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• 1. [Article] Oregon Lake Watch, 2014 Annual Report

  The Oregon Lake Watch (OLW) volunteer monitoring program is now in its second year of operation, continuing its focus on early detection of aquatic invasive species (AIS), with a secondary focus on lake ...

  Citation × Citation Citation Abstract Copy Title: Oregon Lake Watch, 2014 Annual Report Author: Jordan, Meredith, Miller, Rich, Strecker, Angela L. Year: 2015 The Oregon Lake Watch (OLW) volunteer monitoring program is now in its second year of operation, continuing its focus on early detection of aquatic invasive species (AIS), with a secondary focus on lake water quality. The aquatic invasive species chosen as Watch List priorities for the OLW are based on the Oregon Department of Agriculture’s Noxious Weed List (Oregon Department of Agriculture Noxious Weed Control Program 2014) as well as professional judgement (more information can be found in Oregon Lake Watch Final Report 2014). This report summarizes the data collected by 15 of 24 OLW volunteers over 2014, across 110 sampling events and 20 Oregon lakes. Data collected by trained volunteers includes sightings of both native and aquatic invasive plants and animals, as well as recordings of lake temperature profiles, and Secchi depth, a measure of clarity. Of the 16 original water bodies surveyed in OLW’s first year (2013), 12 were surveyed again in 2014, and 8 are new waterbodies. Long-term monitoring of these lakes provides valuable information over time, and expanding the number of lakes monitored, especially in the case of monitoring for invasive species, means that more potentially harmful invasions can be stopped sooner. Ideally, the OLW will continue to monitor these current lakes, and expand their volunteer network to cover more waterbodies across Oregon as this program continues to grow. Title: Oregon Lake Watch, 2014 Annual Report Author: Jordan, Meredith, Miller, Rich, Strecker, Angela L. Year: 2015 The Oregon Lake Watch (OLW) volunteer monitoring program is now in its second year of operation, continuing its focus on early detection of aquatic invasive species (AIS), with a secondary focus on lake water quality. The aquatic invasive species chosen as Watch List priorities for the OLW are based on the Oregon Department of Agriculture’s Noxious Weed List (Oregon Department of Agriculture Noxious Weed Control Program 2014) as well as professional judgement (more information can be found in Oregon Lake Watch Final Report 2014). This report summarizes the data collected by 15 of 24 OLW volunteers over 2014, across 110 sampling events and 20 Oregon lakes. Data collected by trained volunteers includes sightings of both native and aquatic invasive plants and animals, as well as recordings of lake temperature profiles, and Secchi depth, a measure of clarity. Of the 16 original water bodies surveyed in OLW’s first year (2013), 12 were surveyed again in 2014, and 8 are new waterbodies. Long-term monitoring of these lakes provides valuable information over time, and expanding the number of lakes monitored, especially in the case of monitoring for invasive species, means that more potentially harmful invasions can be stopped sooner. Ideally, the OLW will continue to monitor these current lakes, and expand their volunteer network to cover more waterbodies across Oregon as this program continues to grow. Close

• 2. [Article] Oregon Lake Watch, 2015 Annual Report

  The Oregon Lake Watch (OLW) volunteer monitoring program completed its third year of operation during 2015 with a focus on early detection of aquatic invasive species (AIS) and water quality status and ...

