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