Victoria Glenn Christensen, PhD
Victoria is a Research Hydrologist assigned to the Upper Midwest Water Science Center and the Assistant Program Coordinator for Outreach for the Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology). She also serves as the acting Communications Coordinator for the Water Mission Area.
Biography
Victoria Christensen studies cyanotoxins, with a focus on the neurotoxins, anatoxin-a and saxitoxin. Cyanotoxins are produced by cyanobacterial harmful alglal blooms, which are sometimes called blue-green algae. Victoria received a B.A. from Hamline University, B.S. and M.S. degrees from the University of Kansas, and her PhD from North Dakota State University. Her master’s research examined the occurrence and fate of dissolved solids, nutrients, atrazine, and bacteria in an agricultural watershed. Her dissertation research focused on cyanotoxin mixtures with an emphasis neurotoxins—looking at the environmental variables like wind and temperature that may trigger cyanobacteria to produce or release toxins. In addition to the study of harmful algae and their toxins, Victoria's interests and project work include real-time water-quality monitoring, effects of land use on water quality, the fate of nutrients in agricultural and reservoir systems. She also has an interest in writing and communicating science topics to broad audiences and is a trainer and USGS Subject Matter Expert on Scientific Project Management.
Science and Products
Review of Cyanobacterial Neurotoxins—Information for Prioritizing Future Science Directions
The current state of knowledge on the modes of action, production, fate, and occurrence of the freshwater cyanobacterial neurotoxins, anatoxin-a and saxitoxin, was reviewed and synthesized to identify gaps and critical research needs to better understand the health effects of algal toxins.
Mixtures of Algal Toxins Present Prior to and After Formation of Visible Algal Blooms—Science to Inform the Timing of Algal Toxin Exposure
Cyanobacteria with toxin-producing potential, genes indicating an ability for toxin synthesis, or cyanotoxins were present before and after formation of a visible algal bloom in Kabetogama Lake, a popular recreation area in Voyageurs National Park that lies along the border of Minnesota and Canada. The temporal patterns observed in this study indicate that sampling only when there is a visible...
Environmental Effects of Agricultural Practices
As agricultural land in the Minnesota River Basin is retired, tile drains are removed or broken and riparian corridors are planted to reduce runoff. Early studies saw decreased sediment and nitrogen and improved biological indicators but no significant changes in phosphorus. This project continues to investigate the linkages...
Cyanotoxin mixture models: Relating environmental variables and toxin co-occurrence to human exposure risk
Toxic cyanobacterial blooms, often containing multiple toxins, are a serious public health issue. However, there are no known models that predict a cyanotoxin mixture (anatoxin-a, microcystin, saxitoxin). This paper presents two cyanotoxin mixture models (MIX) and compares them to two microcystin (MC) models from data collected in 2016–2017 from...
Christensen, Victoria; Stelzer, Erin; Eikenberry, Barbara C. Scudder; Olds, Hayley T.; LeDuc, Jaime F.; Maki, Ryan P.; Norland, Jack E.; Khan, Eakalak Rapid-assessment test strips: Effectiveness forcyanotoxin monitoring in a northern temperate lake
Precise and rapid methods of determining toxin levels are needed in lakes used for recreation and drinking water to facilitate a quick risk assessment during cyanobacteria blooms. Therefore, we evaluated rapid-assessment test strips, a newer technology for estimating the toxicity of cyanobacterial blooms, in Kabetogama Lake, a popular recreational...
LeDuc, Jaime F.; Christensen, Victoria; Maki, Ryan P. Land use effects on sediment nutrient processes in a heavily modified watershed using structural equation models
Contemporary land use can affect sediment nutrient processes in rivers draining heavily modified watersheds; however, studies linking land use to sediment nutrient processes in large river networks are limited. In this study, we developed and evaluated structural equation models (SE models) for denitrification and phosphorus retention capacity to...
Kreiling, Rebecca; Thoms, Martin C.; Bartsch, Lynn A.; Larson, James H.; Christensen, Victoria Freshwater neurotoxins and concerns for human, animal, and ecosystemhealth: A review of anatoxin-a and saxitoxin
Toxic cyanobacteria are a concern worldwide because they can adversely affect humans, animals, and ecosystems. However, neurotoxins produced by freshwater cyanobacteria are understudied relative to microcystin. Thus, the objective of this critical review was to provide a comprehensive examination of the modes of action, production, fate, and...
