Lecture 20 Competition and Predation 1) Review: intertidal zonation 2) Causes of zonation -Physical...
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Lecture 20 Competition and Predation 1) Review: intertidal zonation 2) Causes of zonation -Physical and biological factors -Temperature and desiccation
Lecture 20 Competition and Predation 1) Review: intertidal
zonation 2) Causes of zonation -Physical and biological factors
-Temperature and desiccation (Foster) -Competition and predation
(Connell) 3) Competition on sediment shores -Deposit feeders
(Levinton, Posey) 4) Keystone species -Pisaster
Slide 2
Intertidal Zonation: -Subclassifcation of ecosystems -Smaller
zones with unique physical characteristics -Unique habitat that
favors particular species
Slide 3
Slide 4
Olympic Peninsula, Washington State
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Newport Beach, CA
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Kodiak Island, AK
Slide 7
Rio De Janeiro, Brazil
Slide 8
Atlantic Coast North America Large kelps (Laminaria) Red algae
Small kelps, mussels Barnacles, predatory snails Microalgae and
grazers: herbivorous snails
Slide 9
Large kelps, Small kelps, mussels Barnacles, predatory snails
Microalgae and grazers: herbivorous snails Pacific Coast North
America Red algae
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Causes of Zonation
Slide 12
water Frank 1965 Observation High shore organisms: exoskeletons
Hypothesis Desiccation sets upper tidal limits Prediction Dripping
water will cause increase in upper tidal limits
Temperature At 100% humidity: Mean lethal time (hours) lethal
temperature (C) high-shore species (Chthamalus) mid-shore species
(Balanus balanoides) subtidal species (Balanus crenatus)
Slide 15
Desiccation Chthamalus (high-shore) S. balanoides (mid-shore)
B. crenatus (subtidal) At 17-20C, 0% humidity:
Slide 16
Slide 17
heat an desiccation stress
Slide 18
Balanus balanoides low shore Chthamalus stellatus high shore
Species Interactions: Competition
Slide 19
Biological factors: Larval settlement Larvae tend to settle on
tidal heights based on environmental cues Barnacles: Gregarious
settlement Barnacle cyprid larva
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Slide 21
Connell (1961) Chthamalus Balanus Upper limits of Both set by
physical stress What sets the lower limits of Chthamalus?
Slide 22
Bottom of Chthamalus zone Top of Chthamalus zone Experimental
removal of Balanus
Slide 23
Balanus grows 70% > than Chthamalus Balanus overgrows and
undercuts Chthamalus Connells Observations:
Temperature and desiccation prevent both Chthamalus and Balanus
from living at higher levels Competition from Balanus prevents
Chthamalus from inhabiting the middle zone Predation by snails sets
the lower limits of the distribution of Balanus Balanus zone
Chthamalus zone
Slide 29
Paradigm of Intertidal Zonation:
Slide 30
Sediment vs Rocky Shores High heat and desiccation stress
Stable substrate Sedentary lifestyles Resident predators Benthic
macroalgae, microalgae Rocky Shores Less heat and desicc stress
Unstable substrate No SSOs Transient and mobile predators
Microalgae, drift macroalgae Sediment Shores
Slide 31
Predator Exclusions on Dissipative Shores large predators
excluded control