2017 LAKE STEWARDS NEWSLETTER | 17 Considering the Past to Understand Current Conditions With increased cyanobacterial bloom events, lake users may wonder if similar blooms have occurred in the past, or if they are part of a ‘new-normal’ for the lake. If the latter is correct, then what is triggering these events today? Unfortunately, there is little long-term lake monitoring information on algal bloom history and factors that may contribute to cyanobacterial bloom formation. However, we can infer much of these data using information archived in lake sediments, a science that is referred to as ‘paleolimnology.’ Our research aims to provide historical context by establishing baseline conditions and pinpointing the timing of changes and onset of disturbances. We begin with the collection of a lake sediment core (see above) that provides a continuous environmental history of that lake. We then use radiometric techniques to date the sediments. Next, we analyze various ‘indicators’ preserved within the sediment intervals corresponding to time periods spanning the past ~250 years. For our study, these indicators include diatoms (microscopic algaecharacterizedbyglasscellwalls),chironomidlarvae (non-biting midges), chlorophyll a (a photosynthetic pigment), and akinetes (resting cysts of blue-green algae). Each indicator fills in a unique piece of the puzzle, including how lake water quality (inferred from diatoms) and deepwater oxygen concentrations (inferred from chironomid larvae) have changed in lakes over time. This approach enables us to determine how important lake characteristics have changed through time and may be contributing to cyanobacterial blooms. Links to Lake Management Current lake management practices in Ontario are focused mainly on reducing phosphorus inputs. Bloom events observed in many Ontario lakes suggest that regional warming might lower critical nutrient thresholds, resulting in blooms in low nutrient lakes. In many cases, blooms are likely triggered by multiple environmental stressors, particularly nutrient enrichment paired with recent climate change. Future management decisions should consider impacts of both of these stressors. ABOUT THE AUTHOR: Elizabeth Favot is a Ph.D. student at the Paleoecological Environmental Assessment & Research Laboratory (PEARL), Queen’s University. Retrieving a sediment core. Following up on a blue-green algae notice in last year’s FOCA Newsletter, we bring you this 2017 update from a press release: The Three Mile Lake Association has partnered with the Muskoka Lakes Association to undertake a small scale demonstration of an innovative technology to manage blue- green algae. “The board of the Three Mile Lake Association has spent a great deal of time researching the pros and cons of various alternatives used to control algae,” said Sue Walker, president of the Association. “When we heard of the use of ultrasonics we felt it offered the most promising approach for our lake.” This environmentally safe technology has been tried and proven effective in the United States, Australia and elsewhere to manage blue-green algae on ponds and reservoirs. Advantages include: it avoids the use of chemicals, requires very little maintenance, and does not trigger the requirement for Environmental Compliance Approval, according to advice from MOECC to the Association. While ultrasound will not eliminate the original conditions that support the proliferations of algae blooms, it is believed to control their growth rate, minimizing their potential to form blooms and scums within the treated area. Ultrasound at frequencies used to control blue-green algae poses no risk to other aquatic life or to humans. It’s the same technology used in fish finders and depth sounders. “We have chosen a small bay, which experiences little boat traffic, in which to conduct the experiment,” said Walker. An initial two month evaluation period will monitor the effectiveness of the ultrasound treatment. If deemed effective, the treatment will be continued for the remainder of the ice-free season. FOCA looks forward to hearing about the results of this project! Innovative Algae Plan