Effect of induced anoxia on nematode densities, vertical distribution patterns
and recovery at the Gulf of Trieste (Northern Adriatic Sea)
Mehrshad Taheri12, Mateja Grego3, Bettina Riedel4, Magda Vincx1 and Jan Vanaverbeke1
anne
i.
Ghent University, Biology Department, Marine Biology Research Group, Krijgslaan 281, S8, 9000 , Ghent, Belgium.
E-mail: mehrshad.taheri@ugent.be
2 . Iranian National Institute for Oceanography. 9 Etemadzadeh Ave, West Fatemi Str, Tehran. Iran.
3. Marine Biology Station Piran, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
4. Department of Limnology and Oceanography, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
08V
Longitude 6
Introduction
45.80°
ITALY
TIMAV
T IM A V O )
4 5 .75°
SOÔA
K (IS O N Z O )
45.6 5 <
4 5 .6 0 °
G U L F O F T R IE S T E
-
\
45.55° -
R IF A N A
S L O V E N IA
4 5 .5 0 °-
D R A G O N JA
13.4
\
13.7«
13.6°
Longitude
13.5
t
Increasing oxygen stress in the gulf:
a semi-enclosed
shallow depth with a fine-grained substrate
a high riverine input
high productivity (marine snow events)
long water residence in summer/autumn
45.70°
%
i
Iranian National Institute
for Oceanography
13.8e
0 - 0.5
0.5 - 1
1 - 1.5
1 .5 - 2
I
/
/
\
Material and Method
cm
cm
cm
cm
duration of the experimental anoxia and recovery
Normoxia 1 9 days anoxia
9 days recovery
1 month recovery
Normoxia 2 1 month anoxia
10 months anoxia 3 months recovery
2 - 3 cm
3 - 4 cm
4 - 5 cm
/
Induced anoxia
Data analysis till 5 cm with 1 cm interval
2 cm with 0.5 cm interval
Three replicates
Identification
Making slides
Results
Recovery
Anoxia
Total density till 5 cm
Total density till 2 cm
Total density till 5 cm
Total density till 2 cm
o
IO
D LO
B
Normoxia 1
Normoxia 2
Anoxia 9D
Anoxia 1M
Normoxia 1
Anoxia 10M
Total species number till 5 cm
Normoxia 2
Anoxia 9D
Normoxia 1
Anoxia 10M
Normoxia 2
Recovery 9D
Recovery
Total species number till 5 cm
Total species number till 2 cm
Total shannon diversity till 2 cm
No significant differences
Norm oxia 1
N orm oxia 2
Anoxia 9D
AB
B
0 1
-
Normoxia 1
D
Normoxia 2
Anoxia 9D
BC
-
A n o x ia l M
Normoxia
Anoxia 10M
D
AB
Normoxia 2
0 1
-
B
12
-
Normoxia 1
Recovery 3M
B
AB
A
AB
Cl
o
B
AB
AB
O
û
D
B
a
o
HH
£
o
2-3
CL
<D
Û
Û
1-1.5-
m
-
o
2-3
Recovery 3M
0-0.5
E
o
Cl
CD
Recovery 1M
0.5-1
E
B
o
Recovery 9D
A
0.5-1
E
Normoxia 2
B
-
AB
1-2
Recovery JM
Vertical density till 2 cm
B
D
B
Recovery 9D
B
0-0.5
AB
Total shannon diversity till 2 cm
Vertical density till 5 cm
Vertical density till 2 cm
A n o x ia l OM
Recovery 3 M
Lowest in recovery 1 month
Anoxia 10 months >normoxia >anoxia1 month
A n o x ia l M
Recovery
No significant differences
Total evenness till 5 cm
Total evenness till 2 cm
Total evenness till 2 cm
Vertical density till 5 cm
Recovery 9D
Total species number till 2 cm
Total shannon diversity till 5 cm
Higest in normoxia and lowest in anoxial and 10 months
Total evenness till 5 cm
Normoxia 2
No significant differences
Higest in normoxia and lowest in anoxia 10 months
Total shannon diversity till 5 cm
Normoxia 1
Recovery 3M
H
-I
1-1.5
3-4
3-4ABCD
B
D
B
1.5-2-
1.5-2-
4-5
4-5
i------------ 1------------ 1------------ r
i
0
500
1000 0
500
1000 0
500
1000 0
100
200
n -------------1-------------1-------------r
0
5
10
15
i------------ 1------------ 1------------ r
0
200 400 600
0
Nematode densities (ind. 10cm 2)
200 400 600
0
200 400 600
0
50 100
0
5
10
Nematode densities (ind. 10cm“2)
Community composition till 5
Community composition till 2
No significant differences
15
i
0
1---------- 1---------- 1---------- r
500
1000
i-----------1-----------1---------- 1---------------------------i------------ 1------------ 1------------ r
0
500
1000
0 200 400 600
T--------- 1-
0
i -------------- 1-------------- 1-------------- r
500
1000
0
200 400 600
0
200 400 600
0
200 400 600
0
200 400 600
0
100
200
0
200 400 600
Nematode densities (ind. 10cm“2)
Nematode densities (ind. 10cm“2)
Community composition till 5
Community composition till 2
No significant differences
conclusion, our results indicated that nematodes communities were tolerant to short term anoxia (9 days). This may relate to adaptation
mechanisms of nematodes to live naturally in low oxygen environments. However, longer term of anoxia (more than one month) had a
negative effect on nematode communities which can be related to an increase in concentration of hydrogen sulphide (Riedel et al., 2012).
Our results also revealed that nematodes communities can be recovered even after 10 months anoxia. This process can result from
^removing unfavoured conditions during the recovery period and or auto-ecological features including nematode reproduction capacity.