Lake Simcoe Phosphorus Cycle Flashcards

A View From Inside the Lake

• Excess phosphorus is the biggest lake management problem worldwide, including Lake Simcoe.
• Reducing phosphorus levels is a key objective of the Lake Simcoe Protection Act and Plan.
• Previous studies focused on how much phosphorus enters the lake.
• This article examines what happens to phosphorus once it's in the lake: where it goes and what it does.

What is Phosphorus?

• Phosphorus is a naturally occurring element essential for all life.
• It's found in plants, animals (including humans), and DNA.
• It's an essential nutrient for healthy growth and development.
• A certain amount is necessary in water bodies, but too much fuels excessive plant and algae growth.
• Excessive plant and algae growth consumes oxygen, negatively affecting coldwater fisheries.

We Use Phosphorus Every Day!

• Phosphorus enters the lake naturally from the weathering of rocks and minerals.
• It's excreted in waste and released during decomposition.
• Phosphorus is found in products like cola, fertilizers, toothpaste, shampoo, matches, and flares.
• It's also used in pesticides, pyrotechnics, and steel production.

The Phosphorus Cycle

• Phosphorus exists in the water, plants, animals, and sediments of the lake.
• These sources interact, share, store, and lock away phosphorus in the "phosphorus cycle".
• LSRCA monitors Lake Simcoe's health by collecting water and sediment samples year-round at:
  • 29 lake stations (8 open-water, 21 nearshore).
  • An additional 142 sites annually.
  • A further 952 sites every 5 years.

Phosphorus Deposits

• Phosphorus deposits in the sediment are not evenly distributed throughout the lake.
• Cook’s Bay: Low sediment phosphorus concentration due to uptake by aquatic plants.
• Kempenfelt Bay & near Beaverton: Higher sediment phosphorus due to lower plant population.

Phosphorus in the Plants

• Plants and algae are major users of phosphorus.
• Zebra mussels have filtered out algae, increasing water clarity and allowing deeper sunlight penetration, encouraging plant growth.
• Aquatic plants get up to 97% of their phosphorus from lake sediments.
• When plants die, some phosphorus is released back into the water, while some remains bound in the plant tissue to be reincorporated into the sediments.

Phosphorus in the Water

• The majority of phosphorus that enters the lake is used by organisms or settles into sediments.
• Some phosphorus remains dissolved in the lake water.
• Lake Simcoe contains 11.6 trillion litres of water.
• Average phosphorus concentration: 14 micrograms per litre.
• Total phosphorus in the lake water: approximately 140 tonnes.
  • 14 \frac{\mu g}{L} * 11.6 * 10^{12} L = 162.4 * 10^{12} \mu g
  • 162.4 * 10^{12} \mu g * \frac{1 g}{10^6 \mu g} * \frac{1 tonne}{10^6 g} = 162.4 tonnes
• Target phosphorus concentration: 10 micrograms per litre.
• Target total phosphorus in the lake: 100 tonnes.
• Dissolved phosphorus leaving the lake at Atherley Narrows: average of 11 tonnes per year.

Phosphorus Cycle Summary

• Phosphorus is constantly cycled: water -> plants/algae -> zebra mussels/invertebrates/fish -> water/sediments.
• The size of circles on the map indicates average phosphorus concentration (micrograms per litre) since 2008.
• All areas have improved since the 1980s when average phosphorus concentration was 20-30 micrograms per litre.

Sediment Depth

• In sediments less than 10 meters deep, plant tissue phosphorus can fuel plant growth in subsequent years.
• If plant material is transported to waters deeper than 10 meters, the phosphorus is essentially locked away in the sediments.

Positive Changes

• Significant phosphorus reservoirs exist in Lake Simcoe, and the lake has natural processes for assimilating excess phosphorus.
• Overwhelmed processes can lead to excessive plant growth or algal blooms, indicating imbalance.
• Excessive phosphorus accumulation took decades and will take decades to reverse.
• Positive changes may not be immediately visible, but the lake is working to restore balance.
• Improvements are being seen in dissolved oxygen, decreasing phosphorus, and the return of environmentally sensitive species.

Distribution of Sediment Phosphorus

• Sediment phosphorus varies considerably across Lake Simcoe.
• High values are recorded near nutrient inputs at Barrie and the Black, Beaver, and Talbot River subwatersheds.

LSRCA

• Established in 1951, the Lake Simcoe Region Conservation Authority provides leadership in the restoration and protection of the environmental health and quality of Lake Simcoe and the surrounding watershed.
• Sample station phosphorus concentration measured in micrograms per gram (μg/g).