Gérard Thouzeau - Academia.edu (original) (raw)

Papers by Gérard Thouzeau

Research paper thumbnail of Experimental collection of postlarvae of Pecten maximus (L.) and other benthic macrofaunal species in the Bay of Saint-Brieuc, France. I. Settlement patterns and biotic interactions among the species collected

Journal of Experimental Marine Biology and Ecology, Jun 1, 1991

... Temperature and trophic resources were the main factors determining these variations, in P.ma... more ... Temperature and trophic resources were the main factors determining these variations, in P.maximus, another source of growth variation, the gamete quality, is ... 1976; Buestel et al., 1977, 1979; Pickett, 1978; Brand et al., 1980; Paul et al., 1981; Wallace, 1982; Richardson et al ...

Research paper thumbnail of Evidence of clandestine harvest and failure of conservation policies for <i>Argopecten purpuratus</i> in the Rinconada Marine Reserve (Chile)

Aquatic Conservation-marine and Freshwater Ecosystems, Feb 10, 2017

1. The study of Argopecten purpuratus reproduction, post-larval settlement, stock size, and popul... more 1. The study of Argopecten purpuratus reproduction, post-larval settlement, stock size, and population size structure and shell growth was undertaken in the 2000s in the Rinconada marine reserve (Chile) to evaluate the effectiveness of scallop recruitment and self-sustainability. 2. The results highlight strong seasonal and inter-annual variations of environmental conditions and scallop gonadosomatic index, spat collection, benthic distribution, total abundance and population size structure. 3. The Von Bertalanffy growth parameters were L ∞ = 120.12 mm and K = 0.9681; commercial size would be reached in about 17.2 months in the bay. Substrate availability, meteorological conditions, hydrodynamics and illegal harvesting explain spatial and temporal variations in scallop distribution and abundance. 4. Recruitment strength depends on one main cohort from year to year. While recruitment made up 81% and 94% of total abundances in May 2002 and May 2003, respectively, there were no overall density-dependent relationships between stock size and recruitment. Spawning asynchrony in the bay supports the hypothesis that multiple gamete releases form part of a reproductive strategy in response to environmental variability. 5. The massive disappearance of large-sized scallops during the study periods was direct evidence of overfishing owing to clandestine harvesting within the marine reserve. The failure of current legislation, strategies and policies for scallop conservation requires new regulations to restore scallop stock size, maintain its reproductive performance and limit illegal harvesting in the Rinconada. 6. A scenario allowing harvesting regulated by stock-dependent fishing quotas would more efficiently ensure stock recovery and self-sustainability. The modalities of this new policy are discussed.

Research paper thumbnail of Flux verticaux pelagos-benthos : problématique, méthodologie et instrumentation nouvelle

HAL (Le Centre pour la Communication Scientifique Directe), Nov 18, 1992

National audienc

Research paper thumbnail of Les introductions d'espèces en milieu marin

HAL (Le Centre pour la Communication Scientifique Directe), Nov 21, 2002

National audienc

Research paper thumbnail of Aspects de la dynamique spatio-temporelle du pré-recrutement de Pecten maximus (L.), en baie de Saint-Brieuc

HAL (Le Centre pour la Communication Scientifique Directe), Jun 25, 1990

International audienc

Research paper thumbnail of Artificial collection and early growth of spat of the scallop <i>Argopecten purpuratus</i> (Lamarck, 1819), in La Rinconada Marine Reserve, Antofagasta, Chile

Scientia Marina, Mar 30, 2007

has in the past been noted for the retention of scallop larvae by local gyres, in which their num... more has in the past been noted for the retention of scallop larvae by local gyres, in which their numbers can vary between 89 and 34175 larvae m-3 , producing larval sets of 400 to 15340 post-larvae (spat) per collector. The results showed no quantitative relationship between larval abundance in the water and the spat density collected per day in the collectors, although high settlement rates were associated with high numbers of umboned larvae in the water. Allowing collectors to remain in situ for extended periods of 88 and 159 days resulted in a severe loss of seed which had settled in the collectors during the first 28 to 40 days of immersion. These losses varied between 50.9 and 99.6% of the spat collected, and were more prejudicial for the smaller cohorts that had settled in the collectors at the end of the first immersion period. The growth rates measured among different cohorts for each immersion period varied between 81.3 and 235.2 μm/day for the first cohort (C 1) and between 64.0 and 167.4 μm/day for the second cohort (C 2). The highest growth rates occurred in collectors containing the lowest numbers of spat after the occurrence of spat losses during the long periods of immersion. Occurrence of intraspecific competition within the collectors is discussed as potentially responsible for the decreases in spat numbers and the variations observed in their growth rates.

