ECOSYM – Ecological of Coastal
Marine Ecosystems
Université Montpellier 2
France
Dynamics of production and mortality
of Aurelia aurita in Thau Lagoon,
Northwerstern Mediterranean.
Raquel Marques12
Corinne Bouvier1, Michel Cantou3, Audrey Darnaude1, Juan-Carlos Molinero4,
Cyrille Przybyla5, Solenn Soriano3, Jean-Antoine Tomasini1, Delphine Bonnet1.
1
Laboratoire ECOSYM, UMR5119, Université Montpellier 2
2Faculdade de
Ciências e Tecnologia, Universidade do Algarve
3 Université Montpellier 2
4 GEOMAR
5
- Helmholtz Centre for Ocean Research Kiel
IFREMER – Institut Français de Recherche pour l’Exploitation de la Mer
ICES Annual Science
Conference
A Coruña 2014
Jellyfish blooms
Increasing (high certainty)
Increasing (low certainty)
Brotz et. al., 2012
Stable/variable
Decrease
No data
In situ
polyps
dynamics
Polyps population play
a key role in jellyfish
blooms formation
Predation
impact
‘Dead end’ of
the food
web???
Boero, 2013
Objectives
Bottom up control
Benthic dynamics
Pelagic dynamics
Aurelia aurita
Bonnet et. al., 2012
Fish predation
Top down control
Benthic distribution
and habitat
What is the distribution and habitat of benthic population?
Study site and
methodology
• Mean depth of 4m
• Residence time of water
masses: 1-4 months
• 20% of lagoon occupied by
oyster-culture tables
• Free diving
• GPS location
• Depth
• Substrate type
• Index of colony coverage
What is the distribution and habitat of benthic population?
Results: Distribution
What is the distribution and habitat of benthic population?
Tires
4%
Wood
1%
Plastics
12%
Results: Settling substrates
Moored or
submerged boats
4%
Breakwater rocks
11%
Concrete
9%
86.6% of colonies settled
on biofouling organisms,
among which 90.4%
were oysters
Contribution of artificial hard
substrates (%)
Metal structures
59%
100
90
80
70
60
50
40
30
20
10
0
Wood
Tires
Plastics
Metal Structures
Concrete
Breakwater rocks
Moored or submerged boats
1 (<0.1m2)
2 (0.10.5m2)
3 (0.5-1m2)
4 (>1m2)
What are the benthic and pelagic population dynamics?
Methodology
Benthic dynamics
Weekly
monitoring of
the same colony
by underwater
picture analysis
Colony density
Population density
Three samples
collected every
week and observed
under the dissecting
microscope
Proportion of
budding
Pelagic dynamics
Zooplankton
tow
(200 and 700 µm)
• Bi weekly monitoring for four
years
• Preservation in 4%
formaldehyde
•Sample analysed under the
dissecting microscope
Abundance
Bell diameter
What is the benthic population dynamics?
Results:
Population density (ind.cm-2)
14
12
Benthic dynamics
A
10
8
6
4
2
Population density
Colony density (ind.cm-2)
0
35
30
B
25
20
15
10
5
• Population and colony density were
influenced
by
temperature
and
zooplankton
abundance,
while
proportion of budding was influenced
only by temperature.
Colony density
0
Mean proportion budding
(%)
100
80
C
60
40
20
0
10/Apr
Proportion of budding
25/Apr
10/May 25/May
9/Jun
24/Jun
9/Jul
24/Jul
• Colony density and proportion of
budding were correlated with each other
(F value=2.91, Pr(>F)=0.017).
What is the pelagic population dynamics?
Results:
Ephyrae abundance
Medusae abundance
Pelagic dynamics
Months
Bonnet et. al., 2012
Advection?
Mortality?
What is the predation pressure on A. aurita populations in the lagoon?
