Gertrud K Nurnberg

Gertrud K Nurnberg
Freshwater Research | FWR

PhD

About

80
Publications
19,750
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3,797
Citations
Introduction
Gertrud K Nurnberg works at Freshwater Research. Gertrud does research in Ecology and Limnology with special emphasis on sediment-water interactions, including phosphorus release and internal loading in lakes.
Additional affiliations
June 1984 - present
Freshwater Research
Freshwater Research
Position
  • Applied Limnology
September 1979 - June 1980
McGill University
Position
  • Research Assistant
Description
  • Ecology, field and laboratory courses
Education
March 1979 - June 1984
McGill University
Field of study
  • Biology - Limnology

Publications

Publications (80)
Article
Full-text available
Internal loading as phosphorus (P) released from anoxic sediment surfaces often represents the main summer P load to lakes and reservoirs and can have an immense effect on their water quality. Many difficulties in internal load assessment exist, however, including ignoring internal load altogether, ambiguity about the origin of sediment released P...
Article
Full-text available
This study represents the first attempt to estimate internal phosphorus (P) loading over many years in polymictic eutrophic Lake Winnipeg, Manitoba, North America's 7th largest lake. Using long-term data, internal load was quantified by several approaches in Lake Winnipeg's North and South Basins and the connecting Narrows. Internal P loading occur...
Article
We hypothesized that north shore water quality of Lake Erie’s Central Basin is impacted by Central Basin hypoxia and, by extension, related to redox-dependant internal phosphorus (P) loading from the profundal sediments. To evaluate this hypothesis, we first quantified Central Basin hypoxia as hypoxic factor (HF, days in Aug–Sep that a sediment are...
Article
Full-text available
The withdrawal of hypolimnetic water enriched with nutrients and reduced substances has been used as a lake restoration technique (hypolimnetic withdrawal, HW) for more than 60 years. By reducing internal phosphorus loading, HW treats the cause of much of the water-quality deterioration in eutrophic stratified lakes, including cyanobacteria blooms....
Article
Formerly acidified lakes and watersheds can become more productive when recovering from acidity, especially when exposed to anthropogenic disturbance and increased nutrient loading. Occasional toxic cyanobacterial blooms and other signs of eutrophication have been observed for a decade in lakes located in the Sudbury, Ontario, mining area that was...
Article
Full-text available
In northern lakes, which are often stained and productive, the impacts of dissolved organic carbon (DOC) on sediment phosphorus (P) release are largely unexplored. Here we elucidated the factors behind experimentally-derived sediment release rates of P by diffusion (DF) in four Finnish lakes with a range of colour. Next, we extended our analysis to...
Article
Full-text available
Sediment phosphorus (P) recycling is one of the key issues in lake water quality management. We studied sediment P mobility in Võrtsjärv, a large shallow lake in Estonia using both sorption experiments and long-term (1985–2020) monitoring data of the lake. Over the years studied, the lake has undergone a decline in external phosphorus loading (EL),...
Preprint
Full-text available
Coloured lakes are often productive. While their increased productivity can be the consequence of internal recycling of phosphorus (P), the impact of humic substances on these interactions is largely unexplored. Here we elucidated the spatial variations in sediment P release by diffusion in four Finnish lakes with high trophic state. For further in...
Article
In large and shallow lakes, the role of the redox-related release of phosphorus (P) from sediments has remained in the shadow of sediment resuspension. In the current study, we concentrated on this knowledge gap regarding factors controlling lake water quality. We combined long-term monitoring data with the studies on sediment P mobility in August...
Article
Full-text available
Shallow lake sediments may be anoxic despite overlying aerated water. In the current study, we aimed to ascertain the contribution of shallow areas to internal phosphorus (P) loading due to sediment anoxia in stratifying lakes. Moreover, we analyzed relationships of the key water quality variables with internal P loading due to sediment anoxia orig...
Chapter
Full-text available
Introduction The importance of hypoxia to aquatic system functioning and water quality has been noted since the beginnings of limnology [1]. Recent increases in organic and nutrient loading and changes in water flow have increased oxygen deficits in lakes, reservoirs, and rivers [2–4]. Investigations of sediments from 365 lakes world-wide confirmed...
Chapter
Internal phosphorus (P) load as phosphate released from lake-bottom sediments is an important nutrient source that can trigger cyanobacteria blooms. Its quantification can be complicated and is affected by the thermal stratification status of the lake; therefore, modeling is often the approach to incorporate internal load into water quality predict...
