Algae, Nutrients and the microbial loop

Question 1

What is the ideal N:P ratio?

Answer 1

16:1

Question 2

Major algal groups

Cyanobacteria

Answer 2

prokaryotic
have flotation devices
<3um
have phycoerythrin and phycocyanin as well as chlorophyll a to absorb yellow and green light as well as blue
have heterocysts for N fixation

Question 3

Major algal groups

Diatoms

Answer 3

Eukaryotic
cell is enclosed in silica frustule
responsible for 23% of carbon fixation

Question 4

Major algal groups

Chlorophytes

Answer 4

Eukaryotic
planktonic
colonial

Question 5

Major algal groups

Autotrophic flagellates

Answer 5

Eukaryotic
move via flagella - to position themselves at preferred light level
eyespot to detect light

Question 6

Major algal groups

Dinoflagellates

Answer 6

Eukaryotic
2 flagella
The second flagella around the waist spins

Question 7

how do algae that cannot move themselves position themselves at preferred light levels?

Answer 7

change shapes to sink or float
colonise to increase surface area and float
produce lipids to sing or gas vacuoles to float

Question 8

what are the problems with eutrophication

Answer 8

biomass increases, biodiversity does not
cyanobacteria dominate - poor food source
cyanobacteria are toxic
decreased oxygen content

Question 9

how do the EA treat eutrophicated lakes?

Why do they have to do this?

Answer 9

blasts with hydrogen peroxide to kill everything
this is because the lake cannot recover as the oxidised microzone breaks down because less oxygen is diffusing into it - this causes a release of more P from sediment

Question 10

What is POC

What is DOC

Answer 10

POC= particulate organic carbon - carbon stored in algae cells
DOC= dissolved organic carbon - simple sugars that diffuse out of cells

Question 11

Bacteria

Guild A - aerobic decomposers

Answer 11

core genus - pseudomonas
biggest group of bacteria
present in microbial loop - feed on DOC and release CO2
when algal productivity is low it can break down humic substances for carbon

Question 12

Bacteria

Guild B - gliding bacteria

Answer 12

break down POC to DOC
glide on surfaces
colonise sediment and fecal particles
core genus - cytophaga

Question 13

Protozoa

Naked Amoebae

Answer 13

blob of cytoplasm
move by cytoplasmic streaming
uses pseudopods to trap prey

Question 14

Protozoa

Testate amoebae

Answer 14

enclosed in shell
planktonic
floats - does not move
projects cytoplasm out of shell to feed by diffusion feeding

Question 15

protozoa

Flagellates

Answer 15

use flagella for movement and feeding
more efficient when attached
some make their own surfaces (making strips of silica into a basket)

Question 16

Protozoa

Ciliates

Answer 16

covered in cillia
eat algae and bacteria
have a cytosome (mouth) and a cytoproct (anus)

Question 17

Protozoa

Functional role

Answer 17

pump out NH4 and PO4 to balance C:N:P ratio - this feeds the bacteria

Question 18

Bacteria

Guild F - green and purple sulfur bacteria

Answer 18

anaerobic
do anoxygenic photosynthesis
produce DOC
use hydrogen sulfide as electron acceptor
produce sulfate which is used by guild E

Question 19

Bacteria

Guild E - sulfate-reducing bacteria

Answer 19

do anaerobic respiration (sulfate respiration)
utilise DOC from guild F or that has diffused from the aerobic zone
produces hydrogen sulfide which is fed to guild F

Question 20

Bacteria

Guild G - methanogens

Answer 20

carry out methanogenesis - forming methane - using CO2

Question 21

Protozoa

sulfur ciliates

Answer 21

anaerobic
feed on bacteria
also contain symbiotic methanogens

Question 22

Protozoa

sulfur ciliates

Answer 22

anaerobic
feed on bacteria
contain symbiotic methanogens