Contribution of surface leaf-litter breakdown and forest composition to benthic oxygen demand and ecosystem respiration in a South Georgia blackwater river

Abstract

Many North American blackwater rivers exhibit low dissolved O 2 (DO) that may be the result of benthic respiration. We examined how tree species affected O 2 demand via the quantity and quality of litter produced. In addition, we compared areal estimates of surface leaf-litter microbial respiration to sediment O 2 demand (SOD) and ecosystem respiration (ER) in stream and swamp reaches of a blackwater river to quantify contributions of surface litter decomposition to O 2 demand. Litter inputs averaged 917 and 678 g m −2 y −1 in the swamp and stream, respectively. Tree species differentially affected O 2 demand via the quantity and quality of litter produced. Bald cypress (Taxodium distichum) contributed most litter inputs because of its dominance and because it produced more litter per tree, thereby making greater relative contributions to O 2 demand in the swamp. In the stream, water oak (Quercus nigra) produced litter supporting lower fungal biomass and O 2 uptake rates, but produced more litter than red maple (Acer rubrum). Breakdown rates in the swamp were faster, whereas standing stock decreases were lower than in the stream, indicating greater organic matter retention. Surface litter microbial respiration accounted for 89% of SOD (6.37 g O 2 m −2 d −1 ), and 57 to 89% of ER in the swamp. Our findings suggest that surface litter drives the majority of O 2 demand in some blackwater swamps, and tree species with higher rates of litterfall may make larger contributions to ER. Forested swamps may be hotspots of O 2 demand in blackwater rivers because low water velocities enhance retention.

Estuarine Hypoxia—Identifying High Risk Catchments Now and Under Future Climate Scenarios

“…Conversely, the bioavailability of organic matter has generally been found to respond more directly to land management practices, such as chemical and nutrient application, harvesting practices and stocking rates (Voß et al., 2015). Thus the potential for blackwater generation over various catchment areas may alternatively be differentiated by assessing variations in land management (both historic and current) and intensity of use (Barlow et al., 2009; Buck et al., 2004) rather than vegetation types or land‐use categories, as the accumulation of surface litter is likely to drive the majority of oxygen demand in many environments (Mehring et al., 2014).…”

Seasonal and spatial variations of greenhouse gas (CO2, CH4 and N2O) emissions from urban ponds in Brussels

“…In addition to the potential positive impact of macrophytes on CH4, the Sonian forest likely transfers allochthonous carbon as plant litter promoting CH4 production compared to other ponds. Litter from trees can induce sediment anoxia (Mehring et al, 2014) enhancing CH4 production. Yet, this potential additional input of allochthonous organic carbon from the Sonian Forest did not seem to affect the pCO2 in ponds for which the effect of size seemed more important.…”

C, N, and P Mass Balances in the Bottom Seawater–Surface Sediment Interface in the Reducing Environment due to Anoxic Water of Gamak Bay, Korea

“…The SOD flux was calculated using Equation ( 3) [44]. The biological and chemical processes were dependent on water temperatures, and the SOD T flux (i.e., ambient temperature) was calibrated to 20 • C using Equation ( 4) [45,46], which has been commonly adopted in the SOD correction [47,48].…”