Seaweeds and colloids

Question 1

When do we think the first seaweeds evolved, based on fossil evidence?

Answer 1

700-800 million years ago

Question 2

What characteristic do all seaweeds share (except one exception)?

Answer 2

They are all benthic, meaning they attach to rock (exception is sargasso mats of Caribbean)

Question 3

Where in the ocean are seaweeds most prominent?

Answer 3

Temperate waters

Question 4

What are 3 common structures present in seaweeds?

Answer 4

1. Gas bladders (“posture”)
2. Holdfasts (attachment)
3. Colloid polysacharrides (hydroskeleton)

Question 5

What percentage of the ocean’s primary productivity is comprised of seaweed?

Answer 5

2-10%

Question 6

What is the most obvious marker for distinguishing the three major groups of seaweed?

Answer 6

Differences in pigment (colouration)

Question 7

What are the 3 major groups of seaweed?

Answer 7

1. Green algae
2. Brown algae
3. Red algae

Question 8

What accounts for the vivid green colour of green algae? What percentage of green algae are marine? Where is this group most common?

Answer 8

Contain clorophyll. Only ~10% of this group are marine and these prefer low salinity waters ex. estuaries

Question 9

What accounts for the brown/tan colour of brown algae? Where is this group most common?

Answer 9

Colouration caused by fucoxanthin. Found in temperate waters (kelp), can form entire ecosystems ex. kelp forests

Question 10

Which of the three major groups of seaweeds is the most common? Describe their common morphology.

Answer 10

Red algae. Mostly grows as blades and small/fine forms, but can also have rigid, calcified forms

Question 11

What accounts for the red to dark purplish colour of red algae? Where can this group be found in the oceans?

Answer 11

Phycoerythrin (red) and phycocyanin (bluish). Widely distributed from temperate to warm waters and up to greater depth than other groups

Question 12

Why do the different major groups of seaweeds have different accessory pigments?

Answer 12

Absorb different wavelengths of light. Colour of seaweed can denote depth of water based on what light it is able to absorb

Question 13

What cultures have consumed seaweeds as a source of food? Why might they do this?

Answer 13

Indigenous peoples of North America as well as Asian populations eat seaweeds as a source of dietary iodine

Question 14

What is a colloid?

Answer 14

A crystalline matrix which keeps molecules in fluid in suspension

Question 15

What are the 3 commonly used colloid polysaccharides harvested from seaweed?

Answer 15

1. Alginic acid
2. Carrageenan
3. Agar

Question 16

What major group of seaweeds does alginic acid come from? How do we use it?

Answer 16

From kelps (brown algae), used as a thickening agent in foods, etc.

Question 17

What major group of seaweeds does carrageenan come from? How do we use it?

Answer 17

From red algae. Used as an emulsifier and a gelling agent in creamy foods and cosmetics ex. ice cream, toothpaste, etc.

Question 18

What major group of seaweeds does agar come from? How do we use it?

Answer 18

From red algae. Used as a gelling agent in laboratory research for growing cultures or mapping DNA (agarose gel)

Question 19

Is agar from algae necessary for lab research? Could it be replaced?

Answer 19

Yes, but it cannot be replaced synthetically and we cannot cultivate red algae at a large enough scale to keep up with demand yet

Question 20

What advantage is there to including seaweed in cow feed? What mechanism causes this? Who first noticed this?

Answer 20

Reduces methane emission from cows almost entirely because of bromoform which interferes with methane producing enzymes in the cow’s rumen. Discovered by a dairy farmer in PEI

Question 21

Do seaweeds absorb nutrients through their base, like other plants?

Answer 21

Not through their holdfasts, rather they absorb nutrients over their their entire surface

Question 22

Why might red algae not grow in the protected waters favoured by green algae?

Answer 22

They require more salt which is more prevalent in exposed coastline

Question 23

Does each algae reproduce the same way? What is characteristic of this reproduction?

Answer 23

No, they all have varied life histories and reproductive cycles. They express alternation of generations