Daniel Selbie - Academia.edu (original) (raw)
Papers by Daniel Selbie
Nature Ecology & Evolution
Dataset of physical limnological observations from Quesnel Lake, British Columbia, Canada produce... more Dataset of physical limnological observations from Quesnel Lake, British Columbia, Canada produced during research conducted into the impact of the 4 August 2014 Mount Polley mine tailings dam spill. Included are conductivity-temperature-depth (CTD) profiles from 2006-2017, and mooring timeseries from 2014-2017.
Ecological, landscape, and climatic regulation of sediment geochemistry in
Pacific salmon (Oncorhynchus spp.) production strongly influences the ecosystems, cultures and ec... more Pacific salmon (Oncorhynchus spp.) production strongly influences the ecosystems, cultures and economies of the Northeast Pacific. Historical variability in population sizes is complex, reflecting natural and human drivers. The nature and extent of such 'exogenous' controls on salmon and their nursery ecosystems are poorly understood, a significant impediment to sustainable fisheries management. Novel applications of paleolimnology demonstrate that past sockeye salmon abundances and nursery system ecology can be reconstructed from lake sediments. This thesis focuses on employing these techniques to establish the forcing mechanisms underlying salmon population and ecosystem dynamics, and determine the effects and interactions of fisheries management. I provided the first reconstruction for a southern North American stock, which demonstrated the influences of both conspicuous (e.g. commercial fishery, main-stem damming) and uncertain human impacts (e.g. local damming) on endangered salmon declines. By reconstructing ecological variability at multiple trophic levels, I established that rehabilitative management (e.g. fish stocking) may have permanently altered nursery lake rearing capacity, a change potentially reinforced by recent atmospheric changes. This work highlights significant impediments to ongoing recovery efforts. I extended my analysis of salmon management by exploring the interactive impacts of exotic salmon stocking on a remote northern lake. I demonstrated the utility of long-term data in pre-emptively understanding the complex impacts of stocking by documenting the long-term trajectories in limnological conditions. Integrating modeling, limnological and paleolimnological analyses, I determined that climate change and salmon introductions compound to alter chemical, physical and biological lake variables, ultimately altering ecosystem structure and functioning. iii Finally I reconstructed salmon abundances over the past six millennia, the longest record and the first Canadian example to date, demonstrating salmon production is cyclical and far more variable than observed in the monitoring record. My analyses established that North Pacific salmon production is forced by ocean-atmospheric teleconnections ultimately linked to climatic variability in the tropical Pacific. Further analyses provided the first evidence for a possible solar forcing of Holocene salmon production on both orbital and higher frequency time scales. Cumulatively this research improves our understanding of the processes underlying variability in Pacific salmon and their natal ecosystems, important to ecologically-informed future management. iv Co-Authorship Chapter 2 (Selbie et al. 2007, Transactions of the American Fisheries Society) was coauthored by Bert A. Lewis, Bruce P. Finney and my supervisor John P. Smol. In this multi-proxy paleolimnological study, I was responsible for the collection of all diatom data, all statistical analyses, and drafted all tables and figures. As primary author, I provided all major interpretations, synthesized supplementary information and prepared the manuscript, with input from all co-authors. B.A. Lewis collected all cladoceran zooplankton abundance and size data. B.P. Finney was responsible for core retrieval and the collection of geochronological (210 Pb, 137 Cs, 14 C, tephra), lithological (magnetic susceptibility, % H 2 O), elemental (% N, %C, C/N) and isotopic data (δ 15 N). Geochronologies for Pettit and Yellowbelly lakes were developed by B.P. Finney. The Redfish Lake geochronology was co-developed with B.P. Finney.
bioRxiv, 2021
Management of data-limited populations is a key challenge to the sustainability of fisheries arou... more Management of data-limited populations is a key challenge to the sustainability of fisheries around the world. For example, sockeye salmon (Oncorhynchus nerka) spawn and rear in many remote coastal watersheds of British Columbia (BC), Canada, making population assessment a challenge. Estimating conservation and management targets for these populations is particularly relevant given their importance to First Nations and commercial fisheries. Most sockeye salmon have obligate lake-rearing as juveniles, and total abundance is typically limited by production in rearing lakes. Although methods have been developed to estimate population capacity based on nursery lake photosynthetic rate (PR) and lake area or volume, they have not yet been widely incorporated into stock-recruit analyses. We tested the value of combining lake-based capacity estimates with traditional stock-recruit based approaches to assess population status using a hierarchical-Bayesian stock-recruit model for 70 populatio...
