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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 • • • • 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 • • • • 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: – – – – 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