Rocky Intertidal Zone Community
Intertidal Zone Area of the shore between the highest high tide and lowest low tide
Mixed Semi-diurnal Tidal Regime Two tides per day Tidal heights not equal
neap spring FullHalfNewHalf Zero datum (MLLW)
A B C Position on Shore
Physical Factors Affecting Distributions Physical Tolerances Temperature (average and extreme) Moisture/Desiccation Light Gasses (respiration) Wave shock Sand scouring
Biological Factors Biological Interactions Predation Grazing Competition Symbioses
Summary Upper distributions of intertidal organisms tend to be determined by physical factors – tolerances Lower distributions of intertidal organisms tend to be determined by biological interactions
Intertidal Zonation
Factors Affecting Height of the Intertidal Zone Slope of the shore Wave exposure Local geomorphology Tidal flux
Behavioral Adaptations
Morphological Adaptations Color Shells
Physiological Adaptations Quiescence Acclimation Anaerobic Respiration/O 2 Debt Aerial Respiration
Latitudinal Submergence
Biological Factors Competition Predation Symbioses
J. Connell Competition between Balanus balanoides and Chthamalus stellatus
Balanus balanoides DISTRIBUTIONS
Chthamalus Balanus Transplant TRANSPLANT ADULTS
Transplant adults Both Chthalamus and Balanus survive
Chthamalus Balanus Clearance BEFORE CLEARANCE EXPERIMENTS
Chthamalus Balanus Clearance RESULTS CLEARANCE EXPERIMENTS
Clear both Balanus and Chthalamus Both Chthalamus and Balanus recolonize
Chthamalus Balanus Clearance CONTINUOUS REMOVAL AND CONTROLS Chthamalus removed CLEARANCE EXPERIMENTS
Continuous removal of Chthalamus from both heights Ex. Balanus recolonizes and Chthalamus does not C. Both species recolonize Chthamalus has no effect on Balanus in lower zone
Chthamalus Balanus Clearance CONTINUOUS REMOVAL AND CONTROLS Balanus removed CLEARANCE EXPERIMENTS
Continuous removal of Balanus from both heights Ex. Chthalamus colonizes in Balanus zone C. Both species recolonize zones Balanus cannot survive in upper zone Chthamalus can survive in lower zone in the absence of Balanus
Chthamalus stellatus Balanus balanoides
Chthamalus Balanus Clearance
Conclusions Balanus exclusion determines lower distribution bound for Chthamalus Competitive interaction responsible Exclusion mechanism is crushing Upper distribution of Balanus determined by physical tolerance
R. Paine Predation by Pisaster ochraceus on Mytilus californianus
Mytilus californianus Algae Pisaster ochraceus
Remove Pisaster No removal BEFORE
Remove Pisaster No removal
AFTER
Conclusions Pisaster determines the lower distribution bound of Mytilus by predation The upper limit of Mytilus distribution determined by physical tolerances