Negligible Greenhouse Gas Release from Sediments in Oyster Habitats

Abstract

After centuries of decline, oyster populations are now on the rise in coastal systems globally following aquaculture development and restoration efforts. Oysters regulate the biogeochemistry of coastal systems in part by promoting sediment nutrient recycling and removing excess nitrogen via denitrification. Less clear is how oysters alter sediment greenhouse gas (GHG) fluxesan important consideration as oyster populations grow. Here, we show that sediments in oyster habitats produce carbon dioxide (CO 2 ), with highest rates in spring (2396.91 ± 381.98 μmol CO 2 m −2 h −1 ) following deposition of seasonal diatom blooms and in summer (2795.20 ± 307.55 μmol CO 2 m −2 h −1 ) when temperatures are high. Sediments in oyster habitats also consistently released methane to the water column (725.94 ± 150.34 nmol CH 4 m −2 h −1 ) with no seasonal pattern. Generally, oyster habitat sediments were a sink for nitrous oxide (N 2 O; −36.11 ± 7.24 nmol N 2 O m −2 h −1 ), only occasionally releasing N 2 O in spring. N 2 O release corresponded to high organic matter and dissolved nitrogen availability, suggesting denitrification as the production pathway. Despite potential CO 2 production increases under aquaculture in some locations, we conclude that in temperate regions oysters have an overall negligible impact on sediment GHG cycling.

Submersed Macrophyte Density Regulates Aquatic Greenhouse Gas Emissions

“…If fluxes were not linear (likely due to an ebullition event), then only the data during the linear portion of the run was considered in flux calculations (all calculations were from at least 2 min of sampling). When the R 2 value of the linear relationship between time and GHG concentration for each run was not R 2 ≥ 0.80, then we manually checked the run (Ray & Fulweiler, 2021). If the slope of the linear relationship was close to 0, then the flux was considered to be 0 (1.92% of CO 2 fluxes ( n = 3), 5.77% of CH 4 fluxes ( n = 9)).…”

High Intra‐Seasonal Variability in Greenhouse Gas Emissions From Temperate Constructed Ponds

“…We estimated diffusive flux as the linear change in gas concentration over time $$\left(\frac{{\increment}\mathrm{p}\mathrm{p}\mathrm{m}}{{\increment}\mathrm{h}\mathrm{r}}\right)$$. We considered fluxes with R 2 ≥ 0.65 as significant and those with R 2 < 0.65 as non‐significant, and equal to zero (33/119 for CO 2 , 10/115 for CH 4 , and 83/119 for N 2 O; Prairie, 1996; Ray & Fulweiler, 2021). We converted non‐zero fluxes from $$\frac{{\increment}\mathrm{p}\mathrm{p}\mathrm{m}}{{\increment}\mathrm{h}\mathrm{r}}$$ to $$\frac{{\increment}\mathrm{a}\mathrm{t}\mathrm{m}}{{\increment}\mathrm{h}\mathrm{r}}$$ by multiplying by the atmospheric pressure (atm) during the incubation divided by 1,000,000 to remove the ppm conversion.…”

“…We considered fluxes with R 2 ≥ 0.65 as significant and those with R 2 < 0.65 as non-significant, and equal to zero (33/119 for CO 2 , 10/115 for CH 4 , and 83/119 for N 2 O; Prairie, 1996;Ray & Fulweiler, 2021). We converted non-zero fluxes from 𝐴𝐴 ∆ppm ∆hr to 𝐴𝐴 ∆atm ∆hr by multiplying by the atmospheric pressure (atm) during the incubation divided by 1,000,000 to remove the ppm conversion.…”

Choice of bead-beater instrument can result in significant differences in the outcome of host-associated microbiome studies

“…Crassostrea virginica, commonly called as the Eastern oyster or the American oyster, are represented in as much as 75% of the commercially harvested oysters in the United States (US), especially along the coastal regions of Florida, Texas, Louisiana, Mississippi, and Alabama; these states contribute to more than 60% of the total oyster harvest in the US. 1 Oysters are valued not only as seafood, but also for their myriad of services rendered to their native ecosystems, such as enhancing water quality, 2 bioextraction of dissolved nitrogen and other pollutants 3 as well as providing refuge and foraging habitat for marine organisms, such as smaller mollusks, invertebrates, fish and crustaceans, 4 within the oyster reefs. 5 Due to their filter feeding mechanism, oysters have been shown to concentrate estuarine microbiomes within their gills and digestive tracts and some microbes remain symbiotically associated with the oyster host species, called as the autochthonous microbiota.…”