Bess WardDepartment of Geosciences

Princeton University

Weddell Sea

Ross Sea

Palmer Peninsula

Pine Island Glacier breaks away from the Palmer Peninsula -- global warming at work?

Cooling Trend in Antarctica -- warmer in polar seas

Doran et al., 2002

Doran et al., 2002

Weddell Sea

Ross Sea

Palmer Peninsula

Doran et al., 2002

Doran et al., 2002

Antarctic Continental Cooling

Climate indicators Reduced T, decreased wind,

increased sunshine Reduced river flow, thicker ice

Ecosystem effects Less primary production Fewer nematodes

Conflicting Signals of Climate Change in Antarctica

Indications of global scale change? Feedback effects of global climate? Ecological consequences?

The Mystery of the Dysfunctional Nitrogen Cycle

Taylor Glacier

South Pole

West LB

East Lake Bonney

West LB

East Lake Bonney

East Lake Bonney

STRANGE…

N cycle non functional:

Way too much nitrous oxide (N2O) and nitrate (NO3)

West Lake Bonney

NORMAL

N cycle functional:

Very little nitrous oxide (N2O) and nitrate (NO3)

One lake, two lobes connected at the surface

WHY????WHY????

N2O = Greenhouse gas

UV radiation

Ozone layer

N2O involved in Catalytic ozone destruction

NO3

bacteria

Nitrous oxide (N2O):

intermediate in denitrification

N2

Nitrogen Concentrations (µM)

NORMAL

Dep

th (

m)

West Lobe

ammonium

nitrate

East Lobe

STRANGE

ammonium

nitrate

Nitrogen Concentrations (µM)

East Lobe

STRANGE

ammonium

nitrate

Nitrogen Concentrations (µM)

East Lobe

STRANGE

ammonium

nitrate

(Priscu et al., 1996; LTER)

nitrous oxide

Dep

th (

m)

East Lobe

REALLY STRANGE

First, drill a hole….

Weather port, West Lobe Lake Bonney

Sampling Hole through the Ice Cover

“Lab” inside the weather port

Isolate denitrifying bacteria and detect them in the lake

Species-specific immunofluorescence

Distribution of strain ELB17 (Marinobacter) in Lake Bonney

(counted by immunofluorescence) East Lobe

Optimal growth conditions for strain ELB17

Nitrite reductase (nirS) genes in Lake Bonney

Central enzyme in denitrificaiton encoded by nirS

nirS genes found in both lobes

Paracoccus pantotrophusParacoccus denitrificans

Roseobacter denitrificans

NogalesAJ440476NogalesAJ440483

Ralstonia eutrophaNogalesAJ440492

NogalesAJ440487Alcaligenes faecalis

Pseudomonas stutzeri 14405Pseudomonas stutzeri JM300

Pseudomonas fluorescens

Pseudomonas aeruginosa[WLB16-24]

NogalesAJ440469NogalesAJ440478

NogalesAJ440471

NogalesAJ440473NogalesAJ440480

NogalesAJ440486NogalesAJ440475

NogalesAJ440489NogalesAJ440470

Braker pA12Braker pB66Braker pA4

Braker pB46Braker pC56

Braker pA90Braker pA29Braker pB76

Braker pA32Braker pA25

Braker pA98Braker pA94

Braker pB4Braker pB49Braker pA50

Braker pB20[WLB16-29]

Braker pA5Braker wF16

Braker wA15

NogalesAJ440477[ELB16-20][ELB16-35][ELB19-20][ELB19-1][ELB19-28][ELB19-3][ELB16-30][ELB16-33][ELB16-40][ELB19-38][ELB16-16][ELB19-24][ELB19-6][ELB19-36][ELB19-30][ELB16-32][ELB16-24][ELB19-16][ELB19-40][ELB19-25][ELB16-25][ELB16-9][ELB19-11][ELB16-4]

[ELB19-14][ELB19-15]

