Submission Type
Oral Presentation
Abstract
Some aquatic macroinvertebrates, including larval midges (Chironomidae), can increase wetland sediment nitrous oxide (N2O) fluxes. Chironomids ingest denitrifying bacteria and bioirrigate their U-shaped burrows which can subject these bacteria to rapidly alternating oxic and anoxic conditions that can produce N2O. Through this same process, chironomids may also modulate methane (CH4) fluxes. Although previous studies have demonstrated the potential for chironomids to enhance N2O flux, most have only incorporated low levels of organic matter (OM). In this study, three densities of Chironomus riparius larvae (0m2, 9,000m2, 18,000m2) were altered along with organic matter (3%, 9%, 15%) in a fully factorial design to determine if differences in OM change the effects that these larvae have on N2O and CH4 fluxes. We predicted that high chironomid densities would enhance N₂O in low-OM sediments, but chironomid effects on N2O flux would not be observed in high-OM sediments. We also predicted that burrow ventilation by chironomids would dampen CH4 fluxes in high OM sediment. High sediment oxygen demand and anoxic conditions there will yield primarily N2 with little enhancement of N2O flux regardless of larval density and higher rates of CH4 oxidation would be prevalent in sediment containing larvae. We found that methane flux did decrease in high OM sediment with an intermediate density of chironomids, but increased with a high density. We also found that effects of N2O enhancement was only prevalent in high OM sediment. This research will improve our understanding of the role that chironomid larvae and OM play in wetland ecosystems.
Included in
How does sediment organic matter content mediate the effects of chironomid larvae on benthic greenhouse gas fluxes
Some aquatic macroinvertebrates, including larval midges (Chironomidae), can increase wetland sediment nitrous oxide (N2O) fluxes. Chironomids ingest denitrifying bacteria and bioirrigate their U-shaped burrows which can subject these bacteria to rapidly alternating oxic and anoxic conditions that can produce N2O. Through this same process, chironomids may also modulate methane (CH4) fluxes. Although previous studies have demonstrated the potential for chironomids to enhance N2O flux, most have only incorporated low levels of organic matter (OM). In this study, three densities of Chironomus riparius larvae (0m2, 9,000m2, 18,000m2) were altered along with organic matter (3%, 9%, 15%) in a fully factorial design to determine if differences in OM change the effects that these larvae have on N2O and CH4 fluxes. We predicted that high chironomid densities would enhance N₂O in low-OM sediments, but chironomid effects on N2O flux would not be observed in high-OM sediments. We also predicted that burrow ventilation by chironomids would dampen CH4 fluxes in high OM sediment. High sediment oxygen demand and anoxic conditions there will yield primarily N2 with little enhancement of N2O flux regardless of larval density and higher rates of CH4 oxidation would be prevalent in sediment containing larvae. We found that methane flux did decrease in high OM sediment with an intermediate density of chironomids, but increased with a high density. We also found that effects of N2O enhancement was only prevalent in high OM sediment. This research will improve our understanding of the role that chironomid larvae and OM play in wetland ecosystems.
Comments
M.C. Tierney1 *, J.A.Swartz1, J.H. Loughrin2, S.W. Antle2 and A.S. Mehring1
1Department of Biology, University of Louisville, Louisville, KY 40292, USA
2Food Animal Environmental Systems Research Unit, Agricultural Research Service, USDA, Bowling Green, KY 42101, USA