Download Marine Organism Population Dynamics

Marine Organism Population Dynamics- Keystone
Species Adaptability With a Special Emphasis on
Dolphins and Elasmobranchs
Cindy Rogers and Christine Bedore
April 14, 2008
North Atlantic Oscillation
• Alternation of pressure difference between subtropic
high‐
pressure zones (Azores) and subarctic low‐ pressure zones (Iceland)
• Robust mode of recurrent atmospheric behavior and is dominant mode in North Atlantic sector throughout the year, especially in winter
Otterson et al. 2001
NAO Positive/High Index Phase
• Intense Icelandic LOW +strong Azores HIGH
= increased pressure difference
• Results in more and stronger winter storms crossing Atlantic
Colder Stratosphere
in northerly track
• Eastern coast of
U.S. gets a milder winter
whoi.edu
NAO Negative/Low Index Phase
• Small Icelandic low +small Azores high
= reduced pressure difference
• Results in fewer and weaker winter storms crossing Atlantic
in easterly track
Less Cold Stratosphere
• Eastern coast of
U.S. gets a colder winter
whoi.edu
The NAO as a Proxy
• Ability to use NAO as a proxy for land or sea temperatures
varies temporally and spatially
ex: good proxy for winter SST in North Sea but weak
proxy for western Iberian peninsula
The NAO as a Proxy
• Dynamic ocean‐atmosphere interactions form complex variations which influence ecological processes
ex: ENSO and NAO
• NAO used as a proxy for linking climate variability to ecological processes since the mid 1990s
Otterson et al. 2001
The NAO as a Proxy
• NAO large scale climate phenomena produce large effects at
various trophic levels
• Winter ecological mechanisms most strongly affected by NAO because it is primarily a winter phenomenon
Otterson et al. 2001
Effects of the NAO
• Natural changes happen on a variety of time scales:
– Large seasonal differences
– Decadal
– Centenniel
• Anthropogenic activities alter NAO
– Affecting how NAO influences ecological communities
– Small changes can produce large scale effects at various trophic levels (Post et al, 1999)
Effects of the NAO
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Main parameters: Temperature
Precipitation
Wind and oceanic circulation
Effects of the NAO
• These and the interaction among them can change ocean‐atmospheric systems and are affected by increased global warming
• Natural fluctuations and human induced changes have far reaching affects:
– Alteration of ecological communities is complex and can cascade up and down trophic levels
Direct Responses
– Direct ecological response to NAO parameter
– Abundance
– Physiological rates
– Affected by temperature (Straile, 2000)
Daphnia: zooplankton
www.sciencefriday.com
Indirect Responses
www.ingvar.is
– Many intermediary steps between NAO and response
– Abundance
– Temperature and wind changes
– regime shift ‐ change pattern of transport of herring (Corten, 1999)
www.mbari.org
Sardines
Integrated responses
– responses occurring during and years after a NAO extreme fluctuation
– Abundance
– decrease volume of Norwegian deep sea water where they overwinter (Heath et al, Calanus finmarchicus
1999)
www.chbr.noaa.gov
Effects of the NAO
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Alter terrestrial and marine populations
+NAO or –NAO
Different responses due to species adaptability
Temperature, winter severity, and wind/ocean circulation
Temperature and NAO
• Temperature is the best documented influence of the NAO (Ottersen et al, 2001)
• Warming is the general trend, +NAO state, increased Sea Surface Temperatures (SST)
– Increased terrestrial plants and phytoplankton growing season
– Birds: increase juvenile survival and affect reproductive timing (temperature or food availability or both)
– Species adaptability: Good for one species; bad for another (e.g. copepods)
C. finmarchicus; C. helgolandicus
Ottersen et al, 2001
Temperature, Prey and NAO
Arcto-Norwegian cod
www.cees.no
Arcto‐Norwegian cod
+NAO, +growth
‐NAO, ‐growth
Affect all life history stages leading to recruitment
• Time lag of effects
•
•
•
•
– See results of NAO anamoly years later in next generations
www.gma.org
Temperature, Prey and NAO
• Changing water temperatures can change prey distributions
• Dependent on species adaptability for temperature changes
• Good for one species (warm water species); bad for another (cold water species)
• Effects cascade up to apex predators (bottom up): cetaceans/sharks
www.sportsmanchoice.com
Dolphins, Prey, Temperature
• Apex predators, such as dolphins, rely on prey
• Warming waters alter prey populations
• Especially important for species specific predators
• Affect distribution, grouping and social interactions of cetaceans
Charles Maxwell underwater video services
Cetaceans
• Bottlenose dolphins (Tursiops truncatus) off California coast
• Resident with no migratory tendencies
• Shift range 600+ km north, remained for several years (integrated effect)
• Resulted from prey shifts due to strong 1982/83 EL Nino warm water incursion in the northern waters
