Algae

Question 1

Algae

Answer 1

photosynthetic eukaryotes, classified as protists (in Animalia kingdom, Eukarya domain)
not a clade, meaning that, in evolutionary terms, they are not a meaningful group
unicellular or multicellular
Mostly aquatic, can be freshwater or marine
Primary producers; autotrophs → they can engage in photosynthesis to make their own food from inorganic materials

Question 2

what causes freshwater HABs?

Answer 2

cyanobacteria

Question 3

what causes marine HABs?

Answer 3

diatoms and dinoflagellates

Question 4

Cyanobacteria

Answer 4

not technically algae
bacteria that can photosynthesize through chlorophylls
live in primarily freshwater systems
Unicellular, can either live individually or as colonies, creating filaments

Question 5

Cyanobacteria cell structure

Answer 5

Thyalokoid membranes
Outer membrane
Cell wall
Cell membrane
Bacterial DNA
Carboxysome (functions as CO2 fixation module)

Question 6

Dinoflagellates

Answer 6

Protists (eukaryotic)
Hard outer cell wall that contains cellulose (main constituent of plant cell walls)
Cause “red tides”

Question 7

Dinoflagellate examples

Answer 7

Karenia brevis: marine dinoflagellate responsible for “Florida red tides” and produces the neurotoxin called brevetoxin, which causes Neurotoxic Shellfish Poisoning (NSP) in humans

Alexandrium: genus of marine dinoflagellates that produce the neurotoxin called saxitoxin, which causes Paralytic Shellfish Poisoning (PSP)

Question 8

Diatoms

Answer 8

Have 2-part silica “shell” w/ pores, where one half fits inside the other half
Somewhat related to brown algae
Single-celled alga which has a cell wall of silica

Question 9

Diatom example

Answer 9

Pseudo-nitzchia: genus of marine diatoms that causes Amnesic Shellfish Poisoning (ASP) by producing the neurotoxin called domoic acid

Question 10

where is cyanobacteria found on tree of life?

Answer 10

bacteria domain

Question 11

where are dinoflagellates found on tree of life?

Answer 11

eukarya domain
Alveolata clade/superphylum

Question 12

where are diatoms found on tree of life?

Answer 12

eukarya domain
Stramenopila clade

Question 13

where are green algae found on tree of life?

Answer 13

eukarya domain

Question 14

how to distinguish between cyanobacteria and algae

Answer 14

Cyanobacteria:
type of bacteria that have a different cell structure due to chlorophylls, they are unicellular (either exist as individuals or as colonies)
Do not have membrane-bound organelles (do not have chloroplasts, engage in photosynthesis through chlorophylls)
Divide/reproduce by fission (nucleus splits in two)
Contain unique set of pigments used in photosynthesis (phycobiliproteins - phycobilins)

Algae:
eukaryotic organisms that can be unicellular or multicellular
Do have cellular organelles (do have chloroplasts)
Can reproduce sexually or asexually

Question 15

What are negative consequences of HABs?

Answer 15

human health, ecosystem health, land/property value and local economies

Question 16

HAB threats to human health

Answer 16

Vomiting
Diarrhea
Liver damage
Respiratory irritation
Muscle paralysis
Neurological issues through blockage of sodium channels; nerve propagation becomes interrupted
Death

Question 17

HAB threats to ecosystems

Answer 17

Aquatic “dead zones” where life cannot exist
Death of shellfish and other organisms due to hypoxic environment (reduced oxygen) and toxins; reduced harvests
Natural landscape threatened
Vegetation destruction
Water too dangerous to touch, develops a stench
Riverbed fills w/ gunk and muck

Question 18

HAB threats to land value and local economies

Answer 18

If natural landscape threatened, people may move away or less people will move to an area, plummeting property values and threatening local economic growth → economic decline
Communities rely on shellfish and oyster harvesting to sell for profit; important way of life is threatened as populations decline
Bodies of water used for recreational activity can no longer be used; can impact tourism

Question 19

Main toxins produced by HABs that we have discussed

Answer 19

Microcystins and Saxitoxins

Question 20

how do microcystins lead to illness?

Answer 20

Effects:
Inhibits phosphatases in organs, especially liver, impacting the gastrointestinal lining because it cannot be broken down by normal digestive enzymes
Abdominal pain
Headache
Sore throat
Vomiting/nausea
Diarrhea
Dry cough
Blistering around mouth
Pneumonia
Worst-case scenario is death

Question 21

how do saxitoxins lead to illness?

Answer 21

Effects:
Causes paralytic shellfish poisoning (PSP)
Leads to muscle paralysis by blocking sodium channels
Inhibits voltage-hgated sodium channel, resulting in reduced action potential
Interrupts nerve propagation, can lead to death

Question 22

what are “dead zones”?

Answer 22

areas where life cannot exist

Question 23

how do “dead zones” form?

Answer 23

Step 1:
Sun-heated freshwater runoff (either from agriculture, sewage systems, etc.) creates a barrier layer in the water
Barrier layer cuts off the saltier water beneath from oxygen in the air → beginning of hypoxic environment (oxygen depletion, oxygen supply cut off)

Step 2:
N and P from fertilizer and sewage cause major algal blooms
When the algae die, they sink into the saltier water beneath and decompose, using up oxygen to make decomposition process more efficient

Step 3:
Deeper water becomes “dead zone” because it is cut off from oxygen and has no supply or resupply
Fish either leave the area or die in massive amounts; “fish kills”
Tiny organisms that form the base of food chain die off, leaving nothing for larger organisms to feed off of

Question 24

what are microcystins?

Answer 24

Class of hepatotoxins
Produced by cyanobacteria
Composed of amino acids
Ring structure makes them very stable and difficult to break down
Exposure through inhalation, absorption, or ingestion

Question 25

what are saxitoxins?

Answer 25

Class of neurotoxins
Produced by certain species of marine dinoflagellates (Alexandrium, Gymnodinium, Pyrodinium) and freshwater cyanobacteria (Anabaena, some Aphanizomenon, Cylindrospermopsis, Lyngbya, Planktothrix)