Fjords as Aquatic Critical Zones (ACZs)

Bianchi, Thomas S.; Arndt, Sandra; Austin, William E. N.; Benn, Douglas I.; Bertrand, Sébastien; Cui, Xingqian; Faust, Johan C.; Koziorowska-Makuch, Katarzyna; Moy, Christopher; Savage, Candida; Smeaton, Craig; Smith, Richard; Syvitski, Jaia

doi:10.1016/j.earscirev.2020.103145

Cited by 127 publications

(138 citation statements)

References 345 publications

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“…Arctic fjord estuaries are biogeochemical hotspots for the cycling of organic matter (OM) (Bianchi et al, 2020) and burial of carbon (Smith et al, 2015;Bianchi et al, 2018). The fate of terrestrial materials in the marine system is linked to physical and biological processes in the water column.…”

Section: Introductionmentioning

confidence: 99%

Terrestrial Inputs Drive Seasonality in Organic Matter and Nutrient Biogeochemistry in a High Arctic Fjord System (Isfjorden, Svalbard)

et al. 2020

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Climate-change driven increases in temperature and precipitation are leading to increased discharge of freshwater and terrestrial material to Arctic coastal ecosystems. These inputs bring sediments, nutrients and organic matter (OM) across the landocean interface with a range of implications for coastal ecosystems and biogeochemical cycling. To investigate responses to terrestrial inputs, physicochemical conditions were characterized in a river-and glacier-influenced Arctic fjord system (Isfjorden, Svalbard) from May to August in 2018 and 2019. Our observations revealed a pervasive freshwater footprint in the inner fjord arms, the geochemical properties of which varied spatially and seasonally as the melt season progressed. In June, during the spring freshet, rivers were a source of dissolved organic carbon (DOC; with concentrations up to 1410 µmol L −1). In August, permafrost and glacial-fed meltwater was a source of inorganic nutrients including NO 2 + NO 3 , with concentrations 12-fold higher in the rivers than in the fjord. While marine OM dominated in May following the spring phytoplankton bloom, terrestrial OM was present throughout Isfjorden in June and August. Results suggest that enhanced land-ocean connectivity could lead to profound changes in the biogeochemistry and ecology of Svalbard fjords. Given the anticipated warming and associated increases in precipitation, permafrost thaw and freshwater discharge, our results highlight the need for more detailed seasonal field sampling in small Arctic catchments and receiving aquatic systems.

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Section: Introductionmentioning

confidence: 99%

Terrestrial Inputs Drive Seasonality in Organic Matter and Nutrient Biogeochemistry in a High Arctic Fjord System (Isfjorden, Svalbard)

et al. 2020

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“…Coastal environments are prominent habitats on a pan-Arctic scale with a high degree of connectivity between land and sea (McClelland et al, 2012). Coastal ecosystems can act as hotspots for carbon burial (Bianchi et al, 2018) and organic matter (OM) cycling (Bianchi et al, 2020), but are also sensitive to ongoing climate change (Jeffries et al, 2013;Bhatt et al, 2014;Fritz et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Terrestrial Inputs Shape Coastal Bacterial and Archaeal Communities in a High Arctic Fjord (Isfjorden, Svalbard)

et al. 2021

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The Arctic is experiencing dramatic changes including increases in precipitation, glacial melt, and permafrost thaw, resulting in increasing freshwater runoff to coastal waters. During the melt season, terrestrial runoff delivers carbon- and nutrient-rich freshwater to Arctic coastal waters, with unknown consequences for the microbial communities that play a key role in determining the cycling and fate of terrestrial matter at the land-ocean interface. To determine the impacts of runoff on coastal microbial (bacteria and archaea) communities, we investigated changes in pelagic microbial community structure between the early (June) and late (August) melt season in 2018 in the Isfjorden system (Svalbard). Amplicon sequences of the 16S rRNA gene were generated from water column, river and sediment samples collected in Isfjorden along fjord transects from shallow river estuaries and glacier fronts to the outer fjord. Community shifts were investigated in relation to environmental gradients, and compared to river and marine sediment microbial communities. We identified strong temporal and spatial reorganizations in the structure and composition of microbial communities during the summer months in relation to environmental conditions. Microbial diversity patterns highlighted a reorganization from rich communities in June toward more even and less rich communities in August. In June, waters enriched in dissolved organic carbon (DOC) provided a niche for copiotrophic taxa including Sulfitobacter and Octadecabacter. In August, lower DOC concentrations and Atlantic water inflow coincided with a shift toward more cosmopolitan taxa usually associated with summer stratified periods (e.g., SAR11 Clade Ia), and prevalent oligotrophic marine clades (OM60, SAR92). Higher riverine inputs of dissolved inorganic nutrients and suspended particulate matter also contributed to spatial reorganizations of communities in August. Sentinel taxa of this late summer fjord environment included taxa from the class Verrucomicrobiae (Roseibacillus, Luteolibacter), potentially indicative of a higher fraction of particle-attached bacteria. This study highlights the ecological relevance of terrestrial runoff for Arctic coastal microbial communities and how its impacts on biogeochemical conditions may make these communities susceptible to climate change.