Environmental Monitoring and Assessment, 2020
Anthropogenic atmospheric emission and subsequent deposition of sulfur (S) has been linked to dis... more Anthropogenic atmospheric emission and subsequent deposition of sulfur (S) has been linked to disrupted watershed biogeochemical processes through soil and surface water acidification. We investigated watershedscale impacts of acidic deposition on tributary concentrations and watershed exports of major nutrients and ions for the Kitimat River Watershed, British Columbia. Since the 1950s, the Kitimat watershed had an aluminum smelting facility with substantial emissions at the river estuary. Emissions load the airshed overlying the watershed and potentially impact western tributaries leaving eastern tributaries available as reference. We assessed concentrations and export of key compounds in three reference and six potentially impacted tributaries and watersheds in 2015 and 2016. Sulfate (SO 4), fluoride (F), nitrate (NO 3), and chloride (Cl) were significantly higher in impacted tributaries. F concentrations exceeded the Canadian Council of Ministers of the Environment guideline for aquatic life in 83% of samples collected from impacted streams. Watershed export and associated uncertainty were determined by bootstrapped flow-stratified Beale's unbiased estimator. Impact of emissions on watershed export was modeled in a Bayesian approach to include variance in the export estimate to inform the uncertainty of model parameters. Export of SO 4 and Ca increased significantly within 16 km and 8 km, respectively, toward the smelter emissions. The corresponding impacted area for SO 4 and Ca was approximately 100 km 2 and 45 km 2 , respectively. SO 4 export is likely due to direct impacts of S deposition, with excess S being flushed from the watersheds. Ca export patterns likely result from indirect impacts of S deposition on soil chemistry and flushing of Ca. These impacts may contribute to effects within tributaries on benthic stream communities and regionally important juvenile Pacific salmon.
Canadian Journal of Remote Sensing, 2019
In Canada, many northern lakes are remote and difficult to access, with limited limnological data... more In Canada, many northern lakes are remote and difficult to access, with limited limnological data. Satellite sensors provide widespread coverage and growing time series of data unavailable via conventional sampling, but global validation is still limited. We evaluated chlorophyll estimates from the MERIS (Medium Resolution Imaging Spectrometer) sensor on board the European Space Agency (ESA) ENVISAT satellite for the ultra-oligotrophic Chilko Lake in the coastal mountains of central British Columbia. This lake supports a valuable sockeye salmon (Oncorhynchus nerka) population. We obtained good temporal coverage, through 1,425 scenes between June 18, 2002 and April 6, 2012. Although pre-processing was required to produce a high-quality dataset, one standard ESA algorithm generated chlorophyll estimates similar to field data. Regional and interannual phenological patterns were clear, and differences that may be important determinants of salmon production were well described. Although MERIS ceased operation in April 2012, it was replaced by the OLCI (Ocean and Land Color Instrument) on the SENTINEL 3a and 3b satellites launched in February 2016 and April 2018, respectively. We conclude that, with appropriate quality control and in situ validation, satellite-generated chlorophyll time series in sockeye salmon rearing lakes have significant potential as a fisheries planning and analysis tool. R ESUM E Au Canada, de nombreux lacs nordiques sont eloign ees et difficiles d'acc es, avec des donn ees limnologiques limit ees. Les capteurs satellites fournissent une couverture etendue et une s erie chronologique croissante de donn ees non disponibles via l' echantillonnage conventionnel, mais la validation globale est encore limit ee. Nous avons evalu e les estimations de la chlorophylle a l'aide du capteur MERIS (spectrom etre imageur a r esolution moyenne) a bord du satellite ENVISAT de l'Agence Spatiale Europ eenne pour le lac Chilko, un lac ultraoligotrophe dans les montagnes côti eres du centre de la Colombie-Britannique. Ce lac abrite une population de saumon rouge (Oncorhynchus nerka). Nous avons obtenu une bonne couverture temporelle, soit 1425 sc enes entre le 18 juin 2002 et le 6 avril 2012. Bien qu'un pr etraitement ait et e n ecessaire pour produire un jeu de donn ees de haute qualit e, un algorithme standard de l'ESA a g en er e des estimations de la chlorophylle similaires aux donn ees de terrain. Les sch emas ph enologiques r egionaux et interannuels etaient clairs et les pouvantêtre des d eterminants importants pour la production de saumon etaient bien d ecrites. Bien que MERIS ait cess e ses activit es en avril 2012, il a et e remplac e par les instruments OLCI (Ocean and Land Color Instrument) des satellites SENTINEL 3a et 3 b lanc es respectivement en f evrier 2016 et en avril 2018. En conclusion, avec un contrôle de qualit e appropri e et une validation in situ, les s eries chronologiques de chlorophylle g en er ees par satellite dans les lacs d' elevage de saumon rouge pr esentent un potentiel important en tant qu'outil de planification et d'analyse des pêches.
