Salt marsh expansion into estuarine mangrove mudflats reduces nitrogen removal capacity

Wang，Fenfang1,2; Lu，Zeyang1,2; Tobias，Craig R.3; Wang，Yao1,2; Xiao，Kai4; Yu，Qibiao1,2; Lin，Jingjie1,2; Huang，Guanmin5; Chen，Nengwang1,2

2023-11-01

10.1016/j.catena.2023.107459

Catena   Impact Factor & Quartile

0341-8162

1872-6887

Salt marsh (Spartina alterniflora) has been rapidly encroaching into mangrove wetlands worldwide. However, the potential effects of salt marsh expansion on coastal nitrogen cycling and ecosystem function remain unclear. In this study, sediment cores were seasonally collected from mangroves, salt marshes and mudflats from 2020 to 2021 to assess their nitrogen cycling. Nitrogen transformation rates of mineralization, immobilization, nitrification, denitrification, anaerobic ammonium oxidization (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were determined using N isotope tracer techniques. Rate measurements were paired with analysis of physicochemical properties, carbon isotopes, and nitrogen functional genes. The results showed that compared to mangrove sediments, salt marsh sediments mostly exhibited lower mineralization and denitrification rates but higher nitrification rates. Mudflat sediments had the lowest mineralization and denitrification rates among the studied habitats, while the nitrification rates were close to those of salt marshes. The differences in carbon quantity and source, nitrogen gene abundances, and carbon and nitrogen substrate availabilities controlled the variations in nitrogen transformation rates. The balance of these rates was used to indicate the net nitrogen retention or removal capacity of the three habitats. On an annual scale, salt marshes exhibited ammonium (NH-N) removal while mangroves had net NH-N retention. Nitrate (NO-N) was removed both in salt marsh and mangrove sediments with larger removal capacity in mangroves. Salt marsh sediments had lower NH-N removal but higher NO-N removal levels than mudflat sediments. In summary, salt marsh invasion decreased the overall nitrogen removal levels in the mangrove-mudflat wetland. The future scenarios of increasing salt marsh coverage suggest a decreased removal of nitrogen loads, which has important implications for mitigating coastal eutrophication.

Eutrophication Gene abundance Nitrogen cycling Plant invasion Stable isotope Wetland sediments

SCI

English

Others

National Natural Science Foundation of China[41976138];

Geology ; Agriculture ; Water Resources

Geosciences, Multidisciplinary ; Soil Science ; Water Resources

WOS:001063154900001

ELSEVIER

AGRICULTURAL SCIENCES

2-s2.0-85167996354

Scopus

1.Key Laboratory of the Coastal and Wetland Ecosystems,College of the Environment and Ecology,Xiamen University,Xiamen,361102,China
2.State Key Laboratory of Marine Environmental Science,Xiamen University,Xiamen,361102,China
3.Department of Marine Sciences,University of Connecticut,Groton,06340,United States
4.State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control,School of Environmental Science and Engineering,South University of Science and Technology of China,Shenzhen,518055,China
5.Administrative Bureau of Zhangjiang Estuary,Mangrove National Nature Reserve,Yunxiao,Fujian,363300,China

Wang，Fenfang,Lu，Zeyang,Tobias，Craig R.,et al. Salt marsh expansion into estuarine mangrove mudflats reduces nitrogen removal capacity[J]. Catena,2023,232.

Wang，Fenfang.,Lu，Zeyang.,Tobias，Craig R..,Wang，Yao.,Xiao，Kai.,...&Chen，Nengwang.(2023).Salt marsh expansion into estuarine mangrove mudflats reduces nitrogen removal capacity.Catena,232.

Wang，Fenfang,et al."Salt marsh expansion into estuarine mangrove mudflats reduces nitrogen removal capacity".Catena 232(2023).