The consequences of climate change on Alaskan marine life

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The consequences of climate change on Alaskan
marine life

• Russ Hopcroft

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Globally air and ocean temperatures are rising
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x
0.5
0
Temperature (C)
-0.5
1000
1200
1400
1600
1800
2000

• Changes in the magnitude of ocean production
• Changes in the timing of ocean production
• Changes in the location of ocean production (and
  where it sinks)
• Changes in marine community composition
• Distribution of species largely determined by
  temperature
• Displacement, invasion, extinction?

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Why care?
Change in catch of a small mesh bottom trawl in
Pavlof Bay, through the regime shift of the
mid-1970s
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The currents and water column properties
throughout the worlds oceans are coupled.
Temperate fauna are easily carried northward in
coastal currents
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COASTAL GULF OF ALASKA SEWARD LINE

• Long-terms observations critical
• Seward-Line Data over 3 decades
• GLOBEC 1997-2004, biology and physics, Why is
  this system so productive.. Climate Salmon
• NPRB 2005 2006

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The success of the large zooplankton that
dominate the spring is related to their unique
adaptations to the production cycles of the Gulf
Neocalanus
They spawn in mid- winter, anticipating the
spring bloom, speed of growth depends on food and
temperature
Once fatten, they descend to depth and hibernate
in warm years, they may be gone before the salmon
arrive to feed on them
Their descent gives way to a summer community of
much smaller species, too small for salmon to eat
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Fall 2005
Several other smaller southern species also
observed
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The most immediate effects may occur in
transitional gateways such as the Bering Sea
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Southeast Bering Sea productivity linked to the
timing of the sea-ice melt and the Spring Algal
Bloom
Hunts OCH BEST program
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Why is the Northern Bering seafloor so productive?

• At present, currents inject high concentration of
  nutrients, stimulating growth of the suspended
  algae
• Zooplankton cannot grow fast enough to eat all
  this algal, and it falls to the bottom, as high
  quality food

SBI Program
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Gateways

• Northern Bering is a complex mixture of different
  water masses, all flowing northward
• How do these different water sources influence
  the composition of animals in the water column
  and the food supply to the seafloor?
• How far do Pacific species and waters penetrate
  into the Chukchi Sea and Arctic Ocean?
• How might this arctic gateway change with
  ongoing warming trends?

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Absence of Feeding Gray Whales in the Chirikov
Basin
Moore, Grebmeir Davies

• Recent work shows benthic community changes and
  biomass declines over much of region (Grebmeier
  et al., unpublished)

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More.

• BASIS program suggests Bering Sea salmon have
  begun to forage northward, with reports north of
  the straights (outside of surveys)
• RUSALCA program found range extensions by a
  number of Pacific fish and seafloor invertebrate
  species into the Chukchi Sea
• Colonies of some sea-birds species have
  contracted, due to loss of preferred foods
• Decreased prevalence of traditional Bering Sea
  zooplankton, and increased prevalence/penetration
  of Pacific plankton species

BASIS 2004 Pinks
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Pacific Input

• 3 related copepod species
• Alaska Coastal water warmer, lower chlorophyll,
  dominated by smaller sub-arctic species (P.
  newmani)
• Anadyr and Arctic waters dominated by larger
  Arctic species (P. acuspes and P. minutus)
• Community composition strongly tied to water
  masses, and traces Alaskan Coastal water as far
  as Harold Canyon

RUSALCA 2004
Temperature
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So what?
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Last decade warmer, with less ice

• In the coastal zone, the impacts are most
  noticeable for animals coupled to the ice
  walrus, seals, bears, whales

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Central basins

• Poorly studied due to limited access
• Production and biomass in basins much higher than
  early estimates
• Diversity is much higher than originally
  believed, due to limited effort, and use of
  inadequate tools

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Questions

• How might ecosystems of the central Arctic Ocean
  change?
• First, we need to how arctic ecosystems are
  currently structured.
• We need to learn this ASAP before changes become
  acute

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Many new species are being discovered
Are they new to science, or new to the Arctic?
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The BIG picture impact

• Increased penetration of southern species will
  lead to changes in composition, AND size
  structure of zooplankton communities
• Coupling between pelagic and benthic communities
  is changing
• Many predators feed based on size of prey, and
  prey preferences, these will have impacts higher
  up the food chain (i.e. fish, birds, mammals)
• Pacific species have different timing and
  duration to their life cycles impact?...
  viability?
• Continued observation is critical to document,
  and understand how these ecosystems are changing