This project is part of the NSERC Canadian Aquatic Invasive Species Network II. I am investigating the effects of invasive trout and climate warming on plankton communities in fishless alpine lakes. As unforeseen synergistic or antagonistic interactions often complicate the effects of multiple ecological stressors, I conducted a mesocosm experiment to elucidate whether the presence of exotic sportfish and higher temperatures exert indirect or direct effects on plankton. My experiment also examines the potential for stress-tolerant colonists arriving from a regional species pool to functionally rescue stressed local communities from the effects of a novel predator and summer heating events.
Mesocosms were established for eight weeks in 1,000 L tanks. Native zooplankton obtained from three fishless alpine lakes in Banff National Park were pooled and used as local species inocula. Three experimental factors were crossed with two treatment levels each ([ambient temperature vs. heating] x [trout absence vs. invasion] x [local vs. local + regional species]). Treatment combinations were replicated four times for a total of 32 mesocosms. The heating treatments were achieved using 300 W submersible heaters to amplify daytime warming events and sustain elevated temperatures through the night. The trout invasion treatment was achieved by the introduction of individual rainbow trout (Oncorhynchus mykiss) fingerlings. O. mykiss were used because of their comparatively high thermal tolerance and their prevalence in our national and provincial mountain parks from historical stocking programs, while also being non-native to Alberta. The regional species pool treatment was achieved by the inoculation of species collected via a survey of 25 mountain lakes and ponds – both with and without fish – at varying elevations (1165–2687 m above sea level). Quantitative zooplankton and chlorophyll samples were collected biweekly from the mesocosms. Response variables include those related to biodiversity (e.g. species richness and evenness) and ecosystem functioning (e.g. biomass production by native producers and consumers). Large zooplankton (i.e. crustaceans) are being enumerated and measured for biomass calculations using light microscopy. Small zooplankton (i.e. rotifers) are being enumerated and measured using advanced flow cytometry. Total phytoplankton biomass is being estimated from chlorophyll samples using high-performance liquid chromatography.
Prairie wetlands provide many important ecosystem services — they filter water, prevent erosion, store greenhouse gases, and are one of the most important breeding habitats for ducks globally — yet over half of the wetlands in the Canadian prairies have been drained for agriculture. Because of their many useful services, there is growing interest in restoring drained wetlands to their natural state. My current research takes a multi-faceted approach to studying the recovery of restored prairie wetlands. First, I characterized wetlands at different stages after restoration through a quantitative comparison of water chemistry, greenhouse gas (GHG) emissions, and biological communities. Second, I will evaluate whole ecosystem function in restored and natural wetlands. Specifically, I am measuring whole ecosystem metabolism (gross primary production, net ecosystem production, respiration) based on diel changes in oxygen concentrations and will try to understand biotic and abiotic drivers of these rates. Finally, I plan to test hypotheses about how diversity across trophic levels may impact ecosystem function in restored and natural wetlands.
Our ability to predict the ecological consequences of global change is limited by the pervasiveness of non-additive responses to environmental drivers that generate “ecological surprises”. Species responses to stressors are often modified by the effects of other stressors and interactions with other organisms. I am using mesocosm experiments and lake surveys to test the hypothesis that non-additive responses of mountain lake communities to invasive stocked sportfish and climate warming are driven by the higher sensitivity of large species to both stressors. I am also investigating whether importation of tolerant regional species can functionally buffer local communities against the negative effects of these two stressors (i.e., the Spatial Insurance Hypothesis) and whether the order of exposure to the stressors influences their net effects on mountain lake communities.
