BC Lake Stewardship Society (BCLSS) 203 - 1889 Springfield Rd. Kelowna, BC V1Y 5V5 Phone: 250.717.1212 Fax: 250.717.1226 Toll Free: 1.877 BC LAKES E-mail: [email protected] Visit us on the web: www.bclss.org Volume 11, Issue 4 January 2009 Reducing Phosphorus Loading in St. Mary Lake Using Hypolimnetic Aeration S t. Mary Lake, located on Salt Spring Island, has experienced cultural eutrophication due to human activities in the watershed. St. Mary Lake is a very important resource for residents as it supplies drinking water and is the focus of considerable recreational activity. Several resorts are located around the lake perimeter and recreational angling has been an impor- tant part of their operations. The water quality of St. Mary Lake has deterio- rated considerably since 1970. Taste and odour problems, low transparency, year-round cyanobacteria blooms and severe hypolimnetic oxygen depletion have impacted fish habitat and degraded the drinking water supply. The decline in water quality has been attributed to In this issue... increased phosphorus (P) loading from water- shed development (septic tank discharges, JANUARY’S FEATURES PAGE road building and land clearing) to the point where the lake sediments have become a net Reducing Phosphorus in St Mary Lake 1 - 2 source of P under anaerobic conditions. Ice Safety Tips 3 - 4 Lake Life - Burbot 5 Internal loading from the sediments was iden- New Environmental Threat in N.A. Lakes 6 - 7 tified as the main source of P to the lake, with Fish Composition Impacts in Lake Baikal 11 - 12 lesser amounts originating from septic tanks, groundwater, dustfall and natural watershed loading. In the 1980’s, St. Mary Lake was se- BCLSS BUSINESS UPDATE lected as a study lake to evaluate the effec- Announcements & Events 8 tiveness of hypolimnetic aeration as a tech- Wetlandkeepers Announcement 9 nique for improving water quality and fish BCLSS Membership / Sponsorship Form 10 habitat. An aerator was installed in St. Mary continued on page 2... 1 Volume 11, Issue 4 BC Lake Stewardship Society January 2009 ….continued from page 1 Lake in 1985 by the Ministry of Environment and operated successfully until the early 1990’s, reducing P concen- trations. It was dismantled in 1994 because of structural corrosion of the inlet and outlet tubes. Phosphorus is an essential nutrient for produc- tivity in lakes and is absorbed by algae from the water. When algae and other organisms die and sink, P is transported to the bottom where it remains bound to sediments. Under anoxic conditions in the hypolimnion, a common oc- currence in many lakes, P is released and made available throughout the water column when the lake turns over, often resulting in al- gal blooms. Hypolimnetic aeration is one strat- egy used to mechanically reduce anoxic condi- tions and prevent the internal loading of P in lakes. Now St. Mary Lake often experiences algal blooms, impacting water quality and contribut- ing to an oxygen deficit. The lake is thermally stratified during the summer months and circulates freely during the winter, rarely experiencing ice cover. The fact that St. Mary Lake circulates all winter has likely prevented the lake from further water quality degradation, as oxygen is present throughout the water column and sediment- water interface for several months allowing the sediments to function as a nutrient sink during these periods. In a review of restoration options for St. Mary Lake, Ashley (2008) identified hypolimnetic aeration as a strong candidate for selection of in-lake water quality improvement techniques. Internal loading is the single largest P source to St. Mary Lake; if the hypolimnion can be kept aerobic, the P inputs can be significantly re- duced and water quality would improve accordingly. In 2008 the North Salt Spring Waterworks District commissioned the construction of a new aeration system, consisting of two units, which were installed in October. Funding for the project was assisted with grants from the Habitat Conservation Trust Fund and the Capital Re- gional District. The new aerators (the largest in Canada) operated for one month to monitor for problems, and then were shut down for the winter. Operation of the units will resume in late May after thermal stratification of the water column has occurred and will run until the lake turns over in the fall, around mid-October. Over several years of operation, the aerators are expected to decrease the internal loading of P, and the frequency and severity of algal blooms. Aeration on its own, however, does not provide the complete answer. The core activity of a water quality improvement program for