Sediment Trap Studies in Lake Superior: Insights into Resuspension, Cross-margin Transport, and Carbon Cycling

Urban, Noel R.; Lu, Xiaopeng; Chai, Yingtao; Apul, Defne

doi:10.1016/s0380-1330(04)70383-4

Cited by 33 publications

(50 citation statements)

References 61 publications

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“…A simple mixing ratio calculation would suggest that 65% of the material in nearshore traps (35 m below water surface) is derived from resuspension and that 44% in offshore traps (again at 35 m below water surface) is derived from resuspension. Similar observations were made for organic carbon, nitrogen, and phosphorus in the sediment trap material collected in this study [ Urban et al , 2004b].…”

Section: Resultssupporting

confidence: 88%

“…The discrepancy between sediment accumulation rates and sedimentation rates in sediment traps is due to sediment resuspension and subsequent focusing. Sedimentation rates at 35‐m depth measured in this study (0.4 ± 0.07 g m −2 d −1 [ Urban et al , 2004b]) are slightly higher than those reported in the central lake area (∼0.14 g m −2 d −1 [ Baker et al , 1991]) because of higher resuspension rates in nearshore areas; the discrepancy is larger in traps placed 5 m above the sediments (1.1 ± 0.3 versus 0.14 ∼ 1.1 g m −2 d −1 ). Hence it is more appropriate to estimate a residence time for 210 Pb in the nearshore water column (mean depth 50 m) of ≤34 days based on the sediment trap fluxes; this residence time suggests the settling velocity is roughly 1.5 m d −1 .…”

Section: Discussionmentioning

confidence: 92%

“…Rates of both mass sedimentation and 210 Pb sedimentation also show clear differences between nearshore and offshore zones. Mass sedimentation rates are higher in the traps moored in 50 m of water (1.5 ± 0.7 g m −2 d −1 , mean ± 95% CI) than in those moored in 120–230 m of water (0.4 ± 0.07 g m −2 d −1 [ Urban et al , 2004b]). Although fluxes of 210 Pb also are higher in the nearshore traps (97 ± 48 dpm m −2 d −1 ) than in the offshore traps (79 ± 16 dpm m −2 d −1 ), the difference is not nearly as large as for mass sedimentation rates.…”

Section: Resultsmentioning

confidence: 99%

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²¹⁰Po and ²¹⁰Pb distributions and residence times in the nearshore region of Lake Superior

Chai

2004

J. Geophys. Res.

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[1] The naturally occurring radionuclide, 210 Pb, and its decay daughter, 210 Po, were measured in the Keweenaw Peninsula region of Lake Superior. Water, suspended particles, sediment trap material (settling particles), and sediment cores and grab samples were collected along three transects that stretched from 1 to 20 km from shore. Departures from secular equilibrium (activity ratio of 210 Po: 210 Pb = 1) were observed for most samples. 210Po-deficiency was observed in both suspended particles (TSP) with a ratio of 0.43 ± 0.05 (±95% confidence interval (CI)) and settling particles with a ratio of 0.57 ± 0.04; higher ratios in the settling particles resulted from an admixture of resuspended sediments. Ratios in the dissolved phase were 0.45 ± 0.12. Approximately 83% and 85% of total 210 Po and 210 Pb in the water column was in the particulate phase. No evidence of biological uptake of Po was found. Seasonal and spatial variability in activities and ratios was small. Using steady state solutions to the mass balance equations for both isotopes, similar residence times in the water column were calculated for 210 Po and 210 Pb (55 $ 75 days in a 150-m-deep water column). It was possible to calibrate a one-box model for the paired isotopes so that the model output closely matched rates of sediment and isotope resuspension estimated from sediment traps. However, this calibration required a fractionation of the isotopes during resuspension. The particle settling velocity was estimated to be 2.3 m d À1 , which also is in agreement with the estimate (2.4 ± 2.2 m d À1) from sediment traps. These results indicate rapid fluxes of radioisotopes and sediments through the water column largely driven by resuspension of sediments in nearshore areas.

