Managed nutrient reduction impacts on nutrient concentrations, water clarity, primary production, and hypoxia in a north temperate estuary

Oviatt, Candace A.; Smith, Leslie; Krumholz, Jason; Coupland, Catherine M.; Stoffel, Heather E.; Keller, Aimee A.; McManus, M. Conor; Reed, Laura

doi:10.1016/j.ecss.2017.09.026

Cited by 58 publications

(48 citation statements)

References 41 publications

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“…The high river flow in CNM, for instance, presents an average higher than 1.0 × 10 5 m 3 /s, velocity's higher than 0.5 m/s and maximal velocity up to 2.0 m/s in this stretch of the Amazon River. These features point towards a lower likelihood of passive or cumulative agents' permanence in the outflow (nutrients, or less pollutants); it would also allow greater ability to avoid eutrophication processes (algae blooming), even in case of severe environmental degradation [75,80,81]. In other words, the longer the water remains in the control volume, the greater the likelihood of passive flow agents remaining in the body of water.…”

Section: Discussionmentioning

confidence: 99%

Hydrodynamic Modeling and Simulation of Water Residence Time in the Estuary of the Lower Amazon River

Abreu

Barros

Brito

et al. 2020

Water

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Studies about the hydrodynamic behavior in the lower Amazon River remain scarce, despite their relevance and complexity, and the Water Residence Time (Rt) of this Amazonian estuary remains poorly unknown. Therefore, the present study aims to numerically simulate three seasonal Rt scenarios based on a calibrated hydrodynamic numerical model (SisbaHiA) applied to a representative stretch of the lower Amazon River. The following methodological steps were performed: (a) establishing experimental water flow in natural channels; (b) statistically test numerical predictions (tidal range cycles for different hydrologic periods); and (c) simulating velocity fields and water discharge associated with Rt numerical outputs of the hydrodynamic model varied from 14 ≤ Rt ≤ 22 days among different seasonal periods. This change has shown the significant influence of hydrologic period and geomorphological features on Rt. Rt, in its turn, has shown significant spatial heterogeneity, depending on location and stretch of the channels. Comparative analyses between simulated and experimental parameters evidenced statistical correlations higher than 0.9. We conclude that the generated Rt scenarios were consistent with other similar studies in the literature. Therefore, they depicted the applicability of the hydrodynamics to the conservation of the Amazonian aquatic ecosystem, as well as its relevance for biochemical and pollutant dispersion studies, which still remain scarce in the literature.

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Section: Discussionmentioning

confidence: 99%

Hydrodynamic Modeling and Simulation of Water Residence Time in the Estuary of the Lower Amazon River

Abreu

Barros

Brito

et al. 2020

Water

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“…For adjusted rates assumptions were made when necessary using a 3:1 ratio to covert acetylene reduction assay (ARA) rates to N 2 fixation rates, a wet sediment density of 1.2 mg l −1 , and active N 2 fixation to a depth of 5 cm ductions in nutrient loading have taken place as well. The treatment upgrades on the wastewater treatment plants alone have reduced concentrations of inorganic nitrogen bay-wide by close to 50% and caused a decrease in overall surface production (30%), improvements in water clarity, and a significant reduction in summer hypoxia in some areas of the upper bay, including the Providence River estuary but not Greenwich Bay (Oviatt et al 2017). These changes in nutrient discharge to Narragansett Bay are sure to affect water column and benthic nutrient cycling in the years of this study and in future years, proving a challenge for making direct comparisons of studies before 2008 and after 2014.…”

Section: Comparison Of Narragansett Bay Sediment N 2 Fixation Rates Tmentioning

confidence: 99%

“…Greatest hypoxic expression is found in the upper third of the estuary, where the major rivers enter and the major wastewater effluents discharge. These conditions generate a clear gradient of chlorophyll, surface salinity, and hypoxia in Narragansett Bay (Oviatt et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Diazotroph activity in surface Narragansett Bay sediments in summer is stimulated by hypoxia and organic matter delivery

Spinette¹,

Brown²,

Ehrlich³

et al. 2019

Mar. Ecol. Prog. Ser.

