Annual biogeochemical cycling in intertidal sediments of a restored estuary reveals dependence of N, P, C and Si cycles to temperature and water column properties. (5th March 2023)

• Record Type: Journal Article
• Authors: Rios-Yunes, Dunia; Tiano, Justin C.; van Oevelen, Dick; van Dalen, Jeroen; Soetaert, Karline
• Is Part Of: Estuarine, coastal and shelf science. Volume 282(2023)
• Publication Date: 2023-03-05
• Subjects: Estuary -- Nutrient -- Organic matter -- Sediment -- Restoration -- Marine -- Coastal -- Intertidal -- Biogeochemistry; Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2023.108227
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: Estuarine intertidal sediments are important centres for organic matter remineralization and nutrients recycling. Nevertheless, there is limited understanding regarding how these processes occur along the salinity gradient and their seasonality. Here, we report on the seasonal biogeochemical cycles from three types of intertidal sedimentary habitats (freshwater, brackish and marine) located in the Western Scheldt estuary (The Netherlands and Belgium). A full year of solute fluxes, porewater nutrient and sediment pigment concentrations at a monthly resolution revealed clear differences in the biogeochemistry of the three sites, indicating that environmental conditions determined the local nutrient dynamics. Temperature controlled sediment oxygen consumption rates and nutrient fluxes, but also affected pore water nutrient concentrations up to 14 cm deep. Fresh and brackish sediments had a net influx of dissolved inorganic nitrogen (DIN) (−1.62 mmol m −2 d −1 and -2.84 mmol m −2 d −1, respectively), while only the freshwater sediments showed a net influx of phosphate (−0.07 mmol m −2 d −1 ). We estimated that intertidal sediments remineralized a total of 10, 000 t C y −1, with 97% of mineralization occurring in the brackish and marine parts. Overall, sediments removed 11% (1500 t N y −1 ) and 15% (∼200 t P y −1 ) of the total nitrogen and phosphorus entering the estuary from riverine input. Moreover, observations revealed the historical improvement of water quality resulting from water treatment policies. This spatiotemporal study of OM remineralization and early diagenesis in estuarine systems highlights the importance of intertidal sediments for estuarine systems. Our observations can be used in models to predict estuarine biogeochemistry or assess climate change scenarios. Graphical abstract: Image 1 Highlights: Water column properties and temperature regulate intertidal sediments biogeochemistry. Intertidal areas retain 11% of N and 15% of P entering the estuary from riverine input. Influx of DIN and P in freshwater sediments is offset by effluxes downstream. Management policies improved water quality in the Western Scheldt.