Marine Ecology May 7, 2007

Between the tides: Interactions 1

Zonation: Role of physical/chemical factors vs. biological interactions

Joe Connell, 1972: HypothesisPhysical factors primarily

responsible for upper limitsBiological 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 Species with small body forms initially settle and forms initially settle and grow (opportunistic)grow (opportunistic)

Slower-growing, larger Slower-growing, larger forms outcompete if no forms outcompete if no disturbance occursdisturbance 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. 11.22

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 zoneOystercatchers affect limpet

distribution

Black oystercatcher (Pacific)Black oystercatcher (Pacific) Variable oystercatcher (New Zealand)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

MorphologicalChemical defensesCrustose vs. erect

formsSize refuges

Limitation of grazers by algae

Symbiotic relationships

One species creating a suitable habitat for anotherExample: Mussel beds

Symbiotic relationships

Mutualistic relationshipsExample: Anthopleura elegantissima