Sutherland, T.F.; Amos, C.L., and Grant, J., 2022. The resuspension and deposition of biomediated... more Sutherland, T.F.; Amos, C.L., and Grant, J., 2022. The resuspension and deposition of biomediated sediments in Upper South Cove, Nova Scotia, Canada. Journal of Coastal Research, 38(1), 19–34. Coconut Creek (Florida), ISSN 0749-0208. Coastal seabed sediment stability is mediated by microalgal and bacterial biofilms. The resuspension of organic suspended particulate matter (SPM) in biomediated sediments increases nutrient fluxes to the water column and supplements particulate food supplies for suspension feeders. Thus, quantifying benthic-pelagic exchange pathways of biogeochemical parameters is essential to provide an accurate assessment of carrying capacities of coastal embayments supporting both natural and cultured bivalve populations. Benthic-pelagic transport coefficients such as erosion threshold (U*CRIT-SPM-EROSION), net erosion rate (NERSPM), peak erosion rate (PERSPM), depositional threshold (U*CRIT-SPM-DEPOSITION), and deposition rate (DRSPM) were determined using an in si...
The effect of growth and carbohydrate production by the diatom Nitzschia cuwilineata on sediment ... more The effect of growth and carbohydrate production by the diatom Nitzschia cuwilineata on sediment erodibility was explored in laboratory flume experiments. Diatom cultures, incubated on sediment, were monitored daily for chlorophyll and carbohydrate concentrations and eroded in a recirculating flume at successive stages of growth. Because variations in erosion rate were far greater than variations in erosion threshold during the diatom growth period, erosion rate may be a more sensitive index of sediment stability. Erosion rate was negatively correlated with sediment chlorophyll (r2 = 0.759; P = 0.024) and bulk carbohydrate (r2 = 0.958; P = 0.001) concentrations. A strong negative correlation was found between the sediment bulk carbohydrate‐to‐chlorophyll ratio and erosion rate (r2 = 0.996; P < 0.00l), suggesting that this ratio would serve as a good indicator of sediment erodibility. The size of eroding particles or aggregates increased with the age of the biofilm, probably due t...
ABSTRACTThe erodibility of natural estuarine sediments was measured in sit along a longitudinal t... more ABSTRACTThe erodibility of natural estuarine sediments was measured in sit along a longitudinal transect of Manitounuk Sound, Hudson Bay, using the benthic flume Sea Carousel. Sedimentation processes along the transect varied from continuous, rapid, post‐glacial sedimentation in the inner Sound, to glacial outcrops and seabed reworking of the outer Sound. The grain size and physical bulk properties reflect changes in depositional environment and correlate with sediment erosion threshold stress (τc), erosion rate (E), erosion type and still‐water mass settling rate. There was a steady increase in τc (0·8–2·0 Pa) with distance down the Sound in parallel with the decreasing sedimentation rate (0·003–0·001 m yr−1) and increasing sediment bulk density (1650–2010 kg m−3). The near‐surface friction coefficient varied up to 68° in proportion to the clay content of post‐glacial material. Glacial sediments were characterized by variable results and generally higher friction coefficients. Seab...