Canadian Journal of Fisheries and Aquatic Sciences, 2019
The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on f... more The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on freshwater ecosystems. Seton and Anderson lakes (British Columbia, Canada) are sockeye salmon (Oncorhynchus nerka) nursery systems. Since the 1940s, the Bridge River Diversion (BRD) introduced glacially turbid water into Seton Lake. To assess the impact of the BRD on the production of Seton Lake, we combined data from limnological surveys with the analysis of subfossil cladocerans and diatoms from sediment cores, using Anderson Lake as a reference. The modern data indicate that the euphotic zone is 14 m shallower and the cladoceran density and biomass are significantly lower in Seton Lake in comparison with Anderson Lake. The paleo-data indicate that following the BRD, the sedimentary fluxes of cladoceran and diatom declined 2- to 10-fold in Seton Lake and remained low thereafter. Together, our data support declines in primary and secondary producers following the BRD, likely due to chang...
Geophysical Research Letters, 2015
On 4 August 2014, a catastrophic breach of the Mount Polley mine tailings impoundment released~25... more On 4 August 2014, a catastrophic breach of the Mount Polley mine tailings impoundment released~25 M m 3 of tailings and water and scoured an unknown quantity of overburden into the West Basin of Quesnel Lake. We document Quesnel Lake and Quesnel River observations for 2 months postspill. Breach inflows raised Quesnel Lake by 7.7 cm, equivalent to~21 M m 3. The West Basin hypolimnion was modified immediately, exhibiting increased temperature (~5°C to 6-7.5°C), conductivity (110 to 160 μS/cm), and turbidity (<1 to 200-1000 nephelometric turbidity units (NTU)). Cooscillating seiches moved West Basin hypolimnetic water both westward and eastward contaminating the Main Basin. Postspill, high-turbidity water propagated eastward (~1 cm/s), introducing a persistent~20 m thick layer below the thermocline and añ 30 m thick layer at the bottom. The contaminant introduction, mobilization, and bioaccumulation may pose risks to resident and anadromous fish stocks, which support recreational, commercial, and First Nations fisheries.
2014 IEEE Geoscience and Remote Sensing Symposium, 2014
Chilko Lake sockeye constitute one of the largest salmon stocks in the Pacific Northwest, for whi... more Chilko Lake sockeye constitute one of the largest salmon stocks in the Pacific Northwest, for which Fisheries and Oceans Canada has maintained a 55-year record, including partitioned freshwater and marine survival. The lake was also the site of fertilization experiments in the 1970s-1990s. This paper examined the use of spaceborne data from MERIS and LANDSAT collected over the Chilko Lake watershed for the purpose of generating long time series of lake chlorophyll and water temperature, testing and validating standard chlorophyll algorithms against in situ measurements, comparing Sockeye survival with lake variables, and assessing the state of glaciers in the watershed.
