Algonquin Provincial Park in

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1 HABs 2017 Assessing Water Quality Trends in Affected Ontario Lakes Elizabeth J. Favot, Kathleen M. Rühland, Andrew M. Paterson, and John P. Smol Using paleolimnology to assess long-term trends in the water quality of cyanobacterial bloom-affected Ontario lakes Algonquin Provincial Park in Ontario is an important nature conservation area and the hundreds of relatively pristine lakes within its boundaries help to make it one of the most popular camping destinations in Canada. For this reason, the public and many scientists were shocked by the formation of cyanobacterial blooms (genus Dolichospermum) in remote Dickson Lake, that resulted in closures to travel and camping on the lake in 2014 and 2015 (Figure 1). Algal blooms in nutrient-enriched (or eutrophied) lakes are a global water quality issue and have been relatively well-studied. It is no surprise that such lakes, which have high anthropogenic inputs of nutrients, often experience cyanobacterial blooms. However, in relatively remote and unimpacted systems like Dickson Lake, with total phosphorus concentrations in the oligotrophic range, the causes of recent cyanobacterial blooms are not clear. Increasing algal bloom reports in Ontario Although rare, cyanobacterial blooms in low-nutrient lakes are not unprecedented. In fact, Ontario Ministry of the Environment and Climate Change scientists have noticed a significant increase in the number of algal blooms reported in Ontario since the 1990s (Figure 2), with many of these events (26 percent) occurring in oligotrophic lakes (Winter et al. 2011). Algal blooms are also now being reported significantly later in the season (often well into the fall), suggesting a link to climate change. Warmer air temperatures can Figure 1. Dolichospermum bloom on Dickson Lake in Algonquin Provincial Park, August have pronounced effects on fundamental lake characteristics such as lake ice phenology and the timing, duration, and strength of thermal stratification. With climate warming, increased heating of the surface waters during a longer and warmer open water season is expected to enhance thermal stratification, and therefore reduce mixing. Relative to other types of algae, many cyanobacteria have higher temperature requirements and can regulate buoyancy using gas vesicles that enable them to maintain their position in areas of the lake with adequate light for photosynthesis. This adaptation is particularly effective under conditions of reduced vertical water column mixing. Additionally, prolonged thermal stratification often results in a depletion of oxygen in the hypolimnion, which can result in internal loading of phosphorus and iron from the sediments. When this occurs, a positive feedback cycle is set up resulting in further eutrophication and algal blooms. For these reasons, climate change is expected to increase 28 Summer 2017 / NALMS LAKELINE

