root morphology (Armstrong, 1979; Jackson, 1985; McKee et al, 1988; Laan et al, 1991; Jackson and Armstrong, 1999; Visser et al, 2003; Frederiksen and Glud, 2006; Visser and Bögemann, 2006; Voesenek et al, 2006; Deborde et al, 2008). During nighttime, sulfide intrusion into roots and rhizomes is highest (Borum et al, 2005).…”

“…During nighttime, sulfide intrusion into roots and rhizomes is highest (Borum et al, 2005). Rhizosphere oxidation provides an obvious potential defense mechanism against the toxicity of reduced components such as sulfide (Pitts et al, 1972; Mendelssohn and McKee, 1988; Armstrong et al, 1996; Smolders and Roelofs, 1996; Hemminga, 1998; Armstrong and Armstrong, 2001, 2005; Holmer and Storkholm, 2001; Deborde et al, 2008), provided that soil aerobic microbial respiration and concomitant consumption of oxygen do not counteract this effect.…”

Manganese, iron and phosphorus cycling in an estuarine mudflat, Loire, France

“…A last parameter, the importance of riverine reactive Fe oxide deposition, has been invoked by Meiggs and Taillefert (2011) to explain a time series dataset in which salinity increases A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 4 without the simultaneous increase in sulphate reduction. Furthermore, numerous studies have described the seasonal variation of diagenesis intensity based on integrative indicators or on dissolved dataset only (Alperin et al, 1994;Beck et al, 2008;Cathalot et al, 2010;Dang et al, 2015;Deborde et al, 2008;Dellwig et al, 2007;Magni and Montani, 2006;Mortimer et al, 1999) and have also explained the observed temporal variability with the concept of steady state diagenesis, which varies with environmental parameters. However, on longer time scales, transient diagenesis is more often invoked.…”

Benthic metabolism and denitrification in a river reach: a comparison between vegetated and bare sediments

“…Phanerogams convert nutrients from inorganic into particulate and dissolved organic forms, control phytoplankton growth, retain suspended matter, stabilise surface sediments and provide nursery areas for invertebrates and fish (Phillips & Menez 1988;Newman 1991;Caffrey & Kemp 1992;Blanchet et al 2004;Hasegawa et al 2008). Additionally, the radial oxygen loss from roots provides oxygen into anoxic sediments, which supports the reoxidation of reduced compounds (i.e., ammonium, methane and sulphides), the precipitation of soluble reactive phosphorus with ferric iron (Deborde et al 2008) and the removal of nitrogen via nitrification coupled denitrification (Reddy et al 1989;Caffrey & Kemp 1992;Ottosen et al 1999). Due to their overall importance, seagrasses have been studied in transitional brackish zones and coastal environments all around the world (Bortone 2000;Hemminga & Duarte 2000;Nielsen et al 2004).…”