Chapter
Observed internal phosphorus (P) load was determined from total P (TP) increases of the euphotic layer for 32 years of two sections of mesotrophic Lake Simcoe, Canada. Modeled internal load was determined from laboratory release rates (RRs) and two measures of the spatial and temporal extent of hypoxia. Hypoxia was determined: (1) from dissolved ox...
Article
Full-text available
Nürnberg GK. 2017. Attempted management of cyanobacteria by Phoslock (lanthanum-modified clay) in Canadian lakes: water quality results and predictions. Lake Reserv Manage. 00:1–8. When internal phosphorus (P) loading from the bottom sediments outweighs external P inputs to lakes, lake water quality and cyanobacteria blooms will not respond to exte...
Article
Full-text available
Urban lakes are important assets to highly populated regions; however, extensive usage and other influences degrade their water quality, which then requires rehabilitation and maintenance. Hyper-eutrophic Swan Lake, Greater Toronto, Canada (5.5 ha, 4.4 m maximum depth) was a gravel pit that became degraded by elevated total phosphorus (TP) concentr...
Article
Full-text available
Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined d...
Article
Full-text available
Hypoxia and cyanobacteria still occur occasionally in large, mesotrophic Lake Simcoe, and total phosphorus (TP) concentration has remained relatively constant despite external nutrient load reduction. This may indicate a potential internal P source. Internal load as redox-dependent P release from bottom sediments is hard to determine in such a rela...
Article
Full-text available
Hypoxia and cyanobacterial blooms were extensive in Lake Simcoe during the 1980s and are still a problem to a lesser degree despite extensive nutrient load reduction from the catchment basin. The continuing signs of productivity indicate a potential internal phosphorus (P) source. Internal P load, as a redox-dependent release from bottom sediments,...
Article
Full-text available
This study evaluated phosphorus (P) and iron (Fe) release from anoxic sediment cores in 3 different water bodies, Lake Winnipeg in Manitoba and Lake Simcoe and Hamilton Harbour in Ontario, and developed empirical models to predict P and Fe release rates as functions of sediment and water chemistry. Maximum P and Fe sediment release rates, which occ...
Article
Full-text available
Des floraisons de cyanobacteries sont repertoriees au lac Nairne (Charlevoix, Quebec) depuis 2001. Ces eclosions sont un symptome de l’eutrophisation du lac qui decoule de l’enrichissement par des nutriments, dont le phosphore. Une etude realisee en 2005 indiquait qu’une partie importante de la charge en phosphore du lac Nairne provenait des sedime...
Article
Full-text available
We quantified internal phosphorus (P) load for 26 years in the polymictic, large (155 km2) and shallow (mean depth 5.5 m) lake Säkylän Pyhäjärvi, which was heavily biomanipulated by fish removal. Internal load was estimated as (1) partially net estimates from in situ P summer increases, (2) net estimates from P budgets (mass balance approach), and...
Article
Full-text available
Cyanobacterial blooms have been recorded in Lake Nairne (Charlevoix, Quebec) since 2001. These blooms are a symptom of the lake's eutrophication caused by nutrient enrichment. In 2005, a study suggested that a significant portion of Lake Nairne's phosphorus loading originates from the lake's bottom sediments. The goal of this study was to estimate...
Article
Full-text available
The availability of hypolimnetic phosphorus was assessed by a short-term bioassay, based on 32P uptake kinetics. In the anoxic hypolimnia of eight lakes and in anoxic model systems (core tubes), at least 80% of soluble reactive phosphorus is biologically available. However, biologically available phosphorus is only a small fraction of soluble react...
Article
Full-text available
The detrimental effect of oxygen depletion on fish is well known. Here a quantitative measure of anoxia is compared with the number of fish species in 52 south-central Ontario lakes. The anoxic factor (AF, days per year or per season) estimates the number of days that a sediment area equal to the lake surface area is overlain by anoxic water. It ca...
Article
Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in botto...
Article
The exchange of phosphorus (P) during the resuspension of sediments into shallow (oxic) waters of deep stratified lakes is regulated by equilibrium dynamics. In this study, we compared the P-sorption characteristics of sediments from 17 shallow and deep littoral sites in an oligo-mesotrophic lake. Zero Equilibrium P Concentration (EPC(0)) ranged fr...
Article
Full-text available
Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in botto...
Article
Full-text available
Hypolimnetic withdrawal is an in-lake restoration technique based on the selective discharge of bottom water to enhance the removal of nutrients and electro-chemically reduced substances that build up when the hypolimnion becomes anoxic. Comparison of water quality variables before and during treatment in about 40 European and 8 North American lake...
