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Lam WY, Mackereth RW, Mitchell CPJ. Mercury concentrations and export from small central Canadian boreal forest catchments before, during, and after forest harvest. Sci Total Environ 2024; 912:168691. [PMID: 37996028 DOI: 10.1016/j.scitotenv.2023.168691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 11/15/2023] [Accepted: 11/16/2023] [Indexed: 11/25/2023]
Abstract
Northern boreal forests are a strong sink for mercury (Hg), a global contaminant of significant concern to wildlife and human health. Mercury stored in forest soils can be mobilized via runoff and erosion, and under suitable conditions can be methylated to its much more bioaccumulative form, methylmercury. Forest harvesting can affect the mobilization and methylation of Hg, though the direction and magnitude of the impact is unclear or conflicting across previous studies. This study examined 5 harvested and 2 reference watersheds in northwestern Ontario, Canada, before, during, and after harvest to quantify changes in stream total and methylmercury concentration and loads and identified potential landscape and management factors that contribute to differences in stream response. In watersheds where streams were buffered by natural vegetation (≥30 m), no significant changes in total Hg or methylmercury concentrations or loads were observed. Significant increases in methylmercury concentrations and loads were observed downstream of a stream crossing in a watershed where the relatively small stream was unmapped and therefore only buffered by a 3 m machine exclusion zone. These results show that when current best management practices that minimize soil and water disturbance are followed, harvest can have a minimal impact on total and methylmercury loads, even in extensively harvested watersheds. However, there is a need for improved mapping of small streams to ensure best management practices are applied adequately across the landscape.
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Affiliation(s)
- W Y Lam
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - R W Mackereth
- Centre for Northern Forest Ecosystem Research, Ontario Ministry of Natural Resources and Forestry, Thunder Bay, ON, Canada
| | - C P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
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Huang H, Mackereth RW, Mitchell CPJ. Impacts of forest harvesting on mercury concentrations and methylmercury production in boreal forest soils and stream sediment. Environ Pollut 2024; 341:122966. [PMID: 37981183 DOI: 10.1016/j.envpol.2023.122966] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/21/2023]
Abstract
Methylmercury (MeHg) is the most neurotoxic and bioaccumulative form of mercury (Hg) present in the terrestrial and aquatic food sources of boreal ecosystems, posing potential risks to wildlife and human health. Harvesting impacts on Hg methylation and MeHg concentrations in forest soils and stream sediment are not fully understood. In this study, a field investigation was carried out in 4 harvested and 2 unharvested boreal forest watersheds, before and after harvest, to better understand impacts on Hg methylation and MeHg concentration in soils and stream sediment, including their responses to different forest management practices. Changes in total Hg (THg) and MeHg concentrations, first-order potential rate constants for Hg methylation and MeHg demethylation (Kmeth and Kdemeth) as well as total carbon content and carbon-to-nitrogen ratio post-harvest in upland, wetland and riparian soils and stream sediment were assessed and compared. Increases in MeHg production were minimal in upland, wetland or riparian soils after harvest. Sediment in streams with minor buffer protection (∼3 m), greater fractions (>75%) of harvested watershed area and more road construction had significantly increased THg and MeHg concentrations, %-MeHg, Kmeth and total carbon content post-harvest. From these patterns, we infer that inputs of carbon and inorganic Hg into harvest-impacted stream sediment are likely sourced from the harvested upland areas and stimulate in situ MeHg production in stream sediment. These findings indicate the importance of stream sediment as potential MeHg pools in harvested forest watersheds. The findings also demonstrate that forest management practices aiming to mitigate organic matter and Hg inputs to streams can effectively alleviate harvesting impacts on Hg methylation and MeHg concentrations in stream sediment.
