Marine softsediment communities

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LARVAL ECOLOGY, DISPERSAL, AND RECRUITMENT
PROCESSES IN MARINE ECOSYSTEMS

• Life histories of marine organisms
• Larval ecology
• Settlement
• Recruitment
• Consequences of complex life histories to
  population structure

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Changes in abundance population demography

• b, d, and e are per capita rates
• In a closed population

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• DIFFERENCES BETWEEN LAND AND OCEAN
• Different life history strategies in 3-D
  environment

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• Life styles in the ocean
• Drifting planktonic/pelagic
• Swimming - nektonic
• Attached - benthic

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1. DRIFTERS
Planktonic passively drifting or weakly
swimming organisms moved
by ocean currents include bacteria,
phytoplankton, zooplankton Pelagic of the
open ocean, not site attached
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Jellyfish, comb jellies, heteropods, pteropods,
salps
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• Most abundant multicellular organism on earth?

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2. Swimmers
organisms that swim actively in open water,
independent of water currents
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3. Attached organisms
Benthic site attached, living attached to or
on the ocean floor
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• DIFFERENCES BETWEEN LAND AND OCEAN
• Different life history strategies in 3-D
  environment

• Most marine species have complex life histories
  and small dispersal stages (larvae) that can
  travel relatively long distances

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More facts of nature you dont see the
bipartite lifestyle often on land
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Many marine species have bipartite life
histories

• Planktonic dispersive early stage
• 2. benthic or site attached adult stage

Larva an independent, often free-living,
developmental stage that undergoes changes in
form and size to mature into the adult
especially common in insects and aquatic
organisms. (From a Latin word meaning "ghost" or
"mask.")
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Marine organismscomplex life cycles
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Sea urchin
Starfish
Sea cucumber
Phoronid
Polychaete
Bryozoa
Gastropod
crabs
barnacle
nemertean
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• DIFFERENCES BETWEEN LAND AND OCEAN
• Different life history strategies in 3-D
  environment
• Most terrestrial animals disperse from adults as
  subadults
• Most marine species have complex life histories
  and small dispersal stages (larvae) that travel
  in the water column
• Ocean currents transport marine organisms
  sometimes for long distances
• -Small animals in the ocean can be transported
  by
• currents, and may not be able to choose where
  to go
• -Adult fish and mammals can swim strongly, and
  adult invertebrates cling to the bottom, but
  larvae are at the mercy of the currents

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Why is a bipartite life history interesting?
For most marine species, we have NO idea where
larvae go
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Standard ecological theory (terrestrial) Animals
are found in comfortable environments Marine
ecological theory -Animals may be found where
the currents put them and where they
survive. -Where they settle and recruit depends
on many factors- larval strategy, larval and
adult behavior, physiology, and hydrographics.
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Larval Types (Thorson 1950 Vance 1973)

• Planktotrophic larvae
• Large number of small eggs
• Feed in the plankton
• Lecithotrophic larvae
• Fewer eggs, more energy to each
• Do no feed in the plankton
• Direct development
• Larval stages within eggs
• Hatch as juveniles

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Expected advantages/disadvantages

• Planktotrophic
• Large number of propagules, wide dispersal
• Dependence on variable resources, high mortality

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Expected advantages/disadvantages

• Lecithotrophic
• Lower mortality, independent of resource
  availability
• Few larvae, short dispersal

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Expected advantages/disadvantages

• Lecithotrophic
• Lower mortality, independent of resource
  availability
• Few larvae, short dispersal

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Expected advantages/disadvantages

• Direct development
• No mortality in the plankton
• Fewer individuals produced and shorter dispersal

1 mm
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Live bearers (viviparous)
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How many larvae produced?

• The bigger the mamma the more the eggs/young

• The healthier the mamma the healthier the
  larvae/young
• The healthier the larva the healthier the juvenile

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DISPERSAL IN MARINE ECOSYSTEMS

• Marine systems is broad dispersal common?
• How far do organisms disperse? What can we
  predict?

