Algal Blooms

1. Algal Blooms

2. What caused these whales to die and wash ashore?

3. Algal Blooms! • Algal Bloom- the rapid growth of a population of algae. They occur when nutrients increase in the water. The whales’ cells contained a deadly toxin produced by a dinoflagellate. When the whales fed on the toxin producing algae, or on the fishes that had eaten the algae, the toxins reached a deadly level and killed the whales. Can you believe such a small organism killed these huge creatures!?

4. Saltwater Blooms • Saltwater algal blooms are usually called red tides. This is because the water usually turns red due to the red pigment in the algae. BUT red tides can also look brown, green, or even be colorless depending on the algae that causes the red tide. • Dinoflagellates and diatoms frequently bloom in red tides.

5. What causes a red tide? • They are usually caused by an increase in nutrients caused by: • Seasonal/Climate changes • Increases in ocean temperature

6. What are the effects of red tides? • They are DANGEROUS when the toxins become concentrated in the bodies of organisms that consume the algae: • Shellfish • Fish • Larger organisms like whales and humans can also get sick from eating the shellfish and fish that have fed off of the algae!

7. Freshwater Blooms • Eutrophication- is the process in which nutrients, such as nitrogen and phosphorus, build up in a lake or pond over time, causing an increase in algae growth.

8. Causes of Eutrophication • Natural events and human activities increase the rate of eutrophication • Human activities: • When farmers and homeowners use fertilizers, run off into nearby ponds and streams can cause eutrophication • Sewage treatment plants leak wastewater into the soil. The nutrients from the water make their way into nearby ponds and streams as well.

9. Effects of eutrophication • Eutrophication triggers a series of events with serious consequences! • Sunlight doesn’t reach plants and other algae below the surface→ those organisms die → decomposers, such as bacteria increase → bacteria uses up the oxygen in the water → fish and other organisms die due to lack of oxygen

10. Did you get it? • Why are saltwater algal blooms called red tides? • Under what water conditions are red tides most likely to occur? • When and how can red tides prove dangerous to humans? • What function does the red pigment provide the algae in red tides? • When does eutrophication occur? • What human sources increase eutrophication? • Why do pond organisms die with eutrophication? • How are saltwater and freshwater blooms similar?