Marine benthic habitats of the George V Land shelf, Antarctica

Marine benthic habitats of the George V Land shelf, Antarctica

Linking geophysical and biological data in a polar environment

Robin J. Beaman

17th Australian Geological Convention, Hobart, Australia, 8-13 February 2004 2

Project acknowledgements

• Geoscience Australiaseismic profiles, grabs, cores, photosDr Peter Harris, Mr Rick Porter-Smith

• Colgate University, USAmultibeam data, grabs, dredges, photosDrs Amy Leventer, Eugene Domack

• University of Tasmania, Antarctic CRCresearch assistance, oceanographic dataDrs Richard Coleman, Nathan Bindoff, Rob Massom


Benthic habitats – nested hierarchy

1. Provinces

2. Biomes

3. Geomorphic Units

1000’s km

100-1000’s km

< 100 km

4. Primary Biotopes 1’s - 10’s km

Scale

5. Secondary Biotopes

6. Biological Facies

7. Micro Communities

Levels Examples Datasets

1’s - 10’s km

< 1 km

cm - m

Aust. Antarctic shelf, SE Aust. slope and rise

coastal, mid shelf, outer shelf, slope

canyons, banks, seamounts, reefs

soft, hard + assoc. benthic communities

mud, sponges, seagrass, coral

sponge spp, seagrassspp, coral spp

kelp communities, vent communities

published reports

bathymetryoceanography

sediments, acoustic facies

backscatter, relief, slope

coarse bio, physical goundtruthing

detailed groundtruthing

very detailed groundtruthing

17th Australian Geological Convention, Hobart, Australia, 8-13 February 2004 5© Canadian Space Agency 2000

MertzGlacier

George V Land

Adelie Land

N

146°E

142°E

66°S

100km


Research cruises

RV Nathaniel B. PalmerNBP0101

Jan – Mar 2001

RV TangaroaWEGA

Feb – Mar 2000


1. Bathymetric model

Results:• DEM at 0.001 degree (~100m) res.• slope and aspect

Data sources:• GEBCO (1997) DEM• WEGA single beam soundings• NBP0101 multibeam bathymetry

Strong relationships between bathymetry and marine habitats.Due to effects on oceanography, biology, sediment transport processes.


N

Mertz Bank

Adelie Bank

George V Basin

300m

1000m

800m

300m

100km

200m


2. Seabed characterDifferent acoustic echo types can be related to physical properties of the sea floor.Need to identify and classify distribution of seabed acoustic facies based upon Damuth (1980).

Data Sources:• WEGA 3.5 and 12 kHz data• limited published material

Results:• Damuth (1980) acoustic facies classification


Damuth (1980) acoustic facies

IA-2

IIB

IIIC

IB

Adelie Bank

Mertz Bank

George V Basin

400

400

200

200

600

2200

8001000

200


0

200

400

600

800

1000

Mertz Glacierice cliff

IB

IIB

IA-2IA-2

IIIC


3. Surficial sediments

Data sources:• 1979 Deep Freeze 79 grabs• 1984 USGS Glacier core• WEGA grabs

Results:• % mud, sand, gravel• Folk (1954) sediment classification

Mud Sand

Gravel

80%

30%

5%

0.01%

1:9 1:1 9:1

M sM mS S

(g)M (g)sM (g)mS (g)S

gM gmS gS

mG msG sG

G

1

234

567

891011

12131415

Reflects source material and current strength, and a valuable proxy for benthic communities.Need to classify sediment texture using Folk (1954).


Gravel %

0-5

5-1010-1515-20

5-10400

200

600

2200

8001000

200


Mud %

80-100

60-80

40-60

20-400-20

400

400

200

200

600

2200

8001000

200


Folk (1954) sediment classification

sM(g)sM

(g)mSgmS

gS

gM, S, G

400

400

200200

600

2200

8001000

200


0

200

400

600

800

1000


IIIC

IB

IIB

IA-2IA-2

gS gmS(g)mS (g)sM sM (g)sM gM, S, G


4. OceanographyCorrelated to sediment distribution on the shelf.Important for helping define the ‘marine climate’.Need to define water masses from Bindoff et al (2001).