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Larval durations of intertidal marine
invertebrates
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What is the Mean Dispersal Distance?

• Range for planktonic periods from 0 to 100s of
  days
• Invasions speeds from meters to 100s km per year
• Genetic estimates of average dispersal gt

Shanks Grantham, Palumbi, Kinlan Gaines
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Interaction of circulation and behavior
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DISPERSAL IN MARINE ECOSYSTEMS SUMMARY

• Dispersal distances depend on
• duration of the larval stage (few hours to
  several months)
• oceanographic patterns
• larval behavior

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Settlement

• Processes by which larval organisms transition
  from pelagic plankton to benthic habitats
• Often includes metamorphosis into adult/juvenile
  form
• Driven be complex set of physiological, physical,
  biochemical, and behavioral factors

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Restoring Coral Reef Fish Communities
The Role of Ecotechnology
Ecotechnology Initiative Moorea Coral Reef
LTER University of California, Santa Barbara
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Coastal Marine Resources Represent Enormous
Value
Examples of Goods and Services

• Food

• Minerals

• Marine Natural Products

• Recreation Tourism

• Waste Management

• Shoreline Protection

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A Plethora of Ecological Problems of
Extraordinary Proportions
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The Challenge

• Sustain Economic Growth Without Critically
  Degrading
• Natural Resources.

• Issue Acute for Coastal Marine Environments.

60 of worlds populationlives within 100
km of a coast
Critical need to maintain restore marine
natural resources
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A Case in Point Coral Reef Ecosystems

• Are of Critical Economic Significance

(potential sustainable annual economic net
benefit 270,000 per square km)

• Are of Critical Ecological Significance

(contain 1/3 of ALL marine fishes despite
constituting lt 1 of all marine habitat)

• Are Being Degraded Faster Than
• Any Other Marine Ecosystem

(sources World Resources Institute, United
Nations, International Coral Reef
Initiative, United States Coral Reef
Presidential Task Force)
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How Bad is the Problem?
Less than 1/3 of Worlds Coral Reefs can be
Considered Pristine
10 Damaged Beyond Their Ability to Recover
Naturally
Another 20 Could Reach This State of
Degradation Within the Next Two Decades

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What is the Solution?
Current Method - Eliminate Threat

• Alter human behavior to slow degradation

Mainly a social / public policy approach
Problem

• Natural recovery may take years to decades

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Harvested populations would take 18 years
to recover
Predicted Recovery Time of Anemonefish
following Harvesting for Aquarium Trade
(experiment)
Colonization rate of anemonefish Data courtesy
of R. Schmitt and S. Holbrook, UCSB
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Estimated Recovery Time from Blast Fishing
70 years
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What About More Pro-Active Approaches?

• Can transplant live coral to degraded areas

Mainly an engineering approach
But, this technique is not very effective and
simply moves the disturbance
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Ecotechnology Approach

• Use ecological knowledge of species life
• histories and physiology to manipulate system

Requires identification of ecological bottlenecks
For many marine species, e.g. corals and fishes,
the bottleneck larval supply/delivery to the
reef
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Typical Life Cycle
A Bottleneck at any life history stage
hinders population recovery
Plankton
Larval Dispersal
Survival Growth
Settlement Metamorphosis
Larval Production
Reef
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Bottlenecks Controlled by Natural Signals in
the Environment

Relieve Bottlenecks by Harnessing Environmental
Signals (e.g., molecules, light, texture, sound)
Plankton
Larval Dispersal
Survival Growth
Settlement Metamorphosis
Larval Production
Reef
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Ecotechnology
Keys to a Restoration Application

• Understand Ecological Bottleneck to Recovery

Coral larva
Coral
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Ecotechnology
Keys to a Restoration Application

• Understand Environmental Signals that
  Control Underlying Biological Process

Coral larva and newly metamorphosed coral
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Ecotechnology
Keys to a Restoration Application

