Algae Lecture

Gross Morphology vs Anatomy vs Thallus Form

Gross Morphology: what it looks like

Anatomy: internal cell structure

Thallus Form: body plan

Convergent vs Divergent Evolution

Convergent: unrelated groups evolve similar forms (blade forms in brown and red algae)

Divergent: related groups evolve different forms (filamentous vs parenchymatous forms in green algae)

Thallus Forms

Filamentous, branched cylinders, blade-like, crustose, saccate

Meristems

Apical (at tips), intercalary (between tissues, basal and distal), diffuse (growth throughout)

Holdfasts

Rhizoidal, discoid, haptera, rhizomatous

Branching Types

Dichotomous, distichous (branches in two rows), whorled (branches radiate from 1 point), spiral (branches wrap around plant)

Distichous vs Dichotomous

Distichous: rows

Dichotomous: equal splitting

Reproductive Structures

Conceptacles: protected chambers for reproduction in thallus

Sori: grouped reproductive spots on the surface of the thallus

Cystocarps: round reproductive structures with developing diploid carposporophyte

Tetrasporangial Structures: spore-producing structures via meiosis

Primary vs Secondary Endosymbiosis

Primary: eukaryotic cell engulfs a cyanobacterium, bacterium becomes a plastid

Secondary: eukaryotic cells engulfs another photosynthetic eukaryote

Green Algae Storage Products

Starch in chloroplast

Isomorphic vs Heteromorphic

Isomorphic: stages look similar (Ulva)

Heteromorphic: stages look different (Laminaria)

Sporophyte-dominant vs Gametophyte dominant

Sporophyte-dominant: diploid stage is larger (kelps)

Gametophyte-dominant: haploid stage is larger (greens)

Ecological Consequence of Pigments in Green Algae

Chlorophyll a and b absorb red and blue

Green algae mainly in shallow water

Acrosiphonia

Thallus: filamentous

Life History: haplodiplontic

Structure: branched filaments

Ulva

Thallus: blade-like

Life History: isomorphic haplodiplontic

Algal Bloom Consequences

1. Eutrophication (rapid algal growth)

2. Hypoxia (low oxygen)

3. Fish die

4. Habitat degradation (blocks light)

Ochrophyta Secondary Endosymbiosis

Eukaryote engulfed a red algae

Plastid has 3-4 membranes

Ochrophyta Adaptations for Deep Water

1. fucoxanthin pigments (capture blue-green light in deeper water)

2. Large thalli (reach towards light, vertical growth)

3. Air bladders (buoyancy, stay near light)

4. Flexible blades (less breakage in currents)

Fucus

Thallus: flat, dichotomously branched

Life History: diplontic

Reproduction: conceptacles, zygotes

Hedophyllum

Thallus: parenchymatous Kelp blade

Life History: haplodiplontic

Reproduction: sori

Why keep Desmarestia separate?

Releases sulfuric acid, acidify surroundings, destroy tissues

Formation of Pit Plugs

1. red algae cells divide by mitosis

2. primary pit connection forms between daughter cells

3. membrane-lined pit remains open

4. proteinaceous plug core deposited in center

5. some: cap layer forms over plug

Mazzaella

Thallus: blade-like

Life History: triphasic

Reproduction: cystocarps, tetrasporangia

Mastocarpus

Life History: heteromorphic triphasic

Reproduction: cystocarps, tetrasporangia

Polysiphonia

Thallus: filamentous

Life History: triphasic

Reproduction: cystocarps, tetrasporangia

Ahnfeltiopsis

Thallus: fleshy blades

Life History: triphasic

Reproduction: cystocarps, tetrasporangia

Coralline Thallus Structure

Epithallus: outer surface layer

Cortex: calcified outer protective layer

Medulla: inner filaments

Conceptacles: reproductive chambers in thallus

Coralline Ocean Acidification Vulnerability

Calcified

lower pH causes reduced calcification

Other Characteristics of Corallines

Reef building

stabilize rocky habitats

grow slowly, long lived

Intertidal Gradients

Vertical (high to low intertidal)

Horizontal (Wave protected/exposed areas)

In a protected cove, plants in the low zone are more wave-exposed than those in the high zone. True or False?

False: Wave exposure is horizontal, not vertical

How seaweeds escape limpet grazing

1. grow vertically

2. rapid growth

3. chemical defenses

Net Primary Production

Gross Primary Production - Respiration

Base of Euphotic Zone

Depth where light intensity is too low to support net photosynthesis

Kelp Aquaculture Benefits

1. Nutrient removal

2. Water quality improvement

3. CO2 uptake

Seagrass Morphology

Roots, rhizomes, leaves, flowers/seeds

Threats to seagrass/eelgrass

1. Nutrient pollution

2. Sedimentation and turbidity

3. Physical disturbance

4. Climate change

5. Disease

Oregon HAB Toxin

Domoic acid

From diatoms

Algae extract products

1. Agar

2. Alginates

3. Carrageenan

Invasive zostera japonica

From Asia (20th century)

Occupies higher intertidal areas

Rockweed/sargassum invasion

1. Northern: 1940s, shipping

2. Southern: 1990s, rafting debris