Article
Full-text available
When nitrate was low in a hypereutrophic, hardwater reservoir, cyanobacteria proliferated into blooms. Based on this observation an index was developed that relates an easily measurable variable, the period of Low-Nitrate-Days (LND), to the period when nuisance cyanobacteria (blue-greens) proliferate and "bloom". The bloom indicator LND (d·yr -1 )...
Chapter
Hypoxic conditions (dissolved oxygen, DO, concentration below saturation) are widely spread in freshwater and saline environments. Especially in recent years, anthropogenic impacts have led to severe increases in estuarine and coastal anoxia [e.g., Gulf of Mexico and European coast-lines]. Diaz describes 44 marine areas of moderate to severe hypoxi...
Article
Full-text available
We used summer epilimnetic means from a large dataset (369 lakes from North America, Europe, Asia, and New Zealand) to examine whether color or mixing regime significantly influence the log-log relationship between chlorophyll a (Chl a) and total phosphorus (TP) in lakes. We found no significant difference in regression models for clear (color < 10...
Article
Full-text available
Hypoxia and anoxia occur frequently in freshwater systems and have biological and chemical implications. Anoxia can be expressed and quantified as the anoxic factor; hypoxia, for a specific level of oxygen depletion, can be expressed as the hypoxic factor in lakes, reservoirs, and river sections. These methods summarize information of individual di...
Article
Full-text available
[1] A steady state lake phosphorus (P) mass balance model was used to predict the equilibrium P concentration (annual, volume-weighted average) of the lake water from natural and anthropogenic, external and internal P inputs. Internal P load was modeled as the product of sediment release rates and anoxic factors. Both these components were predicte...
Article
Full-text available
To combat hypolimnetic anoxia and sediment phosphorus release in a small, mesotrophic kettle lake on the Oakridge Moraine north of the Metropolitan Toronto, Southern Ontario, oxygenation and aeration was applied to the hypolimnion alternately during the summer of 1998 until mid-November and then to the entire water column until the end of December....
Article
Full-text available
The amount of dissolved oxygen (DO) in lake water has biological and chemical implications. There are no easy ways to quantify exeedences of important thresholds of DO in lakes, except the complete lack of DO, quantified as an annual or seasonal anoxic factor (Nürnberg 1995a, b). Here an analogous concept, the “Hypoxic Factor” (HF) is introduced. A...
Article
Full-text available
The relationships between long-term surface average concentrations of humic acids measured as water colour, dissolved organic carbon (DOC) or Secchi disk transparency and trophic state variables were studied with literature data from more than 600 freshwater lakes. The geometric means of summer surface average nutrient (phosphorus and nitrogen) con...
Article
Full-text available
Phosphorus (P) concentrations in lakes are summarized and reported in different ways. Annual whole lake P (P(ann)), epilimnetic summer P (P(epi)), and mixed water column P during fall turnover after summer stratification (P(fall)) were investigated with data from up to 150 lakes. Differences between P averages are caused by temporal variation in th...
Article
Full-text available
Many lakes experience oxygen depletion in their hypolimnia during summer or winter stratification. This study investigates the remedial actions that are available to combat the harmful effects of hypolimnetic anoxia in three types of Central Ontario lakes with different trophic states. In more eutrophic lakes, e.g., Lake Wilcox, southern Ontario, m...
Article
Full-text available
Idiosyncrasies, erroneous assumptions and gaps are still hampering lake evaluations, despite several decades of defining the trophic state of lakes. I reevaluated nutrient and algal biomass limits that group lakes into oligo-, meso-, eu- and hyper eutrophic lakes at transition concentrations of 10, 30 and 100 μg · L−1 average total phosphorus conce...
Article
Full-text available
The anoxic factor (AF, days per year or per season) can be used to quantify anoxia in stratified lakes. AF is calculated from oxygen profiles measured in the stratified season and lake surface area (A,) as AF represents the number of days that a sediment area, equal to the whole-lake surface area, is overlain by anoxic water. Average AF for 56 cent...
Article
Full-text available
The detrimental effect of oxygen depletion on fish is well known. Here a quantitative measure of anoxia is compared with the number of fish species in 52 south-central Ontario lakes. The anoxic factor (AF, days per year or per season) estimates the number of days that a sediment area equal to the lake surface area is overlain by anoxic water. It ca...