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Section: Resultssupporting

confidence: 88%

Section: Discussionmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

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²¹⁰Po and ²¹⁰Pb distributions and residence times in the nearshore region of Lake Superior

Chai

2004

J. Geophys. Res.

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“…Urban et al (2004) also reported higher d 15 N during winter compared to summer in organic matter collected in sediment trap of Lake Superior and concluded seasonal shift in nutrient source for phytoplankton to be the most likely reason. Taken together, patterns in natural abundance d 15 N POM in Lake Superior are consistent with earlier studies in the Great Lakes (McCusker et al 1999;Urban et al 2004;Kumar et al 2008) and provides an insight into the seasonal nutrient utilization with predominantly NH 4 ? utilization during winter and relatively higher NO 3 -use during summer.…”

Section: Pom Formation and Role Of Nutrientsmentioning

confidence: 88%

Isotopic composition of nitrogen in suspended particulate matter of Lake Superior: implications for nutrient cycling and organic matter transformation

2010

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Lake Superior, one of the largest lakes in the world, is an ecosystem where nitrate (NO 3 -) concentration has risen almost fivefold in the last century. Recent studies suggest that this increase may be due to lack of a significant nitrogen (N) sink, such as sedimentary denitrification or burial, because of low organic matter supply to the lake bottom. In light of these new findings, it is imperative to examine the origin and transformation of suspended particulate organic matter (POM) in the lake as N biogeochemistry is inextricably linked to POM dynamics. We present an analysis of spatial and temporal variations in d 15 M of POM (d 15 M POM ) in the lake and draining rivers based on extensive sampling and a synthesis of recent studies of N cycling. The d 15 M POM in the lake ranged from -4.7 to 7.6% and showed a significant (p \ 0.001) temporal variability in the surface waters with relatively enriched d 15 M during winter (mean ± SD * 1.5 ± 2.3%; n = 13) compared to summer (mean ± SD * -2.0 ± 1.4%; n = 20). Temporal variability in d 15 M POM and data for d 15 M of dissolved inorganic nitrogen (DIN) together suggest a seasonal shift in nutrient sources for plankton along with possible detrital and higher trophic level contributions to POM during winter. On an annual basis, ammonium (NH 4 ? ) appears to be the dominant N source to plankton in the lake. NO 3 -use was lower but seasonally variable with higher contributions to plankton in summer than winter. During a period of high riverine discharge, no significant difference in coastal and open-lake d 15 M POM was found, indicating limited effect of riverine POM on the lake. Significant increase in d 15 M POM and decreases in particulate N concentration with depth indicate transformations of organic matter settling to the lake bottom that are consistent with the hypothesized influence of low organic matter supply to the lake bottom leading to limited benthic denitrification.

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“…Auer et al (2013) focused on depth distribution in characterizing a "ring of fire" where amphipod populations reach peaks in density at depths along nearshore-offshore transects in Lake Superior. Here, organic carbon fluxes (Urban et al, 2004) were found to be 2-4 times greater at slope sites (depth, 30-125 m) hosting peak densities than at profundal locations (depth N 125 m) supporting much lower amphipod abundance. The consumption-food availability relationship developed in this paper, applied within the context of a bioenergetics model, may find application in further exploring the "ring of fire" phenomenon.…”

Section: Implications For Patterns In Food Supply and Diporeia Abundancementioning

confidence: 69%

Measuring the effects of food availability on Lake Superior Diporeia consumption rates using radiolabeled algae

Corcoran

Auer

2015

Journal of Great Lakes Research

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Sediment Trap Studies in Lake Superior: Insights into Resuspension, Cross-margin Transport, and Carbon Cycling

Cited by 33 publications

References 61 publications

²¹⁰Po and ²¹⁰Pb distributions and residence times in the nearshore region of Lake Superior

²¹⁰Po and ²¹⁰Pb distributions and residence times in the nearshore region of Lake Superior

Isotopic composition of nitrogen in suspended particulate matter of Lake Superior: implications for nutrient cycling and organic matter transformation

Measuring the effects of food availability on Lake Superior Diporeia consumption rates using radiolabeled algae

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Sediment Trap Studies in Lake Superior: Insights into Resuspension, Cross-margin Transport, and Carbon Cycling

Cited by 33 publications

References 61 publications

210Po and 210Pb distributions and residence times in the nearshore region of Lake Superior

210Po and 210Pb distributions and residence times in the nearshore region of Lake Superior

Isotopic composition of nitrogen in suspended particulate matter of Lake Superior: implications for nutrient cycling and organic matter transformation

Measuring the effects of food availability on Lake Superior Diporeia consumption rates using radiolabeled algae

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²¹⁰Po and ²¹⁰Pb distributions and residence times in the nearshore region of Lake Superior

²¹⁰Po and ²¹⁰Pb distributions and residence times in the nearshore region of Lake Superior