Journal of Paleolimnology, 2014
Pronounced climate warming during the past century has been well documented in highlatitude regio... more Pronounced climate warming during the past century has been well documented in highlatitude regions. Nonetheless, considerable heterogeneity exists in northern climate trends. We examined the roles of cryospheric landscape and lake depth in modulating the rate and magnitude of local climate responses through a paleolimnological study of lakes from southwest Yukon, Canada. By sampling lakes at varying distances from the Wrangell-St. Elias ice fields, we hypothesized that, for lakes of similar maximum depth, sites closest to the ice fields would be relatively complacent in terms of their chironomid and diatom assemblage changes over the past *200 years. This hypothesis is based on the moderating effect of the glaciers on local climate, which would be most pronounced in the lakes nearest to the ice fields. However, given the known ecological differences between deep and shallow lakes, we further predicted that, for a given distance from the ice fields, a sediment record from a shallower lake would show the greatest change in stratigraphic subfossil assemblages. Because of the complicated shape of the ice fields, we applied the longitude for each site (which decreases from west to east) to approximate the proximity of our study lakes to the ice fields. Consistent with our predictions, we observed a
Canadian Journal of Fisheries and Aquatic Sciences, 2011
We integrated limnological, paleolimnological, and fisheries analyses in Tuya Lake, British Colum... more We integrated limnological, paleolimnological, and fisheries analyses in Tuya Lake, British Columbia, Canada, to explore the effects and interactions of climate warming and sockeye salmon introductions on northern lake ecology. We tracked millennially unprecedented, climate-correlated changes in inferred lake production, stratification, and trophic structure since the mid-1800s, most likely resulting from declining ice cover and enhanced stratification. Post-1970s algal (diatom) species turnover, coeval across several remote northern Cordilleran lakes, marked an apparent increase in warming and the induction of inferred nitrogen deficiencies in Tuya Lake. Lower post-stocking phosphorus (P) and nitrogen (N) concentrations and a strong P-modeled salmon biomass correlation (r2 = 0.87) indicated salmon production reduced epilimnetic nutrient availability. Post-stocking chlorophyll reductions, late-summer algal dominance by heterocystous cyanobacteria and low-N-tolerant diatoms, and a strong chlorophyll-modeled salmon biomass correlation (r2 = 0.87) indicated that salmon influenced lake productivity, most likely by enhancing climate-induced N-deficiencies. Predicted smolt-biomass nutrient exports were minimal, with post-introduction nutrient reductions likely related to planktivory and enhanced sedimentation losses. Our study highlights how climate warming changes northern lake ecosystem structure and functioning, influencing responses to subsequent stresses.
ABSTRACT Southwestern Yukon borders the massive Wrangell-St Elias Ice Fields and serves as an ide... more ABSTRACT Southwestern Yukon borders the massive Wrangell-St Elias Ice Fields and serves as an ideal area for examining the relative influence of global warming forcing and regional cryospheric cooling on local climate dynamics. To understand lake responses to spatial heterogeneity in regional climate, we analyzed subfossil chironomid assemblages from modern (ie,“top”) sediments and ca. 1800 AD (ie,“bottom”) sediments across 18 lakes in SW Yukon. The modern chironomid assemblages showed a high degree of community ...
Pacific salmon Oncorhynchus spp. play a central role in coastal ecosystems that rim the North Pac... more Pacific salmon Oncorhynchus spp. play a central role in coastal ecosystems that rim the North Pacific Ocean. Given the ecological, cultural, and economic importance of Pacific salmon, there is great interest in defining the magnitude and frequency of change in these fish stocks. Fisheries scientists, through analyzing harvest records, have demonstrated pronounced salmon production variability. The causes underlying such marked fluctuations are currently debated. Collating harvest records across a broad geographic range over the past ~80 years, fisheries scientists have advanced a plausible argument that climate-induced oceanographic changes explain a significant fraction of the variation in salmon catch records. However, without data that predate the introduction of large-scale human interventions (e.g., commercial harvesting, dams, hatchery releases), it is difficult to isolate the role of climate in shaping fish stock
Lake and Reservoir Management, 2018
Long-term reconstruction of deep-water oxygen conditions in Osoyoos Lake: implications for Okanag... more Long-term reconstruction of deep-water oxygen conditions in Osoyoos Lake: implications for Okanagan River sockeye salmon. Lake Reserve Manage. 34:392-400. Osoyoos Lake is the primary nursery lake supporting sockeye salmon (Onchorhynchus nerka) originating from the Okanagan River system in south-central British Columbia, Canada. By the early 1960s, Osoyoos Lake had experienced significant cultural eutrophication related to rapid human development of the watershed, increasing total phosphorus concentrations, and frequent algal blooms. Concern exists regarding recent (post-1990s) declines in hypolimnetic oxygen concentrations and the potential degradation of salmon habitat in this multi-basin lake. However, reliable observations are largely unavailable for oxygen conditions prior to the mid-1990s. We reconstructed late-summer volume-weighted hypolimnetic oxygen (VWHO) concentrations in Osoyoos Lake from the late 1800s to 2009 by examining past chironomid (Diptera: Chironomidae) subfossil assemblages from 210 Pb-dated lake sediment cores. Chironomid-inferred VWHO revealed only slight variations since the late 1800s (mean values for the north and south basins are 4.4 and 2.9 mg/L, respectively), with seemingly little response to the cultural eutrophication of the mid-20th century. The chironomid-inferred VWHO trends suggest that the current management target of 5.8 mg/L dissolved oxygen for both basins of Osoyoos Lake may require revision to better reflect reference conditions and natural seasonal anoxia.
