Cyanobacteria III/IV

Question 1

What temperature water do cyanobacteria dominate in

Answer 1

In warmer temperatures - Higher temperatures promote increased recycling of nutrients, this causes a shift towards small fish species which eat the zooplankton that would otherwise be eating the algae (so you get a lot of algal biomass then), all the algae then has to go to the top of the water body to get more sunlight leading to shade (here cyanobacteria have a competitive advantage over the others as they can control their buoyancy and rise to the top)

Question 2

The synergistic effect between what two factors can shoot up cyanobacterial blooms

Answer 2

• warm temperatures and nitrogen

Question 3

Phosphorous stimulates cyanobacterial blooms more so in what types of lakes

Answer 3

• In thermally stratified deep lakes rather than in wind mixed shallow lakes
• the thermally stratified deep lakes don’t mix readily and so phosphorous gets stuck at the bottom and highly available to the cyanobacteria

Question 4

What type of metabolites do cyanobacteria produce that function as toxins

Answer 4

They produce secondary metabolites that function as toxins

Question 5

Describe anatoxins

Answer 5

• these are simple alkaloids that function as neurotoxins
• they mimic the neurotransmitter acetylcholine
• they can also block the enzymatic activity of acetylcholinesterase

Question 6

Describe hepatotoxins like microcystin

Answer 6

• these are more molecularly complex proteins that function as toxins that target the liver
• these affect the liver tissues by degrading capillary membranes, resulting in the cell lysis and the accumulation of blood

Question 7

Describe cyanotoxins as an anti predator strategy

Answer 7

• toxic Microcystis can suppress grazing of the zooplankton Daphnia, but Daphnia can acquire tolerance following chronic exposure to cyanotoxins –> so tolerant populations evolve and therefore adaptation suggests that this isn’t a long term strategy then (cyanobacterial toxins are not strong anti predator strategies)

Question 8

How effective is bio remediation

Answer 8

• This is where you biologically alter a lake to suppress how well the cyanobacterial bloom can take place (so like doing manipulation of the trophic cascade)
• Successful bioremediation of cyanobacterial blooms in lakes is often short lived - thereby requiring additional management strategies (e.g. chemical remediation)

Question 9

What is a quick fix for cyanobacteria

Answer 9

going the chemical route and spraying a chemical

Question 10

What is a top down control via the trophic cascade

Answer 10

this is where you control how many predators etc. there are (bioremediation)

Question 11

What is a bottom up control of cyanobacterial blooms

Answer 11

using chemical additives

Question 12

Describe Phoslock

Answer 12

• this is a chemical that locks up the phosphorous so the cyanobacteria don’t have access to nutrients then
• it is a clay based product that is added to the bottom of the water body
• can only add it to artificial water bodies

Question 13

What is less expensive to use than phoslock

Answer 13

using aluminum sulfate or alum to bind phosphorous and reduce the cyanobacterial blooms

Question 14

Describe aeration remediation

Answer 14

• aeration pumps take water from the bottom, pump it out and aerate it
• circulation of water maintains well mixed water column in which oxygen levels remain near saturation
• oxic conditions then enable oxidized iron to bind and precipitate with phosphorous
• anoxia is prevented which otherwise reduces iron and releases bound phosphorous