Cetaceans
• Similar effects from NAO and Pacific Decadal Oscillation (PDO) on cetaceans
• ‐NAO and –PDO detrimintely affect salmonid populations (Lusseau et al, 2004)
– Detriminentaly affect returning numbers
– Lagged effects on freshwater and marine life stages Pacific salmon; http://caviamore.com
Atlantic salmon; http://pond.drn.cornell.edu
• www.americ
Important prey for Atlantic bottlenose dolphins and anrivers.com
Pacific Killer whales (Orcinus Orca)
Cetaceans
• 2 year time lag
– When fish populations affected grow to edible stages
• Affect grouping patterns: – Smaller amount of prey, smaller groups
(Lusseau et al, 2004)
www.farnorthscience.com
Lusseau et al, 2004
Grouping patterns affect
Social Structure
Cetaceans
• Climate change affects the composition and structure of ecological communities (Genner et al, 2004)
– All trophic levels
• Warming waters can directly effect the ranging patterns of cetaceans
– May be related to following changes in prey distribution
• Changes in ranging patterns can alter community composition
Cetaceans
• North‐West Scotland (MacLeod et al, 2001)
• Stranding records: distribution of cetaceans
• Occurrence and abundance from previous studies
• Documented ocean temperature increase:
– 0.2‐0.4oC since 1981 (Fisheries Research Service, 2003)
• Composition of cetacean community has been greatly altered, and directly related to this warming trend
Cetaceans
• 15 species stranded 1948‐1981: stable unchanging community (cold water ranges)
• 1988: rate of new species seen increased (3 new with warm water ranges)
• 4 species restricted to cold waters (or rarely seen in warm) significantly decreased strandings
Cetaceans
Cetaceans
• Species diversity can change
• Possible ecosystem alterations/ regime shifts (Jackson and Sala, 2001)
• Important for conservation measures
– Changing ranges out of protected areas
– Endangered/threatened species
• Warm water species may benefit, but…
• Cold water species may not
Cetaceans
• Some cold water species have specific habitat
– White‐beaked dolphin: continental shelf cold waters (MacLeod et al, 2005)
– Difficult to extend ranges poleward
– Reduce total area and possibly population
http://marinebio.org
Hurricanes and cetaceans
• Climate change related to hurricane frequency and intensity under debate
• Hurricanes can have drastic effects on keystone species
– Through death of individuals
– Shifts in prey distribution and abundance
Hurricanes and cetaceans
• Bahamas spotted and bottlenose dolphins
– Loss of 30‐40% of each species
– 30% influx of new bottlenose individuals
Atlantic spotted dolphin (Stenella frontalis)
Atlantic bottlenose dolphin (Tursiops truncatus)
Hurricanes: case study
Census
100
80
60
# dolphins
30
40
20
8
4
9
Dolphins seen
27
Missing dolphins
2
13
0
2002
2003
2004
2005
2006
0
9
New dolphins
2007
Year
– Changes associations and social/community
structure
Cetaceans
www.britannica.com
www.gla.ac.uk
• Change the structure of ecological communities:
• Bottom up: These changes may be linked to prey
• Top down: Can also affect prey as apex predator abundance changes
Cetaceans
• Community structure of marine keystone species, are altered by:
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Changes in ocean‐atmospheric systems (NAO, PDO)
Water temperature changes
These are being altered by climate change
Effect prey and predator communities in complex ways
• Can produce regime shifts and alter entire ecosystems
• Loss of apex predator populations can have large effects on lower trophic levels: e.g. sharks
What are Elasmobranchs?
Why are Sharks Important?
Economy: food
Why are Sharks Important?
Economy: ecotourism
Why are Sharks Important?
Economy: recreation
Why are Sharks Important?
Culture: Hawai’i
“it was believed that a departed ancestor took the form of a shark after death and appeared in dreams to living relatives. These Hawaiians would feed and pet a special shark whom they believed to be a relative. In turn, the shark would protect the family.”
http://the.honoluluadvertiser.com/article/2004/Sep/28/il/il06a.html
Why are Sharks Important?
Biomedical research: Cancer and immunology:
Dr. Carl Luer and clearnose
skate (Raja eglanteria)
aqua.org
mote.org
Why are Sharks Important?
Ecology: Apex predators
• Dynamic food web interactions‐ feed on all trophic levels
• Sensory biology makes them effective predators
underwatertimes.com
What’s Happening with Sharks Today?
• Sharks have thrived for >400 mill years as apex predators
• Success due in part to mammal‐like life history characteristics:
Slow growth
Late onset sexual maturity
Few number of developed young/mating season
• Humans replacing sharks as apex predators
Life history parameters make them less resilient to
anthropogenic activities
•Populations are declining worldwide by up to 90%!!
What’s Happening with Sharks Today?
Loss of mature animals, smaller sharks being caught ‘72‐’03
Myers et al. 2007
(supporting material)
What’s Happening with Sharks Today?
