Harmful Algal Blooms Flashcards
Define Harmful Algal Blooms
This is the large increase of a microscopic alga that produces toxins or other harmful chemicals
Why is the term “red tide” not used much anymore (and HAB is used instead)?
Used to use red tide to refer to the red tides associate with dinoflagellate HAB, but not all HAB is red or any color so it can be misleading
- Describe the typical phases in a HAB cycle?
1) Cysts sit dormant in the sediment, and when conditions are right they emerge and begin to grow
2) If the conditions remain good, they divide exponentially and grow blooms
3) They will divide and grow until nutrients are depleted
4) They then stop growing and form gametes, they fuse and form zygotes and cysts, which then return to sediment to sit
We discussed in lecture two events (2004, 2015) when massive toxic phytoplankton blooms were detected off the West coast of North America:
i) What algal group was responsible for this event?
ii) Describe how this toxin may also affect the top predators of the marine ecosystem (e.g., marine mammals and birds).
The algal group responsible for this was diatoms, a species of Pseudonitzschia.
It produces domoic acid, which can become concentrated in the tissues of filter-feeding molluscs and arthropods, as well as fish
This can become bioaccumulated up the food chain and eventually eaten by mammals and birds and kill them
Name two shellfish poisoning syndromes. What type of algae are responsible for them?
Paralytic shellfish poisoning: This is from dinoflagellates (Alexandrium) that produce saxitoxin
Diarrhetic Shellfish poisoning: This is from dinoflagellates (Dinophysis) that produce okadaic acid
Neurotoxin shellfish poison: This is from dinoflagellates (Karenia) that produce brevetoxin
Amnesic shellfish poison: This is caused by diatoms (Pseudonitzschia) that produce domoic acid
What are the toxins involved in toxic blooms? What are the general effects of these toxins on humans? Why are they called “shellfish” poisoning syndromes?
PSP: Saxitoxin – numbness, paralyzing, respiratory weakness, death
DSP: Okadaic acid – Diarrhea, nausea, vomit
NSP: Brevetoxin – Diarrhea, vomit, muscle pain
CFP: Cigutoxin/maitotoxin – Diarrhea, cramps, vomit
ASP: Domoic acid – vomit, diarrhea, memory loss
Called shellfish poison, because they are accumulated by the filter-feeding of shellfish and when eaten are harmful to humans and others
What toxin (and what type of syndrome) did the crew of Capitan Vancouver’s expedition encounter in the BC coast in the late 1700?
They encountered Saxitoxin from paralytic shellfish poison
- In what parts of the world ocean is CFP most prevalent?
Mostly in the tropic and subtropics on coral reefs
Briefly explain three consequences of HABs on marine life, in addition to toxin production.
Oxygen depletion
Habitat destruction
Physical damage on fish
- What is food chain/web magnification?
Small filter-feeding animals accumulate toxins, many of which are then eaten by the higher food chain. Those are then eaten in numerous amounts by the higher food chain
Biomagnify the food web
What is the algal group mainly responsible for freshwater and brackish water HABs?
This is caused by cyanobacteria
What kind of toxins are involved in HABs in freshwater? What are their main effects on humans and animals?
Lipopolysaccharides: Fever and inflammation
Hepatotoxins: Poisoning, tumour-producing
Neurotoxins: Block neuromuscular activity
Does eutrophication have an impact on the incidence of HABs? Why?
Yes, eutrophication increases the amount of HAB that occurs.
This is because large inputs of nutrients supply algae with the conditions to bloom
- Are HABs a recent phenomenon?
No, HABs have always happened. They are just more frequent and intense now
Are HABs more widespread now than they were two decades ago? Why?
We are increasing the nutrient input into near-shore waters from run off and agriculture
Temperature is increasing so the conditions are better
More upwelling
