The development of the winter-spring phytoplankton bloom is investigated in the oligotrophic Bay ... more The development of the winter-spring phytoplankton bloom is investigated in the oligotrophic Bay of Calvi (Corsica, Ligurian Sea, Northwestern Mediterranean) since 1979. Time-series results enlighten that changes in environmental conditions in the Corsican sector have altered the coastal phytoplankton dynamics and induced a drastic reduction of the winter-spring phytoplankton biomass over the last three decades. At the local scale, variations in winter wind stress control the development of the winter-spring phytoplankton bloom and the structure of the phytoplankton assemblages. Results emphasize that the total phytoplankton biomass (chl a) is higher during high winter wind stress years. From a specific point of view, flagellates are always the dominant component of the phytoplankton bloom communities. However, diatoms tend to be more abundant during high winter wind stress years. At a wider scale, a link between the intensity of the phytoplankton bloom and the winter NAO index is established. Lastly, the decrease in phytoplankton abundance coincides with changes in zooplankton populations. As a consequence, the entire pelagic food web dynamics is affected by climate variations and the ecosystem resilience is threatened.Peer reviewe
Hydrological measurements (temperature, conductivity, salinity) have been realized in 1982 and 19... more Hydrological measurements (temperature, conductivity, salinity) have been realized in 1982 and 1984 along the Calvi - Nice axis from the Corsican coast to 30 miles offshore. The data have shown a thermohaline front separating low saline coastal waters of atlantic origin from high saline offshore waters of deeper origin. A succession of divergences and convergences is associated to that discontinuity. During spring, the front is emphasized and the water upwellings reach the surface. During summer, the upwellings are limited by the vertical stratification but an isopycnal inclination is always observed from the front to the coast
The spatial distribution of the Siphonophorae has been examined, in Occidental Mediterranean, alo... more The spatial distribution of the Siphonophorae has been examined, in Occidental Mediterranean, along the radial Calvi-Nice, from Calvi up to 30 miles offshore in September 2009. The variation of the abundance of the plankton and of the Siphonophorae was put in relation with the hydrological structures of the Liguro-Provençal front. This structure separates the coastal waters of Atlantic origin from the offshore central Mediterranean waters of deep origin. Globally, the larger abundances of Siphonophorae were present in inshore waters between the front and the coast. Both nectophores (asexual stage) and gonophores and bracts (reproductive stage) of Lensia subtilis occured only in the inshore waters. The nectophores of Chelophyes appendiculata occured at all sampling stations with no significative variation. However, the abundance of the bracts and the gonophores increases when we get closer to the coast. This allows us to hypothesize that the maximum of reproduction is located in waters close to the coast. On the other hand, the larvae abundance of calycophoran siphonophores, in the plankton samples, increase from the coastal waters to the offshore waters with a maximum of abundance at the station located at 25 miles offshore. That contradiction could be explained by plankton net avoidance of small larvae, by current transport or by variable hatching success at the various stations. The larvae of physonect siphonophores are more often found offshore.Peer reviewe
The Calvi Bay, directly accessible since the 70s by STARESO provides the opportunity to reach coa... more The Calvi Bay, directly accessible since the 70s by STARESO provides the opportunity to reach coastal, pelagic, benthic, deep systems with a manageable cost and ship requirements in a well-preserved zone. The multiparametric and interdisciplinary data-bases now available can be used in studies of ecosystems or processes like ecology of seagrass bed, biodiversity of macroalgae, study of trophic food webs, marine ecotoxicology, impact of climate changes on phyto- and zooplankton dynamics, jellyfish dynamics in changing waters, carbon cycle and air - water CO2 fluxes, statistical data analysis and modelling into assimilation approaches, including nested coastal models, development of ecological quality criteria for measuring ecosystem quality and effectiveness of management applications. The database now available, is not only an archive of measurements done in the Bay of Calvi during more than 35 years but is really a tool to exploit and to disseminate the results of years of research...