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Affiliation(s)
- Haiyong Huang
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Robert W Mackereth
- Centre for Northern Forest Ecosystem Research, Ontario Ministry of Natural Resources and Forestry, Thunder Bay, ON, Canada
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
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Harrow-Lyle TJ, Lam WY, Emilson EJS, Mackereth RW, Mitchell CPJ, Melles SJ. Watershed characteristics and chemical properties govern methyl mercury concentrations within headwater streams of boreal forests in Ontario, Canada. J Environ Manage 2023; 345:118526. [PMID: 37418824 DOI: 10.1016/j.jenvman.2023.118526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 06/21/2023] [Accepted: 06/25/2023] [Indexed: 07/09/2023]
Abstract
Methyl mercury (MeHg) concentrations in boreal headwater streams are influenced by complex natural processes and disturbances such as forestry management. Understanding drivers of MeHg within boreal streams in Ontario, Canada, is of particular interest as there are legacy MeHg concerns. However, models accounting for the complexity of underlying processes have not yet been developed. We assessed how catchment characteristics and stream water chemistry influence MeHg concentrations within 19 watersheds of the Dryden - Wabigoon Forest in Ontario, Canada, using a structural equation modelling (SEM) approach. Despite the study area encompassing a large variation of boreal forest watersheds in the Canadian Shield, our SEM had substantial explanatory power across the region (χ251 = 45.37, p-value = 0.70, R2 = 0.75). Nitrate concentrations (p-value <0.001), water temperature (p-value = 0.002), and the latent watershed characteristic (p-value <0.001) had a positive influence on MeHg concentrations once variable interactions were accounted. Due to the inherent strengths of applying an SEM approach, we describe two plausible pathways driving MeHg concentrations: 1) indirect effect of forest-derived nutrients increases in-situ MeHg production in Dryden - Wabigoon Forest streams, and 2) direct supply of MeHg from inundated soils following consistent precipitation and inundation events (i.e., fill, sit, and spill).
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Affiliation(s)
- Tyler J Harrow-Lyle
- Department of Chemistry and Biology, Toronto Metropolitan University, 43 Gerrard St, Toronto, Ontario, M5B 2K, Canada.
| | - Wai Ying Lam
- University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada.
| | - Erik J S Emilson
- Natural Resources Canada, Canadian Forest Service, 1219 Queen Street E., Sault Ste. Marie, Ontario, P6A 2E5, Canada.
| | - Robert W Mackereth
- Ministry Natural Resources and Forestry, 421 James St., Thunder Bay, Ontario, P7E 2V6, Canada.
| | - Carl P J Mitchell
- University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada.
| | - Stephanie J Melles
- Department of Chemistry and Biology, Toronto Metropolitan University, 43 Gerrard St, Toronto, Ontario, M5B 2K, Canada.
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Rempel RS, Carlson M, Rodgers AR, Shuter JL, Farrell CE, Cairns D, Stelfox B, Hunt LM, Mackereth RW, Jackson JM. Modeling Cumulative Effects of Climate and Development on Moose, Wolf, and Caribou Populations. J Wildl Manage 2021. [DOI: 10.1002/jwmg.22094] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Robert S. Rempel
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
| | - Matthew Carlson
- Alces Landscape and Land‐Use 4290 Wheatley Rd, Duncan, British Columbia V9L 6H1 Canada
| | - Arthur R. Rodgers
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
| | - Jennifer L. Shuter
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
| | - Claire E. Farrell
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
| | - Devin Cairns
- Alces Landscape and Land‐Use 7218 Kirk Ave Summerland British Columbia V0H 1Z9 Canada
| | - Brad Stelfox
- Alces Landscape and Land‐Use Unit 1208, 1234‐5th Avenue NW Calgary Alberta T2N 0R9 Canada
| | - Len M. Hunt
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
| | - Robert W. Mackereth
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
| | - Janet M. Jackson
- Ontario Ministry of Natural Resources and Forestry 103‐421 James Street South, Thunder Bay Ontario P7E 2V6 Canada
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Thomas SM, Melles SJ, Mackereth RW, Tunney TD, Chu C, Oswald CJ, Bhavsar SP, Johnston TA. Climate and landscape conditions indirectly affect fish mercury levels by altering lake water chemistry and fish size. Environ Res 2020; 188:109750. [PMID: 32526497 DOI: 10.1016/j.envres.2020.109750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 05/15/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