St. Mary Lake must include a watershed management program to control point and non-point source nutrient loading. Without this approach, no lake restoration technique will be effective in the long term. Sources: Ashley, K. 2008. Review of St. Mary Lake restoration options. Ken Ashley and Associates Ltd. Bob Watson, Salt Spring Island. All photos in this article courtesy of K. Ashley 2 Volume 11, Issue 4 BC Lake Stewardship Society January 2009 Ice Safety Tips Sources: www.besmartbesafe.ca and C. Swan, MoE - Cariboo region n December 30, 2009, a 57 year-old Armstrong man drowned after he fell through the ice on Sugar Lake duringO a fishing trip. In light of this tragedy, the BCLSS would like send out some helpful reminders to anyone who may be heading out onto the ice. 1. Measure ice thickness in several locations Local conditions such as currents and water depths can affect ice thickness. White ice has air or snow within it and should be considered suspect for recreational use. The recommended minimum ice thickness for new, clear, hard ice is as follows: • 3” (7 cm) or less: STAY OFF • 4” (10 cm): ice fishing, walking, cross-country skiing, skating • 5” (12 cm): one snowmobile or ATV • 8-12” (20-30 cm): one car or small pickup • 12-15” (30-38 cm): one medium truck (pickup or van) Be sure you drill test holes along the way to your destination. Watch for slush or unusual looking areas on the snow or ice. In case of thin ice, lay down and spread out your weight and take a new route out of the area (as the ice you already walked on may be compromised now) 2. Avoid travelling on ice at night or when it is snowing. Reduced visibility increases your chances of driving onto an open or weak ice area. This is a frequent cause of ATV and snowmobile-related drowning. 3. Never go onto ice alone. A buddy may be able to rescue you or go for help if you get into difficulty. Each person should carry their own throw rope. Before you leave shore, tell someone where you are going and what time you expect to return. 4. Stay off river ice and avoid the narrows between lakes . River currents and moving water at the narrows where one lake flows into another can quickly change ice thickness or have much thinner ice than other locations on the river or on the lake. 5. Wear a thermal protection buoyant suit or a lifejacket If you don’t have a thermal protection buoyant suit, wear a lifejacket or PFD that isn’t too bulky over your snowmobile suit or layered winter clothing to increase your survival chances if you go through the ice. 6. Take safety equipment with you Pack ice picks and a rope, and carry a small personal safety kit (i.e., a pocketknife, com- pass, whistle, fire starter kit and cell phone) in your pocket. continued on p. 4... 3 Volume 11, Issue 4 BC Lake Stewardship Society January 2009 … continued from p. 3 The ice pick should be 'ready to go’ as they are essential for climbing back onto the ice mantle with minimal energy expenditure. Do NOT keep them in a pocket as they may be too hard to find while you are dog pad- dling to stay afloat. 7. Avoid alcohol Alcohol impairs your judgment, coordination and reaction time and speeds up the onset of hypothermia. 8. Don't drive on ice if you can avoid it. If you can’t avoid it, have an escape plan. Open your windows, unlock your doors, and turn on your lights to allow for a quick escape from your vehicle. Some ice-safety experts recommend that you have your seatbelt unfastened and your door slightly ajar to speed up an escape. Don't wear a lifejacket while riding inside an enclosed vehicle; the extra bulk and flota- tion could hamper your escape through a window. 9. Always supervise children playing on or near ice. Children playing on or near ice should always be with a buddy and under adult supervision. 10. Tips in an emergency situation: • self rescue comes first • if you have to rescue someone do NOT go in the water yourself • throw a rope or reach out with a long object, • follow a new path on the ice to tow the person out. Photo credit: Vaeltaja www.flickr.com 4 Volume 11, Issue 4 BC Lake Stewardship Society January 2009 Lake Life - Burbot (Lota lota) urbot are the only true freshwater cod (Family Gadidae) found in BC and occur in lakes and rivers through- outB central and eastern BC. Adults prefer the cool, deep areas of lakes and rivers while juveniles can be found along rocky lake shores and weedy areas, or hiding between the rocks in tributary streams. Adult burbot are typically 30 – 75 cm in length (maximum length of 90 cm) and 1 – 7 kg in weight (maximum weight of 9 kg). Burbot are predators, able to swallow fish nearly their own size.