ABSTRACT Amos, C.L.; Christian, H.; Buckley, D.E., and Daborn, G.R., 2019. The stability, settlin... more ABSTRACT Amos, C.L.; Christian, H.; Buckley, D.E., and Daborn, G.R., 2019. The stability, settling character, and strength of seabed sediments in the Miramichi estuary, Canada. Journal of Coastal Research, 35(3), 509–523. Coconut Creek (Florida), ISSN 0749-0208. A survey of seabed stability was undertaken in the Miramichi estuary, New Brunswick, Canada: a region subject to intense industrial pollution, channel dredging and maintenance, and the passage of commercial ships. The estuary has a diverse fauna that has been described. The impact of natural and industrial activities on the indigenous fauna is largely unknown. Reworking of dredge spoil tailings has been considered the main cause of sediment dispersal in the system, yet there have been no direct measurements of this. As a result, a study was undertaken to determine the character and stability of dredge spoils and the natural estuarine sediments in which they sit, using the benthic flume Sea Carousel over the years 1991, 1993, and 1994. As well, a limited program of seabed and water column sampling and monitoring was undertaken using a variety of techniques in order to provide a setting for the measurements of stability. Results showed that tidal influence on resuspension was small compared with storm (and ship) waves and other “events” that appeared to be anthropogenic in origin. The erosional and depositional character of natural (control) sites were similar to those from other estuaries described in the literature despite the strong anthropogenic influences. Surprisingly, the strength of disposed dredge spoils (collected using a clam-shell bucket) was similar to the natural sediments at the control site, even after only a few hours of disposing. The stability of the disposed material did not change measurably after 1 year. The erosion flux (E) was found to be a power function of the excess bed shear stress: E = 1.9 × 10-3(τ0 – τc,z)0.71 kg/m2/s. The settling of eroded material took place as aggregates at a mean rate of 1.1 × 10-3 m/s, which corresponds to a mean sedimentation diameter of 75 microns (very fine sand). The fluid mud potential of the system is low: laboratory settling experiments showed that suspended silts/clays underwent free settling at a rate proportional to initial concentration to a maximum concentration of 18 g/L; hindered settling (and fluid mud development) was evident above this value.
The Atlantic Geoscience Centre sediment transport model (SEDTRANS92) is an ANSI standard FORTRAN-... more The Atlantic Geoscience Centre sediment transport model (SEDTRANS92) is an ANSI standard FORTRAN-77 numerical model that has been under development for the last 9 years. For given input data of wave, current, and seabed conditions, SEDTRANS92 applies combined wavexurrent bottom boundary layer theories to derive enhanced bottom shear stresses. Then it calculates sediment transport rates for a given grain size using one of seven algorithms: Engelund and Hansen, total load equation; Einstein-Brown, bedload equation; Bagnold, total load equation; Yalin, bedload equation; Ackers and White, total load equation; Smith, suspended load method; and the cohesive sediment transport algorithm of Amos and Greenberg. This model adopts new advances of bottom boundary layer theory and recently available field measurements of sediment transport rates on the Scotian Shelf. The model gives reasonable predictions compared to the field measurements. Kev Words: Combined wave-current flows. Shelf sediment transport, FORTRAN code, Computer si&lation, Predictions and field data.
The purpose of the cruise was to undertake a summer time reconnaissance of the Bay of Fundy in te... more The purpose of the cruise was to undertake a summer time reconnaissance of the Bay of Fundy in terms of the water quality and bottom sediments for purposes of the evaluation of the impacts of tidal power development. Bottom sediment samples and cores were collected along with high resolution geophysical profiles. Water mass data (biological, physical and chemical) were also collected from anchor stations at strategic points in Chignecto Bay and Inner Bay of Fundy.
Venice Lagoon is the estuary with the largest area and the greatest microtidal range (1 m spring ... more Venice Lagoon is the estuary with the largest area and the greatest microtidal range (1 m spring tide) in the Mediterranean Sea. Presently, the Lagoon is suffering from a sediment loss of ~1 million m 3 /a seawards. The consequence of such a deficit in the sediment budget is the progressive destruction of salt marshes and tidal flats. It is estimated that all the salt marshes will have disappeared by 2040 if this trend continues (Consorzio Venezia Nuova, 1992; 1996). In this study, a multidisciplinary investigation was undertaken at two different spatial scales (regional and local) to determine the factors controlling the stability and evolution of Venice Lagoon. Relationships between the critical erosion threshold of the lagoonal sediments and their biological properties (PATERSON, 2000) reveal that complex feed-back mechanisms exist which enhances the accretion of the intertidal areas in the northern part of the Lagoon.