Limnology and Oceanography
Journal of Paleolimnology
Nature Ecology & Evolution
Dataset of physical limnological observations from Quesnel Lake, British Columbia, Canada produce... more Dataset of physical limnological observations from Quesnel Lake, British Columbia, Canada produced during research conducted into the impact of the 4 August 2014 Mount Polley mine tailings dam spill. Included are conductivity-temperature-depth (CTD) profiles from 2006-2017, and mooring timeseries from 2014-2017.
Ecological, landscape, and climatic regulation of sediment geochemistry in
Pacific salmon (Oncorhynchus spp.) production strongly influences the ecosystems, cultures and ec... more Pacific salmon (Oncorhynchus spp.) production strongly influences the ecosystems, cultures and economies of the Northeast Pacific. Historical variability in population sizes is complex, reflecting natural and human drivers. The nature and extent of such 'exogenous' controls on salmon and their nursery ecosystems are poorly understood, a significant impediment to sustainable fisheries management. Novel applications of paleolimnology demonstrate that past sockeye salmon abundances and nursery system ecology can be reconstructed from lake sediments. This thesis focuses on employing these techniques to establish the forcing mechanisms underlying salmon population and ecosystem dynamics, and determine the effects and interactions of fisheries management. I provided the first reconstruction for a southern North American stock, which demonstrated the influences of both conspicuous (e.g. commercial fishery, main-stem damming) and uncertain human impacts (e.g. local damming) on endangered salmon declines. By reconstructing ecological variability at multiple trophic levels, I established that rehabilitative management (e.g. fish stocking) may have permanently altered nursery lake rearing capacity, a change potentially reinforced by recent atmospheric changes. This work highlights significant impediments to ongoing recovery efforts. I extended my analysis of salmon management by exploring the interactive impacts of exotic salmon stocking on a remote northern lake. I demonstrated the utility of long-term data in pre-emptively understanding the complex impacts of stocking by documenting the long-term trajectories in limnological conditions. Integrating modeling, limnological and paleolimnological analyses, I determined that climate change and salmon introductions compound to alter chemical, physical and biological lake variables, ultimately altering ecosystem structure and functioning. iii Finally I reconstructed salmon abundances over the past six millennia, the longest record and the first Canadian example to date, demonstrating salmon production is cyclical and far more variable than observed in the monitoring record. My analyses established that North Pacific salmon production is forced by ocean-atmospheric teleconnections ultimately linked to climatic variability in the tropical Pacific. Further analyses provided the first evidence for a possible solar forcing of Holocene salmon production on both orbital and higher frequency time scales. Cumulatively this research improves our understanding of the processes underlying variability in Pacific salmon and their natal ecosystems, important to ecologically-informed future management. iv Co-Authorship Chapter 2 (Selbie et al. 2007, Transactions of the American Fisheries Society) was coauthored by Bert A. Lewis, Bruce P. Finney and my supervisor John P. Smol. In this multi-proxy paleolimnological study, I was responsible for the collection of all diatom data, all statistical analyses, and drafted all tables and figures. As primary author, I provided all major interpretations, synthesized supplementary information and prepared the manuscript, with input from all co-authors. B.A. Lewis collected all cladoceran zooplankton abundance and size data. B.P. Finney was responsible for core retrieval and the collection of geochronological (210 Pb, 137 Cs, 14 C, tephra), lithological (magnetic susceptibility, % H 2 O), elemental (% N, %C, C/N) and isotopic data (δ 15 N). Geochronologies for Pettit and Yellowbelly lakes were developed by B.P. Finney. The Redfish Lake geochronology was co-developed with B.P. Finney.
bioRxiv, 2021
Management of data-limited populations is a key challenge to the sustainability of fisheries arou... more Management of data-limited populations is a key challenge to the sustainability of fisheries around the world. For example, sockeye salmon (Oncorhynchus nerka) spawn and rear in many remote coastal watersheds of British Columbia (BC), Canada, making population assessment a challenge. Estimating conservation and management targets for these populations is particularly relevant given their importance to First Nations and commercial fisheries. Most sockeye salmon have obligate lake-rearing as juveniles, and total abundance is typically limited by production in rearing lakes. Although methods have been developed to estimate population capacity based on nursery lake photosynthetic rate (PR) and lake area or volume, they have not yet been widely incorporated into stock-recruit analyses. We tested the value of combining lake-based capacity estimates with traditional stock-recruit based approaches to assess population status using a hierarchical-Bayesian stock-recruit model for 70 populatio...
