Abundance, Distribution, Swimming Behavior and Feeding of Under Ice Larval Krill Along the Western A

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Abundance, Distribution, Swimming Behavior and
Feeding of Under Ice Larval KrillAlong the
Western Antarctic Peninsula

• Scott Gallager, Kendra Daly,
• Gustavo Thompson, Carin Ashjian,
• Phil Alatalo, Andy Girard, and Gaelin Rosenwaks
• Woods Hole Oceanographic Institution

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U.S. Southern Ocean GLOBEC

• The Marguerite Bay continental shelf region
• Hypothesized to be an important krill
  over-wintering site
• Potentially a source for down-stream krill
  populations
• Little is known of its winter ecology

• Program Goals
• To determine circulation processes and their
  effect on sea ice formation and krill
  distribution
• To understand factors that govern krill
  survivorship and availability to higher trophic
  levels

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Objectives

• This Project
• To quantify midwater and under ice distribution,
  abundance and swimming behavior of krill furcilia
  using BIOMAPER II and ROV
• To relate furcilia distribution to under ice
  topography and microplankton prey
• To evaluate the trophic imapct of furcilia
  feeding on microplankton during overwintering

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Midwater Plankton DistributionsVideo Plankton
Recorder on BIOMAPERII

• High and low magnification
• VPR cameras
• CTD, fluorescence
• Plankton images captured and
• identified in near-real time

Up and down looking acoustics 38, 120, 200, 1000
KHz
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Locations of VPR and BIOMAPERII Data
NBP0103 April-May 2001
NBP0104 July-August 2001
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Fall 2001 Backscatter (Wiebe et al.) Relative
to Dynamic Topography (Klink, Hofmann et al.)

• Gyre present over the northern portion of the
  area, and a coastal current running along-shelf
• Suggests across- and along-shelf transport of
  zooplankton

L
H
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Winter 2001 Backscatter Relative to Dynamic
Topography

• High levels of backscatter retained only in
  Marguerite Bay

L
Backscatter (dB)
H
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2001 50 m Drifter Tracks (Beardsley, Limeburner,
Owens)
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Vertical Water Structure
Antarctic Surface Water (AASW)
Winter Water (WW)
Upper Circumpolar Deep Water (UCDW)
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Vertical Distribution of Larval Krill in
Association with Hydrography
Larval Euphausiids (/L)
Temperature (C)

• High abundances above thermocline
• High abundances associated with Winter Water

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Temperature Salinity Plankton Plot
Major source of heat, salt, nutrients
UCDW
mUCDW
AASW
Winter Water

• Larval krill throughout water column but greatest
  abundances in AASW, Winter Water, and the upper
  portion of modified UCDW.

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Total Abundance
Larval Krill April-May,2001
Copepods April-May,2001

• Higher abundances of larval krill at offshore
  portions of the shelf, shelfbreak, in Marguerite
  Bay, and in the southern portion of grid.
• High abundances of copepods on outershelf and
  southern portion of grid.
• Larval krill more abundant than copepods.

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Under Ice Distribution and Behavior of Larval
Krill
Imagenex 881 sonar
Stereo Cameras
Strobe
1200KHz ADCP
CTD
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ROV survey track- typical
NBP
100 m
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ROV Pressure and Distance to Under Ice Surface
ROV 20
ROV altitude
ROV pressure
Depth (m)
Ice Projection
Furcilia Abundance
Abundance (/L)
Distance along trackline (m)
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ROV Pressure and Distance to Under Ice Surface
ROV 20
ROV altitude
ROV pressure
Depth (m)
Ice Projection
Ice motion
flow
Furcilia Abundance
Abundance (/L)
Distance along trackline (m)
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Under Ice Furcilia Abundance April-June 2001
Concentration (/m3)
Concentration (/m3 x 103)
Concentration (/m3)
Concentration (/m3)
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Mean Furcilia Abundance NBP0102
July-Aug 2001
9
79
ind/m3
17,804
10
93
95
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under ice furcilia integrated water
column furcilia (2001 only)
1,388
89
151
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63
55
8
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• Overwintering Survival Strategy
• Furcilia Microplankton Feeding Experiments
• Diver collected krill furcilia were exposed to
  Niskin bottle, bucket collected seawater, and
  fluorescent micro beads
• Functional response curves were established to
  relate ingestion and clearance of microplankton
  as a function of concentration
• Quantified non-invasively in real time using
  video microscopy and image analysis

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Transmitted light
420 excitation 2 um bead
510 excitation 16 um bead
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Functional response of furcilia feeding on 3
particle types over a wide range of particle
concentartions
Ingestion rate (Part / ind / h)
Clearance rate (mL/ ind / h)
Particle concentration ( / mL)
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• At
• concentrations
• gt100 / m3
• furcilia can
• consume 100
• of the
• microplankton
• community

Clearance Rate
1 mL/h
100 mL/h
5 days
1 day
Microplankton generation time
NBP0104
NBP0204
NBP0103, 0202
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Distribution of Krill Furcilia and Microplankton
July-Aug 2002
Microplankton and particle concentration were
inversely proportional to furcilia concentration
suggesting strong grazing pressure imposed by
furcilia.
Particles / mL
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• Summary
• A circulation gyre exists to the north of
  Marguerite Bay that moves water across shelf in
  both directions -retention area
• Mid water furcilia abundance was high in the Bay
  and off the coast of Alexander Island
• Under ice furcilia distribution was patchy and
  associated with ice topology 0 to gt 500,000 /
  m3
• When furcilia are abundant (gt 100 / m3) and
  microplankton growth rates are low (e.g., winter
  months), complete top-down control of the
  microplankton community is possible

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The Team
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Polar Remote Interactive Marine Observatory
(PRIMO)
Palmer Station 100 m depth May 2006
Vernon Asper University of Southern
Mississippi Scott Gallager Keith von der
Heydt Bob Beardsley Woods Hole Oceanographic
Institution
National Science Foundation Office of Polar
Programs
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Polar Remote Interactive Marine Observatory
(PRIMO)
Plankton and Marine Snow Video Plankton Recorder
(60 Hz) Bio-Optical (1-10 Hz) Wetlabs
ac-9 Satlantic radiometers - 412 to 683
nm. Fluorometers Chlor, CDOM Environmental
(1-20 Hz) CTD u, v, w, _at_ 20 Hz (MAVS) pO2
(Aanderaa), ISUS-nitrate Engineering (1-50
Hz) roll, pitch, yaw Communications 10 Base T
Ethernet, Iridium Plenty of room for more
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PRIMO
JUST IN TIME FOR THE INTERNATIONAL POLAR YEAR
2007-08
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AUV/Gliders
Cabled Observatories
The Vision
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Questions, Comments, Collaborations, Are Most
Welcome
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Mass Bay Oct-Nov 2002
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Mass Bay Oct-Nov 2002
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Mass Bay Oct-Nov 2002
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Vertical Water Structure
Antarctic Surface Water (AASW)
Winter Water (WW)
Upper Circumpolar Deep Water (UCDW)
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Vertical Distribution of Larval Krill in
Association with Hydrography
Larval Euphausiids (/L)
Temperature (C)

• High abundances above thermocline
• High abundances associated with Winter Water

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Surface Microplankton and Particulates April-May
2001
Temperature
Concentration
Diameter
/mL
um
Swimming Speed
Station 13
6.3 cm
mm/s
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Vertical Distribution of Larval Krillfurcilia II
gt

• Greatest abundances of larval krill associated
  with the pycnocline
• Greatest fluorescence above the pycnocline
• Depth distributions of krill and fluorescence
  change with changing pycnocline depth