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“…The average depth is 13.4 m reaching a maximum depth of 49 m in the lower basin. Although presently ice-free, Loch Creran is characterised by four basins which are separated by shallow underwater sills (between 3 and 15 m deep at low water) (Black et al, 2000), remnants of past glacial retreat and associated depositional processes (Howe et al, 2010;Bianchi et al, 2020). Sills are important topographic constraints influencing circulation within fjords and therefore the volume and speed of flow (Inall and Gillibrand, 2010).…”

Section: Regional Setting Study Areamentioning

confidence: 99%

“…These fjordic inshore environments are known to be global hotspots for the burial and storage of OC (Smith et al, 2015;Smeaton et al, 2016). The confined nature of fjords (Howe et al, 2010;Bianchi et al, 2020) provides a more controlled environment to allow the development and testing of this novel approach to mapping sedimentary OC that could be applied to the wider marine environment. We use the results from a sampling campaign to elucidate the relationships between sediment grain size, acoustic backscatter and OC.…”

Section: Introductionmentioning

confidence: 99%

Quantifying Marine Sedimentary Carbon: A New Spatial Analysis Approach Using Seafloor Acoustics, Imagery, and Ground-Truthing Data in Scotland

et al. 2020

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Marine sediments are important repositories of organic matter, effectively burying organic carbon (OC) over geological timescales thus providing a climate regulation service. However, the spatial distribution of this marine sedimentary OC store is not well constrained. In this study we leverage a high resolution multibeam echosounder (MBES) survey taken at Loch Creran, a model fjordic site on the west coast of Scotland, to develop a new methodology for predicting the distribution of OC in surface sediments. Using an integrated approach, we use MBES survey, video imagery and ground-truthing data to produce a high-resolution (2 × 2 m) map of surficial carbon and calculate a 10 cm stock. We find that the backscatter survey reliably uncovers a heterogeneous seabed and that OC correlates strongly with the MBES backscatter signal as a function of sediment composition. We estimate that there are approximately 12,346 ± 2,677 t of OC held within the top 10 cm of mixed sediments across the MBES survey area (7.96 km 2 ; 60% of the total area), upscaled to 20,577 ± 4,462 t of OC across Loch Creran (13.27 km 2). Normalised by area, we find that fine sediments with small fractions of sand and gravel hold more OC than homogenous fine sediments. This initial work proposes a novel methodological approach to using high resolution MBES surveys to improve the spatial mapping of sedimentary carbon (C) and identification of C hotspots, enabling consideration of this resource in sedimentary carbon accounting, seabed management and climate mitigation strategies.

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Fjords as Aquatic Critical Zones (ACZs)

Cited by 127 publications

References 345 publications

Terrestrial Inputs Drive Seasonality in Organic Matter and Nutrient Biogeochemistry in a High Arctic Fjord System (Isfjorden, Svalbard)

Terrestrial Inputs Drive Seasonality in Organic Matter and Nutrient Biogeochemistry in a High Arctic Fjord System (Isfjorden, Svalbard)

Terrestrial Inputs Shape Coastal Bacterial and Archaeal Communities in a High Arctic Fjord (Isfjorden, Svalbard)

Quantifying Marine Sedimentary Carbon: A New Spatial Analysis Approach Using Seafloor Acoustics, Imagery, and Ground-Truthing Data in Scotland

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