Contrasting Estuarine Processing of Dissolved Organic Matter Derived From Natural and Human‐Impacted Landscapes

García-Martín, Enma Elena; Sanders, Richard J.; Evans, Chris; Kitidis, Vassilis; Lapworth, Dan; Spears, Bryan M.; Tye, A.M.; Williamson, Jennifer; Balfour, C.; Best, Mike; Bowes, Michael J.; Breimann, Sarah; Brown, Ian J.; Burden, Annette; Callaghan, Nathan; Felgate, Stacey L.; Fishwick, James; Fraser, Mike; Gibb, Stuart W.; Gilbert, Peter J.; Godsell, Nina; Gomez-Castillo, Africa P.; Hargreaves, Geoff; Jones, Oban; Kennedy, Paul; Lichtschlag, Anna; Martin, Adrian P.; May, Rebecca; Mawji, Edward; Mounteney, Ian; Olszewska, Justyna; Painter, Stuart C.; Pearce, Christopher R.; Pereira, M. Glória; Peel, Kate; Pickard, Amy; Stephens, John A.; Stinchcombe, Mark C.; Williams, Peter J.; Woodward, E. Malcolm S.; Yarrow, Deborah; Mayor, Daniel J.

doi:10.1029/2021gb007023

Cited by 14 publications

(16 citation statements)

References 73 publications

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“…Land cover ranges from predominantly seminatural land such as peatland (∼67% in Halladale) to intensive arable agriculture and urban/suburban land (>46% in Humber‐Trent, Thames, and Test for the sum of these two land covers) (see Section 2.2 for method applied in the determination of the proportion of land cover, data in García‐Martín et al. (2021) and Table S2 in Supporting Information ). Collectively the estuaries sampled drain 16% of the mainland area of Great Britain.…”

Section: Methodsmentioning

confidence: 99%

“…Catchment areas range from <200 to >8,000 km 2 (Table S1 in Supporting Information S1), and hydrological regimes vary from high-rainfall, surface water dominated catchments in the north and west of Great Britain to dry, groundwater dominated catchments in the south and east (Figure 1b). Land cover ranges from predominantly seminatural land such as peatland (∼67% in Halladale) to intensive arable agriculture and urban/suburban land (>46% in Humber-Trent, Thames, and Test for the sum of these two land covers) (see Section 2.2 for method applied in the determination of the proportion of land cover, data in García-Martín et al (2021) and Table S2 in Supporting Information S1). Collectively the estuaries sampled drain 16% of the mainland area of Great Britain.…”

Section: Study Area and Sampling Sitesmentioning

confidence: 99%

“…The UKCEH Wallingford Digital Terrain Model (Morris et al, 1990) was used to derive catchment boundaries based on the zero salinity sampling points. A full description of catchment land cover can be found in García-Martín et al (2021).…”

Section: Field Data Collection and Environmental Parametersmentioning

confidence: 99%

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Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries

et al. 2023

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Estuaries receive and process a large amount of particulate organic carbon (POC) prior to its export into coastal waters. Studying the origin of this POC is key to understanding the fate of POC and the role of estuaries in the global carbon cycle. Here, we evaluated the concentrations of POC, as well as particulate organic nitrogen (PON), and used stable carbon and nitrogen isotopes to assess their sources across 13 contrasting British estuaries during five different sampling campaigns over 1 year. We found a high variability in POC and PON concentrations across the salinity gradient, reflecting inputs, and losses of organic material within the estuaries. Catchment land cover appeared to influence the contribution of POC to the total organic carbon flux from the estuary to coastal waters, with POC contributions >36% in estuaries draining catchments with a high percentage of urban/suburban land, and <11% in estuaries draining catchments with a high peatland cover. There was no seasonal pattern in the isotopic composition of POC and PON, suggesting similar sources for each estuary over time. Carbon isotopic ratios were depleted (−26.7 ± 0.42‰, average ± sd) at the lowest salinity waters, indicating mainly terrigenous POC (TPOC). Applying a two-source mixing model, we observed high variability in the contribution of TPOC at the highest salinity waters between estuaries, with a median value of 57%. Our results indicate a large transport of terrigenous organic carbon into coastal waters, where it may be buried, remineralized, or transported offshore.Plain Language Summary Estuaries transport and process a large amount terrigenous particulate organic matter (i.e., carbon and nitrogen) prior to its export to coastal waters. In order to understand the fate of organic carbon and the role of estuaries in the global carbon cycle it is essential to improve our knowledge on its composition, origin, and amount of carbon transported. We quantified the elemental concentrations and stable isotopes composition of carbon and nitrogen to quantify the amount of terrigenous particulate organic matter transported by 13 British estuaries, which drain catchments of diverse land cover under different hydrological conditions. We found a great variability in particulate organic carbon (POC) and particulate organic nitrogen concentrations across the salinity gradient, implying inputs, and losses of material within the estuaries. Each estuary had similar sources of particulate material throughout the year. In most of the estuaries, the POC had a terrigenous origin at the lowest salinity waters. The terrigenous organic carbon contribution decreased toward coastal waters with an average contribution of 57% at the highest salinity waters, indicating a large transport of terrigenous organic carbon into coastal waters.

