Harmful algal blooms

Question 1

What are harmful algal blooms (HABs)

Answer 1

Can occur in marine, brackish or freshwater environments
Micro-algae produce toxins harmful to fish or humans if consumed
Dormant, resting cysts in sediment germinate when conditions optimal. Cysts can remain viable for considerable time
When population of the algae ‘bloom’, sufficient toxin is present to create problems

Question 2

What are the causes of HABs?

Answer 2

Main causes are generally nutrient increase e.g. from sewage, run off from land and temperature increase e.g. stagnant water, climate change
Causative organisms frequently cyanobacteria in freshwater, dinoflagellates or diatoms in marine environments
Blooms may be nuisance but referred to as harmful when the cyanobacteria/algae produce toxins that may be concentrated in food chain
Majority of public health issues arise from dinoflagellate/diatom blooms, particularly through concentration of toxins in fish

Question 3

How do algal blooms arise?

Answer 3

Dormant, resting cyst in sediment. Can remain viable for considerable time, spread via weather events
Warm temp, increased light stimulate germination. Swimming cell emerges. Reproduces by simple division
Under optimal conditions cells divide exponentially
Nutrients decrease, growth stops, gametes formed. 2 gametes join to form 1 cell, develops into zygote then into cyst

Question 4

What is an example of causative organisms of HABs?

Answer 4

Pseudonitzschia
Diatom, causing Amnesiac shellfish poisoning (ASP)
Toxin- Domoic acid
Symptoms include gastroenteritis, plus neurological effects in humans
Acts as excitatory neurotransmitter

Question 5

What is Gambierdiscus?

Answer 5

Dinoflagellate, causing Ciguatera Fish Poisoning (CFP)
Most commonly reported marine toxin, associated with consumption of reef fish

Question 6

What two toxins do Gambierdiscus produce?

Answer 6

2 toxins:
Ciguatoxin: lipid soluble. Neurotoxin, opens Na channels in cell membranes
Maitotoxin: water soluble. Increases Ca influx through membranes
Now known to be 12 species >100 fold variation in toxicity, plus variations in toxin profiles

Question 7

What is Dinophysis spp?

Answer 7

Dinoflagellate, causing Diarrhetic shellfish poisoning (DSP)
DSP toxin group includes okadaic acid, plus it’s analogues
Common in Europe

Question 8

What does Okadoic acid do?

Answer 8

lipophillic, contracts smooth muscle in arteries, inhibits cellular activity by binding to enzymes

Question 9

What is Karenia brevis?

Answer 9

Dinoflagellate, causing Neurotoxic shellfish poisoning
Toxin: brevotoxins ‘red tide’

Question 10

What do brevetoxins do?

Answer 10

Neurotoxic, open Na channels in membranes; immunotoxic, inhibit enzyme activities in immune cells
Not easily detectable or removable from food
Fragile, easily broken, thus releasing toxin as an aerosol

Question 11

What sectors are affected most by HABs?

Answer 11

Human health impacts
Fishery impacts
Tourism and recreation impacts
Monitoring and management costs

Question 12

What is the need for biotechnology in HABs?

Answer 12

Early accurate detection (water and organism content)
Measure of severity
Control of causative organism
Antidote/neutralization of toxin

Question 13

What is looked at for detection of HABs?

Answer 13

Optical
Biological (species: genetic)
Chemical (toxin)

Question 14

What is ecogenomics?

Answer 14

Quantify functions and interactions if organisms at an ecosystem level to understand causes and consequences of HABs
- Phylogenetic relationship
- Biosynthetic/metabolic pathways
- Diversity patterns
- Gene expression/regulation re. competitors/grazers

Question 15

What is an example of detection of HABs?

Answer 15

Imagine FlowCytobot
Automated underwater imaging flow cytometer designed by Rob OLsen and Heidi Sosik

Question 16

What is the BreveBuster?

Answer 16

Detection of HABs Karenia brevis pigment
BreveBuster: shines deuterium and tungsten light through seawater samples
Compares light absorption fingerprint of red tide
Quantifies biomarker for K. brevis
Chemical toxin detection

Question 17

Can bioassays be used for detection of HABs?

Answer 17

Yes toxic quantification
Standard test since 1960’s
Mice injected with 1ml (soluble sample)
Time taken for death recorded
Toxicity of sample calculated

Question 18

What interference factors are known in using bioassays for HAB detection?

Answer 18

High salt content
Zn accumulation in oysters
Gender and mouse strain

Question 19

How else can toxic quantification be used to detect HAB’s?

Answer 19

by ELISA
Quantification via antibody detecting toxin and visualized substrate reaction
Kits contain standards from which standard curve is created and toxin quantified

Question 20

What are biosensors?

Answer 20

Device that incorporates biological sensing element in close proximity to signal transducer
Transducers: optical, electrochemical, thermometric magnetic
Also hormone receptors, lectins, proteins, organelles, whole cells, microorganisms

Question 21

How can antibodies be used to detect algal cells?

Answer 21

Detection of algal cells using specific antibody
Antibody generated against the algal cell, enabling rapid recognition of the algae

Question 22

What is a microarray?

Answer 22

Detection of algal cells using nucleic acids
Microassay based on sequences of 15 species, aiming to streamline identification in the field focusing on diatom Pseudoitzschia
Array used electrochemical signal detection

Question 23

What is pyrosequencing

Answer 23

A DNA sequencing technique that uses a chain reaction to detect the nucleotides incorporated by DNA polymerase

Question 24

Why is pyrosequencing used?

Answer 24

High throughput sequencing, capable of generating 40-600 million base pairs in ca 10 hours
High level of speed/accuracy
Can detect rare, novel variants
Wide range of applications