Article
Full-text available
An attempt is made to classify lakes that are especially prone to high internal phosphorus load derived from anoxic sediment surfaces. Morphometric, hydrological and geochemical characteristics of lakes with high internal P load are discussed. For example a lake with a mean depth between 5 and 12 m and an averagc flushing rate is a candidate for in...
Article
Full-text available
Iron mass balances for eight lakes (79 lake-years of data) on the Precambrian Shield were measured including catchment, atmospheric, and internal sources of iron and compared with literature data. In most cases, internal load from anoxic sediment surfaces was important. Net (Rext) and gross (Rtot) Fe retentions were correlated with internal load an...
Article
Full-text available
The trophic status of the Laurentian Great Lakes is greatly influenced by phosphorus (P) derived from anoxic sediment surfaces. Data from the Great Lakes and data from smaller lakes of Eastern North America can be used to demonstrate how such an internal P load influences trophic state. To facilitate predictions for the future of the Great Lakes or...
Article
Full-text available
The date of fall turnover can be predicted from average midsummer hypolimnetic temperature in acidic and non-acidic lakes in central Ontario. The prediction of fall turnover date is improved by inclusion of two further independent variables, mean depth and adjusted latitude (for altitude), in a global data set. The models explain 67-80% of the vari...
Article
Full-text available
Release rates of phosphorus from anoxic sediment surfaces in seven North American lakes were determined from core tube incubations. These rates were compared with several P fractions within the 0-5 and 5-10 cm layers of the corresponding sediment. Regressions of release rates both on total sediment P and on reductant-soluble P were highly significa...
Article
Full-text available
Hypolimnetic withdrawal is a lake restoration technique based on the damming of surface outflow and the discharge of hypolimnetic water. In 17 lakes, hypolimnetic withdrawal has been used for 1-10 yrs. In general, anoxia and total phosphorus (TP) concentrations of epi- and hypolimnetic water decreased after the commencement of withdrawal. The decre...
Article
Full-text available
This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Article
Full-text available
Hypolimnetic withdrawal has been used to decrease eutrophication in two Connecticut lakes. This restoration technique is based on the forced discharge of nutrient-rich bottom waters in lakes with anoxic hypolimnia, while surface outflows are dammed. Internal phosphorus load amounted to 600 mg m−2 summer−1 before withdrawal. Most of this load probab...
Article
Full-text available
Phosphorus release rates from anoxic sediments were determined from laboratory incubations of minimally disturbed sediment cores from 7 lakes. Release rates were multiplied by an 'anoxic factor', based on the area and duration of hypolimnetic anoxia, to estimate internal P load. Despite individual variation, the experimentally derived internal load...
Article
Full-text available
The release of phosphorus from sediments into the anoxic water of oligotrophic Chub Lake, Ontario, determined with three different methods, showed that the average release rate of 2.2 mg∙m−2∙d−1 is much smaller than release rates of more eutrophic lakes (14 mg∙m−2∙d−1). Our hypothesis that anoxic release rates depend on lake trophy was confirmed by...
Article
Full-text available
Cerenkov radiation was used to measure ingestion and release by Brachionus calyciflorus and Daphnia pulex that were fed 32P-labeled Rhodotorula glutinus. A method is described that uses automatic pipet tips as cages, permitting measurement of ingestion rates and isotope loss by individual animals. Estimated gut renewal times were 16 min for B. caly...
Article
Full-text available
Anoxic water from eight lakes containing various amounts of ferrous iron, hydrogen sulfide, calcium and total phosphorus was analysed for soluble reactive phosphorus (SRP). Hydrogen sulfide concentrations higher than 1 mg l−1 and ferrous iron concentration above 0.20 mg l−1 produce interferences in the SRP analysis in many occasions (e.g. 80% under...
Article
Full-text available
Lakes with anoxic hypolimnia (anoxic lakes) have significantly lower values for phosphorus retention than do lakes with aerobic hypolimnia (oxic lakes). This difference may reflect an increased internal phosphorus load from the anoxic hypolimnia. Two models are given to predict internal phosphorus load (L;,,) in such lakes. The first predicts inter...
Article
Includes abstracts in English and French. Thesis (Ph. D.)--McGill University, 1984. Includes bibliographical references.
Article
The availability of phosphorus from the anoxic hypolimnia of lakes to epilimnetic plankton was investigated by experimental studies on eight lakes in Ontario and Quebec. Availability was determined with a short-term bioassay based on the standardized retardation of planktonic uptake of phosphorus tracer in the presence of orthophosphate; availabili...