This work is based on a long time series of data collected in the well-preserved Bay of Calvi (Co... more This work is based on a long time series of data collected in the well-preserved Bay of Calvi (Corsica island, Ligurian Sea, NW Mediterranean) between 1979 and 2011, which include physical characteristics (31 years), chlorophyll a (chl a, 15 years), and inorganic nutrients (13 years). Because samples were collected at relatively high frequencies, which ranged from daily to biweekly during the winter-spring period, it was possible to (1) evidence the key role of two interacting physical variables, i.e. water temperature and wind intensity, on nutrient replenishment and phytoplankton dynamics during the winter-spring period, (2) determine critical values of physical factors that explained interannual variability in the replenishment of surface nutrients and the winter-spring phytoplankton bloom, and (3) identify previously unrecognized characteristics of the planktonic ecosystem. Over the >30 year observation period, the main driver of nutrient replenishment and phytoplankton (chl a) development was the number of wind events (mean daily wind speed >5 m s-1) during the cold-water period (subsurface water <13.5°C). According to winter intensity, there were strong differences in both the duration and intensity of nutrient fertilization and phytoplankton blooms (chl a). The trophic character of the Bay of Calvi changed according to years, and ranged from very oligotrophic (i.e. subtropical regime, characterized by low seasonal variability) to mesotrophic (i.e. temperate regime, with a well-marked increase in nutrient concentrations and chl a during the winter-spring period) during mild and moderate winters, respectively. A third regime occurred during severe winters characterized by specific wind conditions (i.e. high frequency of northeasterly winds), when Mediterranean "high nutrient - low chlorophyll" conditions occurred as a result of enhanced crossshore exchanges and associated offshore export of the nutrient-rich water. There was no long-term trend (e.g. climatic) in either nutrient replenishment or the [...]
La partie belge du bassin de la Gueule, dans la region des trois frontieres, comporte de nombreus... more La partie belge du bassin de la Gueule, dans la region des trois frontieres, comporte de nombreuses zones d'habitat qui constituent une source de pollution de la riviere. La mise en service d'une station d'epuration a Plombieres en 1998 a permis d'ameliorer l'etat des eaux de la riviere a la frontiere neerlandaise, sans toutefois atteindre une qualite superieure a celle de la fin des annees 70 avant la mise en place des reseaux d'egouttage. C'est afin d'expliquer ce paradoxe que la qualite de l'eau du bassin versant de la Gueule a ete simulee avec le logiciel PEGASE (Planification Et Gestion de l'Assainissement des Eaux), en correlation avec le developpement de son reseau d'assainissement. La petitesse du bassin (205 km 2 repartis sur seulement 4 communes) a en effet permis de rassembler et structurer l'ensemble des donnees historiques relatives a l'urbanisation et aux differents stades de l'extension du reseau d'assainisse...
The development of the winter-spring phytoplankton bloom is investigated in the oligotrophic Bay ... more The development of the winter-spring phytoplankton bloom is investigated in the oligotrophic Bay of Calvi (Corsica, Ligurian Sea, Northwestern Mediterranean) since 1979. Time-series results enlighten that changes in environmental conditions in the Corsican sector have altered the coastal phytoplankton dynamics and induced a drastic reduction of the winter-spring phytoplankton biomass over the last three decades. At the local scale, variations in winter wind stress control the development of the winter-spring phytoplankton bloom and the structure of the phytoplankton assemblages. Results emphasize that the total phytoplankton biomass (chl a) is higher during high winter wind stress years. From a specific point of view, flagellates are always the dominant component of the phytoplankton bloom communities. However, diatoms tend to be more abundant during high winter wind stress years. At a wider scale, a link between the intensity of the phytoplankton bloom and the winter NAO index is established. Lastly, the decrease in phytoplankton abundance coincides with changes in zooplankton populations. As a consequence, the entire pelagic food web dynamics is affected by climate variations and the ecosystem resilience is threatened.Peer reviewe
Hydrological measurements (temperature, conductivity, salinity) have been realized in 1982 and 19... more Hydrological measurements (temperature, conductivity, salinity) have been realized in 1982 and 1984 along the Calvi - Nice axis from the Corsican coast to 30 miles offshore. The data have shown a thermohaline front separating low saline coastal waters of atlantic origin from high saline offshore waters of deeper origin. A succession of divergences and convergences is associated to that discontinuity. During spring, the front is emphasized and the water upwellings reach the surface. During summer, the upwellings are limited by the vertical stratification but an isopycnal inclination is always observed from the front to the coast
