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Environmental stress model. stress amelioration. competition. predation. diversity of basal species. Relative importance. associational defenses. Environmental stress. Bruno, Stachowicz & Bertness (2003). Richness of primary space holders

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slide1

Environmental stress model

stress

amelioration

competition

predation

diversity of

basal species

Relative importance

associational

defenses

Environmental stress

Bruno, Stachowicz & Bertness (2003)

slide2

Richness of primary space holders

Richness of secondary space holders (sessile and mobile associated species)

Overall richness

Scrosati & Heaven (2007,

Marine Ecology Progress Series 342: 1-14)

Bruno, Stachowicz & Bertness (2003,

Trends in Ecology and Evolution 18: 119-125)

scrosati heaven 2007 in atlantic canada
Scrosati & Heaven (2007) in Atlantic Canada

Vertical gradient

Desiccation - Temperature

Irradiance - Osmotic potential

Horizontal gradient

Wave exposure - Ice scour

slide4

- Gulf of St. Lawrence coast

- Atlantic coast

Nova Scotia

Nova Scotia

New England

slide5

Methods

Environmental stress gradients

Vertical gradient (3 levels)

High - Mid - Low intertidal

Upper limit determined using barnacles

Horizontal gradient (2-3 levels)

Gulf (wave + ice): Sheltered - Exposed

Atlantic (wave): Sheltered - Intermediate - Exposed

dynamometers

(wave exposure)

cages

(ice scour)

slide6

Methods

Richness, Diversity & Evenness

• Summer

• Abundance of all seaweeds and invertebrates

(% cover)

• 25 cm x 25 cm quadrats

(n = 20 per Elevation x Exposure combination)

RichnessSr of species

Diversity (Simpson's index) 1 - D = 1 -  (pi)

Evenness (Simpson's index)E = (D * S)-1

slide7

Results

38 seaweeds - 29 invertebrates

slide8

Results - Richness across Elevation

Means ± SE

Gulf of St. Lawrence

2 = 39 %

Elevation

Atlantic

2 = 41 %

Elevation

slide9

Results - Richness across Exposure

Means ± SE

Gulf of St. Lawrence

2 = 10 %

Wave - Ice Exposure

Atlantic

2 = 12 %

Wave Exposure

environmental stress model esm
Environmental stress model (ESM)

Predation Hypothesis

Intermediate Disturbance Hypothesis

RICHNESS

SESSILE SPECIES

(PRIMARY SPACE HOLDERS)

Menge & Sutherland (1987, American Naturalist 130: 730-757)