TY - JOUR
T1 - Seasonal variation of nitrogen transformations in a subterranean estuary on the Ria Formosa lagoon barrier islands, Portugal
AU - Jiang, Shan
AU - Ibánhez, Juan Severino Pino
AU - Carvalho, Liliana
AU - Veiga-Pires, Cristina
AU - Aníbal, Jaime
AU - Rio, Inês
AU - Lai, Longyun
AU - Sun, Danqing
AU - Xu, Yi
AU - Rocha, Carlos
N1 - Publisher Copyright:
© Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2026.
PY - 2026/2
Y1 - 2026/2
N2 - The barrier islands of the Ria Formosa lagoon are known to host substantial land-derived nitrogen (N) originated in the adjacent coastal plain. The permeable subterranean estuary (STE) of the barrier islands may modulate the magnitude of N fluxes derived from submarine groundwater discharge (SGD) into the lagoon. To understand the temporal dynamics of benthic N reactivity of the STE, a seven-month field survey was conducted. Results showed that the STE shifted seasonally between acting as a source and a sink for nitrate (NO3−) and total dissolved nitrogen (TDN). In particular, biogeochemical processes within the sandy sediment that removed reactive N from porewater followed either canonical denitrification or oxygen-limited autotrophic nitrification/denitrification (OLAND). The maximum net removal rates for NO3− and TDN were observed in May and February, reaching 0.67 mmol/(m3·h) and 13.11 mmol/(m3·h), respectively. On the other hand, the STE could increase concentrations of NO3− and TDN in the seeped water via remineralisation and nitrification. The maximum net production rate for NO3− reached 2.44 mmol/(m3·h), while the net TDN addition rate was 21.49 mmol/(m3·h). Compared to the estimated N concentrations in the fresh groundwater endmember, the STE from December to February may lead to an increase of 152% in the magnitude of NO3− fluxes. In contrast, from March to June, the STE may foster a decrease of 22% of the NO3− fluxes into the lagoon. These observations suggest that the STE significantly regulates N fluxes and is an important reaction node within coastal systems.
AB - The barrier islands of the Ria Formosa lagoon are known to host substantial land-derived nitrogen (N) originated in the adjacent coastal plain. The permeable subterranean estuary (STE) of the barrier islands may modulate the magnitude of N fluxes derived from submarine groundwater discharge (SGD) into the lagoon. To understand the temporal dynamics of benthic N reactivity of the STE, a seven-month field survey was conducted. Results showed that the STE shifted seasonally between acting as a source and a sink for nitrate (NO3−) and total dissolved nitrogen (TDN). In particular, biogeochemical processes within the sandy sediment that removed reactive N from porewater followed either canonical denitrification or oxygen-limited autotrophic nitrification/denitrification (OLAND). The maximum net removal rates for NO3− and TDN were observed in May and February, reaching 0.67 mmol/(m3·h) and 13.11 mmol/(m3·h), respectively. On the other hand, the STE could increase concentrations of NO3− and TDN in the seeped water via remineralisation and nitrification. The maximum net production rate for NO3− reached 2.44 mmol/(m3·h), while the net TDN addition rate was 21.49 mmol/(m3·h). Compared to the estimated N concentrations in the fresh groundwater endmember, the STE from December to February may lead to an increase of 152% in the magnitude of NO3− fluxes. In contrast, from March to June, the STE may foster a decrease of 22% of the NO3− fluxes into the lagoon. These observations suggest that the STE significantly regulates N fluxes and is an important reaction node within coastal systems.
KW - nitrogen
KW - sediment reactivity
KW - seepage face
KW - submarine groundwater discharge
KW - subterranean estuary
UR - https://www.scopus.com/pages/publications/105039617708
U2 - 10.1007/s13131-025-2597-7
DO - 10.1007/s13131-025-2597-7
M3 - 文章
AN - SCOPUS:105039617708
SN - 0253-505X
VL - 45
SP - 117
EP - 129
JO - Acta Oceanologica Sinica
JF - Acta Oceanologica Sinica
IS - 2
ER -