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Changes in Deep Sea Ecosystems of Antarctica over the last 30 years
Roberto Danovaro
Polytechnic University of Marche
Stazione Zoologica Anton Dohrn
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Is there a global change impact on Atarctica?
Meehl et al., 2019
Antarctic sea ice extent
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Meehl et al., 2019
Surface ocean warming in 2016-2017
Surface ocean cooling in 2000-2014
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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)
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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
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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)
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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
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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
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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
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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
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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
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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.
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Taxonomic composition of prokaryotic assemblages
Shift in prokaryotic community composition from 1995 to 2017
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Collapse of Flavobacteriacee
Collapse of Chaetoceros and Thalassiosira
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Increase in ammonia oxidizers
(Thaumarchaeota and Pirellulaceae)
B
C
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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
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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
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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
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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