L7 - Rocky Shore Ecosystems II Flashcards
Aim
Demonstrate how biological interactions influence species distribution & abundance
Use of manipulative experiments to test ecological theory
Marine Biology: An Ecological Approach, Nybakken, Chapter 6 pp 236-245
Marine Biology, Function, Biodiversity, Ecology, Levinton, Chapter 14 pp 305-333
Coastal Marine Ecology, Underwood & Chapman, Chapter 5
Zonation
-Concept that organisms occur in discrete bands driven by exposure
-Outdated, organisms are patchy in their distribution
- Tolerance to desiccation
- Transplant experiments & polar bears
- Birth place of manipulative ecology and experiment design
Key biological interactions
Competition
Grazing
Predation
Recruitment
Competition: Barnacles
Pioneering work by Connell on Scottish intertidal shores
Grazing
- Experiments by Underwood (1980) in NSW
- Observation: Ulva is restricted to the lower midlittoral region of the shore
Explanations
Grazing?
Desiccation?
Encrusting species?
Grazing: Experimental Design
Roof (clear/not cleared) -Desiccation +grazing
Cage (clear/not clear) -Desiccation - grazing
Fence (clear/not clear) +Desiccation - grazing
Control (clear/not clear) +Desiccation + grazing
Grazing: Results
Within a month for ulva to restore 100%
Grazing: Results
Light reduction from biota settling on enhabiting cage reduced photosynthesis
Predation
West Coast USA community structure
Community manipulations by Dayton & Paine
*Logs/debri removed encrusting community with Impact
Predator removal
- Starfish are active predators during high tide
- Predation defines lower limit of mussels
- Mussels are dominant space competitor
- Succession
- Keystone predator
*Seastar constantly opening up new colenisation areas
*Removing starfish *keystone predator then habitat dominated by one species that benefits from starfish predatorial absense
Keystone Predators
Keystone predators have a disproportionately large effects on their communities relative to their biomassa
Predator-grazer interactions
Subtle effects of grazers & predators on barnacle diversity
Complicated experimental design
starfish exclusion
Predation & community dynamics
High predation = low diversity
Innefective predation = outbreak of competitive dominant
Middle ground predation = Predator-mediated coexistance
Disturbances & Recruitment
West Coast USA
Recovery determined by patch size and larval availability
Scale of disturbances
Mussel survival and patch size, East Coast USA
Patches cleared and planted with mussels, survival monitored
Disturbances & stable states
Localised disturbances can result in several alternative stable states
Following clearance successional patterns may differ due to larval availability
eg. East Coast USA
Summary
Be able to describe how biological interactions regulate organism distribution on the rocky shore
Importance of disturbances in maintaining species diversity
Availability of new recruits
Disturbances and how they affect biota