Research paper thumbnail of Estimate of state variables of a trophic web model in the Bay of Brest

HAL (Le Centre pour la Communication Scientifique Directe), 1995

International audienceWinter biomasses of the benthic fauna in the Bay of Brest were estimated to... more International audienceWinter biomasses of the benthic fauna in the Bay of Brest were estimated to model carbon fluxes through the benthic food web. Total biomass (9.59 g C m(-2)) is dominated by macrofaunal suspension feeders (53%) and carnivores (25%). Macrofaunal deposit feeders and herbivores, meiofauna, bacteria and demersal fishes accounted for 22% of total biomass. Most of the biomass was found on coarse coralline algae bottoms, in relation to environmental and biotic factors. Mean macrofaunal biomass is significantly higher in the Bay of Brest than in many other temperate coastal ecosystems. The proliferation of suspension feeders in the Bay would correspond to the first perturbation level of the ecosystem, due to organic enrichment. Suspension feeders would prevent eutrophication by controlling phytoplankton biomass

Research paper thumbnail of Determination of Pecten maximus (L.) pre-recruitment in the Bay of Saint-Brieuc: processes regulating the abundance, survival and growth of post-larvae and juveniles

Research paper thumbnail of Déterminisme du pré-recrutement de Pecten maximus L. En baie de Saint-Brieuc

Research paper thumbnail of Reproduction of the invasive slipper limpet, Crepidula fornicata, in the Bay of Brest, France

Marine Biology, Mar 28, 2006

Research paper thumbnail of Les flux de CO2 face à la marée : avec ou sans eau ?

HAL (Le Centre pour la Communication Scientifique Directe), 2018

Il est difficile d'admettre que, dans ses angoisses de racines, d'ombres moussues, la man... more Il est difficile d'admettre que, dans ses angoisses de racines, d'ombres moussues, la mangrove puisse etre un tel berceau de vie (...) Elle ne semble appartenir ni a la terre, ni a la mer. " Patrick Chamoiseau La mangrove, cette foret entre terre et mer qui borde les littoraux tropicaux, a longtemps ete percue comme un milieu hostile ou inutile... Elle renvoie aussi a un puissant imaginaire des tropiques qui a inspire bon nombre de nos plus grands ecrivains. Cet ecosysteme, complexe, abrite les paletuviers capables de vivre les pieds dans l'eau salee, des poissons pouvant respirer hors de l'eau, des crabes ingenieurs et une multitude de bacteries indispensables au recyclage de la matiere organique. Aujourd'hui, confrontee a la crevetticulture, aux coupes de bois, a la pollution mais aussi sous l'emprise directe des changements climatiques, cette mangrove, grignotee de toute part, est en danger. Cet ouvrage, redige par des chercheurs specialistes du milieu, nous montre combien sa preservation devient un enjeu ecologique mondial tant cet ecosysteme contribue a l'equilibre des littoraux tropicaux et a ceux de la planete tout entiere. Sait-on par exemple que ces forets maritimes jouent le role de puits de carbone en absorbant de grandes quantites de CO2 ? Qu'elles peuvent servir de filtres ou d'eponges face aux pollutions humaines ? Qu'elles constituent un rempart contre les tempetes ou les tsunamis ? Un livre qui nous invite a poser un regard nouveau sur cette foret si secrete au coeur des enjeux ecologiques tropicaux. Un ouvrage collectif illustre sous la direction de Francois Fromard, Emma Michaud, Martine Hossaert-McKey, Institut ecologie et environnement (INEE) du CNRS.

