L2-Algae-Lastovetsky_2024

Introduction to Algae

  • Dr. Olga Lastovetsky, Assistant Professor at the School of Biology and Environmental Sciences.

Definition and Types of Algae

  • Algae: Informal term for a large group of photosynthetic eukaryotic organisms.

    • Single-celled Algae

    • Multicellular Algae

Origins of Algae

  • Algae are ancestors to plants; however, not all algae are plant ancestors.

  • Four major eukaryotic supergroups contain algae.

    • Algae are interspersed in the SAR and Archaeplastida groups.

      • Examples of algae: Diatoms, Golden algae, Brown algae, Dinoflagellates, Red algae, Green algae.

Different Types of Algae

Diatoms

  • Part of SAR supergroup.

    • Unicellular with glass-like cell walls.

    • Over 100,000 living species; abundant photosynthetic organisms in water bodies.

Golden Algae

  • Part of SAR supergroup.

    • Characterized by yellow and brown carotenoids.

    • Mainly unicellular and forms part of plankton.

Brown Algae

  • Largest and most complex algae from SAR supergroup.

    • All are multicellular, predominantly marine.

    • Examples include giant kelp, which can grow up to 60 m.

Seaweeds

  • Seaweeds are not true plants. Basic structure includes:

    • Blade: Leaf-like part.

    • Stipe: Stem-like structure.

    • Holdfast: Anchor that attaches to the substrate.

    • Gas Bladder: Helps in buoyancy.

Dinoflagellates

  • Part of SAR supergroup.

    • Move with two flagella, causing a spinning motion.

    • Can be phototrophic or heterotrophic; important in marine ecosystems.

Red Algae

  • From Archaeplastida group, considered plant ancestors.

    • Over 6,000 species known, many appear red due to phycoerythrin.

    • Capable of living in deep water (>250 m).

    • Example: Porphyra species (nori used in sushi).

Green Algae

  • Closest relatives to land plants and members of Archaeplastida.

    • Over 7,000 species, primarily live in freshwater.

    • Examples are Chlamydomonas (unicellular) and edible sea lettuce (multicellular).

Cyanobacteria (Blue-green algae)

  • Not eukaryotic; belong to the Bacteria domain.

Habitat of Algae

  • Algae thrive in oceans, forming diverse seaweed ecosystems.

    • Giant kelp forests provide crucial habitats and food for marine life.

Ecological Role of Algae

  • Algae are primary producers in oceans, serving as the foundation of marine food webs.

  • Algae contribute significantly to oxygen production (up to 50% of the world's oxygen).

  • They play a vital role in carbon fixation, helping mitigate climate change by sequestering carbon.

  • Blue Carbon: Refers to carbon stored in marine and coastal ecosystems.

Algal Growth and Blooms

  • Algal blooms result from rapid algae growth due to nutrient availability.

    • Consequences:

      • Benign blooms: Support higher trophic levels.

      • Harmful blooms: Cause oxygen depletion and can be toxic to marine life and humans.

    • Causes of blooms include nutrient input from rivers and anthropogenic sources.

Extremophilic Algae

Hot Springs

  • Algae, especially species from Cyanidiophyceae group, adapt to extreme environments (high temperatures, acidity).

Pink Snow (Watermelon Snow)

  • Chlamydomonas nivalis which thrive in freezing conditions due to carotenoid pigments.

Symbiotic Relationships

Lichens

  • Symbiotic relationship between filamentous fungi and photosynthetic green algae.

    • Mutual benefits: fungi get carbon; algae get protection.

Corals

  • Coral-dinoflagellate symbiosis critical for reef survival; the expulsion due to temperature rise leads to coral bleaching.

Industrial Applications of Algae

Food Industry

  • Seaweeds are consumed locally (e.g., nori, Irish moss).

  • Microalgae are sources of protein and dietary supplements.

  • Gelling agents such as agar and carrageenan derived from algae.

Sustainable Agriculture

  • Algae used as soil improvers and biostimulants to reduce chemical fertilizer usage.

Wastewater Treatment

  • Algae like Chlorella are efficient in nutrient removal, also generating oxygen for biodegradation of contaminants.

Biofuels

  • Algae-based biofuels show potential for high yield compared to traditional sources.

  • Current production costs challenge viability; research focuses on optimizing growth and oil extraction.

Conclusion

  • Algae have significant ecological, industrial, and economic importance, providing critical functionalities in both natural and human-made systems.