Ex: Northwest Atlantic large coastal and oceanic sharks
Baum et al. 2003
fao.org
What’s Happening with Sharks Today?
Baum et al. 2003
What Happens if We Lose Sharks?
• Top‐down effects and bottom‐up effects both likely to occur
• Unsure due to dynamism of food web
• Myers et al. 2007‐ only empirical data so far
Shows weakened top=down control by elasmobranch
consuming shark species
(bull shark and cownose ray pictures)
What Happens if We Lose Sharks?
One scenario:
Loss of apex predators = ↑ mesopredators = ↓ prey
What Challenges Are Sharks Facing?
Pollution: EDCs (PCBs, Ocs), Mercury
• Exposure from agriculture runoff (pesticides*),
sewage discharge, stormwater discharge, industrial pollution
• Reproductive disorders: feminizing in males, sterility, low
rate of pregnant females
• Impaired immune function
• BIOACCUMULATION!!
(Walker 1997‐graph?)
What Challenges Are Sharks Facing?
Habitat loss/degradation: Nursery and mating grounds
• Mangroves and estuaries
What Challenges Are Sharks Facing?
Overfishing: Fins, meat, cartilage, jaws/teeth, bycatch
What Challenges Are Sharks Facing?
Climate change
• Exacerbates all other challenges
• Biology (prey, reproduction) • Physiology (thermoregulation, osmoregulation)
• Behavior (migration/distribution)
How Does Climate Affect Sharks?
• Affected by all topics covered so far:
Nutrient cycling and phytoplankton
Subarctic ecosystem changes
Ocean chemistry and acidification
Tropical organism stress
Sea level rise
How Does Climate Affect Sharks?
Temperature
• Most are ectotherms (ex: blue shark‐ Prionace glauca)
‐ distribution limited by temperature
Kubodera et al. 2007
How Does Climate Affect Sharks?
Temperature
• Some local endotherms (ex: Salmon shark‐Lamna ditropis)
‐ distribution expanded due to larger thermal tolerance
Kubodera et al. 2007
How Does Climate Affect Sharks?
P. glauca‐ ectotherm
more coastal,
lower latitude
L. ditropis‐ endotherm
more pelagic
higher latitude
Kubodera et al. 2007
How Does Climate Affect Sharks?
Temperature
• Timing of reproduction
‐Cycling hormone levels maintain mating seasons
‐Induced by environmental cues
Tricas et al. 2000
How Does Climate Affect Sharks?
Salinity
• Osmoregulation is expensive!!
• Isosmotic due to storage of urea in tissues
• Rapid salinity changes are highly stressful
How Does Climate Affect Sharks?
CO2/ ↓ pH
• Skeletal growth‐ calcification
biomechanics.bio.uci.edu
Climate Change and Sharks
• No direct evidence yet of climate change influence on
elasmos (ALL areas of elasmo research limited still)
• But‐ we can speculate that elasmos will be affected in
a variety of ways
“ecological and economic risks associated with being partially correct outweigh the social risks of being wrong”
‐ Okey et al. 2007
Climate Change and Sharks
Observable changes/local effects of human‐induced
env. changes:
salmon shark niche expansion
round stingrays in seal beach
blacktip response to hurricanes
local carcharias extinction in e. pac
basking sharks in scotland
Climate Change and Sharks
Okey et al. 2007: salmon shark niche expansion
• Regional endotherms
• Undergo long‐distance migrations (Alaska to Hawai’i)
• Increased abundance observed during the 1990’s in the
North Pacific Ocean, although numbers declined recently
Climate Change and Sharks
Okey et al. 2007: salmon shark niche expansion
norbert wu
calstatela.edu
Weng et al. 2005
Climate Change and Sharks
Okey et al. 2007: salmon shark niche expansion
• Possible explanations for “increased abundance”:
1. Northward expansion in distribution due to
rises in temperature
2. Ban of high seas gillnets decreasing mortality
3. Competitive release due to declines in blue
shark populations
Climate Change and Sharks
Hoisington and Lowe 2005: Seal Beach, CA stingrays
cnsm.csulb.edu
Climate Change and Sharks
Heupel et al. 2003: blacktip response to hurricanes
• Hurricane Gabrielle 2001
• Young of the year blacktip sharks (Carcharhinus limbatus)
left nursery area in response to falling barometric pressure
hours before storm made landfall
• All returned about 2 weeks later, after salinity increased
following rainfall
• Purpose of leaving unknown, but may be linked to
physiological tide‐guage mechanism so sharks don’t get
trapped in nursery area
Climate Change and Sharks
Cione et al. 2007: local Carcharias extinction in E. Pacific
• Relatives of modern day sandtiger (Carcharias taurus)
inhabited western coast of S. America
• Became extinct at same time as decrease in temperature during the Pleistocene
Climate Change and Sharks
Basking sharks in Scotland
• Planktivorous sharks
• Increased in abundance near Scotland where plankton has also increased in abundance