Research paper thumbnail of Experimental collection of postlarvae of Pecten maximus (L.) and other benthic macrofaunal species in the Bay of Saint-Brieuc, France. II. Reproduction patterns and postlarval growth of five mollusc species

Journal of Experimental Marine Biology and Ecology, Jun 1, 1991

Settlement patterns ofPecten maximus (L.) postlarvae and 105 other species of benthic macrofauna ... more Settlement patterns ofPecten maximus (L.) postlarvae and 105 other species of benthic macrofauna in the Bay of Saint-Brieuc were studied from spat collectors in order to clarify biotic interactions at the postlarval stage. Between-sites differences in taxonomic group abundances reflected the bottom sediment type beneath the collectors and were partly explained by hydrographic mechanisms; larval retention occurred in the collection areas. Other factors regulating settlement process were the water turbulence and trophic resources. Temporal variability in collection occurred between and within the taxonomic groups. Optimal collection for all the species was within 2 m above the seabed for an immersion period of < 1 month. Anomia ephippium L., Crepidulafornicata L. and Chlamys varia L. were the main spatio-trophic competitors ofP. maximus collected in the bay while brachyuran crustaceans accounted for 96 % of the potential scallop predators. Possible ways of improving scallop spat collection and cultivation in the bay are discussed.

Research paper thumbnail of Experimental collection of post-larvae of Pecten maximus (L.) and other benthic macrofaunal species, in the Bay of Saint-Brieuc. II - Reproduction patterns and post-larval growth of 5 mollusc species

HAL (Le Centre pour la Communication Scientifique Directe), 1991

... Temperature and trophic resources were the main factors determining these variations, in P.ma... more ... Temperature and trophic resources were the main factors determining these variations, in P.maximus, another source of growth variation, the gamete quality, is ... 1976; Buestel et al., 1977, 1979; Pickett, 1978; Brand et al., 1980; Paul et al., 1981; Wallace, 1982; Richardson et al ...

Research paper thumbnail of Variabilité saisonnière de la structure trophique et de la biodiversité du macrobenthos en Manche occidentale

HAL (Le Centre pour la Communication Scientifique Directe), Nov 24, 1994

National audienc

Research paper thumbnail of Corals adapted to extreme and fluctuating seawater <scp>pH</scp> increase calcification rates and have unique symbiont communities

Ecology and Evolution, May 1, 2023

Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification... more Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification rate. Identifying the resilience factors of corals to decreasing seawater pH is of paramount importance to predict the survivability of coral reefs in the future. This study compared corals adapted to variable pHT (i.e., 7.23–8.06) from the semi‐enclosed lagoon of Bouraké, New Caledonia, to corals adapted to more stable seawater pHT (i.e., 7.90–8.18). In a 100‐day aquarium experiment, we examined the physiological response and genetic diversity of Symbiodiniaceae from three coral species (Acropora tenuis, Montipora digitata, and Porites sp.) from both sites under three stable pHNBS conditions (8.11, 7.76, 7.54) and one fluctuating pHNBS regime (between 7.56 and 8.07). Bouraké corals consistently exhibited higher growth rates than corals from the stable pH environment. Interestingly, A. tenuis from Bouraké showed the highest growth rate under the 7.76 pHNBS condition, whereas for M. digitata, and Porites sp. from Bouraké, growth was highest under the fluctuating regime and the 8.11 pHNBS conditions, respectively. While OA generally decreased coral calcification by ca. 16%, Bouraké corals showed higher growth rates than corals from the stable pH environment (21% increase for A. tenuis to 93% for M. digitata, with all pH conditions pooled). This superior performance coincided with divergent symbiont communities that were more homogenous for Bouraké corals. Corals adapted to variable pH conditions appear to have a better capacity to calcify under reduced pH compared to corals native to more stable pH condition. This response was not gained by corals from the more stable environment exposed to variable pH during the 100‐day experiment, suggesting that long‐term exposure to pH fluctuations and/or differences in symbiont communities benefit calcification under OA.

Research paper thumbnail of Size‐based survival of cultured <i>Argopecten purpuratus</i> (L, 1819) under severe hypoxia

Journal of the World Aquaculture Society, May 3, 2021

During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays.... more During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays. One of the main drivers related to these mortalities was hypoxic events. This study was designed to understand the hypoxia phenomenon in these bays and to assess how the Peruvian scallop, Argopecten purpuratus, can cope with reduced oxygen levels in seawater based on individual size. First, we analyzed the relationships between dissolved oxygen saturation and other environmental parameters (the Coastal El Niño Index, temperature, salinity and pH) in bottom seawater, the frequency and intensity of hypoxic events in two main culture areas (Sechura and Paracas Bays), and their relationship with scallop mass mortalities. Then, we performed experiments with two size groups of A. purpuratus (31 and 80 mm shell height; seed and commercial size, respectively) to assess their respective survival time under severe hypoxia (1% oxygen saturation) at 16 C and a salinity of 35. Finally, the results of the field records and the experimental data are used to suggest ways to improve scallop cultivation along the Peruvian coast.