2 Figure 2. Increasing reports of total and cyanobacterial blooms in Ontario lakes over the past two decades. Data from Winter et al. (2011) and figure updated by Ontario MOECC. the geographical range, frequency, and severity of cyanobacterial bloom events on a global scale. Many lakes in Ontario have already reported a longer ice-free period, as well as stronger thermal stratification (Stainsby et al. 2008) over the last several decades because of warming. It is now clear that climate change should be investigated as a potential trigger, or a likely contributing factor, for the recent increase in Ontario cyanobacterial bloom reports. Our project targets lakes that have been identified by the Ontario government as having management concerns related to the prevalence of cyanobacterial blooms. To help understand potential causes of these blooms, we strategically selected lakes that vary considerably in surface area and morphological complexity, and levels of anthropogenic stress and catchment disturbance. This diversity in lake characteristics will allow for a broader understanding of differences in trends of sedimentary indicators, and therefore provide better insights into the potential drivers for recent blooms. In the wake of recent algal blooms in the study lakes that have not experienced increases in nutrient inputs, lake users are left wondering whether these lakes have had similar blooms in the past, which perhaps went unnoticed or unreported, or if the blooms are part of a new normal for the lake. If the latter is correct, then what is triggering these events now? Our project aims to address these questions by placing current trends in the study lakes into a historical context. To do this, we focus on environmental information preserved in lake sediments. How paleolimnology can help Unfortunately, for many lakes, longterm monitoring information on bloom history, productivity and nutrient levels, water column temperature, and other factors that may contribute to algal bloom formation often only exist for the last few years, if at all. However, we can infer much of these data using microfossils and geochemical signals archived in dated lake sediments using paleolimnological approaches. Paleolimnology offers valuable insights into past environmental conditions to improve our understanding of current lake management issues (Smol 2008). Such studies can provide a history of pre-disturbance conditions, a measure of natural background variability, as well as inferring the timing of changes with links to known disturbances. A typical paleolimnological study (Figure 3A) begins with the collection and subsampling of a sediment core (Figure 3B, C), for which ages are established using radiometric dating techniques. Next, we analyze various indicators preserved within the sediment intervals (Figure 3D) to infer past changes in environmental and water quality conditions. Project-specific aims determine the type and diversity of data collected at this step. However, microfossils of aquatic biota that are used as proxies for environmental change have several common characteristics: they preserve well and are abundantly recovered from lake sediments, they are taxonomically distinguishable, and species often have defined tolerances and optima for various environmental variables. For this project, we collected species abundance data for fossil diatoms (a type of microscopic algae) and chironomid larvae (non-biting midges), akinetes (resting stages of cyanobacteria), as well as used visible reflectance spectroscopy (VRS) to infer concentration data of chlorophyll-a (a photosynthetic pigment) as a past measure of overall primary production. Our sediment cores allowed us to examine changes over time periods spanning the past ~250 years. These indicators can provide information on long-term trends in overall primary production, nutrient status, water column stability, and the presence or absence of cyanobacteria. Most importantly, we were able to determine how these attributes have changed through time. Case study: Bright Lake (Iron Bridge, Ontario) Bright Lake is located in the Algoma District of Ontario, near the northern shore of Lake Huron, about 30 km southeast of Sault Ste. Marie. It is a medium-sized lake with a surface area of km 2, a maximum depth of 12 meters, and sits on Precambrian Shield bedrock. The lake has had moderate human influences on the shoreline including the establishment of about 32 permanent, and 121 seasonal residents, as well as small-scale agriculture. In 2008 and 2014, blooms of potentially toxic Aphanizomenon flos-aquae developed on Bright Lake that generated local concerns about water quality. Water samples taken for a few years after the 2008 bloom show average total phosphorus levels in the mesotrophic range around 14 µg/l (Nürnberg and LaZerte 2011). Sedimentary diatoms and chlorophyll-a for Bright Lake (Figure 4) show trends that are consistent with a lake being influenced by multiple stressors. Stephanodiscus niagarae and Cyclostephanos invisitatus are diatom Summer 2017 / NALMS LAKELINE 29

3 A B C D Figure 3. (A) Steps in a paleolimnological study (diagram from Smol 2008), including (B) core extraction, (C) sectioning (photo credit: Brian Cumming), and (D) examination of indicator species (photomicrograph of diatoms from Rühland et al. 2015). species that characterize higher nutrient conditions, and we record them increasing in abundance and appearing, respectively, in the sediment record around This suggests that the lake experienced increases in nutrients beginning around this time. A pronounced increase in small-celled Discostella diatom species and simultaneous declines in large-celled Aulacoseira species, beginning around 1950 and accelerating since ~1999, is a trend that has been documented in many Canadian and other lakes and is indicative of prolonged thermal stratification (Rühland et al. 2015). It is also worth noting that these trends are consistent with an increasing trend in mean annual air temperature recorded at the nearby climate station in Sault Ste. Marie of about 1.5 o C over the 69-year record (Figure 5). Sedimentary chlorophyll-a, which is an indicator of temporal trends in whole lake primary production, matches the timing of changes in the diatom assemblages, showing a slight increase around 1950, and a more pronounced increase from ~2008 to the most recent sediments. Together, these data suggest that increases in nutrients in Bright Lake, followed by increasing thermal stability as a result of climate change, may have led to the highest levels of primary production in the lake in most recent years, which is consistent with the known bloom history. 30 Summer 2017 / NALMS LAKELINE