Predation pressure was assessed by two complementary
approaches:
Methodology:
In situ
 In situ gut content analysis
 Fish predation in laboratory
In situ fish gut content analysis
PCR
analysis
Fishes collected in Thau
lagoon during A. aurita
bloom events
Collection of fish
gut contents
Amplification of partial
sequences of mt-16S rDNA
(primer pair AS3) and mt-COI
(primer pair AC3)
Results: In situ
Negative control
Medusae (Ethanol 100%)
Medusae (sea water)
Small medusae
Sarpa
salpa
Ephyrae
Sparus
aurata
Polyps
Molecular marker
What is the predation pressure on A. aurita populations in the lagoon?
• Anguilla anguilla
• Atherina sp.
• Mugilidae
• Sarpa salpa
• Sparus aurata
• One of the most common species in
Thau lagoon
• Easily reared
• Biology well known
• Feeding history known
• Possibility to obtain two generations
(G1 and G2)
Positive control
What is the predation pressure on A. aurita populations in the lagoon?
Methodology:
In laboratory
Sparus aurata predation in laboratory
Medusae (Ø1/4/7-8cm)
Medusae (Ø1cm)
5 ind.tank-1
-1
10 ind.tank
3 x G1-1
15 ind.tank
OR
30 ind.tank-1
2 x G2-1
40 ind.tank
50 ind.tank-1
Monospecific
diets
Gradient of
concentration
Dry pellets (control)
Artemia (high quality)
3 x G1
OR
Ephyrae
2 x G2
Polyps
Ephyrae
+ Artemia
3 x G1
OR
Polyps
2 x G2
+ Artemia
Selectivity
Ingestion rate was calculated from the difference of
prey concentration between the beginning and the
end of the experiment (2h).
Tank=40L
What is the predation pressure on A. aurita populations in the lagoon?
Mean Ingestion rate (prey.g-1.h-1)
0.25
Results: Monospecific diets
G1
ac
b
0.20
0.15
ab
ab
0.10
c
0.05
d
d
0.00
Dry
Artemia Polyps Ephyrae Medusae Medusae Medusae
n=390
n=44 (Ø1cm) (Ø4cm) (Ø7-8cm)
pellets n=44
n=1
n=1
n=50
n=44
Mean Ingestion rate (prey.g-1.h-1)
0.25
G2
0.20
0.15
ac
a
0.10
b
c
b
0.05
d
d
0.00
Dry
Artemia Polyps Ephyrae Medusae Medusae Medusae
pellets n=80
n=448
n=80 (Ø1cm) (Ø4cm) (Ø7-8cm)
n=1
n=1
n=50
n=80
What is the predation pressure on A. aurita populations in the lagoon?
Mean Ingestion rate (prey.g-1.h-1)
0.20
0.18
0.16
Results: Gradient of
concentration and
Selectivity
G1
G2
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
n=5
n=10
n=15
n=30
n=40
n=50
0.14
0.12
0.10
0.16
G1
Ephyrae (n=22)
Artemia (n=22)
Polyps (n=215)
0.08
*
0.06
0.04
0.02
0.00
Mean Ingestion rate (prey.g-1.h-1)
Mean Ingestion rate (prey.g-1.h-1)
0.16
0.14
0.12
0.10
0.08
0.06
G2
Ephyrae (n=40)
Artemia (n=40)
Polyps (n=400)
*
0.04
0.02
0.00
Diet 1
Diet 2
Diet 1
Diet 2
Conclusions
Bottom up control
 Human mediated habitat modifications benefited
A. aurita population. Increasing suitable hard
substrates enhanced the distribution, abundance
and survivorship of polyps and consequently pelagic
populations.
 Temperature and salinity seem to be the main
driving forces of benthic and pelagic populations.
 Jellyfish are not ‘dead end’ of food webs and with
predictions of a possible ‘gelatinous future’, jellyfish
will became an available and easy food source for a
variety of fish diets. As a consequence, fish might
control jellyfish blooms reducing its detrimental
consequences on human activities.
Top down control
Thank you!
Gracias!