Benthic metabolism and nutrient regeneration in hydrographically different regions on the inner continental shelf of Southern New England

Fields, Lindsey; Nixon, Scott W.; Oviatt, Candace A.; Fulweiler, Robinson W.

doi:10.1016/j.ecss.2014.06.007

Cited by 15 publications

(11 citation statements)

References 65 publications

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“…Immediately after collection, cores were loosely capped and stabilized, upright, in the dark inside coolers filled with site water to maintain them at site temperature. We also collected in situ bottom water from each site using a high volume diaphragm pump and filtered on board using a series of in‐line cartridge filters (nominally 50, 10, 1, and 0.2 μm; Fields et al, ; Giblin et al, ; Heiss et al, ). We used filtered station water in our incubations in an effort to remove water column biota and focus our analyses to processes occurring at the sediment‐water interface (Fields et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…We also collected in situ bottom water from each site using a high volume diaphragm pump and filtered on board using a series of in‐line cartridge filters (nominally 50, 10, 1, and 0.2 μm; Fields et al, ; Giblin et al, ; Heiss et al, ). We used filtered station water in our incubations in an effort to remove water column biota and focus our analyses to processes occurring at the sediment‐water interface (Fields et al, ). We transported the sediment cores and filtered station bottom water back to our Boston University laboratories, typically within 8 hr of collection.…”

Section: Methodsmentioning

confidence: 99%

“…We uncapped the sediment cores, placed them in a water bath, and gently bubbled ambient air into the overlying water overnight while the cores equilibrated to the chamber conditions. The following morning we conducted static core incubations in the dark using well‐established methods to determine fluxes across the sediment–water interface (e.g., Banta et al, ; Fields et al, ; Giblin et al, ). First, we siphoned off the overlying water above the sediments and replaced the water with filtered bottom station water (Fields et al, ; Fulweiler et al, ; Giblin et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…The following morning we conducted static core incubations in the dark using well‐established methods to determine fluxes across the sediment–water interface (e.g., Banta et al, ; Fields et al, ; Giblin et al, ). First, we siphoned off the overlying water above the sediments and replaced the water with filtered bottom station water (Fields et al, ; Fulweiler et al, ; Giblin et al, ). In order to preserve the chemical and physical components of our sediment cores, we were careful not to disturb the sediment‐water interface while siphoning or refilling the cores (Hopkinson & Smith, ).…”

Section: Methodsmentioning

confidence: 99%

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Estuarine Sediments Exhibit Dynamic and Variable Biogeochemical Responses to Hypoxia

Foster

Fulweiler

2019

JGR Biogeosciences

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Estuarine ecosystems are considered among the most valuable regions worldwide because of the wealth of ecosystem services they provide. Given their proximity to the land, they are also vulnerable to excessive nutrient inputs, which can lead to eutrophication and hypoxia. Water column hypoxia can dramatically alter sediment biogeochemistry, yet the response of specific processes varies widely. Predicting whether sediments are sources or sinks of ecologically and climatologically relevant nutrients and gases remains elusive, particularly for shallow coastal regions. In this study, we conducted experiments with sediments collected from Waquoit Bay (Massachusetts, United States) and measured dissolved nutrient and gas fluxes across the sediment-water interface to investigate the impact of water column hypoxia (defined here as dissolved oxygen ≤3 mg/L) on three important ecosystem functions: nutrient regeneration, removal of reactive nitrogen, and the regulation of greenhouse gases. Under hypoxia we observed variable responses in sediment biogeochemical cycling, including little to no change in important nitrogen cycling processes such as ammonium efflux and nitrogen removal through denitrification. As expected, low oxygen conditions stimulated sediment phosphate efflux. This caused nutrient ratios for both nitrogen to phosphorus and silica to phosphorus in the overlying water to decrease by 50%. Such changes can alter both the composition of water column primary producers as well as the rate of primary production. Hypoxia led to an almost 60% decrease in sediment nitrous oxide consumption but had little impact on sediment methane emissions. Taken together, these experimental results suggest sediment biogeochemical cycling has variable and dynamic responses to hypoxia.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Estuarine Sediments Exhibit Dynamic and Variable Biogeochemical Responses to Hypoxia

Foster

Fulweiler

2019

JGR Biogeosciences

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“…6), the N-NO 3 − levels were low, often close to 0.5 μM, which is considered limiting to phytoplankton growth (Fasham et al 1990) but always higher (1-2 orders of magnitude) than N-NO 2 − (whose concentration was negligible) at both the sites, ranging from 0.3 to 0.9 μM and from 0.7 to 2.0 μM, at 1E and 1I, respectively. The changes of N-NO 3 − concentrations, which could be also attributed to benthic infauna causing either increases or decreases in nitrate release from the sediment, depending on the depth of their burrowing and their amount of irrigation activity (Fields et al 2014), showed that at both sites, nitrate, although low in concentration, did not become completely consumed during incubations. Ammonium concentrations ranged from 1.1 to 2.8 μM and from 1.0 to 1.7 μM at 1E and 1I, respectively (Fig.…”