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Bacteria that carry out many processes of the nitrogen cycle inhabit estuarine sediments. Denitrification is known to be a dominant process causing estuarine sediments to behave as net nitrogen sinks. However, measurements of nitrogen fluxes in the sediments of Narragansett Bay, Rhode Island, USA, have at times revealed high rates of net nitrogen (N 2 ) fixation. Whereas changes in primary production, in magnitude and phenology, within Narragansett Bay have been identified as possible causes for these changes in nitrogen cycling within the benthos, a factor that has not been examined thus far is seasonal hypoxia. Since anaerobic diazotrophs figure so prominently within the sediments of Narragansett Bay, we hypothesized that dissolved oxygen concentrations in the bottom waters affect their activity. In order to explore this relationship, we measured the activity of diazotrophs in the surface sediments of 3 study areas during the summers of 2013 and 2014 using the acetylene reduction assay. We explored the effects of several water quality parameters on nitrogenase activity including, among others, dissolved oxygen and chlorophyll concentrations. Our measurements of nitrogenase activity were generally low, ranging between 2 and 5 nmol ethylene g −1 d −1 but spiked to 16 nmol ethylene g −1 d −1 at an area experiencing severe hypoxia in July 2013. Our data suggest that diazotrophy in estuarine sediments is enhanced when the benthos experiences very low dissolved oxygen in conjunction with recent influxes of autochthonous organic matter. Experiments with sediment core incubations conducted in the laboratory support our hypothesis that low dissolved oxygen and organic matter additions promote N 2 fixation.

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“…However, earlier trends of increasing eutrophication have been reversed and the Baltic Sea has entered a phase of recovery (Andersen et al, 2017). Examples of oligotrophication and partial recovery have been documented in many coastal waters, e.g., in Denmark (Riemann et al, 2016;Staehr et al, 2017), in Sweden (Walve et al, 2018), in the North Sea (Andersen et al, 2016;OSPAR, 2017;van Beusekom et al, 2018) and in United States (Bricker et al, 2008;Oviatt et al, 2017;Zhang et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Past, Present and Future Eutrophication Status of the Baltic Sea

Murray¹,

Müller‐Karulis²,

Carstensen

et al. 2019

Front. Mar. Sci.

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We modelled and assessed the past, present and predicted future eutrophication status of the Baltic Sea. The assessment covers a 350-year period from 1850 to 2200 and is based on: (1) modelled concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorous (DIP), chlorophyll-a, Secchi depth, and oxygen under four different of nutrient input scenarios and (2) the application of a multi-metric indicatorbased tool for assessment of eutrophication status: HEAT 3.0. This tool was previously applied using historical observations to determine eutrophication status from 1901 to 2012. Here we apply HEAT 3.0 using results of a biogeochemical model to reveal significant changes in eutrophication status from 1850 to 2200. Under two scenarios where Baltic Sea Action Plan (BSAP) nutrient reduction targets are met, we expect future good status will be achieved in most Baltic Sea basins. Under two scenarios where nutrient loads remain at 1997-2003 levels or increase, good status will not be achieved. The change from a healthy state without eutrophication problems in the open waters took place in the late 1950s and early 1960s. Following introduction of the first nutrient abatement measures, recovery began in some basins in the late 1990s, whilst in others it commenced in the beginning of the 21st century. Based on model results, we expect that the first basin to achieve a status without eutrophication will be Arkona, between 2030 and 2040. By 2060-2070, a status without eutrophication is anticipated for the Kattegat, Bornholm Basin and Gulf of Finland, followed by the Danish straits around 2090. For the Baltic Proper and Bothnian Sea, a good status with regard to eutrophication is not expected before 2200. Further, we conclude that two basins are not likely to meet the targets agreed upon and to attain a status unaffected by eutrophication, i.e., the Gulf of Riga and Bothnian Bay. These results, especially the prediction that some basins will not achieve a good status, can be used in support of continuous development and implementation of the regional ecosystem-based nutrient management strategy, the HELCOM Baltic Sea Action Plan.

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Managed nutrient reduction impacts on nutrient concentrations, water clarity, primary production, and hypoxia in a north temperate estuary

Cited by 58 publications

References 41 publications

Hydrodynamic Modeling and Simulation of Water Residence Time in the Estuary of the Lower Amazon River

Hydrodynamic Modeling and Simulation of Water Residence Time in the Estuary of the Lower Amazon River

Diazotroph activity in surface Narragansett Bay sediments in summer is stimulated by hypoxia and organic matter delivery

Past, Present and Future Eutrophication Status of the Baltic Sea

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