4 Links to lake management Paleolimnological analyses allow us to identify potential limnological shifts outside the range of natural variability for the study lakes, and help pinpoint likely factors that may be contributing to recent algal blooms. Current lake management practices in Ontario are focused mainly on reducing phosphorus inputs. However, bloom events, such as the ones observed in some of our study lakes, suggest that regional warming might increase the likelihood of blooms in lakes that have not experienced increases in nutrients. In many cases, blooms are likely caused by multiple stressors, particularly nutrient enrichment from catchment activities paired with recent climate change. Future management decisions should consider impacts of both of these stressors. Figure 4. Relative percent abundance of dominant diatom taxa in Bright Lake through time. Corresponding 210 Pb dates, and VRS-inferred sedimentary chlorophyll-a are also plotted. The profile is divided into three zones that contain similar diatom assemblages as determined by a constrained incremental sum of squares (CONISS) cluster analysis. References Nürnberg, G.K. and B.D. LaZerte Water quality and remediation options for Bright Lake, Pakawagamengan. Freshwater Research, Baysville, Ontario. Smol, J.P Pollution of Lakes and Rivers: a Paleoenvironmental Perspective. 2 nd ed. Wiley-Blackwell, London, UK. Stainsby, E.A., J.G. Winter, H. Jarjanazi, A.M. Paterson, D.O. Evans and J.D. Young Changes in thermal stability of Lake Simcoe from 1980 to J Great Lakes Res, 37: Rühland, K., A.M. Paterson and J.P. Smol Lake diatom responses to warming: reviewing the evidence. J Paleolimnol, 54: Winter, J.G., A.M. DeSellas, R. Fletcher, L. Heintsch, A. Morley, L. Nakamoto and K. Utsumi Algal blooms in Ontario, Canada: Increases in reports since Lake Reserv Manage, 27: Liz Favot is a Ph.D. student at the Paleoecological and Environmental Assessment and Research Laboratory (PEARL) at Queen s University in Kingston, Ontario. Her research involves placing current water quality trends in Figure 5. Sault Ste. Marie climate station mean annual air temperature between 1946 and 2015, fitted with a regression line. (Favot et al., continued on p ) Summer 2017 / NALMS LAKELINE 31

5 Ken Gibbons is the 2016 Great Lakes Commission Fellow. Ken assists the Commission with a range of water quality projects, including HABs Collaboratory and ErieStat (a program that is developing an online information delivery system to track trends in phosphorus loading to Lake Erie). Prior to joining the Commission, Ken studied harmful algal blooms in Lake Erie, specifically investigating internal loading of phosphorus. Victoria Pebbles is a program director with the Great Lakes Commission where she manages and facilitates multidisciplinary project teams to analyze information, build consensus and develop policy solutions to address complex ecological and related socioeconomic issues, including clean energy, climate change, water resource management, habitat conservation, land use, and coastal management. She has published dozens of articles and technical reports, delivered copious presentations, and served on and facilitated numerous multistakeholder project teams and task forces. Before joining the Commission in 1993, Ms. Pebbles held positions with the University of Michigan, the U.S. Senate, and the U.S. Environmental Protection Agency. c (Favot et al., continued from p ) cyanobacterial bloom-affected Ontario lakes into a historical context using paleolimnological techniques. Kathleen Rühland is a research scientist at PEARL (Queen s University) whose work focuses on using diatoms as environmental indicators to understand spatial and temporal trends in climatic and environmental change. Her research spans many geographic regions and covers various time scales, but has centered largely on humaninduced impacts of the past century. Andrew Paterson is a research scientist with the Ontario Ministry of the Environment and Climate Change. Working at the Dorset Environmental Science Centre (DESC), located in the heart of Ontario s cottage country, Andrew carries out research on the effects of multiple environmental stressors on the water quality and ecology of inland lakes. John Smol is a professor of biology at Queen s University (Kingston, Ontario), where he also holds the Canada Research Chair in Environmental Change. Smol founded and co-directs the Paleoecological Environmental Assessment and Research Lab (PEARL), a group of ~40 students and other scientists dedicated to the study of long-term global environmental change, and especially as it relates to lake ecosystems. John has authored over 500 journal publications and chapters since 1980, as well as completed 21 books. c Summer 2017 / NALMS LAKELINE 39