macroalgae Flashcards
evolutionary history of macroalgae
Cyanobacteria 3.5 billion years old prokaryote precursors of chloroplasts.
The oldest plant-like fossils are red algae found in remains of cyanobacteria mats (called stromatolites) dating back 1.6 billion years, 400 million years older than any other plant-like fossils.
The oldest fossil eukaryote(1.05 billion years) that belongs to a modern taxon is Bangiomorpha pubescens, which strongly resembles the modern red algal genusBangia.
Chlorophyta are thought to have evolved around 1 billion years ago and are the ancestors of land plants.
Ochrophyta only evolved 150-200 million years ago. These heterokonts are thought to have incorporated red algae in their cells which became their chloroplasts (bound by 4 membranes).
macroalgae
~ 12,000 known species worldwide
Found in all ocean basins
Distribution is determined by temperature, light, salinity, nutrients, pH, wave exposure, grazing, human impacts, etc.
635 species of seaweed are found in UK waters (350 reds, 185 browns) making it a hot spot for macroalgal biodiversity
macroalgae importance
Primary producers
Highly important from an ecological and economic point of view
Habitat builders providing food and shelter for many marine organisms
Many commercial uses
seaweed morphology
Blades/Frond
Stipe
Holdfast
Spores
No conductive tissues EXCEPT for Laminarales (order) – KELPS
seagrass morphology
Leaves
Stalk
Roots, rhizomes
Seeds or fruits
Xylem/phloem tissues
reproductive modes
Vegetative:
- Fragmentation (e.g. Ectocarpus sp.)
- Propagules (e.g. Sphacelaria sp.)
Asexual:
- Non-motile spores (e.g. Lithothamnion sp.)
- Zoospores (e.g. browns and greens)
Sexual:
- Involves gamete fusion
algae - life history/cycles
In a gametic life history, the gamete (egg or sperm) is the only haploid cell produced. Examples include humans and Fucus spp.
In a zygotic life history, thezygote is the only diploid cell produced.
In a sporic life history, there are alternating multicellular 2n and 1n generations. A sporophyte is a multicellular 2n thallus that produces 1n spores by meiosis.
Variety is the spice of life (in the following slides…)!
chlorophyta - green algae
About 1700 species worldwide
Storage product: Starch, sometimes stored in pyrenoids
Contain cellulose and sometimes pectin and hemi-cellulose in cell walls
Phaeophycaea - brown algae
Not a true plant, belongs to the kingdom Chromista
About 2000 species worldwide
Storage product: laminarin
Contain cellulose and alginic acid in cell walls
the kelps
Found in 43% of the world’s marine ecoregions along coastlines of all continents except Antarctica
kelp forests
Tallest species in the world (Macrocystis pyrifera); Regularly grows up to 35 m, but can reach 65 m
Foster huge biodiversity
- Amongst fronds
- Within the holdfast / haptera
Can fix a lot of carbon!
Rhodophyta - red algae
~7000 species worldwide
Storage product: Floridian starch
Contain cellulose, agar and carrageenan in their cell walls
Calcareous algae
Precipitate calcium carbonate (CaCO3) within, between or upon their tissues
Calcium is either in the form calcite or aragonite
Different forms; crustlike, branched, nodular or epiphytic
Found in all three macroalgal groups (Green, Red & Brown)
maerl beds
Important in the carbonate budget of the ocean
High biodiversity within these habitats
Sensitive ecosystems
invasive seaweed
Non-native, have arrived from elsewhere in the recent past
Often introduced through human activities
Are they always bad for ecosystems?
