MARKET 1 Lecture Notes - Lecture 16: Photic Zone, Seaweed, Periphyton
Algae
What are algae?
• Algae are defined by ecological traits due to not having been descended from a common
ancestor
• Mostly photosynthetic species that produce oxygen and live in aquatic habitats
• Lack body, vascular system and reproductive features of terrestrial plants
• Often eukaryotic except cyanobacteria that are prokaryotic
• Can consist of single cells, colonies or complex organisms that must work together as simple
tissues
• Tremendously important component of life on Earth
➢ Up to 80% of biomass and primary productivity in ocean waters is contributed by
eukaryotic ultraplankton found in photic zone
➢ Productivity measured by satellite cameras that record info on clearly defined
optical bends about chlorophyll a cone
Algae sizes and terminology
Macroalgae = largest algae
• Algae observable with naked eye
• Include coenocytes with large bodies comprised of one very large multinucleate cell (e.g.
Caulerpa) – lack internal cell walls except when forming reproductive strategy
• Majority are parenchymatous bodies composed of tissues, 3D arrays of cells (e.g. Fucus)
Microalgae = smallest algae
• Vast majority are unicellular and form most of the phytoplankton
• Mostly solitary coccoid round balls but may aggregate in colonies
• May also grow in (un)branched filaments
• Branched filaments usually grow attached = periphyton
• Biofilms = algae that aggregate on rocks e.g. diatoms, cyanobacteria
• Phytoplankton (e.g. coccolithophores, dinoflagellates) float in the ocean
• Coenobia = highly organised colonies that feature a genetically defined number and pattern
of cells
Green Algae – Chlorophyta
• contain chlorophyll a and b that are not concealed by differently coloured accessory
pigments
• monophyletic group that has heavily diversed – higher plants emerge from this group
• range of body types including non-flagellate and flagellate unicells or colonies, (un)branched
filaments and multicellular parenchythatous sheets
• primarily aquatic but also found in terrestrial environments
Brown Algae – Heteromontophyta
• Belong to diverse group known as stramenophiles
➢ Includes phytoplankton, periphton, macroalgae
Document Summary
Algae: algae are defined by ecological traits due to not having been descended from a common ancestor. Up to 80% of biomass and primary productivity in ocean waters is contributed by eukaryotic ultraplankton found in photic zone. Productivity measured by satellite cameras that record info on clearly defined optical bends about chlorophyll a cone. Macroalgae = largest algae: algae observable with naked eye. Include coenocytes with large bodies comprised of one very large multinucleate cell (e. g. caulerpa) lack internal cell walls except when forming reproductive strategy: majority are parenchymatous bodies composed of tissues, 3d arrays of cells (e. g. fucus) Brown algae heteromontophyta: belong to diverse group known as stramenophiles. Red algae rhodophyta: phycoerythrin obscures green of chlorophyll a. Extremely efficient at harvesting blue and green light in subtidal zones: also contain phycocyanin and allophycocyanin. Dinoflagellates: are mostly microscopic photosynthetic cells or heterotrophic cells that have two distinct flagella. Motion of flagella causes cells to rotate as they swim.
