Marine Organism Population Dynamics- Keystone Species ...biology.fau.edu/koch/Documents/Climate...

Marine Organism Population Dynamics- Keystone Species Adaptability With a Special Emphasis on

Dolphins and Elasmobranchs

Cindy Rogers and Christine BedoreApril 14, 2008

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

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

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

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

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

The NAO as a Proxy


• 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

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

• 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: zooplanktonwww.sciencefriday.com

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

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

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

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

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

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

• 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

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

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

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

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

What are Elasmobranchs?

Why are Sharks Important?

Economy: food


Economy: ecotourism


Economy: recreation


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


Biomedical research: Cancer and immunology:Dr. Carl Luer and clearnoseskate (Raja eglanteria)

mote.org

aqua.org


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 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%!!

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. 2003fao.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 farShows weakened top=down control by elasmobranchconsuming 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, lowrate of pregnant females

• Impaired immune function

• BIOACCUMULATION!!(Walker 1997‐graph?)


Habitat loss/degradation: Nursery and mating grounds

• Mangroves and estuaries


Overfishing: Fins, meat, cartilage, jaws/teeth, bycatch


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


Temperature• Most are ectotherms (ex: blue shark‐ Prionace glauca)

‐ distribution limited by temperature

Kubodera et al. 2007


Temperature• Some local endotherms (ex: Salmon shark‐Lamna ditropis)‐ distribution expanded due to larger thermal tolerance


How Does Climate Affect Sharks?P. glauca‐ ectothermmore coastal,lower latitude

L. ditropis‐ endothermmore pelagichigher latitude



Temperature• Timing of reproduction‐Cycling hormone levels maintain mating seasons

‐Induced by environmental cues

Tricas et al. 2000


Salinity• Osmoregulation is expensive!!

• Isosmotic due to storage of urea in tissues

• Rapid salinity changes are highly stressful


CO2/ ↓ pH• Skeletal growth‐ calcification

biomechanics.bio.uci.edu

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

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

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


Weng et al. 2005

norbert wu

calstatela.edu


• 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

Climate Change and SharksHoisington and Lowe 2005: Seal Beach, CA stingrays

cnsm.csulb.edu

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

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

Climate Change and SharksBasking sharks in Scotland

• Planktivorous sharks

• Increased in abundance near Scotland where plankton has also increased in abundance

Marine Organism Population Dynamics- Keystone Species ...biology.fau.edu/koch/Documents/Climate...

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Transcript of Marine Organism Population Dynamics- Keystone Species ...biology.fau.edu/koch/Documents/Climate...