Research paper thumbnail of Predicting the energy budget of the scallop Argopecten purpuratus in an oxygen–limiting environment

Journal of Sea Research, 2019

Low concentrations of oxygen determine marine species distribution and abundance along the Peruvi... more Low concentrations of oxygen determine marine species distribution and abundance along the Peruvian coast with consequences for human activity such as fishing and aquaculture. In order to assess bioenergetic consequences of oxygen limitation on the Peruvian scallop Argopecten purpuratus, we first developed a Dynamic Energy Budget (DEB) model of growth and reproduction calibrated on field experimental datasets. Then, we included oxygen availability as an additional forcing variable using a simple rule based on the ability of the scallop to regulate oxygen consumption. The resulting model was tested using growth/reproduction monitoring and simultaneous high frequency environmental records in Paracas Bay (Peru) at two different depths: suspended in the water column and on the sea bottom. Simulations indicated that scallops growth and reproduction was not food-limited. The negative observed effects of hypoxia on growth and reproduction could be explained by a decrease in both assimilation and reserve mobilization. However, hypoxic conditions in summer were not sufficient to explain the observed losses in somatic tissue weights and the disruption of reproduction. The latter two patterns were better simulated when assuming increased somatic maintenance costs due to the presence of H 2 S during milky turquoise water discolouration events observed during summer.

Research paper thumbnail of Feeding behaviour and growth of the Peruvian scallop ( Argopecten purpuratus ) under daily cyclic hypoxia conditions

Journal of Sea Research, 2018

As a secondary consequence of the high productivity of the upwelling system, organisms inhabiting... more As a secondary consequence of the high productivity of the upwelling system, organisms inhabiting Peruvian coastal bays are frequently exposed to hypoxic conditions. The aim of the present paper was to investigate the effects of daily-cyclic-severe hypoxia on energetics of a species presenting little escape ability when facing hypoxia. For this purpose, juvenile Peruvian scallops (Argopecten purpuratus) were exposed to four experimental conditions: fed and starved, combined or not to nightly severe hypoxia (5% oxygen saturation) for ≈ 12 hours over a 21-day experiment. In both fed conditions, clearance rate was measured by the mean of an open-flow system. Our results indicate that the Peruvian scallop is able to maintain an active filtration even at low oxygen saturation, at least during expositions up to 12 hours. During the first phase of exposure to hypoxia, clearance rate decreased abruptly when oxygen saturation dropped below 10%, but rapidly recovered to values close to those found under normoxia. As a consequence of this ability to feed during hypoxia, no difference in soft tissue dry weight (digestive gland not included) was observed at the end of the experimental period between oxic conditions among fed scallops. However, shell growth was negatively affected by hypoxic condition. Starved individuals exhibited similar weight loss between hypoxic and normoxic conditions indicating no or little effect of oxic condition on maintenance costs. Considering the observed responses for feeding, growth and maintenance, we can hypothesize that this species presents metabolic/bioenergetic efficient adaptations to deal with hypoxic conditions that are recurrent in Peruvian coastal bays. We hypothesize that the small observed effects might be modeled in the context of the Dynamic Energy Budget theory as a restriction of reserve mobilization under hypoxic conditions.

