Marine Ecology May 7, 2007 Between the tides: Interactions 1
Zonation: Role of physical/chemical factors vs. biological interactions Joe Connell, 1972: Hypothesis Physical factors primarily responsible for upper limits Biological interactions primarily responsible for lower limits Support for hypothesis?
Effects of biological interactions on zonation/distribution in intertidal Competition for space Predator-prey interactions Role of grazers Symbiotic relationships and species distribution Larval ecology Role of disturbance
Competition for space Example: Vertical distribution of the intertidal barnacles Chthamalus Balanus
Barnacle zonation (after Connell, 1961)
Barnacle zonation in New England
Competition for space Example: Algal distribution Species with small body forms initially settle and grow (opportunistic) Species with small body forms initially settle and grow (opportunistic) Slower-growing, larger forms outcompete if no disturbance occurs Slower-growing, larger forms outcompete if no disturbance occurs
Competition for space Example: Lottia gigantea (owl limpet) territoriality
Competition for space Example: Mussel bed succession
Predator-prey interactions Example: Pisaster ochraceus and the mussel Mytilus californianus Caging experiments Follow-up (14-17 yrs) Comparisons to Chile and New Zealand studies
Bob Paine’s experiments Castro and Huber, Fig
Fig. 6.18: Pisaster ochraceus as a Keystone species
Fig. 6.19: Natural experiments on New England coast (Menge and Lubchenco)
Predator-prey interactions Example: Nucella sp. Predatory snail Excretes enzymes with an accessory boring organ to dissolve “shell” of barnacles Has operculum: enables it to retreat into shell at low tide
Predator-prey interactions Distribution within a zone Oystercatchers affect limpet distribution Black oystercatcher (Pacific) Variable oystercatcher (New Zealand)
Role of grazers Limitation of algae by grazers Overview Case study: Katharina tunicata (chiton)
Role of grazers Maintenance of diversity by grazers Example: Effects of snails on algal diversity in a tidepool.
And then the gulls move in…
Role of grazers Grazing deterrents Morphological Chemical defenses Crustose vs. erect forms Size refuges Limitation of grazers by algae
Symbiotic relationships One species creating a suitable habitat for another Example: Mussel beds
Symbiotic relationships Mutualistic relationships Example: Anthopleura elegantissima