Lake Erie Offshore in 1990: Restoration and Resilience in the Central Basin

Charlton, Murray N.; Milne, Jacqui; Booth, W.G.; Chiocchio, F.

doi:10.1016/s0380-1330(93)71218-6

Cited by 58 publications

(33 citation statements)

References 41 publications

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“…This finding is consistent with observed reduction in total P, chlorophyll a, and phytoplankton biomass in the water column during the 1970s and 1980s (Makarewicz and Bartram 199 1). Other expected ecosystem responses to reduced P loading, such as reduced rates of hypolimnetic oxygen depletion in the central basin, have not been found (see Charlton et al 1993). The use of 613C,,,, to infer trends in paleoproductivity is strengthened by our results from Lake Erie in which the inferences about productivity are similar for two cores with distinctly different stratigraphies.…”

Section: Discussionmentioning

confidence: 58%

Using carbon isotopes of bulk sedimentary organic matter to reconstruct the history of nutrient loading and eutrophication in Lake Erie

1995

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Lacustrine productivity in Lake Erie was reconstructed using measurements of V3C of sedimented organic C (S13C,,,) and non-apatite inorganic P (NAIP) in three cores. Inferred changes in lacustrine productivity were related to historic changes in phosphorus loading. P loading increased slowly after forest clearance and early settlement in the late 18OOs, then increased exponentially from the late 1940s to early 197Os, and finally decreased after the mid-1970s in response to management practices implemented to improve water quality. Similarly, the sediment accumulation rate of NAIP increased rapidly during the 1940s and 195Os, peaked during the late 1960s and early 197Os, and then decreased after the mid-1970s. The signal of 613C,, normalized to account for the historic 1.4o/oo depletion in V3C of atmospheric CO, mirrors that for accumulation of NAIP in sediments. Our results show that paleoproductivity peaked in the lower Great Lakes during the mid-1970s but has since declined as a result of P abatement programs. Inferred trends for NAIP and 613C Orgc are those predicted in P-limited lacustrine systems and demonstrate that the carbon isotopic ratio of organic C can be used as a proxy for paleoproductivity in large, deep lakes.

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Section: Discussionmentioning

confidence: 58%

Using carbon isotopes of bulk sedimentary organic matter to reconstruct the history of nutrient loading and eutrophication in Lake Erie

1995

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“…Eadie et al (1995) suggested that most of the historic increase in 61SN may be due to denitrification in the seasonally anoxic central basin of Lake Erie, with subsequent transport of this signal downstream to Lake Ontario. During denitrification in suboxic environments, NO,-is converted to N,, with a strong fractionation leaving the dissolved NO, enriched in "N. The area of central basin anoxia in Lake Erie increased substantially from the 1930s to the early 1970s (Herdendorf 1980), and has not decreased significantly since the 1970s despite large decreases in P loading (Bertram 1993;Charlton et al 1993). The fact that the iY5N increased in both cores until 1960 and then remained relatively constant thereafter is broadly consistent with the history of anoxia in the central basin of Lake Erie.…”

Section: Discussionmentioning

confidence: 99%

Production, sedimentation, and isotopic composition of organic matter in Lake Ontario

Hodell

Schelske

1998

Limnology & Oceanography

351

278

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Organic matter and its carbon and nitrogen isotopic composition were measured in sequential sediment trap and core samples from the Rochester Basin of Lake Ontario to evaluate their usefulness in reconstructing historic changes in lake productivity. The greatest flux of organic matter from the epilimnion occurred during late summer and coincided with whiting events, indicating that calcite precipitation is an effective mechanism for sedimenting organic matter. Carbon isotopes of organic matter were low prior to the onset of stratification, increased to maximum values in late summer, and then decreased following fall overturn. This pattern is controlled mainly by the timing of stratification and primary productivity, which preferentially removes "COZ from the epilimnion. The physiological effect of decreased carbon isotopic fractionation with decreasing supplies of [CO,],,, may have also contributed to increased PC orgc' Nitrogen isotopes showed a seasonal pattern opposite to that of carbon, whereby S"N values were low during the summer stratified period and high for the remainder of the year. Seasonal variability in S'INorgN probably reflects changes in the source of sedimented organic particles, which is dominated by isotopically depleted phytodetritus during the stratified period and isotopically enriched organic matter from heterotrophic or detrital sources during the mixed period. A comparison of organic carbon accumulation rates and 6'&, between sediment cores collected in 1987 and 1993-1994 confirms earlier predictions that diagenetic processes reduce the mass accumulation of organic carbon in the zone of oxic pore waters, but will not change the S"C,,,,,. values. All cores analyzed for PC,,,, display the reproducible pattern of a progressive increase in the 19OOs, peaking in the early to mid-1970s, and then decreasing to the present. This pattern matches the historical trends of phosphorus loading to the basin, suggesting that 613C of organic carbon is a reliable proxy for paleoproductivity and responds to spring phosphorus supplies in the water column. The 6"N of sedimentary organic matter increased linearly from 1840 to 1960 at a rate of 0.3%0 per decade, and remained relatively constant thereafter except for an increase in the upper few centimeters of sediment. The increase in @N,,,,, reflects a combination of factors, including early forest clearance by Europeans, increased sewering by municipalities after 1940, and increased nitrate utilization as productivity increased in the lower Great Lakes. Increased rates of denitrification in the central basin of upstream Lake Erie from the 1930s to the early 1970s may have also contributed to the rise in P5N,,,, values. Proxy indicators of past changes in primary productivity have long been sought in both marine and lacustrine sedimentary records. In the Laurentian Great Lakes, historical information on nutrient loading and productivity is limited before 1964 (Stevens and Neilson 1987), and thus paleolimnological studies have been used to infer nut...

