ESM 260 Applied Marine Ecology

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ESM 260 Applied Marine Ecology
Focus Application of Ecology to
Environmental Issues in Marine Habitats
Emphasis Science as a Process
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Need to Understand

• HOW ECOLOGICAL SYSTEMS BEHAVE (responses to
  perturbation)

• TOOLS METHODS

(Models, Statistics, Experiments, Monitoring
Designs)
Disturbances Occur across Different Spatial
Scales

• LOCAL (e.g. Sewage Outfall)
• REGIONAL (e.g. Fishing)
• GLOBAL (e.g. Climate Change)

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Today ABUNDANCE DYNAMICS Definitions
POPULATION Collection of individuals of
same species in
same area
ABUNDANCE Number of Individuals in a
Population
DENSITY Number of Individuals per unit of
Space
DYNAMICS Change in abundance through time
COMMUNITY Collection of populations of
different species in
same area
IMPACT Induced Change in Population /
Community
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Kinds of Impacts

• QUANTITATIVE
• Abundance(s) altered by some amount
• No Species has gone Locally Extinct
• No Exotic Species has Invaded

CHALLENGE DETECTION QUANTIFICATION
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Kinds of Impacts

• QUALITATIVE
• Wholesale Changes in Community -
• Some Species Gone Locally Extinct
• Invasion of Exotic Species
• Altered Trophic Structure

DETECTION NOT A PROBLEM
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What Causes Change in Abundance?
Simple Population Growth Model
-
Inputs
Losses
? Abundance
? ABUNDANCE (BIRTHS IMMIGRATION) - (DEATHS
EMIGRATION)
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Surfperch Example to Illustrate 1.
Ecological Impacts arise from induced change
in 1 or more Demographic Rates
2. Level of Understanding needed to Predict
Responses to Perturbation
3. Integration of Observation
Experimentation to Resolve Ecological Question
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What Influences Abundance Dynamics of
Local Surfperch Populations?
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Santa Cruz Island
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SURVEY ABUNDANCE SURFPERCH
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BLACK SURFPERCH
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STRIPED SURFPERCH
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BOTH SPECIES FEED FROM BENTHIC SUBSTRATA
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CONSUME SMALL CRUSTACEANS ON SUBSTRATA
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SURFPERCH - LIVE BEARERS
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Abundance Dynamics of Surfperch
Populations
WHERE TO START?
Measure Patterns of Abundance - Visual
Surveys
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ABUNDANCE VARIES SPATIALLY - SOME SITES HAVE
FEW SURFPERCH...
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OTHER SITES HAVE MANY SURFPERCH
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Spatial Variation in Abundance Ubiquitous
What Causes Spatial Variation in Abundance
of Surfperches?
NEXT STEP?
Explore Correlations between Variation in
Surfperch Abundance Variation in
Environmental Features
Measure What Features?
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MULTIPLE REGRESSION RESULTS
SPECIES
VARIABLE
CUMULATIVE R2
EFFECT
BLACK SURFPERCH

TURF
0.73
-
UNDERSTORY KELPS
0.81
-
STRIPED SURFPERCH
0.86
STRIPED SURFPERCH

GELIDIUM ROBUSTUM
0.75
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RHODYMENIA SPP.
0.80
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BLACK SURFPERCH
0.86
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TURF
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GELIDIUM ROBUSTUM
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RELATIONSHIPS BETWEEN SURFPERCH ABUNDANCE
HABITAT (EACH POINT 1 POPULATION DATA AVERAGED
ON 9 YEARS)
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Turf Gelidium Good Predictors of Black
Surfperch Striped Surfperch Abundance
But Correlation does Not Imply Causation
How to Explore Causal Relationship?
1. Determine Plausible Biological Connection
DO SURFPERCHES FEED FROM THESE SUBSTRATA?
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BLACK SURFPERCH PREFERENTIALLY FEED FROM TURF
STRIPED SURFPERCH PREFERENTIALLY FEED FROM
GELIDIUM
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Biological Connection between Spatial
Variation in Fish Abundance Their Favored
Foraging Microhabitat
STILL JUST CORRELATIONAL EVIDENCE WHAT DO
TO NEXT TO EXPLORE CASUATION?
2. Perform Field Experiment
Manipulate amount of Turf or Gelidium
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MANIPULATING GELIDIUM
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SWATH WHERE GELIDIUM WAS REMOVED
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EXPERIMENTAL RESULTS
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Experiment Confirmed Causal Relationship
between Spatial Variation in Surfperch
Abundance Favored Foraging Microhabitats
What About Dynamics? What Causes Surfperch
Populations to Fluctuate Through Time?
In General Fluctuations Arise From Changes
in Per Capita Birth /or Death Rates
Do Birth /or Death Rates of Surfperch
Vary with Fluctuations in Food Supply?
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YEAR-TO-YEAR CHANGES IN FOOD SUPPLY TOTAL
SURFPERCH POPULATION
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CHANGES IN ADULT NUMBERS LAG 1 YEAR BEHIND
FOOD
BUT BIRTH RATE VARIES WITH CHANGE IN FOOD
WITHOUT LAG
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NUMBER OF BABIES BORN PER ADULT VARIES
POSITIVELY WITH AMOUNT OF FOOD EACH ADULT
RECEIVES
PER CAPITA BIRTH RATE COUPLED TO FOOD
RESOURCE - TURF or GELIDIUM
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SURVIVORSHIP OF BABIES ALSO COUPLED TO FOOD
SUPPLY
SUVIVORSHIP DECLINES WHEN FOOD SUPPLY DECLINES
AFTER BIRTH
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Some Surfperch Populations Fluctuate a lot -
others Fluctuate Little
Why Variation in Dynamics?
Perhaps Reefs Differ in How Much Turf or
Gelidium Varies through Time
What Causes Foraging Microhabitats to Vary?
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SEA URCHIN OUTBREAKS CONSUME FOLIOSE ALGAE
LIKE GELIDIUM
URCHIN OUTBREAKS CAN BE HIGHLY PATCHY
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POTENTIALLY CAN REMOVE SOME OR ALL SURFPERCH
FOOD
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OUTBREAK OF SEA CUCUMBER PACHYTHIONE
ALSO CAN BE HIGHLY PATCHY
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CAN COVER TURF AND HINDER FEEDING BY BLACK
SURFPERCH
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AMOUNT OF FLUCTUATION IN A SURFPERCH
POPULATION RELATED TO AMOUNT OF FLUCTUATION
IN FAVORED MICROHABITAT (EACH POINT 1
POPULATION OVER 9 YEARS)
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HOW DO SURFPERCH POPULATIONS RESPOND TO
VARIATION IN GIANT KELP?