Environmental Monitoring and Assessment, 2020
Anthropogenic atmospheric emission and subsequent deposition of sulfur (S) has been linked to dis... more Anthropogenic atmospheric emission and subsequent deposition of sulfur (S) has been linked to disrupted watershed biogeochemical processes through soil and surface water acidification. We investigated watershedscale impacts of acidic deposition on tributary concentrations and watershed exports of major nutrients and ions for the Kitimat River Watershed, British Columbia. Since the 1950s, the Kitimat watershed had an aluminum smelting facility with substantial emissions at the river estuary. Emissions load the airshed overlying the watershed and potentially impact western tributaries leaving eastern tributaries available as reference. We assessed concentrations and export of key compounds in three reference and six potentially impacted tributaries and watersheds in 2015 and 2016. Sulfate (SO 4), fluoride (F), nitrate (NO 3), and chloride (Cl) were significantly higher in impacted tributaries. F concentrations exceeded the Canadian Council of Ministers of the Environment guideline for aquatic life in 83% of samples collected from impacted streams. Watershed export and associated uncertainty were determined by bootstrapped flow-stratified Beale's unbiased estimator. Impact of emissions on watershed export was modeled in a Bayesian approach to include variance in the export estimate to inform the uncertainty of model parameters. Export of SO 4 and Ca increased significantly within 16 km and 8 km, respectively, toward the smelter emissions. The corresponding impacted area for SO 4 and Ca was approximately 100 km 2 and 45 km 2 , respectively. SO 4 export is likely due to direct impacts of S deposition, with excess S being flushed from the watersheds. Ca export patterns likely result from indirect impacts of S deposition on soil chemistry and flushing of Ca. These impacts may contribute to effects within tributaries on benthic stream communities and regionally important juvenile Pacific salmon.
Canadian Journal of Remote Sensing, 2019
In Canada, many northern lakes are remote and difficult to access, with limited limnological data... more In Canada, many northern lakes are remote and difficult to access, with limited limnological data. Satellite sensors provide widespread coverage and growing time series of data unavailable via conventional sampling, but global validation is still limited. We evaluated chlorophyll estimates from the MERIS (Medium Resolution Imaging Spectrometer) sensor on board the European Space Agency (ESA) ENVISAT satellite for the ultra-oligotrophic Chilko Lake in the coastal mountains of central British Columbia. This lake supports a valuable sockeye salmon (Oncorhynchus nerka) population. We obtained good temporal coverage, through 1,425 scenes between June 18, 2002 and April 6, 2012. Although pre-processing was required to produce a high-quality dataset, one standard ESA algorithm generated chlorophyll estimates similar to field data. Regional and interannual phenological patterns were clear, and differences that may be important determinants of salmon production were well described. Although MERIS ceased operation in April 2012, it was replaced by the OLCI (Ocean and Land Color Instrument) on the SENTINEL 3a and 3b satellites launched in February 2016 and April 2018, respectively. We conclude that, with appropriate quality control and in situ validation, satellite-generated chlorophyll time series in sockeye salmon rearing lakes have significant potential as a fisheries planning and analysis tool. R ESUM E Au Canada, de nombreux lacs nordiques sont eloign ees et difficiles d'acc es, avec des donn ees limnologiques limit ees. Les capteurs satellites fournissent une couverture etendue et une s erie chronologique croissante de donn ees non disponibles via l' echantillonnage conventionnel, mais la validation globale est encore limit ee. Nous avons evalu e les estimations de la chlorophylle a l'aide du capteur MERIS (spectrom etre imageur a r esolution moyenne) a bord du satellite ENVISAT de l'Agence Spatiale Europ eenne pour le lac Chilko, un lac ultraoligotrophe dans les montagnes côti eres du centre de la Colombie-Britannique. Ce lac abrite une population de saumon rouge (Oncorhynchus nerka). Nous avons obtenu une bonne couverture temporelle, soit 1425 sc enes entre le 18 juin 2002 et le 6 avril 2012. Bien qu'un pr etraitement ait et e n ecessaire pour produire un jeu de donn ees de haute qualit e, un algorithme standard de l'ESA a g en er e des estimations de la chlorophylle similaires aux donn ees de terrain. Les sch emas ph enologiques r egionaux et interannuels etaient clairs et les pouvantêtre des d eterminants importants pour la production de saumon etaient bien d ecrites. Bien que MERIS ait cess e ses activit es en avril 2012, il a et e remplac e par les instruments OLCI (Ocean and Land Color Instrument) des satellites SENTINEL 3a et 3 b lanc es respectivement en f evrier 2016 et en avril 2018. En conclusion, avec un contrôle de qualit e appropri e et une validation in situ, les s eries chronologiques de chlorophylle g en er ees par satellite dans les lacs d' elevage de saumon rouge pr esentent un potentiel important en tant qu'outil de planification et d'analyse des pêches.
