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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 spring Half Full neap Half spring Zero datum New (MLLW) A Position on Shore B C 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/O2 Debt Aerial Respiration Latitudinal Submergence Biological Factors • Competition • Predation • Symbioses J. Connell Competition between Balanus balanoides and Chthamalus stellatus Chthamalus stellatus Balanus balanoides DISTRIBUTIONS Chthamalus Transplant Balanus Transplant TRANSPLANT ADULTS Transplant adults Both Chthalamus and Balanus survive Chthamalus Clearance BEFORE Balanus Clearance CLEARANCE EXPERIMENTS Chthamalus Clearance RESULTS Balanus Clearance CLEARANCE EXPERIMENTS Clear both Balanus and Chthalamus Both Chthalamus and Balanus recolonize Chthamalus CONTINUOUS REMOVAL AND CONTROLS Chthamalus removed Clearance Balanus Chthamalus removed CLEARANCE EXPERIMENTS Clearance 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 CONTINUOUS REMOVAL AND CONTROLS Balanus removed Clearance Balanus removed Clearance Balanus 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 Clearance 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 BEFORE No removal Remove Pisaster No removal Remove Pisaster AFTER No removal Conclusions • Pisaster determines the lower distribution bound of Mytilus by predation • The upper limit of Mytilus distribution determined by physical tolerances
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