The spatial distribution of the Siphonophorae has been examined, in Occidental Mediterranean, alo... more The spatial distribution of the Siphonophorae has been examined, in Occidental Mediterranean, along the radial Calvi-Nice, from Calvi up to 30 miles offshore in September 2009. The variation of the abundance of the plankton and of the Siphonophorae was put in relation with the hydrological structures of the Liguro-Provençal front. This structure separates the coastal waters of Atlantic origin from the offshore central Mediterranean waters of deep origin. Globally, the larger abundances of Siphonophorae were present in inshore waters between the front and the coast. Both nectophores (asexual stage) and gonophores and bracts (reproductive stage) of Lensia subtilis occured only in the inshore waters. The nectophores of Chelophyes appendiculata occured at all sampling stations with no significative variation. However, the abundance of the bracts and the gonophores increases when we get closer to the coast. This allows us to hypothesize that the maximum of reproduction is located in waters close to the coast. On the other hand, the larvae abundance of calycophoran siphonophores, in the plankton samples, increase from the coastal waters to the offshore waters with a maximum of abundance at the station located at 25 miles offshore. That contradiction could be explained by plankton net avoidance of small larvae, by current transport or by variable hatching success at the various stations. The larvae of physonect siphonophores are more often found offshore.Peer reviewe
The Calvi Bay, directly accessible since the 70s by STARESO provides the opportunity to reach coa... more The Calvi Bay, directly accessible since the 70s by STARESO provides the opportunity to reach coastal, pelagic, benthic, deep systems with a manageable cost and ship requirements in a well-preserved zone. The multiparametric and interdisciplinary data-bases now available can be used in studies of ecosystems or processes like ecology of seagrass bed, biodiversity of macroalgae, study of trophic food webs, marine ecotoxicology, impact of climate changes on phyto- and zooplankton dynamics, jellyfish dynamics in changing waters, carbon cycle and air - water CO2 fluxes, statistical data analysis and modelling into assimilation approaches, including nested coastal models, development of ecological quality criteria for measuring ecosystem quality and effectiveness of management applications. The database now available, is not only an archive of measurements done in the Bay of Calvi during more than 35 years but is really a tool to exploit and to disseminate the results of years of research...
This work is based on a long time series of data collected in the well-preserved Bay of Calvi (Co... more This work is based on a long time series of data collected in the well-preserved Bay of Calvi (Corsica island, Ligurian Sea, NW Mediterranean) between 1979 and 2011, which include physical characteristics (31 years), chlorophyll a (chl a, 15 years), and inorganic nutrients (13 years). Because samples were collected at relatively high frequencies, which ranged from daily to biweekly during the winter-spring period, it was possible to (1) evidence the key role of two interacting physical variables, i.e. water temperature and wind intensity, on nutrient replenishment and phytoplankton dynamics during the winter-spring period, (2) determine critical values of physical factors that explained interannual variability in the replenishment of surface nutrients and the winter-spring phytoplankton bloom, and (3) identify previously unrecognized characteristics of the planktonic ecosystem. Over the >30 year observation period, the main driver of nutrient replenishment and phytoplankton (chl a) development was the number of wind events (mean daily wind speed >5 m s-1) during the cold-water period (subsurface water <13.5°C). According to winter intensity, there were strong differences in both the duration and intensity of nutrient fertilization and phytoplankton blooms (chl a). The trophic character of the Bay of Calvi changed according to years, and ranged from very oligotrophic (i.e. subtropical regime, characterized by low seasonal variability) to mesotrophic (i.e. temperate regime, with a well-marked increase in nutrient concentrations and chl a during the winter-spring period) during mild and moderate winters, respectively. A third regime occurred during severe winters characterized by specific wind conditions (i.e. high frequency of northeasterly winds), when Mediterranean "high nutrient - low chlorophyll" conditions occurred as a result of enhanced crossshore exchanges and associated offshore export of the nutrient-rich water. There was no long-term trend (e.g. climatic) in either nutrient replenishment or the [...]
La partie belge du bassin de la Gueule, dans la region des trois frontieres, comporte de nombreus... more La partie belge du bassin de la Gueule, dans la region des trois frontieres, comporte de nombreuses zones d'habitat qui constituent une source de pollution de la riviere. La mise en service d'une station d'epuration a Plombieres en 1998 a permis d'ameliorer l'etat des eaux de la riviere a la frontiere neerlandaise, sans toutefois atteindre une qualite superieure a celle de la fin des annees 70 avant la mise en place des reseaux d'egouttage. C'est afin d'expliquer ce paradoxe que la qualite de l'eau du bassin versant de la Gueule a ete simulee avec le logiciel PEGASE (Planification Et Gestion de l'Assainissement des Eaux), en correlation avec le developpement de son reseau d'assainissement. La petitesse du bassin (205 km 2 repartis sur seulement 4 communes) a en effet permis de rassembler et structurer l'ensemble des donnees historiques relatives a l'urbanisation et aux differents stades de l'extension du reseau d'assainisse...
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