Frequent outbreaks of toxic and other problematic algae, collectively termed harmful algal blooms (HABs), represent major health risks and nuisances for humans, livestock, and wildlife. In Alberta, we have shown that these algae (primarily cyanobacteria such as the genus Microcystis) can produce the highest concentrations in all of Canada of liver-damaging microcystins (Orihel et al., 2012. Canadian Journal of Fisheries and Aquatic Sciences 69:1457-63), neurotoxins, and odour-causing compounds. For instance, in 2010 and 2011, Alberta Health Services’ cyanobacterial monitoring program revealed that HABs across 126 lakes often exceeded the accepted Health Canada guidelines for recreational water quality in terms of HAB cell counts (100,000 cells/mL) and microcystin production. Recreational exposure to HABs also risks gastrointestinal, respiratory, skin, and eye irritation , along with other allergic reactions. Furthermore, predicted invasions of Alberta by non-native algae (e.g., cyanotoxic Cylindrospermopsis) increasingly pose a future threat to aquatic habitat and water quality.
Effective risk management of HABs requires an early warning system in which rapid and cost-effective technology can be used to quickly detect, quantify, and respond to early indicators of potentially toxic cyanobacteria in Alberta. Elsewhere, HAB-monitoring programs often rely on very time-consuming and slow microscopy techniques for detecting and quantifying cyanobacterial cells and/or their toxin concentrations as the first criteria for issuing health warnings to the public regarding potentially toxic outbreaks in recreational and drinking water sites. Alternatively, visual accounts of algal blooms are often unreliable and too late for determining the risk of HABs because of the highly variable nature of cyanobacteria and their production of toxins. Fast-growing cyanobacteria can vary tremendously in their appearance within a lake, producing either vast arrays of toxins or none at all. Further, water quality can deteriorate rapidly during the summer as previously rare forms of toxic and/or non-toxic cyanobacteria begin to proliferate exponentially. Consequently, the substantial lag times associated with microscopy-based quantification of cyanobacterial cell counts can endanger the public as any delay in the issuing of health warning risks exposure to rising HABs . Therefore, the method of analytical detection and cell-enumeration of these species must be as rapid as their production rates to closely track potential risk to humans.
The main goal of our research here is to employ state-of-the-art continuous-imaging flow cytometry to develop the first on-line searchable electronic library of HAB species for the purpose of automated rapid early detection and cell-count quantification of potential "hotspots" in Alberta recreational and surface waters. Continuous-imaging flow cytometry paired with automated digitalized image matching software offers a more accurate means of detection in a fraction of the time (e.g., minutes versus hours) relative to traditional microscopic methods, thereby making for more rapid and confident assessment of the presence and abundance of HAB species. As a result, adaptive strategies can be put into action sooner than ever before. In comparison, microscopic enumerations are not only more labour-intensive, but also more costly and tedious (e.g., operator fatigue can reduce the likelihood of detection of rare species). The technology behind advanced flow cytometry has evolved rapidly over the past decade, making it the most sought after new approach for biomonitoring HABs in lakes and oceans (e.g., toxic shellfish-poisoning red tides). Our automated electronic library of HAB species images will be linked to a geographic information system (GIS) as an on-line resource of bioindicators for aquatic ecosystem health across Alberta.
An end goal of the research is to develop the first quantitative model for predicting HABs in lakes of Alberta. The four-year database generated by the use of the flow cytometer in tracking the onset of HABs would be paired with meteorological and environmental data obtained from the monitored lakes. Multivariate models using a combination of direct gradient ordinations and structural equation modeling would then be constructed to identify the best set of environmental predictors of HABs. The model would generate early forecasts of subsequent mid- to late-summer HABs in specific lakes, thereby providing lake managers with advanced warning and enabling them to take adaptive measures.
This innovative approach to automated early detection and cell-counting quantification of problematic algae strongly supports goals #1, #2, and #4 of the Alberta Water for Life Strategy Plan. First, delivery of our on-line analytical services will aid in “Albertans [general public and water managers] being assured that their drinking water is safe” of potential HAB species. Second, quick detection of invasive species that can potentially impair the recreational and water quality of lakes and streams will help assure Albertans that these aquatic ecosystems are maintained and protected. Third, the online accessibility of our web-based information product will provide Albertans with the knowledge needed to monitor their aquatic ecosystems and make informed decisions regarding their use and management.