Algae

Question 1

What are algae?

Answer 1

Photosynthetic autotrophs Chlorophyll a is the major pigment Lack morphological differentiation into roots, stems and leaves Lack a sterile covering around their reproductive cells Not monophyletic, include prokaryote and eukaryote members.

Question 2

Origins of algae?

Answer 2

Each algal taxa has a characteristic type of chloroplast Each type of chloroplast can be explained by one or more endosymbiotic events Chloroplast in some groups is very degenerate

Question 3

What are cyanobacteria?

Answer 3

Blue green algae - have three types of pigments, which are all expensive to make.

Question 4

Illustrate the relationship between the incident light spectrum, algal photosynthetic pigment composition and ecological distribution of algae.

Answer 4

Light varies with depth:

• Beyond 100m there isn’t enough light for photosynthetic organisms

Green algae are usually found in the upper littoral zone. Brown algae are mostly found in the middle littoral zone, whereas red algae are commonly seen in the lower littoral zone or in the deep ocean.

Pigmentation determines the depth where an algal group can survive.

Green algae at surface
Blue green algae
Brown algae
Red algae

Carotenoids contribute to red algae and are shorter wavelengths than other pigments such as phycocyanin which contributes to blue green algae, found higher up.

Question 5

Algal contributions to CO2 fixation?

Answer 5

Fix 60% of the total CO2 fixed.

Unaided diffusion cannot account for photosynthetic rates in macroalgae. Increasing turbulence assists CO₂ diffusion, but cconsequences of increased turbulence on drag forces

Algae have various strategies to utilise HCO₃^- to supplement CO₂. CO₂ concentrating mechanisms – carbonic anhydrase, carboxysomes

Question 6

Phylogenetic tree showing the relationships between green algae and main groups of land plants?

Answer 6

Question 7

Evidence for a secondary endosymbiosis?

Answer 7

Chloroplast has 4 membranes
Features within first pair of membranes are consistent with endosymbiosis of a cyanobacterium
A nucleomorph and 80S ribosomes within the second pair of membranes, consistent with remnants of first eukaryotic host
Sequence comparisons group the nucleomorph with red algae, and the main nucleus with acanthamoeba.

Question 8

Example of an algae that has lost it’s 4th membrane?

Answer 8

Dinoflagellates

Question 9

Problems with an algal life in water?

Answer 9

• Light regime (light varies throughout the water)
• Diffusion of nutrients and CO2 is slower
• Drag forces moulding morphology
• Salinity and desiccation tolerance (the amount of salt varies throughout the day)
• Temperature (thermocline forms with different layers which don’t mix)

Question 10

Techniques employed by algae to remain in the photic zone?

Answer 10

1. Buoyancy in cyanobacteria
2. Motility in flagellates
3. Anchorage in intertidal and benthic algae

Question 11

Algae as a biofuel?

Answer 11

There is a need for biofuels which don’t impact on food supply chains.

Algal biofuels have the potential to be sustainable but new industrial processes will need to be developed.

New strains with desirable fuel traits to be developed.

Source of oils and other hydrocarbons.

Question 12

What happens when there are high levels of nutrients in water?

Answer 12

Algal blooms and eutrophication.

Light reductions

from algal blooms, along with increased sediment and pollutant influx into the Black Sea have killed off the Benthic Phyllophora fields. Also rendered the area anoxic.

Certain regions are rich in major nutrients but only support a low algal biomass – High Nitrogen Low Chlorophyll regions (HNLC). It is thought that iron might be limiting growth.
Iron fertilisation in the equatorial Pacific. Iron feeds the thermocline. Can then store more CO2 in the algae. No net increase in CO2 fixation, as that area eventually reaches the coasts which are CO2 rich anyway. CO2 fixed can also then get used by fish which feed on the algae.

Often due to coastal inputs.