Data sources:• Deep Freeze 1979 (summer)• WEGA (summer)• AU9901 (winter)

Results:• summer, winter temperature, salinity, oxygen• Bindoff et al (2001) water mass classification

MCDW> -1.91< 34.63

WW> 34.63<34.66

ISW< -1.91< 34.63

HSSW> 34.66

1 2 3

4 5 6

SALINITY (psu)

-1.91

0

34.63 34.66


Summer temperature (°C)

< -1.8

-1.6to-1.8

-1.4to-1.6-1.2to-1.4-1.0to-1.2

-0.8to-1.0-0.6to-0.8

400

400

200200

600

2200

8001000

200


Winter salinity (psu)

>34.70

34.65-34.70

34.60-34.65

34.55-34.60 34.50-34.55

400

400

200200

600

2200

8001000

200


Winter water masses

HSSW

WW

MCDW

ISW

400

400

200200

600

2200

8001000

200


remnant WW

HSSW

MCDW MCDW

400

400

200200

600

2200

1000

200

800

Summer water masses


0

200

400

600

800

1000

ISW

HSSW

MCDWWWCDW

sea iceice cliff

IIIC

IB

IIB

IA-2IA-2

Mertz Glacier

Winter


0

200

400

600

800

1000

HSSW

MCDW

Remnant WWCDW


IIIC

IB

IIB

IA-2IA-2

AASW

Summer


5. Iceberg ScourHighest natural disturbances in marine ecosystems are from icebergs.Density and frequency of iceberg scouring influences sediment distribution and benthic colonisation.Need to classify scour as per Gutt & Starmans (2001).

Data sources:• summer, winter Radarsat images

Results:• Gutt & Starmans (2001) classification

level plateau

small iceberg bank

large iceberg bank

17th Australian Geological Convention, Hobart, Australia, 8-13 February 2004 26© Canadian Space Agency 2000

MertzGlacier

George V Land

Adelie Land

N

146°E

142°E

66°S

100km


Iceberg Density - George V Shelf

0.00000.02000.04000.06000.08000.10000.1200

NE Adeli

e Ban

kSE A

delie

Bank

Bucha

nan B

ayMert

z Ridg

eAde

lie B

ank

Mertz B

ank

Grounded iceberg zones

Iceb

erg

dens

ity (N

o/km

sqr

SummerWinter

high scourmed scour

low scour



1. Provinces

2. Biomes

3. Geomorphic Units

1000’s km

100-1000’s km

< 100 km


Scale





1’s - 10’s km

< 1 km

cm - m








published reports








Geomorphic units

bankbank

basin

canyonscoast

shelf edge

ridge

drift

megaflutes

400

400

200

200

600

2200

8001000

200


Linking habitat and biota

Data sources:• Australian Antarctic Expedition (1911)• NBP0101 grabs, dredges and photos• WEGA grabs and photos

Results:• taxon diversity• % motility, % trophic structure, % biomass• PCA, cluster and MDS plots, BIOENV

What are the community patterns and how do they relate to the environmental data?Need to conduct multivariate analysis of bio. and phys. data, then compare statistically.


Biota• foram• sponge• polychaete• nonpoly worm• bryozoa• brachiopod• gastropod• bivalve• scaphopod• octopus• anemone• hydroid• soft coral

• sea pen• sea cucumber• sea star• sea urchin• brittle star• feather star• amphipod• isopod• decapod• barnacle• sea spider• tunicate


400

400

200

200

600

2200

1000

200

800


GC

11

GB

18

GB

16

GB

06

GB

14

GB

08

GB

13

GB

04

GB

17

GB

05

GB

02

GB

07

GB

03

GB

15

GB

12

GB

10

GB

01

GB

11

GB

09

100

80

60

40

20

0

Sim

ilarit

y

WEGA grab data - %weight


WEGA grab data - %weight + sponge

GC11

GB18GB17GB16

GB01

GB15

GB08

GB07

GB06 GB12GB05

GB10GB11

GB04GB02GB03GB14GB13

GB09Stress: 0.02


BIOENVbiota and environment matching• Variables: depth, sand, mud, salinity,

oxygen, temperature

• Best results: mud, salinity, temperature correlation coefficient 0.37

• Therefore, this combination of variables best relates to (‘explains’) the observed biological pattern



1. Provinces

2. Biomes

3. Geomorphic Units

1000’s km

100-1000’s km

< 100 km


Scale





1’s - 10’s km

< 1 km

cm - m








published reports








N• depth: > 700m• acoustic facies: IB• substrate: sandy mud• disturbance: sediment• iceberg scour: nil• current: moderate• watermass winter: HSSW• watermass summer: remnant WW• habitat complexity: low• predominant biota: sponges• benthic motility: about 50%• trophic structure: 50% susp. feeder• benthic forams: arenaceaous basin

Properties

3. Geomorphic Unit: drift4. Primary Biotope: western lower basin5. Secondary Biotope: deep basin, suspension-feeders

Levels


Conclusion• Marine habitats should be considered within a

nested hierarchy, driven from the bottom units.

• It is possible to create datasets from dispersed sample points on the Antarctic shelf.

• Ideally, collect physical data at the same sites as the biological data, then use statistics to explain the patterns.

• Use the physical datasets to help define the boundaries of benthic communities.

• A list of features should describe each community, which reveals any gaps in knowledge.

Marine benthic habitats of the George V Land shelf, Antarctica

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