  Citation × Citation Citation Abstract Copy Title: Oregon Lake Watch, 2015 Annual Report Author: Cimino, Samuel, Miller, Rich, Strecker, Angela L. Year: 2015 The Oregon Lake Watch (OLW) volunteer monitoring program completed its third year of operation during 2015 with a focus on early detection of aquatic invasive species (AIS) and water quality status and trend assessments for the better management of Oregon’s lakes and reservoirs. AIS surveys emphasized the detection of Watch List aquatic plant and species that can have a negative impacts on the beneficial uses of our waterbodies. Water transparency and temperature measurements were used to track the condition of volunteers' lakes. Thirty-one Oregon lakes have been surveyed during the OLW’s three years, 16 of which were surveyed during 2015. Seven lakes have been surveyed all three years and seven more have been surveyed two of the three years. Four Watch List plant and one animal species were found during 2015. Eurasian watermilfoil (Myriophyllum spicatum) was found in three lakes, Brazilian elodea (Egeria densa) and curly leaf pondweed (Potamogeton crispus) were each found in two lakes, and yellow flag iris (Iris pseudacorus) was found in one lake. Asian clams (Corbicula fluminea) were found in one lake. A diverse array of native plants were found along with native signal crayfish (Pacifasticus leniusculus). Water quality ranged from eutrophic to oligotrophic conditions based on water transparency and water temperatures ranged as high as 28°C (82°F). More years of data collection are necessary to track water quality trends. Title: Oregon Lake Watch, 2015 Annual Report Author: Cimino, Samuel, Miller, Rich, Strecker, Angela L. Year: 2015 The Oregon Lake Watch (OLW) volunteer monitoring program completed its third year of operation during 2015 with a focus on early detection of aquatic invasive species (AIS) and water quality status and trend assessments for the better management of Oregon’s lakes and reservoirs. AIS surveys emphasized the detection of Watch List aquatic plant and species that can have a negative impacts on the beneficial uses of our waterbodies. Water transparency and temperature measurements were used to track the condition of volunteers' lakes. Thirty-one Oregon lakes have been surveyed during the OLW’s three years, 16 of which were surveyed during 2015. Seven lakes have been surveyed all three years and seven more have been surveyed two of the three years. Four Watch List plant and one animal species were found during 2015. Eurasian watermilfoil (Myriophyllum spicatum) was found in three lakes, Brazilian elodea (Egeria densa) and curly leaf pondweed (Potamogeton crispus) were each found in two lakes, and yellow flag iris (Iris pseudacorus) was found in one lake. Asian clams (Corbicula fluminea) were found in one lake. A diverse array of native plants were found along with native signal crayfish (Pacifasticus leniusculus). Water quality ranged from eutrophic to oligotrophic conditions based on water transparency and water temperatures ranged as high as 28°C (82°F). More years of data collection are necessary to track water quality trends. Close

• 3. [Article] OSMB Final Report, Task 4: Oregon Lake Watch

  The Oregon Lake Watch (OLW) volunteer monitoring program was resurrected after over a decade in hibernation. The new program was designed to educate the public about threats of aquatic invasive species ...

  Citation × Citation Citation Abstract Copy Title: OSMB Final Report, Task 4: Oregon Lake Watch Author: Strecker, Angela L., Miller, Rich, Morgan, Vanessa Year: 2014 The Oregon Lake Watch (OLW) volunteer monitoring program was resurrected after over a decade in hibernation. The new program was designed to educate the public about threats of aquatic invasive species (AIS), provide early detection of AIS invasions, and provide long term water quality data for the better management of Oregon’s lakes and reservoirs. Protocols were created for citizen scientists to survey for AIS, collect temperature and water clarity data, and record the data through an online data entry portal. An OLW website was developed to educate about AIS and provide survey protocols and identification materials to volunteers. AIS surveys were focused on Watch List Species which are selected AIS that have a negative impact on the beneficial uses of our waterbodies. Eighteen volunteers were trained during five sessions conducted in western and central Oregon. Fourteen of the trained volunteers collected data from sixteen waterbodies. Six Watch List species and one other AIS species were observed in four of the waterbodies. The three Watch List Species observed in Salish Pond and one in Olallie Lake were new observations. Temperature measurements indicated a wide range of thermal profiles and Secchi transparency measurement indicated a range of trophic status from oligotrophic to eutrophic. Title: OSMB Final Report, Task 4: Oregon Lake Watch Author: Strecker, Angela L., Miller, Rich, Morgan, Vanessa Year: 2014 The Oregon Lake Watch (OLW) volunteer monitoring program was resurrected after over a decade in hibernation. The new program was designed to educate the public about threats of aquatic invasive species (AIS), provide early detection of AIS invasions, and provide long term water quality data for the better management of Oregon’s lakes and reservoirs. Protocols were created for citizen scientists to survey for AIS, collect temperature and water clarity data, and record the data through an online data entry portal. An OLW website was developed to educate about AIS and provide survey protocols and identification materials to volunteers. AIS surveys were focused on Watch List Species which are selected AIS that have a negative impact on the beneficial uses of our waterbodies. Eighteen volunteers were trained during five sessions conducted in western and central Oregon. Fourteen of the trained volunteers collected data from sixteen waterbodies. Six Watch List species and one other AIS species were observed in four of the waterbodies. The three Watch List Species observed in Salish Pond and one in Olallie Lake were new observations. Temperature measurements indicated a wide range of thermal profiles and Secchi transparency measurement indicated a range of trophic status from oligotrophic to eutrophic. Close

