Anthropogenic influences on the sedimentary geochemical record in western Lake Superior (1800–present)

O'Beirne, Molly D.; Strzok, Ladislaus J.; Werne, Josef P.; Johnson, Thomas C.; Hecky, Robert E.

doi:10.1016/j.jglr.2014.11.005

Cited by 26 publications

(13 citation statements)

References 46 publications

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“…Increasing δ 13 C org values after 1900AD are consistent with increasing autochthonous PP (Fig. 3) and coincide with increased anthropogenic disturbance (increasing nutrient flux) within the Lake Superior watershed1318. Beginning in late 1970AD strict regulation on anthropogenic nutrient inputs to Lake Superior were initiated19.…”

Section: Discussionmentioning

confidence: 55%

Anthropogenic climate change has altered primary productivity in Lake Superior

et al. 2017

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Anthropogenic climate change has the potential to alter many facets of Earth's freshwater resources, especially lacustrine ecosystems. The effects of anthropogenic changes in Lake Superior, which is Earth's largest freshwater lake by area, are not well documented (spatially or temporally) and predicted future states in response to climate change vary. Here we show that Lake Superior experienced a slow, steady increase in production throughout the Holocene using (paleo)productivity proxies in lacustrine sediments to reconstruct past changes in primary production. Furthermore, data from the last century indicate a rapid increase in primary production, which we attribute to increasing surface water temperatures and longer seasonal stratification related to longer ice-free periods in Lake Superior due to anthropogenic climate warming. These observations demonstrate that anthropogenic effects have become a prominent influence on one of Earth's largest, most pristine lacustrine ecosystems.

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Section: Discussionmentioning

confidence: 55%

Anthropogenic climate change has altered primary productivity in Lake Superior

et al. 2017

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“…Signs of change in the primary producers in Lake Superior as a response to warming have been noted previously by others. Increasing relative abundance of Cyclotella sensu lato in Lake Superior sediment cores in recent decades have been attributed to warming (Reavie et al 2016) as has an increase in primary production inferred with δ 13 C (O'Beirne et al 2015). We saw here that Lake Superior cyanobacterial blooms occurred only in seasons where DD were at the high end of the observed range, a product of warming occurring relatively early in the season so affecting the length of the potential growing season.…”

Section: Discussionmentioning

confidence: 99%

A first assessment of cyanobacterial blooms in oligotrophic Lake Superior

Sterner

Reinl

Lafrancois

et al. 2020

Limnology & Oceanography

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Lake Superior is often described as the most pristine of the Laurentian Great Lakes, but in the past decade Dolichospermum blooms have been observed. Land use in the adjacent watershed has not changed appreciably during this time, but the lake is warming and climatological variables correspond with presence of blooms. Blooms occurred only in relatively warm years as measured by degree days. Furthermore, the two largest blooms, in 2012 and 2018, occurred during years of especially extreme rainfall, providing coincidental evidence that intense storms provide nutrients or living propagules to the blooms from the watershed. Nearshore lake water in the narrow zone where blooms appear shows some riverine influence compared to water further offshore even in the absence of blooms. Nevertheless, water chemistry associated with the largest bloom in 2018 more closely resembled nonbloom nearshore lake water than river water, suggesting that blooms develop or at least persist outside of distinct river plumes. Concentrations of P and N during peak bloom density greatly exceeded any nonbloom lake or river waters, indicating that a buildup of phytoplankton biomass perhaps by floating and drifting to shore also is a significant factor in bloom occurrence. One potentially toxic substance (Anabaenopeptin A) was observed but at low concentration. At peak phytoplankton concentration, high seston C : P indicated severe P limitation while low C : N pointed against N limitation. If these newly observed blooms are indeed driven by temperature and rainfall as this evidence suggests, blooms may continue. Cyanobacterial blooms (defined as "a massive accumulation of cyanobacterial biomass, formed through growth, migration, and physical-chemical forces"; Tromas et al. 2017) are a significant and increasingly prevalent global water quality problem (Paerl and Otten 2013; Ho et al. 2019). Blooms of cyanobacteria are most often associated with eutrophic or

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“…For much of the Anthropocene (1850-1968), several hundred million metric tons of mine tailings were dumped into the lake (Kerfoot, Lauster & Robbins, 1994), an event that is clearly present in the geochemical profile of the eastern core, where Cu concentration peaked in 1958, lagging behind the largest period of mine openings, showing the long term impact of mining on this system. The highest population density around Lake Superior is in the St. Louis River drainage, which is the 2 nd largest inflow to Lake Superior (O'Beirne et al, 2015), just upgradient from the western core location (Fig. 1).…”

Section: Discussionmentioning

confidence: 99%

Peer Review #1 of "Anthropocene geochemistry of metals in sediment cores from the Laurentian Great Lakes (v0.1)"

2020

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Geochemical analyses applied to lake sedimentary records can reveal the history of pollution by metals and the effects of remedial efforts. Lakes provide ideal environments for geochemical studies because they have steady deposition of fine grained material suitable for fixation of pollutants. The Laurentian Great Lakes are the most studied system in this field, and they have well-preserved chronological profiles. To date, this important system has been considered in parts for inorganic geochemistry, hampering basin-wide conclusions regarding metal contamination. We filled spatial and temporal gaps in a comprehensive geochemical analysis of 11 sediment cores collected from all five Great Lakes. Hierarchical cluster analysis of all Great Lakes samples divided the metal analytes into five functional groups: (1) carbonate elements; (2) metals and oxides with diverse natural sources, including a subgroup of analytes known to be anthropogenically enriched (Cd, Pb, Sn, Zn, and Sb); (3) common crustal elements; (4) metals related to coal and nuclear power generation; and (5) all of the co-occurring rare earth elements. Two contamination indices (I geo and EF) applied to sedimentary metals indicated that Na, Co, Mn, Cd, Pb, Ta, and Cu were each, at some point during the Anthropocene, the most enriched metal pollutants in Great Lakes sediments. Land uses correlated with the metal analytes, such as increases in contaminant metals with the rise in catchment population and increases in carbonate elements (e.g. Ca) with agriculture. Certain contamination trends were observed basin-wide, such as for the atmospheric pollutant Pb, which followed a rise associated with fossil fuel combustion and a decline following the ban of leaded gasoline. Other trends were lake-specific, such as recent high concentrations of Na in Lake Superior, likely due to road salt applications, and a late-20 th-century peak in Ca associated with algal whiting events in Lake Ontario. Some metals exceeded guidelines for sediment quality, in some cases prior to European settlement of the basin, indicating that a paleolimnological context is important for appropriate management of sediment contamination. The Great Lakes are sensitive to environmental changes such as pollution

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Anthropogenic influences on the sedimentary geochemical record in western Lake Superior (1800–present)

Cited by 26 publications

References 46 publications

Anthropogenic climate change has altered primary productivity in Lake Superior

Anthropogenic climate change has altered primary productivity in Lake Superior

A first assessment of cyanobacterial blooms in oligotrophic Lake Superior

Peer Review #1 of "Anthropocene geochemistry of metals in sediment cores from the Laurentian Great Lakes (v0.1)"

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