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Coral Reef Succession. Ecological Succession. The progressive change in the species composition of an ecosystem. New Bare Substrate. Colonizing Stage. Successionist Stage. Climax Stage. Ecological Succession. 2 types of succession. SECONDARY. PRIMARY.
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Ecological Succession The progressive change in the species composition of an ecosystem.
New Bare Substrate Colonizing Stage Successionist Stage Climax Stage Ecological Succession
2 types of succession SECONDARY PRIMARY • Growth occurring after a disturbance changes a community without removing the soil • Growth occurs on newly exposed surfaces where no soil exists • Ex. Surfaces of volcanic eruptions
Primary Succession For example, new land created by a volcanic eruption is colonized by various living organisms
Secondary Succession Disturbances responsible can include cleared and plowed land, burned woodlands
Mount St. Helens prior 1980
Mount St. Helens Sep. 24, 1980 May 18, 1980
Mount St. Helens Fireweed 1980 after eruption 2004 2012
Succession after Volcanic Eruption What organisms would appear first? How do organisms arrive, i.e., methods for dispersal? Volcanic eruption creates sterile environment Hanauma Bay Tuff Ring (shield volcano)
Early species improve habitat. Ex. Early marine colonists provide a substrate conducive for settling of later arriving species. First arrivals take precedence. Competition for space, nutrients and light; allopathic chemicals. As resources become scarce due to depletion and competition, species capable of tolerating the lowest resource levels will survive. Mechanisms of Succession Facilitation Inhibition Tolerance
high reproductive output high growth rate short life span low competitive ability low reproductive output higher maternal investment per offspring high competitive ability long life span slow growth rate r & K Selected Species Pioneer species- 1st species to colonize a newly disturbed area r selected r & K refer to parameters in logistic growth equation Late successional species K selected
Successional Models and their Impacts (p.133) • Case 1: No Disturbance (Competitive Exclusion Model) • Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model) • Case 3: Constant Strong Disturbance (Colonial Model)
Case 1: No Disturbance (Competitive Exclusion Model) • As the reef becomes complex, organisms • compete for space. • Dominant organism outcompetes other • species. • Occurs in stable environments. • Results in low species diversity. • Highly protected patch reefs within • lagoons or protected bays • Deeper water
Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model) • Storms and hurricanes allow for other • species to move in • Dominant species would not be allowed to • reach competitive exclusion • After each disturbance have a recovery • period • Area of high diversity
Case 3: Constant Strong Disturbance (Colonial Model) • Constant exposure to disturbance • Shallow environment • High turnover of species • r-selected species
Case 3 Near reef crest Case 2 Reef slope beneath reef crest Reef Case 1 Deep reef slope
a) The slopes of a newly formed volcanic island b) Wetlands in Texas, following Hurricane Rita c) A receding glacier d) A dried up lake e) Primary succession would not occur on any of these. Primary succession would take place on all of the following EXCEPT:
QUESTION: Review A “K” selected species generally has all of the following characteristics EXCEPT: a) Large size b) Short-lived c) Good competitor d) Constant population size e) Slow population growth