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“…Although this target load was met by the mid-1980s (Dolan 1993) and remains near the target load with weather-induced annual variation (Dolan and McGunagle 2005), total phytoplankton biomass has increased after a mid-1990s minimum (Conroy et al 2005b), cyanobacterial blooms have increased (Conroy and Culver 2005), hypolimnetic hypoxia occurs annually to varying extents in the central basin (Charlton and Milne 2004;Burns et al 2005;Conroy 2007; Rao et al 2008), and indicators of overall system ''health'' continue to show impairment (Conroy et al 2008). Charlton et al (1993) proposed that the actual range of external P load change from an estimated \5 Gg P year -1 prior to European settlement (Harris and Vollenweider 1982), to a maximum of about 30 Gg P year -1 at the height of cultural eutrophication (Sly 1976) and back to about 11 Gg P year -1 post GLWQA implementation (Dolan 1993;Dolan and McGunagle 2005) was insufficient to affect HOD rates or Lake Erie in general, due to system resilience or the continued oxidation of reduced substances present in historically loaded sediments (Matzinger et al 2010). That is, processes and features such as P sorption to suspended sediments with concomitant sedimentation and burial, the large distance between the site of most P loading in the western basin and the hypoxic area of the central basin, and re-aeration of the hypolimnion due to physical entrainment and mixing events (Ivey and Boyce 1982), were sufficient to buffer Lake Erie from observable changes in HOD rates as external P loading increased and subsequently was reduced.…”

Section: Introductionmentioning

confidence: 99%

“Dead Zone” dynamics in Lake Erie: the importance of weather and sampling intensity for calculated hypolimnetic oxygen depletion rates

et al. 2010

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Calculated hypolimnetic oxygen depletion (HOD) rates depend not only on environmental factors but also logistical ones. In particular, lack of understanding of the effects of weather in addition to how sampling effort determines calculated HOD rates complicates ecological understanding and environmental management of lake ecosystems. To better determine the roles of weather and sampling effort, we combined (1) weekly measurements of temperature and dissolved oxygen (DO) concentrations from seven stations in the Sandusky subbasin of Lake Erie's central basin during 2005, (2) contemporaneous measures of storm activity and tributary discharge, and (3) a two-dimensional coupled hydrodynamic, chemical, and biological model of Lake Erie to investigate (1) how increased storm activity and tributary discharge affected short-(daily) and long-term (seasonal) dynamics of hypolimnetic hypoxia, and (2) how spatial (number of sites sampled) and temporal (sampling frequency) sampling effort affected calculated HOD rates. Our model closely replicated field-observed DO dynamics. When comparing baseline modeled dynamics to those in a second simulation with twice the number of days with high winds, however, we found that with more storm activity (1) periods of entrainment became more frequent, (2) the hypolimnion was warmer, (3) thermal stratification occurred 1 month later, whereas autumnal turnover occurred at least 1 week earlier shortening the duration of stratification by 1-2 months, and (4) HOD rates increased 12%. Further, spatial and temporal sampling intensity also affected calculated HOD rates. Consequently, adequately quantifying actual HOD rates requires sufficient sampling effort and the particular role of weather should be assessed with rigorous field and simulation studies, especially if HOD rates are used to indicate management success.

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Lake Erie Offshore in 1990: Restoration and Resilience in the Central Basin

Cited by 58 publications

References 41 publications

Using carbon isotopes of bulk sedimentary organic matter to reconstruct the history of nutrient loading and eutrophication in Lake Erie

Using carbon isotopes of bulk sedimentary organic matter to reconstruct the history of nutrient loading and eutrophication in Lake Erie

Production, sedimentation, and isotopic composition of organic matter in Lake Ontario

“Dead Zone” dynamics in Lake Erie: the importance of weather and sampling intensity for calculated hypolimnetic oxygen depletion rates

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