Canadian Journal of Fisheries and Aquatic Sciences, 2019
The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on f... more The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on freshwater ecosystems. Seton and Anderson lakes (British Columbia, Canada) are sockeye salmon (Oncorhynchus nerka) nursery systems. Since the 1940s, the Bridge River Diversion (BRD) introduced glacially turbid water into Seton Lake. To assess the impact of the BRD on the production of Seton Lake, we combined data from limnological surveys with the analysis of subfossil cladocerans and diatoms from sediment cores, using Anderson Lake as a reference. The modern data indicate that the euphotic zone is 14 m shallower and the cladoceran density and biomass are significantly lower in Seton Lake in comparison with Anderson Lake. The paleo-data indicate that following the BRD, the sedimentary fluxes of cladoceran and diatom declined 2- to 10-fold in Seton Lake and remained low thereafter. Together, our data support declines in primary and secondary producers following the BRD, likely due to chang...
Geophysical Research Letters, 2015
On 4 August 2014, a catastrophic breach of the Mount Polley mine tailings impoundment released~25... more On 4 August 2014, a catastrophic breach of the Mount Polley mine tailings impoundment released~25 M m 3 of tailings and water and scoured an unknown quantity of overburden into the West Basin of Quesnel Lake. We document Quesnel Lake and Quesnel River observations for 2 months postspill. Breach inflows raised Quesnel Lake by 7.7 cm, equivalent to~21 M m 3. The West Basin hypolimnion was modified immediately, exhibiting increased temperature (~5°C to 6-7.5°C), conductivity (110 to 160 μS/cm), and turbidity (<1 to 200-1000 nephelometric turbidity units (NTU)). Cooscillating seiches moved West Basin hypolimnetic water both westward and eastward contaminating the Main Basin. Postspill, high-turbidity water propagated eastward (~1 cm/s), introducing a persistent~20 m thick layer below the thermocline and añ 30 m thick layer at the bottom. The contaminant introduction, mobilization, and bioaccumulation may pose risks to resident and anadromous fish stocks, which support recreational, commercial, and First Nations fisheries.
2014 IEEE Geoscience and Remote Sensing Symposium, 2014
Chilko Lake sockeye constitute one of the largest salmon stocks in the Pacific Northwest, for whi... more Chilko Lake sockeye constitute one of the largest salmon stocks in the Pacific Northwest, for which Fisheries and Oceans Canada has maintained a 55-year record, including partitioned freshwater and marine survival. The lake was also the site of fertilization experiments in the 1970s-1990s. This paper examined the use of spaceborne data from MERIS and LANDSAT collected over the Chilko Lake watershed for the purpose of generating long time series of lake chlorophyll and water temperature, testing and validating standard chlorophyll algorithms against in situ measurements, comparing Sockeye survival with lake variables, and assessing the state of glaciers in the watershed.
