BIO3021 Lecture Notes - Lecture 12: Macrocystis Pyrifera, Ecklonia Radiata, Kelp Forest
25 May 2018
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Lecture 12 – Macroalgae: kelps
• Forms dense forests (40 m high)
• Kelps: large brown algae
Kelp Forests
• Very dense structures
• Phylogenetically diverse (>20 phyla of animals, algae and other protists)
• Structurally complex
• Highly productive, rapid growth
• Two dominant orders: Laminariales and Fucales
Kelp Ecosystems
• Well developed at 40-60˚ latitude
• Shallow open coastal waters, 15-40 m depth
• Cold (<20˚c) nutrient rich waters
• Global distribution kelp forests constrained by
o Light at high latitudes
o Nutrients, warm water and competition with other macroalgae at low
latitudes
Morphological Groups of Kelp
• Canopy kelp
o Floating canopy
o Macrocystis pyrifera up to 45 m long
o Keep canopy dampens waves – affects water flow and sedimentation
▪ Enhances sedimentation
o Kelp canopy reduces light creating understorey for species adapted to
low light intensity
• Stipitate kelp
o Held above benthos by rigid stipe in water column
o E.g. Ecklonia radiata, Lessonia nigrescens
• Prostrate kelp
o Cover benthos with fronds
Animal Assemblages in Kelp Forests
• Invertebrates
o In holdfasts: polychaetes, amphipods, decapods, gastropods
o On Stipes: squid eggs (Loligo gahi)
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