Lake Water Quality Myths and Misconceptions. Jana Tondu & Vanessa Swarbrick Limnologist s with Alberta Environment and Parks

Transcription

1 Lake Water Quality Myths and Misconceptions Jana Tondu & Vanessa Swarbrick Limnologist s with Alberta Environment and Parks

2 Facts about Alberta Lakes Lake levels fluctuate in response to climate Many of Alberta lakes are naturally productive Parkland lakes are shallow, warm, and naturally rich in nutrients Parkland lakes have frequent natural blooms of algae and plants

3 Dispelling Common Myths About Lake Water Quality 1. Nutrient sources 2. Algal community composition 3. Aquatic vegetation 4. Shoreline alterations

4 1. All nutrients are from Agriculture There are many sources of nutrient inputs into lakes Agriculture is one source of nutrients to lakes

5 Nutrient Sources Major inputs: Catchment area runoff Tributaries Direct precipitation Lake sediments In many Alberta lakes, over 50% of phosphorous is from internal loading

6 Dispelling Common Myths About Lake Water Quality 1. Nutrient sources 2. Algal community composition 3. Aquatic vegetation 4. Shoreline alterations

7 2. All algae are bad for my lake

8 Seasonal succession in algal communities Sommer et al (2012) Annu. Rev. Ecol.Ecol. Syst.

9 Seasonal succession: Spring blooms Diatoms Microscopic fast growing, non-motile Bradbury (2004) PLoS Biol 2

10 Seasonal succession: Clear water phase Zooplankton Intense grazing pressure on edible algae Photo: Jake Walsh

11 Seasonal succession: Mid summer blooms Greens Resistant to grazing Fast growing, canopy forming

12 Seasonal succession: Mid-Late summer blooms Cyanobacteria Resistant to grazing Vertical migration

13 Harmful Algal Blooms (HABs) Green, blue, red, brown Toxins Hypoxia Fish kills

14 Is my lake getting worse? Seasonality and community composition? Environmental conditions?

15 Dispelling Common Myths About Lake Water Quality 1. Nutrient sources 2. Algal community composition 3. Aquatic vegetation 4. Shoreline alterations

16 3. Aquatic plants are bad or a sign of an unhealthy lake Dense plant growth can impede boating and swimming Aquatic plants are sometimes considered unaesthetic However, aquatic plants are an essential part of the lake ecosystem

17 Aquatic plants what are they good for? Provide important habitat for small animals (zooplankton, aquatic insects, snails, shrimp) that are a food supply for larger animals (fish and waterfowl) Provide cover for fish and amphibians to escape from predators Nursery for young fish, frogs, salamanders Provide housing supplies for birds and mammals (nests and dens)

18 Aquatic plants what are they good for? Erosion control Protect shorelines from erosive wave action and currents Trap sediments on the bottom of the lake to help increase water clarity

19 Aquatic plants what are they good for? Improve Water Quality Maintain clear water conditions Compete with algae for nutrients and light Nutrient Cycling Absorb nutrients (N and P) from the water column to grow (roots and shoots) Influence dissolved oxygen supply Stabilize sediment Soak up pollutants from contaminated water

20 Dispelling Common Myths About Lake Water Quality 1. Nutrient sources 2. Algal community composition 3. Aquatic vegetation 4. Shoreline alterations

21 4. Shoreline alteration doesn t have an impact on water quality Lakes with poor shoreline habitat are three times more likely to be in poor biological condition Shoreline alteration is the most significant stressor to biological condition of a lake (USEPA, 2009)

22 Shoreline alterations impacts to water quality Runoff from lawns can be 10 times greater than wooded sites Lawns transport 10 to 100 times more nutrients Lawns have reduced ground-water recharge compared to wood Shoreline alteration can have significant impact on flow of water and nutrients to lakes (USGS, 2006)

23 Shoreline alteration impacts to vegetation Studies have shown that shoreline development dramatically alters the structure and function of aquatic vegetation Less shoreline tree cover Less habitat complexity More sand and sediment Impacts to aquatic invertebrate community (Merrell et al., 2009)

24 Shoreline alteration impacts to fish Misconception that development will increase fish growth rates (more nutrients = more algae = more fish food) Studies have shown altered shorelines reduce the capacity of lakes to maintain productive fish populations habitat loss loss of habitat complexity (exposure) changes to the food web increased siltation from erosion warmer temperatures (reduced shading) (Schindler et al., 2000)

25 Maintain or restore as much natural shoreline as possible Manicured lawns and retaining walls are not conducive to a healthy lake Natural shorelines are easier to maintain and provide ecological benefits

26 Thank you! Vanessa Swarbrick, M.Sc., PhD Candidate Limnologist/Water Quality Specialist North Saskatchewan Region Alberta Environment and Parks Jana Tondu, M.Sc., P.Biol Limnologist/Water Quality Specialist Upper Athabasca Region Alberta Environment and Parks

27 References Government of Alberta Facts about water in Alberta. Groves Watershed management what every riparian property owner should know and do. Progressive AE. Merrell, K., Howe, E.A., Warren, S Examining shorelines, littorally. Lakeline, 29(1): p Schindler, D.E., Geib, S.I., Williams, M.R Patterns of fish growth along a residential development gradient in north temperate lakes. Ecosystems. 3: USEPA National lakes assessment: A collaborative survey of the nation s lakes. EPA 841-R USGS Evaluating the effects of nearshore development on Wisconsin lakes. Fact Sheet Sommer et al Beyond the Plankton Ecology Group (PEG) Model: Mechanisms Driving Plankton Succession. Annual Reviews in Ecology. Evolution and Systematics, 43: