Nitrogen enrichment increases greenhouse gas emissions from emerged intertidal sandflats

Abstract

Unvegetated, intertidal sandflats play a critical role in estuarine carbon and nutrient dynamics. However, these ecosystems are under increasing threat from anthropogenic stressors, especially nitrogen enrichment. While research in this area typically focuses on sediment-water exchanges of carbon and nutrients during tidal inundation, there remain significant gaps in our understanding of GHG (Greenhouse Gas) fluxes during tidal emergence. Here we use in situ benthic chambers to quantify GHG fluxes during tidal emergence and investigate the impact of nitrogen enrichment on these fluxes. Our results demonstrate significant differences in magnitude and direction of GHG fluxes between emerged and submerged flats, demonstrating the importance of considering tidal state when estimating GHG emissions from intertidal flats. These responses were related to differences in microphytobenthic and macrofaunal activity, illustrating the important role of ecology in mediating fluxes from intertidal flats. Our results further demonstrate that nitrogen enrichment of 600 gN m −2 was associated with, on average, a 1.65x increase in CO 2 uptake under light (photosynthetically active) conditions and a 1.35x increase in co 2 emission under dark conditions, a 3.8x increase in CH 4 emission and a 15x increase in n 2 O emission overall. This is particularly significant given the large area intertidal flats cover globally, and their increasing exposure to anthropogenic stressors.

Belowground bud banks and land use change: roles of vegetation and soil properties in mediating the composition of bud banks in different ecosystems

“…Lastly, total N strongly correlated with and was the most crucial factor influencing bud banks, explaining 12.6% of bud bank variation in farmlands and provides empirical evidence of the extent and magnitude of human-derived disturbances via nutrient enrichments in agrosystems (Isbell et al, 2013;Ren et al, 2019;Adomako et al, 2022). Although N limitation substantially limits plant growth (De Tezanos Pinto and Litchman, 2010;Bracken et al, 2015;Fay et al, 2015;Du et al, 2020;Adomako et al, 2022) and increased fertilization aimed at increasing agricultural output in agrosystems may promote the proliferation of bud banks in short-term period (Liu et al, 2021;Qian et al, 2021;Adomako and Yu, 2023), the long-term effects of N influxes in farmland ecosystems can trigger land degradation (Hamilton et al, 2020;Qian et al, 2021;Owusu et al, 2024). Notably, the FL ecosystem had the least attributes of all bud types measured, which can likely be linked to land use intensification.…”

Enabling coastal blue carbon in Aotearoa New Zealand: opportunities and challenges

“…The implementation of a blue carbon methodology requires carbon sequestration data from blue carbon habitats, ideally gathered from ANZ estuaries/coasts. Much of the data required already exists for ANZ, including the distribution of blue carbon habitats (Townsend and Wadwha, 2017;Lundquist et al, 2018;Suyadi, 2018;Suyadi et al, 2019;Ha et al, 2020;Martin et al, 2020;Ha et al, 2021;Ha et al, 2023), their rates of above-and belowground carbon sequestration (Swales et al, 2007;Lovelock et al, 2010;Swales et al, 2015, Bulmer et al, 2016aBulmer et al, 2016b, as well as emissions of each habitat type (Pratt et al, 2014a;Pratt et al, 2014b;Bulmer et al, 2015;Pratt et al, 2015;Bulmer et al, 2017;Peŕez et al, 2017;Bulmer et al, 2018;Drylie et al, 2018;Hamilton et al, 2020;Mangan et al, 2020;Thrush et al, 2021). Many projects are currently underway to further enhance this dataset, however, sufficient data exists now to inform a blue carbon methodology.…”

Spartina alterniflora has the highest methane emissions in a St. Lawrence estuary salt marsh

“…In the mudflat, chambers were carefully inserted directly into the mudflat to approximately 3 cm. Chambers were allowed to equilibrate with the air for 10 min after installation to minimise the effect of any disturbance during installation on initial GHG concentrations (Hamilton et al 2020). After this time, sampling assemblies were gently inserted into the chamber opening and sampled as described for the vegetated zones, except that gas samples were taken at 0, 20 and 40 min.…”