Sutherland, T.F.; Amos, C.L., and Grant, J., 2022. The resuspension and deposition of biomediated... more Sutherland, T.F.; Amos, C.L., and Grant, J., 2022. The resuspension and deposition of biomediated sediments in Upper South Cove, Nova Scotia, Canada. Journal of Coastal Research, 38(1), 19–34. Coconut Creek (Florida), ISSN 0749-0208. Coastal seabed sediment stability is mediated by microalgal and bacterial biofilms. The resuspension of organic suspended particulate matter (SPM) in biomediated sediments increases nutrient fluxes to the water column and supplements particulate food supplies for suspension feeders. Thus, quantifying benthic-pelagic exchange pathways of biogeochemical parameters is essential to provide an accurate assessment of carrying capacities of coastal embayments supporting both natural and cultured bivalve populations. Benthic-pelagic transport coefficients such as erosion threshold (U*CRIT-SPM-EROSION), net erosion rate (NERSPM), peak erosion rate (PERSPM), depositional threshold (U*CRIT-SPM-DEPOSITION), and deposition rate (DRSPM) were determined using an in si...
The effect of growth and carbohydrate production by the diatom Nitzschia cuwilineata on sediment ... more The effect of growth and carbohydrate production by the diatom Nitzschia cuwilineata on sediment erodibility was explored in laboratory flume experiments. Diatom cultures, incubated on sediment, were monitored daily for chlorophyll and carbohydrate concentrations and eroded in a recirculating flume at successive stages of growth. Because variations in erosion rate were far greater than variations in erosion threshold during the diatom growth period, erosion rate may be a more sensitive index of sediment stability. Erosion rate was negatively correlated with sediment chlorophyll (r2 = 0.759; P = 0.024) and bulk carbohydrate (r2 = 0.958; P = 0.001) concentrations. A strong negative correlation was found between the sediment bulk carbohydrate‐to‐chlorophyll ratio and erosion rate (r2 = 0.996; P < 0.00l), suggesting that this ratio would serve as a good indicator of sediment erodibility. The size of eroding particles or aggregates increased with the age of the biofilm, probably due t...
ABSTRACTThe erodibility of natural estuarine sediments was measured in sit along a longitudinal t... more ABSTRACTThe erodibility of natural estuarine sediments was measured in sit along a longitudinal transect of Manitounuk Sound, Hudson Bay, using the benthic flume Sea Carousel. Sedimentation processes along the transect varied from continuous, rapid, post‐glacial sedimentation in the inner Sound, to glacial outcrops and seabed reworking of the outer Sound. The grain size and physical bulk properties reflect changes in depositional environment and correlate with sediment erosion threshold stress (τc), erosion rate (E), erosion type and still‐water mass settling rate. There was a steady increase in τc (0·8–2·0 Pa) with distance down the Sound in parallel with the decreasing sedimentation rate (0·003–0·001 m yr−1) and increasing sediment bulk density (1650–2010 kg m−3). The near‐surface friction coefficient varied up to 68° in proportion to the clay content of post‐glacial material. Glacial sediments were characterized by variable results and generally higher friction coefficients. Seab...
