Variations in sediment organic carbon between different types of small natural ponds along Druridge Bay, Northumberland, UK

Abstract

Small natural ponds from Druridge Bay, Northumberland (UK), were sampled to investigate the variations in sediment organic carbon (OC) content among pond types. Sediment OC was highest in uncompacted sediments from permanent ponds with extensive natural vegetation (means ranged between 7.68 and 12.86% OC) but lower in compacted sediments (mean 3.72% OC) or from ponds in arable or pasture fields (mean 3.44% OC) and from adjacent soil controls (means of 3.13-3.38% OC). The extent of 4 distinct pond types (permanent naturally vegetated, arable field, grass pasture field, and dune slack) varied across years. This study highlights ecological variations among pond types that can result in large variations in sediment OC content and, combined with annual variations to the extent of ponds, poses significant implications for upscaling carbon burial rates based solely on combined surface area.

High carbon burial rates by small ponds in the landscape

“…This may arise from the greater amount of refractory OC (ie that which does not readily degrade) biosynthesized by these species (Reverey et al 2016). Previous studies (Gilbert et al 2014) have noted that establishment of L riparium swards kept sediments damp, with anoxic conditions often apparent under decomposing vegetation; development of moss swards, which usually cover the bed of the ponds after 3-4 years, triggered a shift in ecosystem functioning, indicating the start of sedimentation and accumulation of OC. These ponds can switch between being net sources or sinks of C within days of drying or wetting, respectively (Gilbert et al 2016), and vegetation cover slows the drying and exposure of sediments to the air.…”

“…Previous studies (Gilbert et al . ) have noted that establishment of L riparium swards kept sediments damp, with anoxic conditions often apparent under decomposing vegetation; development of moss swards, which usually cover the bed of the ponds after 3–4 years, triggered a shift in ecosystem functioning, indicating the start of sedimentation and accumulation of OC. These ponds can switch between being net sources or sinks of C within days of drying or wetting, respectively (Gilbert et al .…”

“…Gilbert et al . (), one of the first studies to report sediment OC and burial rates in ponds, observed an OC burial rate of ~149 g OC m −2 yr −1 . This represents one of the highest rates of OC burial reported across natural habitats.…”

“…Although the potential for small ponds to capture and store OC has been spotlighted (eg Downing et al 2008), accurately quantified rates of OC burial are rare, leading to the question of whether ponds bury OC fast enough to be worthwhile C sinks. Gilbert et al (2014), one of the first studies to report sediment OC and burial rates in ponds, observed an OC burial rate of ~149 g OC m −2 yr −1 . This represents one of the highest rates of OC burial reported across natural habitats.…”

Flood, drought and the inter-annual variation to the number and size of ponds and small wetlands in an English lowland landscape over three years of weather extremes

“…More recently their potential significance for ecosystem services has been highlighted, e.g. for controlling eutrophication or carbon sequestration (Downing, 2010;Céréghino et al, 2014;Gilbert et al, 2014) but uncertainty about the number and size of small ponds, especially those\0.1 km 2 in area, makes generalisations difficult (Downing et al, 2006).…”