[ELB16-7][ELB16-28][ELB16-27][ELB16-26][ELB16-5]

[ELB19-33][ELB19-8][ELB19-4][ELB19-17][ELB19-35][ELB16-36][ELB16-31]

[ELB19-32][ELB19-26]

[ELB19-39][ELB16-39][ELB16-6][ELB19-18][ELB19-5][ELB16-34][ELB16-38][ELB16-11][ELB16-1][ELB19-42]

Halomonas variablis B9-12[ELB25-5]Marinobacter sp. C10-1

Marinobacter sp. D4-14[WLB16-4]

[WLB16-94][WLB16-58][WLB16-5]

[WLB16-35][WLB16-53][ELB25-43][WLB16-51][WLB16-74]

[WLB16-90][WLB16-93][WLB16-30][WLB16-40][WLB16-47]

[ELB25-7][ELB25-75][ELB25-19]

[ELB25-14][ELB25-55]

[ELB25-9][WLB16-10][WLB16-89][ELB25-56][ELB25-50][WLB16-7][WLB16-1][ELB25-78][WLB16-16][WLB16-82][WLB16-73][ELB25-31]

[WLB16-70][ELB25-59]

[ELB25-23][ELB25-41][ELB25-27][ELB25-39][ELB25-3][ELB25-2][ELB25-52][ELB25-76][ELB25-11][ELB25-62][ELB25-74][ELB25-18][ELB25-57][ELB25-79][ELB25-10][ELB25-13][ELB25-84][ELB25-34]

5%

100

10084

95

88

100

100

72

10062

70

100

85

78

62 100

100

77

66

86

95

99

96

99

72

62

93

100

64

75

90

63

100

91

90

Chris Francis

Sharon Harris: Teacher Experiencing Antarctica

Measuring denitrification rates based on N2O production

Dep

th (

m)

West Lobe

Denitrification rate

Dep

th (

m)

East Lobe

Denitrification rate

Denitrification does not occur in the East Lobe…but all the

ingredients are present

Denitrifiers can be isolated from the lake The strains survive under in situ conditions Denitrifying cells are detected in the lake Denitrifying genes are detected in the lake Denitrification happens in the bags, not in the

lake

So what is the #?@@*#&^&*$ problem??

Nitrogen Concentrations (µM)

East Lobe

STRANGE

ammonium

nitrate

(Priscu et al., 1996; LTER)

nitrous oxide

Dep

th (

m)

East Lobe

REALLY STRANGE

East West

Copper

low hi

SilverSilver hi low

Mark Wells

Nitrite Reductase, Nitrous Oxide Reductase

NO3 NO2 NO N2O N2

Inducible, conserved, gas metabolism

(Cu, heme) (Cu)

The Copper Hypothesis

CuCu is required for denitrification AgAg substitutes for CuCu in denitrification

enzymes, and makes them nonfunctional

AgAg toxicity or competition with CuCu inhibits denitrification in the East

But how did the two lobes end up with such different AgAg / CuCu ratios?

LTEREast Lobe

West Lobe

Taylor Glacier

Blood Falls, West Lake Bonney

Blood Falls, West Lake Bonney

Cross section of Lake Bonney today

W E

Taylor Glacier

Lake Bonney 3000 years ago

“cold-dry” period

W E

Taylor Glacier

W E

Taylor Glacier

W E

Taylor Glacier

W E

Taylor Glacier

W E

Taylor Glacier

Lake Bonney 1200 years ago

Hypersaline pool in the East Lobe

W E

Taylor Glacier

W E

Taylor Glacier

W E

Taylor Glacier

Cross section of Lake Bonney today

W E

Taylor Glacier

Geochemical Evidence

West and East Lobes have different histories

History reflected in chemical composition of the water

Modern biogeochemistry depends on past climate change

Future climate change depends on current biogeochemistry

Bonney Hoppers

Sunrise at McMurdo, 11 July 2001