8.2 Canopy Forming Seaweeds Flashcards
what are canopy forming seaweeds?
- Kelps, fucoids and other complex, erect mainly brown macroalgae that produce relatively large biogenic habitats
- They include some of the largest marine algae, with thallus divided into basal part, stem and frond.
life cycle of fucoids (Facales)
- fucoids are diploid
- life cycle is a diploid monogenetic cycle
- reproduction through gametes
- gametes produced by meiosis
- gametes carried by antheridia and oogones (found within apical male and female conceptacles)
- fertilization in water
- new diploid plants will be generated again from the zygote
life cycle of kelps (Laminariales)
- haplodiplont cycle
- alternation of two morphologically distinct phases:
1) diploid sporophyte (macroscopic)
2) haploid gametophyte (microscopic)
Distribution of canopy forming seaweeds
(facts and map)
- widespread on shallow hard substrata
- in temperate and polar coastal ecosystems
- main genera along coasts of north-west Europe: Laminaria and Fucus
- main genera in Mediterranean Sea: Cystoseira and Sargassum
facts about canopy forming FOUNDATION species
- they modify light, flow, sedimentation and nutrients
- they buffer erosion
- they are nursery areas
- highly productive
- habitat for diverse assemblages
human usage
- food
- cosmetics
- fertilizer
- stabilizers and emulsifiers
- medicines
- thalassotherapy
estimated value of canopy habitats
these systems (canopy forming seaweeds) are___ ?
- naturally dynamic
- resilient
- have a generally rapid recovery from disturbances (ms to a few years)
they are influenced by
- dispersal
- biotic interactions (competition with understory species, herbivores)
- habitat characteristics
retraction of canopies
where?
(Rückgang)
documented widespread range retractions and declines since 1900’s in
- Europe (examples of Sweden and Mediterranean Sea were shown in slides)
- North and South America
- Japan
- Korea
- South Africa
- Australia
- New Zealand
- Alaska
what are canopies replaced by?
- turfs
- ephemeral algae
- mussels
- barrens
what are algal turfs?
- they are loosely to densely aggregated thalli
- < 15cm tall
- composed of more or 1 species
- often associated with sediments (sediment-trapping morphology)
- covering large areas
global map of canopy-shifts to turf
where are losses particularly severe?
- in urban areas
- e.g. Italy:
- 13 sites around Italy
- 40% of losses of C. compress explained by urban-related indicatorsw
what are canopy-losses accelerated by?
- climatic changes
- drives shifts in species compositions (e.g. Laminaria along
- Shift from canopy to less complex systems is globally happening
- Functional consequence?
- here: example of temperate seaweeds
- System shifty in many different ways
- lost and replaced by b, c, d
b) function don’t change too much
most similar to system befor
novel system with similar function
c) d) different system , diff. species and functions
multiple stressors that drive changes in kelp forests
- pollution
- fishing
- harvesting
- invasions
- herbivory
- warming
- others