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Marine Organism Population Dynamics- Keystone Species Adaptability With a Special Emphasis on
Dolphins and Elasmobranchs
Cindy Rogers and Christine BedoreApril 14, 2008
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North Atlantic Oscillation
Otterson et al. 2001
• Alternation of pressure difference between subtropichigh‐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
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Colder Stratosphere
NAO Positive/High Index Phase• Intense Icelandic LOW +strong Azores HIGH= increased pressure difference
• Results in more and stronger winter storms crossing Atlanticin northerly track
• Eastern coast ofU.S. gets a milder winter
whoi.edu
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NAO Negative/Low Index Phase• Small Icelandic low +small Azores high= reduced pressure difference
• Results in fewer and weaker winter storms crossing Atlanticin easterly track
• Eastern coast ofU.S. gets a colder winter
whoi.edu
Less Cold Stratosphere
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The NAO as a Proxy• Ability to use NAO as a proxy for land or sea temperaturesvaries temporally and spatially
ex: good proxy for winter SST in North Sea but weakproxy for western Iberian peninsula
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The NAO as a Proxy
Otterson et al. 2001
• 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
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The NAO as a Proxy
Otterson et al. 2001
• NAO large scale climate phenomena produce large effects atvarious trophic levels
• Winter ecological mechanisms most strongly affected by NAO because it is primarily a winter phenomenon
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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)
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Effects of the NAO
• Main parameters:
• Temperature
• Precipitation
• Wind and oceanic circulation
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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
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Direct Responses
– Direct ecological response to NAO parameter
– Abundance
– Physiological rates
– Affected by temperature (Straile, 2000)
Daphnia: zooplanktonwww.sciencefriday.com
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Indirect Responses
– Many intermediary steps between NAO and response
– Abundance
– Temperature and wind changes
– regime shift ‐ change pattern of transport of herring (Corten, 1999)
Sardines
www.ingvar.is
www.mbari.org
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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, 1999)
www.chbr.noaa.gov
Calanus finmarchicus
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Effects of the NAO• Alter terrestrial and marine populations
• +NAO or –NAO
• Different responses due to species adaptability
• Temperature, winter severity, and wind/ocean circulation
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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)
Ottersen et al, 2001C. finmarchicus; C. helgolandicus
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Temperature, Prey and NAO
• 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.cees.noArcto-Norwegian cod
www.gma.org
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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
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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
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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
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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
• Important prey for Atlantic bottlenose dolphins and Pacific Killer whales (Orcinus Orca)
Atlantic salmon; http://pond.drn.cornell.eduPacific salmon; http://caviamore.com
www.americanrivers.com
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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
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Lusseau et al, 2004
Grouping patterns affect Social Structure
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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
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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
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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
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Cetaceans
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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
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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
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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
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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)
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Hurricanes: case study
8 4 9
3027
213
09
0
20
40
60
80
100
# dolphins
2002 2003 2004 2005 2006 2007
Year
Census
Dolphins seen
Missing dolphins
New dolphins
– Changes associations and social/community structure
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Cetaceans
• 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
www.britannica.com www.gla.ac.uk
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Cetaceans• Community structure of marine keystone species, are altered by:– 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
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What are Elasmobranchs?
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Why are Sharks Important?
Economy: food
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Why are Sharks Important?
Economy: ecotourism
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Why are Sharks Important?
Economy: recreation
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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
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Why are Sharks Important?
Biomedical research: Cancer and immunology:Dr. Carl Luer and clearnoseskate (Raja eglanteria)
mote.org
aqua.org
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Why are Sharks Important?
Ecology: Apex predators• Dynamic food web interactions‐ feed on all trophic levels• Sensory biology makes them effective predators
underwatertimes.com
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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 growthLate onset sexual maturityFew number of developed young/mating season
• Humans replacing sharks as apex predatorsLife history parameters make them less resilient toanthropogenic activities
•Populations are declining worldwide by up to 90%!!
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What’s Happening with Sharks Today?Loss of mature animals, smaller sharks being caught ‘72‐’03
Myers et al. 2007(supporting material)
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What’s Happening with Sharks Today?Ex: Northwest Atlantic large coastal and oceanic sharks
Baum et al. 2003fao.org
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What’s Happening with Sharks Today?
Baum et al. 2003
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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 farShows weakened top=down control by elasmobranchconsuming shark species
(bull shark and cownose ray pictures)
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What Happens if We Lose Sharks?One scenario:Loss of apex predators = ↑ mesopredators = ↓ prey
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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, lowrate of pregnant females
• Impaired immune function
• BIOACCUMULATION!!(Walker 1997‐graph?)
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What Challenges Are Sharks Facing?
Habitat loss/degradation: Nursery and mating grounds
• Mangroves and estuaries
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What Challenges Are Sharks Facing?
Overfishing: Fins, meat, cartilage, jaws/teeth, bycatch
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What Challenges Are Sharks Facing?
Climate change
• Exacerbates all other challenges
• Biology (prey, reproduction)
• Physiology (thermoregulation, osmoregulation)
• Behavior (migration/distribution)
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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
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How Does Climate Affect Sharks?
Temperature• Most are ectotherms (ex: blue shark‐ Prionace glauca)
‐ distribution limited by temperature
Kubodera et al. 2007
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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
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How Does Climate Affect Sharks?P. glauca‐ ectothermmore coastal,lower latitude
L. ditropis‐ endothermmore pelagichigher latitude
Kubodera et al. 2007
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How Does Climate Affect Sharks?
Temperature• Timing of reproduction‐Cycling hormone levels maintain mating seasons
‐Induced by environmental cues
Tricas et al. 2000
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How Does Climate Affect Sharks?
Salinity• Osmoregulation is expensive!!
• Isosmotic due to storage of urea in tissues
• Rapid salinity changes are highly stressful
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How Does Climate Affect Sharks?
CO2/ ↓ pH• Skeletal growth‐ calcification
biomechanics.bio.uci.edu
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Climate Change and Sharks
• No direct evidence yet of climate change influence onelasmos (ALL areas of elasmo research limited still)
• But‐ we can speculate that elasmos will be affected ina variety of ways
“ecological and economic risks associated with being partially correct outweigh the social risks of
being wrong”‐ Okey et al. 2007
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Climate Change and Sharks
Observable changes/local effects of human‐inducedenv. changes:
salmon shark niche expansion
round stingrays in seal beach
blacktip response to hurricanes
local carcharias extinction in e. pac
basking sharks in scotland
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Climate Change and SharksOkey 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 theNorth Pacific Ocean, although numbers declined recently
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Climate Change and SharksOkey et al. 2007: salmon shark niche expansion
Weng et al. 2005
norbert wu
calstatela.edu
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Climate Change and SharksOkey et al. 2007: salmon shark niche expansion
• Possible explanations for “increased abundance”:
1. Northward expansion in distribution due torises in temperature
2. Ban of high seas gillnets decreasing mortality
3. Competitive release due to declines in blueshark populations
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Climate Change and SharksHoisington and Lowe 2005: Seal Beach, CA stingrays
cnsm.csulb.edu
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Climate Change and SharksHeupel 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 pressurehours before storm made landfall
• All returned about 2 weeks later, after salinity increasedfollowing rainfall
• Purpose of leaving unknown, but may be linked tophysiological tide‐guage mechanism so sharks don’t gettrapped in nursery area
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Climate Change and SharksCione 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
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Climate Change and SharksBasking sharks in Scotland
• Planktivorous sharks
• Increased in abundance near Scotland where plankton has also increased in abundance