Changes in Deep Sea Ecosystems of Antarctica over the last 30 years

Roberto Danovaro

Polytechnic University of Marche

Stazione Zoologica Anton Dohrn

Is there a global change impact on Atarctica?

Meehl et al., 2019

Antarctic sea ice extent

Meehl et al., 2019

Surface ocean warming in 2016-2017

Surface ocean cooling in 2000-2014

Gutt et al., 2015

Which are the consequences of such changes on primary production, C export and functioning on deep-sea ecosystems?

Major sea-ice decrease next to the Ross Sea area (data @2015, before the 2016-2017 major sea-ice decrease in the Ross Sea)

Project BEDROSEBEnthic biodiversity and ecosystem functioning of the Deep

ROss SEa in a changing SouthernOcean

Sediments were collected during the X and XXXII Italian Antarctic Expeditions in 1995 and in 2017Ross Sea

ROSSMIZE (RossSea Marginal Ice Zone, X Spedizione Antartica, 1994-1995)

Ross Sea

C1995

C1995

CT1CT2

B1995BT1BT2

Study area and sample collection

Variables investigated

Sedimentary organic matter (OM) quantity and composition

OM degradation rates in the sediments (Extracellular enzymatic activities)

Prokaryotic abundance, biomass Prokaryote biodiversity Viral abundance and production Meiofauna abundance, biomass Faunal biodiversity (higher taxonomic composition)

Environmental parameters

Site B Site C

SITE DATE DEPTH (M) BOTTOM WATER TEMPERATURE (°C)

SALINITY

B1995 15/02/1995 567 -1.8 34.7

BT1 17/01/2017 587 -1.8 34.7

BT2 30/01/2017 586 -1.8 34.7

C1995 12/02/1995 439 -0.4 34.6

CT1 31/01/2017 432 -0.5 34.6

CT2 09/02/2017 433 -0.04 34.6

Primary Organic Matter inputs

0

1.5

3

4.5

B1995 BT1 BT2 C1995 CT1 CT2

μg g

-1

Chlorophyll a

0

1.5

3

4.5

B1995 BT1 BT2 C1995 CT1 CT2

μg

g-1

Phaeopigments0

1.5

3

4.5

B1995 BT1 BT2 C1995 CT1 CT2μ

g g-

1

TOTAL Phytopigments

Organic Matter Composition

0

1.5

3

4.5

mg

g-1

Proteins

0

1.5

3

4.5

mg

g-1

Carbohydrates

0

0.9

1.8

2.7

mg

g-1

Lipids

0

1.42

2.84

4.26

B1995 BT1 BT2 C1995 CT1 CT2

mg

g-1

Biopolymeric Carbon

0%

25%

50%

75%

100%

B1995 BT1 BT2 C1995 CT1 CT2

Relative Contribution to BPC

LIP

CHO

PRT

β-glucosidase activities were lower compared to 1995.

Aminopeptidase activities were lower compared to 1995.

Extracellular Enzymatic Activities

0

1.5

3

4.5

B1995 BT1 BT2 C1995 CT1 CT2

log(

nm

ol g

-1h

-1)

Aminopeptidase Activativity

0

1.5

3

4.5

B1995 BT1 BT2 C1995 CT1 CT2

log(

nm

ol g

-1h

-1)

β-glucosidase Activity

Prokaryotic biomass valuesdecreased by a factor of 14 to>130 in 20 years.

Our results suggest a decreaseof 2 to >20 times of theprokaryotic abundancescompared to 1994.

Prokaryotic Abundance and Biomass

0.0E+00

8.2E+08

1.6E+09

2.5E+09

B1995 BT1 BT2 C1995 CT1 CT2

n c

el g

-1

Prokaryotic Abundance

1

10

100

1000

B1995 BT1 BT2 C1995 CT1 CT2

μgC

g-1

Prokaryotic Biomass

Viral Abundance and Viral Production

0.0E+00

1.5E+09

3.0E+09

4.5E+09

B1995 BT1 BT2 C1995 CT1 CT2

n v

iru

s g-

1

Viral Abundance

0.0E+00

9.5E+07

1.9E+08

2.9E+08

B1995 BT1 BT2 C1995 CT1 CT2

n v

iru

s g

-1

Viral Production

Our results suggest a decrease of5 and 6 times of the viralabundances compared to 1994 atsite B and C respectively

Viral production decreased by afactor of 5 to >40 in 20 years.

Taxonomic composition of prokaryotic assemblages

Shift in prokaryotic community composition from 1995 to 2017

Collapse of Flavobacteriacee

Collapse of Chaetoceros and Thalassiosira

Increase in ammonia oxidizers

(Thaumarchaeota and Pirellulaceae)

B

C

Meiofauna abundance and thenumber of taxa did not changecompared to 1995

Meiofauna Abundance and Number of Taxa

0

700

1400

2100

B1995 BT1 BT2 C1995 CT1 CT2

ind

10cm

-2

Meiofauna Abundance

0

5

10

15

B1995 BT1 BT2 C1995 CT1 CT2

N°

of

Tax

a

Meiofauna Taxa

Shift in meiofauna community structure at St. C with decrease ofthe Copepoda

Meiofauna Community Structure

0%

25%

50%

75%

100%

B1995 BT1 BT2 C1995 CT1 CT2

Re

lati

ve c

on

trib

uti

on

Nematoda

Copepoda

Polychaeta

Bivalvia

Ostracoda

Tardigrada

Amphipoda

Acarina

Gastropoda

Ophiura

Other Taxa

Rare Taxa

0%

25%

50%

75%

100%

B1995 BT1 BT2 C1995 CT1 CT2

Re

lati

ve C

on

trib

uti

on

of

Rar

e T

axa Kinorhyncha

Turbellaria

Oligochaeta

Gastrotrica

Isopoda

Tanaidacea

Nemertina

Loricifera

Collapse of Gastrotrica and increase of kinorincha, isopoda andoligochaeta

Conclusions The analysis of the last 30 years reveals the presence

of major shifts in:

Inputs of primary organic matter

Amounts of sedimentary organic matter

Biogeochemical cycling

Abundance and diversity of microbial communities

Shift in faunal taxa

Caveats

Need of more frequent temporal data

Need of understanding the presence of deep-sea habitats and

their extension

Need of better understanding spatial variability