Journal of Paleolimnology, 2014
Pronounced climate warming during the past century has been well documented in highlatitude regio... more Pronounced climate warming during the past century has been well documented in highlatitude regions. Nonetheless, considerable heterogeneity exists in northern climate trends. We examined the roles of cryospheric landscape and lake depth in modulating the rate and magnitude of local climate responses through a paleolimnological study of lakes from southwest Yukon, Canada. By sampling lakes at varying distances from the Wrangell-St. Elias ice fields, we hypothesized that, for lakes of similar maximum depth, sites closest to the ice fields would be relatively complacent in terms of their chironomid and diatom assemblage changes over the past *200 years. This hypothesis is based on the moderating effect of the glaciers on local climate, which would be most pronounced in the lakes nearest to the ice fields. However, given the known ecological differences between deep and shallow lakes, we further predicted that, for a given distance from the ice fields, a sediment record from a shallower lake would show the greatest change in stratigraphic subfossil assemblages. Because of the complicated shape of the ice fields, we applied the longitude for each site (which decreases from west to east) to approximate the proximity of our study lakes to the ice fields. Consistent with our predictions, we observed a
Canadian Journal of Fisheries and Aquatic Sciences, 2011
We integrated limnological, paleolimnological, and fisheries analyses in Tuya Lake, British Colum... more We integrated limnological, paleolimnological, and fisheries analyses in Tuya Lake, British Columbia, Canada, to explore the effects and interactions of climate warming and sockeye salmon introductions on northern lake ecology. We tracked millennially unprecedented, climate-correlated changes in inferred lake production, stratification, and trophic structure since the mid-1800s, most likely resulting from declining ice cover and enhanced stratification. Post-1970s algal (diatom) species turnover, coeval across several remote northern Cordilleran lakes, marked an apparent increase in warming and the induction of inferred nitrogen deficiencies in Tuya Lake. Lower post-stocking phosphorus (P) and nitrogen (N) concentrations and a strong P-modeled salmon biomass correlation (r2 = 0.87) indicated salmon production reduced epilimnetic nutrient availability. Post-stocking chlorophyll reductions, late-summer algal dominance by heterocystous cyanobacteria and low-N-tolerant diatoms, and a strong chlorophyll-modeled salmon biomass correlation (r2 = 0.87) indicated that salmon influenced lake productivity, most likely by enhancing climate-induced N-deficiencies. Predicted smolt-biomass nutrient exports were minimal, with post-introduction nutrient reductions likely related to planktivory and enhanced sedimentation losses. Our study highlights how climate warming changes northern lake ecosystem structure and functioning, influencing responses to subsequent stresses.
ABSTRACT Southwestern Yukon borders the massive Wrangell-St Elias Ice Fields and serves as an ide... more ABSTRACT Southwestern Yukon borders the massive Wrangell-St Elias Ice Fields and serves as an ideal area for examining the relative influence of global warming forcing and regional cryospheric cooling on local climate dynamics. To understand lake responses to spatial heterogeneity in regional climate, we analyzed subfossil chironomid assemblages from modern (ie,“top”) sediments and ca. 1800 AD (ie,“bottom”) sediments across 18 lakes in SW Yukon. The modern chironomid assemblages showed a high degree of community ...
Pacific salmon Oncorhynchus spp. play a central role in coastal ecosystems that rim the North Pac... more Pacific salmon Oncorhynchus spp. play a central role in coastal ecosystems that rim the North Pacific Ocean. Given the ecological, cultural, and economic importance of Pacific salmon, there is great interest in defining the magnitude and frequency of change in these fish stocks. Fisheries scientists, through analyzing harvest records, have demonstrated pronounced salmon production variability. The causes underlying such marked fluctuations are currently debated. Collating harvest records across a broad geographic range over the past ~80 years, fisheries scientists have advanced a plausible argument that climate-induced oceanographic changes explain a significant fraction of the variation in salmon catch records. However, without data that predate the introduction of large-scale human interventions (e.g., commercial harvesting, dams, hatchery releases), it is difficult to isolate the role of climate in shaping fish stock
Lake and Reservoir Management, 2018
Long-term reconstruction of deep-water oxygen conditions in Osoyoos Lake: implications for Okanag... more Long-term reconstruction of deep-water oxygen conditions in Osoyoos Lake: implications for Okanagan River sockeye salmon. Lake Reserve Manage. 34:392-400. Osoyoos Lake is the primary nursery lake supporting sockeye salmon (Onchorhynchus nerka) originating from the Okanagan River system in south-central British Columbia, Canada. By the early 1960s, Osoyoos Lake had experienced significant cultural eutrophication related to rapid human development of the watershed, increasing total phosphorus concentrations, and frequent algal blooms. Concern exists regarding recent (post-1990s) declines in hypolimnetic oxygen concentrations and the potential degradation of salmon habitat in this multi-basin lake. However, reliable observations are largely unavailable for oxygen conditions prior to the mid-1990s. We reconstructed late-summer volume-weighted hypolimnetic oxygen (VWHO) concentrations in Osoyoos Lake from the late 1800s to 2009 by examining past chironomid (Diptera: Chironomidae) subfossil assemblages from 210 Pb-dated lake sediment cores. Chironomid-inferred VWHO revealed only slight variations since the late 1800s (mean values for the north and south basins are 4.4 and 2.9 mg/L, respectively), with seemingly little response to the cultural eutrophication of the mid-20th century. The chironomid-inferred VWHO trends suggest that the current management target of 5.8 mg/L dissolved oxygen for both basins of Osoyoos Lake may require revision to better reflect reference conditions and natural seasonal anoxia.
Limnology and Oceanography
Journal of Paleolimnology