Section: Concentration Variations In Benthic Chambersmentioning

confidence: 98%

Oxygen, carbon, and nutrient exchanges at the sediment–water interface in the Mar Piccolo of Taranto (Ionian Sea, southern Italy)

Vittor

Relitti

Kralj

et al. 2015

Environ Sci Pollut Res

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In the shallow environment, the nutrient and carbon exchanges at the sediment-water interface contribute significantly to determine the trophic status of the whole water column. The intensity of the allochthonous input in a coastal environment subjected to strong anthropogenic pressures determines an increase in the benthic oxygen demand leading to depressed oxygen levels in the bottom waters. Anoxic conditions resulting from organic enrichment can enhance the exchange of nutrients between sediments and the overlying water. In the present study, carbon and nutrient fluxes at the sediment-water interface were measured at two experimental sites, one highly and one moderately contaminated, as reference point. In situ benthic flux measurements of dissolved species (O2, DIC, DOC, N-NO3 (-), N-NO2 (-), N-NH4 (+), P-PO4 (3-), Si-Si(OH)4, H2S) were conducted using benthic chambers. Furthermore, undisturbed sediment cores were collected for analyses of total and organic C, total N, and biopolymeric carbon (carbohydrates, proteins, and lipids) as well as of dissolved species in porewaters and supernatant in order to calculate the diffusive fluxes. The sediments were characterized by suboxic to anoxic conditions with redox values more negative in the highly contaminated site, which was also characterized by higher biopolymeric carbon content (most of all lipids), lower C/N ratios and generally higher diffusive fluxes, which could result in a higher release of contaminants. A great difference was observed between diffusive and in situ benthic fluxes suggesting the enhancing of fluxes by bioturbation and the occurrence of biogeochemically important processes at the sediment-water interface. The multi-contamination of both inorganic and organic pollutants, in the sediments of the Mar Piccolo of Taranto (declared SIN in 1998), potentially transferable to the water column and to the aquatic trophic chain, is of serious concern for its ecological relevance, also considering the widespread fishing and mussel farming activities in the area.

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Time series of phytoplankton net primary production reveals intense interannual variability and size‐dependent chlorophyll‐specific productivity on a continental shelf

Fontaine,

Marrec,

Menden‐Deuer

et al. 2024

Limnology & Oceanography

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Phytoplankton community size structure influences the production and fate of organic carbon in marine food webs and can undergo strong seasonal shifts in temperate regions. As part of the Northeast US Shelf (NES) Long‐Term Ecological Research program, we measured net primary production (NPP) rates and chlorophyll a (Chl a) concentrations in three phytoplankton size classes (< 5, 5–20, and > 20 μm) during winter and summer for 3 yr along a coastal‐to‐offshore transect. Mean depth‐integrated NPP was 37% higher in summer than winter, with limited cross‐shelf differences because of significant interannual variability. When averaged across the shelf, depth‐integrated NPP was dominated by the > 20 μm size class in winter and generated equally by the three size fractions in summer because of substantial contributions from cells > 20 μm at the Chl a maximum depth. Furthermore, the relationship between Chl a and NPP, in terms of relative contributions, varied by size class. Variations in this relationship have implications for models of primary productivity on the NES and beyond. In comparison to historical NPP data, we identified equivalent levels of winter NPP but observed a 25% decrease in summer NPP, suggesting a potential reduction in the seasonality of NPP on the NES. Together, our results highlight seasonal shifts in NPP rates of different phytoplankton size classes, with implications for food web structure and export production. These data emphasize the importance of quantifying size‐fractionated NPP over time to constrain its variability and better predict the fate of organic carbon in coastal systems under environmental change.

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Benthic metabolism and nutrient regeneration in hydrographically different regions on the inner continental shelf of Southern New England

Cited by 15 publications

References 65 publications

Estuarine Sediments Exhibit Dynamic and Variable Biogeochemical Responses to Hypoxia

Estuarine Sediments Exhibit Dynamic and Variable Biogeochemical Responses to Hypoxia

Oxygen, carbon, and nutrient exchanges at the sediment–water interface in the Mar Piccolo of Taranto (Ionian Sea, southern Italy)

Time series of phytoplankton net primary production reveals intense interannual variability and size‐dependent chlorophyll‐specific productivity on a continental shelf

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