Transcript Algal Blooms - Stanwich School

What caused these whales to
die and wash ashore?
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!?
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.
What causes a red tide?
 They are usually caused by an increase in nutrients
caused by:
Seasonal/Climate changes
 Increases in ocean temperature
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What are the effects of red tides?
 They are DANGEROUS when the toxins become
concentrated in the bodies of organisms that consume
the algae:
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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!
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.
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.
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
Did you get it?
 Why are saltwater algal blooms called red tides?
 Under what water conditions are red tides most likely to
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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?