• 4. [Article] Effects of Water Development on Arid Land Freshwater Ecosystems

  This presentation focuses on the Columbia Basin Project

  Citation × Citation Citation Abstract Copy Title: Effects of Water Development on Arid Land Freshwater Ecosystems Author: Strecker, Angela L. Year: 2013 This presentation focuses on the Columbia Basin Project Title: Effects of Water Development on Arid Land Freshwater Ecosystems Author: Strecker, Angela L. Year: 2013 This presentation focuses on the Columbia Basin Project Close

• 5. [Article] Emerging Contaminants in Oregon Coastal Waters: Hotspots, Landscape Drivers and Synergistic Effects on Bivalves

  This presentation focuses on the following research questions: Types and levels of contaminants of emerging concern (CECs) in Oregon’s coastal ocean? Levels of CECs in native and commercial oysters? ...

  Citation × Citation Citation Abstract Copy Title: Emerging Contaminants in Oregon Coastal Waters: Hotspots, Landscape Drivers and Synergistic Effects on Bivalves Author: Granek, Elise F., Fish, William, Strecker, Angela L. Year: 2013 This presentation focuses on the following research questions: Types and levels of contaminants of emerging concern (CECs) in Oregon’s coastal ocean? Levels of CECs in native and commercial oysters? Ecological effects (growth, reproductive output, etc.) of these contaminants in marine bivalves? Title: Emerging Contaminants in Oregon Coastal Waters: Hotspots, Landscape Drivers and Synergistic Effects on Bivalves Author: Granek, Elise F., Fish, William, Strecker, Angela L. Year: 2013 This presentation focuses on the following research questions: Types and levels of contaminants of emerging concern (CECs) in Oregon’s coastal ocean? Levels of CECs in native and commercial oysters? Ecological effects (growth, reproductive output, etc.) of these contaminants in marine bivalves? Close

• 6. [Article] OSMB Final Report: Task 6. Tenmile Lake Boat Wash Effectiveness Monitoring

  Public awareness of aquatic invasive species and proper boat cleaning procedures may prove to be beneficial in reducing the transport and establishment of aquatic invasive species like New Zealand mud ...