Christensen, Victoria; Khan, Eakalak Phytoplankton community and algal toxicity at a recurring bloom in Sullivan Bay, Kabetogama Lake, Minnesota, USA
Kabetogama Lake in Voyageurs National Park, Minnesota, USA suffers from recurring late summer algal blooms that often contain toxin-producing cyanobacteria. Previous research identified the toxin microcystin in blooms, but we wanted to better understand how the algal and cyanobacterial community changed throughout an open water season and how...
Christensen, Victoria; Ryan P. Maki; Stelzer, Erin; Norland, Jack E.; Khan, Eakalak Complex response of sediment phosphorus to land use and management within a river network
Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load through sediment retention and burial. Determining the influence of land use and management on sediment P concentrations and P retention in fluvial ecosystems is challenging because of different stressors operating at multiple spatial and temporal scales....
Kreiling, Rebecca; Thoms, Martin C.; Bartsch, Lynn A.; Richardson, William B.; Christensen, Victoria G. Denitrification in the river network of a mixed land use watershed: Unpacking the complexities
River networks have the potential to permanently remove nitrogen through denitrification. Few studies have measured denitrification rates within an entire river network or assessed how land use affect rates at larger spatial scales. We sampled 108 sites throughout the network of the Fox River watershed, Wisconsin, to determine if land use...
Kreiling, Rebecca; Richardson, William B.; Bartsch, Lynn A.; Thoms, Martin C.; Christensen, Victoria G.
Techniques for estimating the magnitude and frequency of peak flows on small streams in the binational U.S. and Canadian Lake of the Woods–Rainy River Basin upstream from Kenora, Ontario, Canada, based on data through water year 2013
A binational study was initiated to update statistical equations that are used to estimate the magnitude and frequency of peak flows on streams in Manitoba and Ontario, Canada, and Minnesota that are contained within the binational Lake of the Woods–Rainy River Basin upstream from Kenora, Ontario, Canada. Hydraulic engineers use peak streamflow...
Sanocki, Christopher A.; Williams-Sether, Tara; Steeves, Peter A.; Christensen, Victoria G. Sediment oxygen demand: A review of in situ methods
Sediment oxygen demand (SOD) plays a fundamental role in biological and chemical processes within the benthic layer of a water body. Land use, including agricultural land use, can affect SOD. However, a wide variety of approaches have been used for in situ SOD chamber construction and data collection, and modelers frequently use SOD values from...
Coenen, Erin N.; Christensen, Victoria G.; Bartsch, Lynn; Kreiling, Rebecca; Richardson, William B. A history of trade routes and water-level regulation on waterways in Voyageurs National Park, Minnesota, USA
Unlike most national parks, main access to Voyageurs National Park is by boat. This remote system of interconnected waterways along the USA-Canada border was an important transportation route for thousands of years of American Indian occupation, leading up to and including the trade route of the voyageurs, or French-Canadian fur traders from...
Christensen, Victoria G.; LaBounty, Andrew E. Voyageurs National Park: Water-level regulation and effects on water quality and aquatic biology
Following dam installations in the remote Rainy Lake Basin during the early 1900s, water-level fluctuations were considered extreme (1914–1949) compared to more natural conditions. In 1949, the International Joint Commission (IJC), which sets rules governing dam operation on waters shared by the United States and Canada,...
Christensen, Victoria G.; Maki, Ryan P.; LeDuc, Jaime F. Mercury and water level fluctuations in lakes of northern Minnesota
Large lake ecosystems support a variety of ecosystem services in surrounding communities, including recreational and commercial fishing. However, many northern temperate fisheries are contaminated by mercury. Annual variation in mercury accumulation in fish has previously been linked to water level (WL) fluctuations, opening the possibility of...
Larson, James H.; Maki, Ryan P.; Christensen, Victoria G.; Sandheinrich, Mark B.; LeDuc, Jaime F.; Kissane, Claire; Knights, Brent C.
New study predicts levels of algal bloom toxins from readily available measurements
Emerald-green harmful algal blooms have become an all-too-familiar summertime sight in many U.S. lakes and reservoirs. A new study successfully predicts when mixtures of the toxins produced by these blooms in Kabetogama Lake, Voyageurs National Park, will exceed drinking-water guidelines.