STARESO
Station de Recherches Sous-Marineset Océanographiques
Response of plankton communities of the Bay of Calvi
(northwestern Mediterranean) to climate variation over
the past three decades (1979 – 2010)
Anne GOFFART *, Amandine COLLIGNON and Jean-Henri HECQUniversity of Liège, Belgium
Vulnerability of coastal ecosystems to global change and extreme events
Biarritz - October 2011
Data acquisition partly funded by :
* A.Goffart@ulg.ac.be
STARESO
Station de Recherches Sous-Marineset Océanographiques
The studied area : the Bay of Calvi, Corsica
• Open bay and narrow shelf • Oligotrophic characteristics • Few anthropogenic pressures • Reference for the WFD
Bay of Calvi 4 kms
Phyto- and zooplankton time-series from 1979
STARESO
Station de Recherches Sous-Marineset Océanographiques
Time-series
STARESO - STAtion
de REcherches Sous-marines et Océanographiques de l’Université de Liège
A.Goffart@ulg.ac.be JH.Hecq@ulg.ac.be
High sampling frequency during phyto- and zooplankton blooms (1-7 times per week)
• To detect trends in changes in plankton communities between 1979 and 2010
• To show how climate variation affect the dynamics of the plankton of the Bay of Calvi
• To assess the response of the pelagic ecosystem to extreme climate conditions
STARESO
Station de Recherches Sous-Marineset Océanographiques
Objectives
STARESO
Station de Recherches Sous-Marineset Océanographiques
Trends in environmental and plankton parameters
0 10 20 30 40 50
Wind - number of days with mean wind > 5 m s-1
January - April 0,0 0,2 0,4 0,6 0,8 1,0 1975 1980 1985 1990 1995 2000 2005 2010 NO 3 µM 0,0 0,5 1,0 1,5 2,0 Si(OH) 4 µM 0,0 0,3 0,5 0,8 1,0 Chl a µg l -1 0,0 0,2 0,4 0,6 0,8 1,0 1975 1980 1985 1990 1995 2000 2005 2010 Mesozooplankton - biovolume ml m-3 12,0 13,0 14,0 15,0 Subsurface temperature °C
Phytoplankton biomass is controlled by wind forcing
STARESO
Station de Recherches Sous-Marineset Océanographiques
Control of phytoplankton by wind stress
0,0 0,2 0,4 0,6 0,8 1,0 1,2 5 10 15 20 25 30 y = 0,05 * e^(0,12x) R2= 0,63
Wind : January - February Chl a : January - April 1979 - 2010 Mean Chl a µ g l -1
Number of days with mean wind > 5 m s-1
09 0,0 0,2 0,4 0,6 0,8 1,0 1,2 5 10 15 20 25 30 y = 0,07 * e^(0,10x) R2= 0,57
Number of days with mean wind > 5 m s-1
Mean Chl a µ g l -1
Wind : January - February Chl a : January - April 1979 - 2010
In unstratified water column (surface temperature < 13,5 °C), surface nutrient enrichment is strongly controlled by wind stress - annual example -
STARESO
Station de Recherches Sous-Marineset Océanographiques
Control of nutrient availability by wind stress
5 6 7 8 9 10 11 0,0 0,5 1,0 1,5 2,0 2,5 3,0 D ai ly a ve ra ge d w in d m s -1 Da ily N O 3 µ M Wind 15/01 01/02 15/02 01/03 15/03 01/04
In unstratified water column (surface temperature < 13,5 °C), surface nutrient enrichment is strongly controlled by wind stress - time-series example -
STARESO
Station de Recherches Sous-Marineset Océanographiques
Control of nutrient availability by wind stress
0,0 0,5 1,0 1,5 2,0 0 10 20 30 40 50 y = 0,77 + 0,02x R2= 0,46
Number of days with mean wind > 5 m s-1
Mean Si
(OH
)4
µ
M
Period of cold water (< 13,5 °C) Si(OH)4 1997 - 2010 0,0 0,5 1,0 1,5 2,0 0 10 20 30 40 50 y = 0,26 + 0,02x R2= 0,57
Number of days with mean wind > 5 m s-1
M ea n NO 3 µ M
Period of cold water (< 13,5 °C) NO3 1997 - 2010
STARESO
Station de Recherches Sous-Marineset Océanographiques
Control of phytoplankton by wind stress
0,0 0,2 0,4 0,6 0,8 0 0,2 0,4 0,6 0,8 1 y = 0,05 + 0,38x R2= 0,49 Mean NO 3 µM Mean Chl a µ g l -1 January - April 1997 - 2010
Bottom-up control of phytoplankton production
High nutrients
High nutrients Diatoms
Nanophyto Picophyto
Low nutrients
Low nutrients Diatoms
Nanophyto Picophyto
Phytoplankton biomass and composition are controlled by wind forcing and subsequent nutrient enrichment
Mesozooplankton biomass and composition are controlled by phytoplankton availability AND interactions with higher trophic levels (e.g. jellyfishes)
STARESO
Station de Recherches Sous-Marineset Océanographiques
Control of mesozooplankton dynamics
Bottom-up & top-down control of mesozooplankton communities Composition : still a lot of work ...
0,0 0,2 0,4 0,6 0,8 1,0 1,2 0 0,2 0,4 0,6 0,8 1 y = 0,06 + 2,56x R2= 0,38 y = -0,11 + 1,10x R2= 0,75 M ea n m eso zo opl an kto n bi ov ol u m e m l m -3 Mean Chl a µg l-1 January - April 1986 - 2010
STARESO
Station de Recherches Sous-Marineset Océanographiques