  Citation × Citation Citation Abstract Copy Title: OSMB Final Report: Task 6. Tenmile Lake Boat Wash Effectiveness Monitoring Author: Cimino, Samuel, Strecker, Angela L. Year: 2014 Public awareness of aquatic invasive species and proper boat cleaning procedures may prove to be beneficial in reducing the transport and establishment of aquatic invasive species like New Zealand mud snails and zebra and quagga mussels as well as hydrilla and Eurasian watermilfoil. The primary objectives of this research project were to observe the use and determine the efficacy of a public boat wash station as well as increase the public’s awareness of proper boat cleaning procedures and aquatic invasive species. The Tenmile Lakes Basin Partnership, Oregon State Marine Board, and the United States Forest Service (USFS) have undertaken an initiative to increase public awareness of invasive species and proper cleaning procedures by building a boat wash station at the Tenmile Lake public boat launch. In the summer of 2012, 199 qualitative human subject surveys were administered at Tenmile Lake in Lakeside, Oregon to boaters on their boating habits and knowledge of invasive species prior to building the boat wash (“pre-boat wash”). An extension of the 2012 study was conducted in the summer of 2013 on 200 boaters after the completion of the Tenmile Lake boat wash station (“post-boat wash”). Comparisons were made on the observations and answers of boaters prior to and after the boat wash installation. Of the boaters surveyed in the pre-boat wash field season, 75.9% of boaters claimed they would use a boat wash station at Tenmile Lake. The actual use of the boat wash station based on observations made by the field researcher during the post-boat wash field season indicated only 38.5% of surveyed boaters used the station. Furthermore, more than 20% of boaters could not verbally identify an invasive species in either field season when asked their awareness of aquatic invasive species. However, the majority of boaters surveyed at Tenmile Lake in the pre-boat wash field season (63.3%) and post-boat wash field season (66%) were aware of the phrase “Clean, Drain, Dry”. These results identify a disconnect in what boaters say and what boaters do and the knowledge gaps boaters have on aquatic invasive species, but these results also identify a growing awareness of proper boat cleaning procedures. Title: OSMB Final Report: Task 6. Tenmile Lake Boat Wash Effectiveness Monitoring Author: Cimino, Samuel, Strecker, Angela L. Year: 2014 Public awareness of aquatic invasive species and proper boat cleaning procedures may prove to be beneficial in reducing the transport and establishment of aquatic invasive species like New Zealand mud snails and zebra and quagga mussels as well as hydrilla and Eurasian watermilfoil. The primary objectives of this research project were to observe the use and determine the efficacy of a public boat wash station as well as increase the public’s awareness of proper boat cleaning procedures and aquatic invasive species. The Tenmile Lakes Basin Partnership, Oregon State Marine Board, and the United States Forest Service (USFS) have undertaken an initiative to increase public awareness of invasive species and proper cleaning procedures by building a boat wash station at the Tenmile Lake public boat launch. In the summer of 2012, 199 qualitative human subject surveys were administered at Tenmile Lake in Lakeside, Oregon to boaters on their boating habits and knowledge of invasive species prior to building the boat wash (“pre-boat wash”). An extension of the 2012 study was conducted in the summer of 2013 on 200 boaters after the completion of the Tenmile Lake boat wash station (“post-boat wash”). Comparisons were made on the observations and answers of boaters prior to and after the boat wash installation. Of the boaters surveyed in the pre-boat wash field season, 75.9% of boaters claimed they would use a boat wash station at Tenmile Lake. The actual use of the boat wash station based on observations made by the field researcher during the post-boat wash field season indicated only 38.5% of surveyed boaters used the station. Furthermore, more than 20% of boaters could not verbally identify an invasive species in either field season when asked their awareness of aquatic invasive species. However, the majority of boaters surveyed at Tenmile Lake in the pre-boat wash field season (63.3%) and post-boat wash field season (66%) were aware of the phrase “Clean, Drain, Dry”. These results identify a disconnect in what boaters say and what boaters do and the knowledge gaps boaters have on aquatic invasive species, but these results also identify a growing awareness of proper boat cleaning procedures. Close

• 7. [Article] The Interplay Between Landscape Structure and Biotic Interactions

  Landscape structure and biotic interactions are closely linked. We identify five aspects of landscape structure that contribute to the co-occurrence of species and restrict or enable different types of ...

