EVSC20004 Lecture Notes - Lecture 7: Evaporative Cooler, Intraspecific Competition
18 May 2018
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LECTURE 7: ROCKY SHORES – DESIGN OF INTERTIDAL
ORGANISMS
Zonation
• Typical in the intertidal zone, highest species abundance in middle of rocky shores, highest
diversity at landward edge
• Similar patterns of species vertical ranges’ combined with sharp boundaries suggest zonation
caused by simple patterns
Causes
Interaction of biological and physical factors to form zonation
Heat Stress
&
Desiccation
Size
• As body size increases, the surface area relative to body volume decreases, aids in
reducing water loss
• However, a decreased SA:V comes with increased size which is a disadvantage for
heat loss (and lift/drag)
• Intertidal organisms trade off water and heat loss in their body sizes
• Increasing SA:V is only effective to prevent water and heat loss when you have a
hard shell
Shape
• Long thin organisms lose water more rapidly than spherical organisms
• Sea anemones contract into small cylinder at low tide to reduce SA and water loss
• Mobile animals like crabs can move around and hide - behavioural adaptation
Physiological adaptations to Heat Stress
• Higher intertidal species better adapted than lower intertidal species
• Evaporative cooling and circulation of body fluids
• Gastropods - different species found in different parts, due to retention of
cellular function at higher temps - changes in performance
• Feeding capabilities differ for upper intertidal and lower intertidal organisms
• Difference in response to temp, upper intertidal better performers
• Colour: can vary with latitude - due to temperature (heat up faster in colder areas)
• Mussels vary with latitude, higher latitude = higher percentage of black
(compared to brown)
Adaptation to Desiccation
• Many intertidal organisms have gills which they use to breathe when exposed to air
as long as gills are moist
• High intertidal crab has membrane on each leg designed to exchange gas from the
air for uptake into arterial blood
• Periwinkles: close their operculum to remain moist during low tide when exposed to
air
• Limpets: make the edge of their shell fit the exact configuration of the rock where
they live, keeping water inside - are able to create home scars to fit exactly
Wave Shock
• Organisms lower in the intertidal are more resistant to wave shock
• At high tide, waves may damage intertidal organisms through:
• Abrasion (particles hitting against rock)
• Pressure (crushing of delicate or compressible structures)
• Pressure drag (directional forces of waves may rip apart or dislodge organisms
or support structures)
• Morphological adaptations:
• Mussels: thick shells and threads for attachment, change attachment strength
with season, individual mussels more vulnerable to waves, dense beds dissipate
wave forces along the surface of the mussel bed - yet more competition
• Mussel bed - clump together for low velocity - easier to hold onto rock
Document Summary
Lecture 7: rocky shores design of intertidal. Zonation: typical in the intertidal zone, highest species abundance in middle of rocky shores, highest diversity at landward edge, si(cid:373)ilar patter(cid:374)s of spe(cid:272)ies (cid:448)erti(cid:272)al ra(cid:374)ges" (cid:272)o(cid:373)(cid:271)i(cid:374)ed (cid:449)ith sharp boundaries suggest zonation caused by simple patterns. Interaction of biological and physical factors to form zonation. Size: as body size increases, the surface area relative to body volume decreases, aids in reducing water loss, however, a decreased sa:v comes with increased size which is a disadvantage for heat loss (and lift/drag) Intertidal organisms trade off water and heat loss in their body sizes. Increasing sa:v is only effective to prevent water and heat loss when you have a hard shell. Long thin organisms lose water more rapidly than spherical organisms. Sea anemones contract into small cylinder at low tide to reduce sa and water loss. Shape: mobile animals like crabs can move around and hide - behavioural adaptation.