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Section: Methodsmentioning

confidence: 99%

Section: Study Area and Sampling Sitesmentioning

confidence: 99%

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Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries

et al. 2023

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“…As a matter of fact, more and more allochthonous DOM is imported into estuarine systems with the increase of anthropogenic activities like industrialization, urbanization, and agricultural practices (Boesch, 2002;Felgate et al, 2021). They will change the quality and quantity of DOM, which in turn impact the biogeochemical cycle, decomposition of organic matter, and recycling of chemical elements in sediments (Spilling et al, 2018;Felgate et al, 2021;García-Martín et al, 2021). Due to the different sources of DOM, their conversion, retention, and output fluxes in biogeochemical processes including flocculation, photochemistry, and biodegradation in estuaries also differ (Carlson and Hansell, 2015;García-Martín et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…They will change the quality and quantity of DOM, which in turn impact the biogeochemical cycle, decomposition of organic matter, and recycling of chemical elements in sediments (Spilling et al, 2018;Felgate et al, 2021;García-Martín et al, 2021). Due to the different sources of DOM, their conversion, retention, and output fluxes in biogeochemical processes including flocculation, photochemistry, and biodegradation in estuaries also differ (Carlson and Hansell, 2015;García-Martín et al, 2021). Therefore, discriminating main sources of DOM and their contributions will be an important basis for evaluating the fate of estuarine DOM, which also is of great significance to evaluate the effects of terrestrial runoff and ocean tides on estuarine organic matter .…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Dissolved Organic Matter in a Semi-closed Bay in Summer: Insights from Stable Isotope and Optical Analyses

Zhong

Pan²,

Zhao³

et al. 2022

Front. Mar. Sci.

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Dissolved organic matter (DOM) serves as the most active and sensitive organic component in the bay, and its biogeochemical characteristics and reactivity are affected by the properties of terrestrial and marine substances significantly. In this study, in order to study the distribution and characteristics of DOM in a semi-closed bay, 34 water samples from 19 stations were collected from Zhanjiang Bay and analyzed for δ13C of dissolved inorganic carbon (DIC) and fluorescent components of DOM. The results showed that there were many sources of organic matter in the bay, including soil input, algae input, and sewage input. Influenced by freshwater input, DOM in the bay decreased from the upper bay to the outer bay. The organic matter in the bay displayed two characteristics, where the northern bay is composed of terrigenous organic matter mainly with high humus, while the southern bay is more inclined to marine sources with a high biological index (BIX) and low humification index (HIX). The correlation between organic matter with different characteristics and environmental parameters such as salinity, pH, and chlorophyll a was analyzed. The discrepancy may be caused by the weak turbulent mixing in the semi-closed bay.

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Marine nutrient subsidies promote biogeochemical hotspots in undisturbed, highly humic estuaries

Evans

Felgate

Carter

et al. 2023

Limnology & Oceanography

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The land‐ocean dissolved organic carbon (DOC) flux represents a significant term within the global carbon budget, with peatland‐dominated regions representing the most intense sources of terrestrial DOC export. As the interface between freshwater and marine systems, estuaries have the potential to act as a filter of the land‐ocean carbon flux, removing terrestrially derived DOC, which is present at low concentrations in the oceans, via a combination of physicochemical and biological processes. However, the fate of peat‐derived DOC within estuaries remains poorly quantified, partly due to the complicating influences of heterogeneous soils, land‐use, point sources, and upstream modification of organic matter. To minimize these modifying factors, we studied DOC and inorganic nutrients in four small, peat‐dominated, minimally disturbed, and oligotrophic Falkland Island estuaries. Contrary to expectations, we found limited evidence of physicochemical estuarine DOC removal, and instead observed apparent “hot zones” of biogeochemical activity, where terrestrially‐derived silicate mixed with inorganic nitrogen and phosphorus entering the estuaries from the nutrient‐rich marine ecosystem. In two estuaries, this coincided with apparent in situ DOC production. We suggest that the observed phenomena of marine nutrient subsidy of estuarine productivity, and flexible utilization of multiple nutrients within the oligotrophic system, may once have been widespread in temperate estuaries. However, this function has been lost in many ecosystems due to catchment eutrophication by agricultural and urban development. We conclude that the estuaries of the Falkland Islands provide a valuable pre‐disturbance analogue for natural biogeochemical functioning in temperate estuaries receiving high organic matter inputs.

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Contrasting Estuarine Processing of Dissolved Organic Matter Derived From Natural and Human‐Impacted Landscapes

Cited by 14 publications

References 73 publications

Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries

Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries

Characteristics of Dissolved Organic Matter in a Semi-closed Bay in Summer: Insights from Stable Isotope and Optical Analyses

Marine nutrient subsidies promote biogeochemical hotspots in undisturbed, highly humic estuaries

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