  Citation × Citation Citation Abstract Copy Title: The Interplay Between Landscape Structure and Biotic Interactions Author: Zarnetske, Phoebe, Baiser, Benjamin, Strecker, Angela L., Record, Sydne, Belmaker, Jonathan, Tuanmu, Mao-Ning Year: 2017 Landscape structure and biotic interactions are closely linked. We identify five aspects of landscape structure that contribute to the co-occurrence of species and restrict or enable different types of biotic interactions: patch size and habitat amount, isolation of patches, barriers to dispersal and movement, persistence of landscape structure, and landscape complexity. In addition, these aspects of landscape structure influence the strength and outcome of biotic interactions. Whereas most research focuses on the effects of the abiotic environment on species and their biotic interactions, research on foundation species and ecosystem engineers demonstrates the important influence of biotic interactions on landscape structure itself, including effects on landscape complexity, extent of habitat, and the structure of landscape features. In this review, we describe ecological theories that lay the foundation for interplay between landscape structure and biotic interactions, and summarize these connections across an array of interacting species in freshwater, marine, and terrestrial systems. We end with suggestions for integrating the fields of landscape ecology and community ecology to better understand the connections between landscape structure and biotic interactions and better predict their dynamics in light of global change. Title: The Interplay Between Landscape Structure and Biotic Interactions Author: Zarnetske, Phoebe, Baiser, Benjamin, Strecker, Angela L., Record, Sydne, Belmaker, Jonathan, Tuanmu, Mao-Ning Year: 2017 Landscape structure and biotic interactions are closely linked. We identify five aspects of landscape structure that contribute to the co-occurrence of species and restrict or enable different types of biotic interactions: patch size and habitat amount, isolation of patches, barriers to dispersal and movement, persistence of landscape structure, and landscape complexity. In addition, these aspects of landscape structure influence the strength and outcome of biotic interactions. Whereas most research focuses on the effects of the abiotic environment on species and their biotic interactions, research on foundation species and ecosystem engineers demonstrates the important influence of biotic interactions on landscape structure itself, including effects on landscape complexity, extent of habitat, and the structure of landscape features. In this review, we describe ecological theories that lay the foundation for interplay between landscape structure and biotic interactions, and summarize these connections across an array of interacting species in freshwater, marine, and terrestrial systems. We end with suggestions for integrating the fields of landscape ecology and community ecology to better understand the connections between landscape structure and biotic interactions and better predict their dynamics in light of global change. Close

• 8. [Article] The Aquarium Trade as an Invasion Pathway in the Pacific Northwest

  The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation ...

  Citation × Citation Citation Abstract Copy Title: The Aquarium Trade as an Invasion Pathway in the Pacific Northwest Author: Strecker, Angela L., Campbell, Philip M., Olden, Julian D. Year: 2011 The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation of the ornamental pet trade as an invasion pathway in the Pacific Northwest region of the United States, where a moderate climate and a large human population present ample opportunities for the introduction and establishment of aquarium trade species. Results from a regional survey of pet stores found that the number of fish (n=400) and plant (n=124) species currently in the aquarium trade is vast. Pet stores import thousands of fish every month, the majority of which (58%) are considered to pose an ecological threat to native ecosystems. Our propagule pressure model suggests that approximately 2,500 fish (maximum 21,000 individuals) are likely released annually to the Puget Sound region by aquarists, and that water temperatures in many parts of Washington are suitable for establishment of populations. In conclusion, the aquarium trade may be a significant source of past and future invasions in the Pacific Northwest, and we recommend enhanced public education programs, greater regulation of the aquarium industry, and improved legislation of nonnative species in the ornamental trade. Title: The Aquarium Trade as an Invasion Pathway in the Pacific Northwest Author: Strecker, Angela L., Campbell, Philip M., Olden, Julian D. Year: 2011 The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation of the ornamental pet trade as an invasion pathway in the Pacific Northwest region of the United States, where a moderate climate and a large human population present ample opportunities for the introduction and establishment of aquarium trade species. Results from a regional survey of pet stores found that the number of fish (n=400) and plant (n=124) species currently in the aquarium trade is vast. Pet stores import thousands of fish every month, the majority of which (58%) are considered to pose an ecological threat to native ecosystems. Our propagule pressure model suggests that approximately 2,500 fish (maximum 21,000 individuals) are likely released annually to the Puget Sound region by aquarists, and that water temperatures in many parts of Washington are suitable for establishment of populations. In conclusion, the aquarium trade may be a significant source of past and future invasions in the Pacific Northwest, and we recommend enhanced public education programs, greater regulation of the aquarium industry, and improved legislation of nonnative species in the ornamental trade. Close

• 9. [Article] Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters

  Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. ...