ABSTRACT Amos, C.L.; Christian, H.; Buckley, D.E., and Daborn, G.R., 2019. The stability, settlin... more ABSTRACT Amos, C.L.; Christian, H.; Buckley, D.E., and Daborn, G.R., 2019. The stability, settling character, and strength of seabed sediments in the Miramichi estuary, Canada. Journal of Coastal Research, 35(3), 509–523. Coconut Creek (Florida), ISSN 0749-0208. A survey of seabed stability was undertaken in the Miramichi estuary, New Brunswick, Canada: a region subject to intense industrial pollution, channel dredging and maintenance, and the passage of commercial ships. The estuary has a diverse fauna that has been described. The impact of natural and industrial activities on the indigenous fauna is largely unknown. Reworking of dredge spoil tailings has been considered the main cause of sediment dispersal in the system, yet there have been no direct measurements of this. As a result, a study was undertaken to determine the character and stability of dredge spoils and the natural estuarine sediments in which they sit, using the benthic flume Sea Carousel over the years 1991, 1993, and 1994. As well, a limited program of seabed and water column sampling and monitoring was undertaken using a variety of techniques in order to provide a setting for the measurements of stability. Results showed that tidal influence on resuspension was small compared with storm (and ship) waves and other “events” that appeared to be anthropogenic in origin. The erosional and depositional character of natural (control) sites were similar to those from other estuaries described in the literature despite the strong anthropogenic influences. Surprisingly, the strength of disposed dredge spoils (collected using a clam-shell bucket) was similar to the natural sediments at the control site, even after only a few hours of disposing. The stability of the disposed material did not change measurably after 1 year. The erosion flux (E) was found to be a power function of the excess bed shear stress: E = 1.9 × 10-3(τ0 – τc,z)0.71 kg/m2/s. The settling of eroded material took place as aggregates at a mean rate of 1.1 × 10-3 m/s, which corresponds to a mean sedimentation diameter of 75 microns (very fine sand). The fluid mud potential of the system is low: laboratory settling experiments showed that suspended silts/clays underwent free settling at a rate proportional to initial concentration to a maximum concentration of 18 g/L; hindered settling (and fluid mud development) was evident above this value.
The Atlantic Geoscience Centre sediment transport model (SEDTRANS92) is an ANSI standard FORTRAN-... more The Atlantic Geoscience Centre sediment transport model (SEDTRANS92) is an ANSI standard FORTRAN-77 numerical model that has been under development for the last 9 years. For given input data of wave, current, and seabed conditions, SEDTRANS92 applies combined wavexurrent bottom boundary layer theories to derive enhanced bottom shear stresses. Then it calculates sediment transport rates for a given grain size using one of seven algorithms: Engelund and Hansen, total load equation; Einstein-Brown, bedload equation; Bagnold, total load equation; Yalin, bedload equation; Ackers and White, total load equation; Smith, suspended load method; and the cohesive sediment transport algorithm of Amos and Greenberg. This model adopts new advances of bottom boundary layer theory and recently available field measurements of sediment transport rates on the Scotian Shelf. The model gives reasonable predictions compared to the field measurements. Kev Words: Combined wave-current flows. Shelf sediment transport, FORTRAN code, Computer si&lation, Predictions and field data.
The purpose of the cruise was to undertake a summer time reconnaissance of the Bay of Fundy in te... more The purpose of the cruise was to undertake a summer time reconnaissance of the Bay of Fundy in terms of the water quality and bottom sediments for purposes of the evaluation of the impacts of tidal power development. Bottom sediment samples and cores were collected along with high resolution geophysical profiles. Water mass data (biological, physical and chemical) were also collected from anchor stations at strategic points in Chignecto Bay and Inner Bay of Fundy.
Venice Lagoon is the estuary with the largest area and the greatest microtidal range (1 m spring ... more Venice Lagoon is the estuary with the largest area and the greatest microtidal range (1 m spring tide) in the Mediterranean Sea. Presently, the Lagoon is suffering from a sediment loss of ~1 million m 3 /a seawards. The consequence of such a deficit in the sediment budget is the progressive destruction of salt marshes and tidal flats. It is estimated that all the salt marshes will have disappeared by 2040 if this trend continues (Consorzio Venezia Nuova, 1992; 1996). In this study, a multidisciplinary investigation was undertaken at two different spatial scales (regional and local) to determine the factors controlling the stability and evolution of Venice Lagoon. Relationships between the critical erosion threshold of the lagoonal sediments and their biological properties (PATERSON, 2000) reveal that complex feed-back mechanisms exist which enhances the accretion of the intertidal areas in the northern part of the Lagoon.
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