Marine Biology Intertidal Ecology: Focus on Biological Interactions

Zonation: Role of physical/chemical factors vs. biological interactions Joe Connell, 1972: Hypothesis Joe Connell, 1972: Hypothesis Physical factors primarily responsible for upper limits Physical factors primarily responsible for upper limits Biological interactions primarily responsible for lower limits Biological interactions primarily responsible for lower limits Support for hypothesis? Support for hypothesis?

Effects of biological interactions on zonation/distribution in intertidal Competition for space Competition for space Predator-prey interactions Predator-prey interactions Role of grazers Role of grazers Symbiotic relationships and species distribution Symbiotic relationships and species distribution Larval ecology Larval ecology Role of disturbance Role of disturbance

Competition for space Example: Vertical distribution of the intertidal barnacles Example: Vertical distribution of the intertidal barnacles Chthamalus Balanus Chthamalus Balanus

Barnacle zonation (after Connell, 1961)

Barnacle zonation in New England

Competition for space Example: Algal distribution 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 Example: Lottia gigantea (owl limpet) territoriality

Competition for space Example: Mussel bed succession Example: Mussel bed succession

Predator-prey interactions Example: Pisaster ochraceus and the mussel Mytilus californianus 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. 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 Distribution within a zone Oystercatchers affect limpet distribution Oystercatchers affect limpet distribution Black oystercatcher (Pacific) Variable oystercatcher (New Zealand)

Role of grazers Limitation of algae by grazers Limitation of algae by grazers Overview Overview Case study: Katharina tunicata (chiton) Case study: Katharina tunicata (chiton)

Role of grazers Maintenance of diversity by grazers Maintenance of diversity by grazers Example: Effects of snails on algal diversity in a tidepool. Example: Effects of snails on algal diversity in a tidepool.

Role of grazers Grazing deterrents Grazing deterrents Morphological Morphological Chemical defenses Chemical defenses Crustose vs. erect forms Crustose vs. erect forms Size refuges Size refuges Limitation of grazers by algae Limitation of grazers by algae

Symbiotic relationships One species creating a suitable habitat for another One species creating a suitable habitat for another Example: Mussel beds Example: Mussel beds

Symbiotic relationships Mutualistic relationships Mutualistic relationships Example: Anthopleura elegantissima Example: Anthopleura elegantissima