Mercury pollution is a global environmental problem that threatens ecosystems, and negatively impacts human health and well-being. Mercury accumulation in fish within freshwater lakes is a complex process that appears to be driven by factors such as individual fish biology and water chemistry at the lake-scale, whereas, climate, and land-use/land-cover conditions within lake catchments can be influential at relatively larger scales. Nevertheless, unravelling the intricate network of pathways that govern how lake-scale and large-scale factors interact to affect mercury levels in fish remains an important scientific challenge. Using structural equation models (SEMs) and multiple long-term databases we identified direct and indirect effects of lake-scale and larger-scale factors on mercury levels in Walleye and Northern Pike - two species that are valued in inland fisheries. At the lake-level, the most parsimonious path models contained direct effects of fish weight, DOC, and pH, as well as an indirect effect of DOC on fish mercury levels via fish weight. Interestingly, lakeshed-, climate-, and full-path models that combine the effects of both lakeshed and climate revealed indirect effects of surrounding landscape conditions and latitude via DOC, pH, and fish weight but no direct effects on fish mercury levels. These results are generally consistent across species and lakes, except for some differences between stratified and non-stratified lakes. Our findings imply that understanding climate and land-use driven alterations of water chemistry and fish biology will be critical to predicting and mitigating fish mercury bioaccumulation in the future.
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Affiliation(s)
- Shyam M Thomas
- Department of Chemistry & Biology, Ryerson University, Toronto, ON M5B 2K3, Canada.
| | - Stephanie J Melles
- Department of Chemistry & Biology, Ryerson University, Toronto, ON M5B 2K3, Canada
| | - Robert W Mackereth
- Ontario Ministry of Natural Resources & Forestry, Centre for Northern Forest Ecosystem Research, Thunder Bay, ON P7E 2V6, Canada
| | - Tyler D Tunney
- Fisheries and Oceans Canada, Freshwater Habitat Section, Gulf Fisheries Centre, Moncton, NB E1C 9B6, Canada
| | - Cindy Chu
- Ontario Ministry of Natural Resources & Forestry, Aquatic Research and Monitoring Section, Peterborough, ON K9L 0G2, Canada
| | - Claire J Oswald
- Department of Geography and Environmental Studies, Ryerson University, Toronto, ON M5B 2K3, Canada
| | - Satyendra P Bhavsar
- Environmental Monitoring and Reporting Branch, Ontario Ministry of the Environment, Conservation and Parks, Toronto, ON M9P 3V6, Canada
| | - Thomas A Johnston
- Ontario Ministry of Natural Resources and Forestry, Cooperative Freshwater Ecology Unit, Vale Living with Lakes Centre, Laurentian University, Sudbury, ON P3E 2C6, Canada
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Mackereth RW, Keenleyside MHA. Breeding territoriality and pair formation in the convict cichlid (Cichlasoma nigrofasciatum; Pisces, Cichlidae). CAN J ZOOL 1993. [DOI: 10.1139/z93-126] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In many biparental species a sex difference in parental investment in a brood before fertilization, such as establishing a breeding territory or preparing a nest, may be an important component of the overall pattern of parental investment. Prefertilization investment patterns have been described for several species of biparental cichlid fishes, but there are discrepancies in the descriptions for the convict cichlid, Cichlasoma nigrofasciatum. This study describes quantitatively the prespawning behaviour of male and female convict cichlids and examines the influence on their behaviour of limiting the number of available spawning sites. The results indicate that pair formation begins several days before spawning when the female begins to follow a male and chase other females away from him. The pair then begins to spend more time in a smaller area where spawning eventually occurs. The breeding territory is usually established by the pair on the day of spawning. There was little difference in the pattern of prespawning behaviour offish with abundant versus limited spawning sites. It appears that neither sex will establish a territory until the female is ready to spawn and the pair has formed.
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Lavery RJ, Mackereth RW, Robilliard DR, Keenleyside MH. Factors determining parental preference of convict cichlid fry, Cichlasoma nigrofasciatum (Pisces: Cichlidae). Anim Behav 1990. [DOI: 10.1016/s0003-3472(05)80424-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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