  Citation × Citation Citation Abstract Copy Title: Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters Author: Strecker, Angela L., Olden, Julian D. Year: 2014 Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. We quantify phylogenetic clustering and overdispersion of native and non-native fishes of a large river basin in the American Southwest to test for the mechanisms (environmental filtering versus competitive exclusion) and spatial scales influencing community structure. Contrary to expectations, non-native species were phylogenetically clustered and related to natural environmental conditions, whereas native species were not phylogenetically structured, likely reflecting human-related changes to the basin. The species that are most invasive (in terms of ecological impacts) tended to be the most phylogenetically divergent from natives across watersheds, but not within watersheds, supporting the hypothesis that Darwin's naturalization conundrum is driven by the spatial scale. Phylogenetic distinctiveness may facilitate non-native establishment at regional scales, but environmental filtering restricts local membership to closely related species with physiological tolerances for current environments. By contrast, native species may have been phylogenetically clustered in historical times, but species loss from contemporary populations by anthropogenic activities has likely shaped the phylogenetic signal. Our study implies that fundamental mechanisms of community assembly have changed, with fundamental consequences for the biogeography of both native and non-native species. Title: Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters Author: Strecker, Angela L., Olden, Julian D. Year: 2014 Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. We quantify phylogenetic clustering and overdispersion of native and non-native fishes of a large river basin in the American Southwest to test for the mechanisms (environmental filtering versus competitive exclusion) and spatial scales influencing community structure. Contrary to expectations, non-native species were phylogenetically clustered and related to natural environmental conditions, whereas native species were not phylogenetically structured, likely reflecting human-related changes to the basin. The species that are most invasive (in terms of ecological impacts) tended to be the most phylogenetically divergent from natives across watersheds, but not within watersheds, supporting the hypothesis that Darwin's naturalization conundrum is driven by the spatial scale. Phylogenetic distinctiveness may facilitate non-native establishment at regional scales, but environmental filtering restricts local membership to closely related species with physiological tolerances for current environments. By contrast, native species may have been phylogenetically clustered in historical times, but species loss from contemporary populations by anthropogenic activities has likely shaped the phylogenetic signal. Our study implies that fundamental mechanisms of community assembly have changed, with fundamental consequences for the biogeography of both native and non-native species. Close

• 10. [Article] Dispersal Limitation and Climate-Related Environmental Gradients Structure Microcrustacean Composition in Freshwater Lakes, Ellesmere Island, Canada

  Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future ...

  Citation × Citation Citation Abstract Copy Title: Dispersal Limitation and Climate-Related Environmental Gradients Structure Microcrustacean Composition in Freshwater Lakes, Ellesmere Island, Canada Author: Strecker, Angela L., Milne, Rebecca, Arnott, Shelley E. Year: 2008 Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra, Tachidius discipes, and Artemeopsis stefanssoni. Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, and conductivity and negatively affected by elevation. In contrast to most findings in temperate systems, we detected a negative relationship between species richness and surface area. Community composition was influenced by DOC, nutrients, and elevation but was also related to spatial variables, suggesting that spatial gradients in environmental conditions and dispersal are important drivers of differences among sites. Arctic ecosystems are expected to change rapidly in the coming years because of climate change and ozone thinning, and we expect that associated changes in DOC, temperature, and nutrients will affect microcrustacean species richness and distribution throughout the landscape. Title: Dispersal Limitation and Climate-Related Environmental Gradients Structure Microcrustacean Composition in Freshwater Lakes, Ellesmere Island, Canada Author: Strecker, Angela L., Milne, Rebecca, Arnott, Shelley E. Year: 2008 Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra, Tachidius discipes, and Artemeopsis stefanssoni. Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, and conductivity and negatively affected by elevation. In contrast to most findings in temperate systems, we detected a negative relationship between species richness and surface area. Community composition was influenced by DOC, nutrients, and elevation but was also related to spatial variables, suggesting that spatial gradients in environmental conditions and dispersal are important drivers of differences among sites. Arctic ecosystems are expected to change rapidly in the coming years because of climate change and ozone thinning, and we expect that associated changes in DOC, temperature, and nutrients will affect microcrustacean species richness and distribution throughout the landscape. Close