• Develop Engineering Solutions to Harness
  Critical Environmental Signal

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Ultimate goal is to attract larvae to newly
created habitat which may lack the appropriate
natural cues by providing artificial cues.
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Most larvae fail to find settlement sites
Model System Coral Reef Fishes
Often surplus of larvae, but most doomed
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Problem how to guide larvae to suitable
habitat
Strategy harness gradient sensed cue used
by fish larvae

• Goal rapid restoration of abundance /
  diversity

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Possible Gradient Sensed Cues

• Chemical
• - Species - specific

• Sound
• - Possibly general attractor

• Light
• - General attractant

Our infra-red camera system for studying
fish settlement behavior at night
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Feasibility of Larval Light Beacons
Light trap
Bug Zapper

• Fluorescent light traps collect larval fish
  at night
• Attract many species

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Larval fish respond to

• Wavelength - larvae most sensitive to UV
  through blue - green
• - some species - specific sensitivity
  (tailoring possible?)

• Intensity ?
• Pulsed vs. continuous ?
• Directionality ?

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Light environment of reef includes a variety of
wavelengths
Fluorescent wavelengths displayed by corals is
species specific
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Developing Sophisticated Larval Light Beacons
using Gallium Nitride (GaN) LEDs
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Initial Field Trial Prototype Light Beacon
Preliminary Search for Optimal Wavelengths
(Color)
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Initial Field Trial Prototype Light Beacon
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Initial Field Trial Prototype Light Beacon
Abundance of Settlers
Number of Species
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Species Richness Increased with Decreasing
Wavelength
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Species Composition Varied with Wavelength
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• First demonstration that
• LED Light Beacons can
• Increase Fish Biodiversity
• Increase Number of Individuals
• Influence Species Composition

Great Promise for Restoration Efforts
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Recruitment to adult populations

• Major determinant of population and community
  structure and dynamics
• Historical perspective awareness about
  importance of recruitment processes has changed
  through time

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Variation in Recruitment

• Driven by
• Production of larvae
• Dispersal
• Mortality during dispersal
• Availability
• Settlement
• Growth and survival after settlement

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Population Biology
Mortality Dispersal Development
How B relates to N
Larval availability Larval behavior
Spawning behavior Egg production Fertilization
rates
Mortality Movement Maturation
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Demographically closed
Pelagic fisheries perspective Hjort (1914)
Retention
Stock-recruitment relationships
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Demographically closed
Retention
Benthic ecology perspective Thorson (1950)
Larval pool
Dispersal
For organisms with multi-phase life histories,
understanding the biotic and physical mechanisms
that regulate abundance/distribution of adults
requires integrating the dynamics and
distributions of several aspects of the life
cycle.
Demographically open
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Demographically closed
Retention
Larval pool
Mixture of larval inputs
Tagging Studies
Swearer et al. 1999 Jones et al. 1999
(Nature) Genetic pop. structure Barber et al.
2000 (Nature)
Larval pool
Dispersal
Demographically open
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• Larval Transport on Ocean Currents
• Physical-biological coupling
• Determines where and when larval settle and
  become adults
• Affects where and when a given species is found

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Making Connections Design Criteria for Reserve
Networks
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• Restoring populations of bay scallops in NC

Argopectins irradians
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• Red tide advected from Florida in 1987
• Entered NC estuaries via warm core
• ring
• Wiped out scallops in all NC sounds

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• Scallop population declines
• Area specific recovery

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• Scallop population of coastal
• NC consists of many sub-
• populations connected by
• larval transport and recruitment
• Bogue Sound hydrographically
• isolated from other sounds
• Why did Bogue Sound populations
• not recover?

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• Transferred 100 thousands of scallops
• Increased density in receiver sites

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• Measuring scallop recruitment after
  transplants

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• Reestablished recruitment in Bogue Sound
• Example of recruitment limitation