Intertidal11 - Geneseo

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I.  Physical Environment

III. Patterns in the Biota

III. Processes

IV. Regulation

Zones of the Ocean

Only lines on the outline of the ocean; belies its importance 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

Fucoid brown

Kelp

Green algae Red algae

Some of the abundant animal groups

mussels snailsanemones

barnacles

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Community Structure in the Pacific

Physical Factors: species 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.

Chthamalus (higher up) & Balanus

Joe Connell conducted translocation and separation experiments

III.A. Role of Competition

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

Cyprid larva Juvenile barnacle

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Translocation Experiments

Chthamalus to the mid intertidal and Balanus removed

Adult Balanus added to the upper zone

Adult Balanus were also transplanted to the Low Intertidal Zone to determine why they were absent from there

Balanus removed

With transplanted Balanus

Balanus

Present

Balanus not present

Chthamalus is routinely excluded from the 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 snails…Thais

Conclusions: III.B. Role of Predation

Dominant competitor Apex predator

Bob Paine: Pisaster removal experiments

with w/o Pisaster

Results of exclusion of Pisaster 1.  Predation can control the diversity of species

2.  Established concept of Keystone species

3.  First clear demonstration of indirect effects

Paine’s study was important in showing:

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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?

Green algae

Ulva Foliose &

articulated

Red algae

Corallina

Chondrus (Irish moss)

Mastocarpus (false irish moss)

At Pemaquid Point etc.

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

1-8% Semibalanus ~25-65% Mytilus; 6-70% fucoids

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

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.

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

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

Thais lapillus

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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

WHAT CONDITIONS REGULATE THE IMPORTANCE OF THESE PROCESSES?

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


Lubchenko & Menge 1978

Space utilization varies with sites (local scales)

Predators particularly Asterias are

generally ineffective at exposed sites

but prey heavily on

Mytilus and barnacles in sheltered

sites

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B.  Recruitment-Limited Regulation: coastal subsidies set the pace for intertidal community dynamics


Discussion of paper by Menge et al (2003)

Coastal Oceanography sets the pace for rocky intertidal community dynamics.

PNAS



B.  Recruitment-Limited Regulation: coastal subsidies set the pace for intertidal community dynamics


According to the Nutrient/Productivity Models, the abundance of species and interaction strengths of the rocky community are directly proportional to the amount of productivity in local nearshore regions

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

Predictions

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, 1994 In contrast to Maine, Pacific

predators are MORE active in wave-exposed sites, yet at SH

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

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

Predictions

Where in the model would Boiler Bay belong? Strawberry Hill?

Summary/Conclusions:

-- Rocky intertidal communities show parallels in composition organization, processes, and regulation worldwide

-- 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

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Intertidal11 - Geneseo