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Zones of the Ocean

I. Physical Environment

III. Patterns in the Biota

III. Processes Only lines on the outline of the ocean; belies its importance IV. Regulation to humankind as a key component of nearshore coastal systems, and to science as a center for scientific ferment

-wave exposure along vertical & horizontal scales

-tidal excursion with exposure to air, thermal and UV stress

- produce a wide range of conditions

Some of the abundant groups Green algae Red algae

mussels

snails Kelp anemones

Fucoid brown

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Community Structure in the Pacific

Physical Factors: tolerances to waves, dessication, temperature determine patterns; dominated early explanations of organization.

Biological Interactions: in 1960’s attention shifted dramatically toward view that patterns were controlled by biotic factors.

III.A. Role of Competition

Joe Connell conducted translocation and separation experiments

Chthamalus (higher up) & Balanus

Is it due the preferential settlement of larvae in specific habitats?

Juvenile Cyprid larva

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Translocation Experiments

Chthamalus to the mid intertidal and

Balanus removed removed not present Adult Balanus added to the upper zone With transplanted Balanus Balanus Adult Balanus were also transplanted to Present the Low Intertidal Zone to determine why they were absent from there

Conclusions: III.B. Role of Predation Chthamalus is routinely excluded from the Dominant competitor Apex predator mid intertidal zone habitat by Balanus

It “coexists” in the community by taking refuge in upper zone where Balanus young cannot survive

What keeps both Chthamalus and especially Balanus from moving into the lower intertidal?

Competition from Mussels and Predation by Bob Paine: Pisaster removal snails…Thais experiments

Results of exclusion of Pisaster Paine’s study was important in showing: 1. Predation can control the diversity of species 2. Established concept of Keystone species 3. First clear demonstration of indirect effects

with w/o Pisaster

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Keystone species: one with a powerful influence which is highly disproportionate to its biomass

Do these observations apply to intertidal in other regions?

Corallina Green algae Foliose & Ulva At Pemaquid Point etc. articulated

Red algae 60-85% Semibalanus 4-13% Mytilus; fucoids

1-8% Semibalanus ~25-65% Mytilus; Chondrus (Irish moss) 6-70% fucoids

24-87% Chondras Some Mytilus, Semibalanus especially at exposed sites; not in sheltered sites

Mastocarpus (false irish moss) Predators are Thais and Asterias Herbivores are Littorina and Strongylocentrotus

-- Remove Mytilus from mid intertidal and Semibalanus spreads downward

-- Exclusion of Thais : Mytilus to spread downward; in absence of Mytilus, Semibalanus spreads downward.

-- If Chondrus and Littorina are removed: Fucus moves into the low intertidal. Thais lapillus

-- If Littorina is left: Fucus moves down but not as successfully.

-- Sea urchins removed from the subtidal kelp area and Chondrus extends downward

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A. Environmental Stress Regulation

(wave forces, cobble scour, physiological stress) B. Recruitment-Limited Regulation: coastal subsidies C. Nutrient/Productivity Models: underlying gradients of nutrients and plant productivity determine intensity of competiton for space, herbivory and predation: strength of interactions

Space utilization varies with sites (local scales) WHAT CONDITIONS REGULATE THE Lubchenko & IMPORTANCE OF THESE PROCESSES? Menge 1978

A. Environmental Stress Regulation: differences are predictably related to environmental stress

(wave forces, cobble scour, physiological stress)

Predators particularly Asterias are generally ineffective at exposed sites but prey heavily on Mytilus and barnacles in sheltered sites

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A. Environmental Stress Regulation: differences are predictably related to environmental stress

(wave forces, cobble scour, physiological stress) B. Recruitment-Limited Regulation: coastal subsidies set the pace for intertidal community dynamics

C. Nutrient/Productivity Models: underlying gradients of nutrients and plant productivity determine intensity of competiton for space, herbivory and predation: strength of interactions

Discussion of paper by Menge et al (2003) Coastal Oceanography sets the pace for rocky intertidal community dynamics. PNAS

A. Environmental Stress Regulation: differences are predictably related to environmental stress

(wave forces, cobble scour, physiological stress) B. Recruitment-Limited Regulation: coastal subsidies set the pace for intertidal community dynamics

C. Nutrient/Productivity Models: underlying gradients of nutrients and plant productivity determine intensity of competiton for space, herbivory and predation: strength of interactions

According to the Nutrient/Productivity Models, the abundance of species and interaction strengths of the Along the coast of rocky community are directly proportional to the amount central Oregon, studies at Boiler Bay of productivity in local nearshore regions and Strawberry Hill sites revealed different Predictions communities; at BB, benthic plants dominate and invertebrates were scarce, at SH the opposite trend was evident

Menge In contrast to Maine, Pacific 1992, 1994 A combination of bottom up and top-down forces interact predators are MORE active in wave-exposed sites, yet at SH to determine community dynamics mussels still dominate!

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Along the coast of central Oregon, studies at Boiler Bay and Strawberry Hill sites revealed different communities; at BB, benthic plants dominate and invertebrates were scarce, at SH the opposite trend was evident

Menge 1992 etc.

Conclusions: Bottom up forces interact with top down forces to establish community dynamics. Keystone and top down effect are still present but bottom up forces prevent complete top down control

Summary/Conclusions: Where in the model would Boiler Bay belong? Strawberry Hill? -- Rocky intertidal communities show parallels in composition organization, processes, and regulation worldwide Predictions -- Steep environmental gradients produce a wide range of conditions that, along with biotic interactions, establish a series of biological zones dominated by different species

-- The interplay of competition, herbivory and predation are key determinants of species distribution and abundance

-- Horizontal variation in environmental stress, recruitment and productivity in coastal waters at local and regional scales regulate the magnitude and pace of community dynamics

A combination of bottom up and top-down forces interact to determine community dynamics

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