Research paper thumbnail of Marine Species Introduced on the French Channel-Atlantic Coasts: A Review of Main Biological Invasions and Impacts

Open Journal of Ecology, 2015

The impacts of anthropogenisation modify permanently the distribution patterns of brackish and ma... more The impacts of anthropogenisation modify permanently the distribution patterns of brackish and marine species. Globalization leads to a rapid increase of the numbers of introduced species anywhere in the world. Biological invasions often result in significant losses in the economic value, biological diversity and function of invaded ecosystems. This review presents the main pathways of introduction of non-indigenous species and the main benthic taxonomic groups being established and/or invasive along the French Channel-Atlantic coasts. A focus is put on main invasive marine species in the intertidal and subtidal zones of Brittany (France), among macroalgae (Sargassum muticum, Grateloupia turuturu, Undaria pinnatifida, Codium fragile and Gracilaria vermiculophylla), halophytes (Spartina alterniflora) and benthic invertebrates (Mollusks: Crepidula fornicata, Crassostrea gigas and Venerupis philippinarum). The species biology, introduction vectors, reproductive and dispersal capacities are considered, together with proliferation patterns along the Channel-Atlantic coasts. The ecological impacts of these species on the environment are also described, as well as the European regulations existing to limit alien species introduction and some examples of struggle against the invaders including eradication trials and biomass valorization. Last, the ongoing impacts of global changes on alien species invasiveness along the Channel-Atlantic coasts are discussed.

Research paper thumbnail of Les espèces marines introduites sur la façade Manche-Atlantique : invasions biologiques ou immigration contrôlée ?

HAL (Le Centre pour la Communication Scientifique Directe), 2015

National audienc

Research paper thumbnail of Experimental collection of postlarvae of Pecten maximus (L.) and other benthic macrofaunal species in the Bay of Saint-Brieuc, France. I. Settlement patterns and biotic interactions among the species collected

Journal of Experimental Marine Biology and Ecology, Jun 1, 1991

... Temperature and trophic resources were the main factors determining these variations, in P.ma... more ... Temperature and trophic resources were the main factors determining these variations, in P.maximus, another source of growth variation, the gamete quality, is ... 1976; Buestel et al., 1977, 1979; Pickett, 1978; Brand et al., 1980; Paul et al., 1981; Wallace, 1982; Richardson et al ...

Research paper thumbnail of Evidence of clandestine harvest and failure of conservation policies for <i>Argopecten purpuratus</i> in the Rinconada Marine Reserve (Chile)

Aquatic Conservation-marine and Freshwater Ecosystems, Feb 10, 2017

1. The study of Argopecten purpuratus reproduction, post-larval settlement, stock size, and popul... more 1. The study of Argopecten purpuratus reproduction, post-larval settlement, stock size, and population size structure and shell growth was undertaken in the 2000s in the Rinconada marine reserve (Chile) to evaluate the effectiveness of scallop recruitment and self-sustainability. 2. The results highlight strong seasonal and inter-annual variations of environmental conditions and scallop gonadosomatic index, spat collection, benthic distribution, total abundance and population size structure. 3. The Von Bertalanffy growth parameters were L ∞ = 120.12 mm and K = 0.9681; commercial size would be reached in about 17.2 months in the bay. Substrate availability, meteorological conditions, hydrodynamics and illegal harvesting explain spatial and temporal variations in scallop distribution and abundance. 4. Recruitment strength depends on one main cohort from year to year. While recruitment made up 81% and 94% of total abundances in May 2002 and May 2003, respectively, there were no overall density-dependent relationships between stock size and recruitment. Spawning asynchrony in the bay supports the hypothesis that multiple gamete releases form part of a reproductive strategy in response to environmental variability. 5. The massive disappearance of large-sized scallops during the study periods was direct evidence of overfishing owing to clandestine harvesting within the marine reserve. The failure of current legislation, strategies and policies for scallop conservation requires new regulations to restore scallop stock size, maintain its reproductive performance and limit illegal harvesting in the Rinconada. 6. A scenario allowing harvesting regulated by stock-dependent fishing quotas would more efficiently ensure stock recovery and self-sustainability. The modalities of this new policy are discussed.

Research paper thumbnail of Flux verticaux pelagos-benthos : problématique, méthodologie et instrumentation nouvelle

HAL (Le Centre pour la Communication Scientifique Directe), Nov 18, 1992

National audienc

Research paper thumbnail of Les introductions d'espèces en milieu marin

HAL (Le Centre pour la Communication Scientifique Directe), Nov 21, 2002

National audienc

Research paper thumbnail of Aspects de la dynamique spatio-temporelle du pré-recrutement de Pecten maximus (L.), en baie de Saint-Brieuc

HAL (Le Centre pour la Communication Scientifique Directe), Jun 25, 1990

International audienc

Research paper thumbnail of Artificial collection and early growth of spat of the scallop <i>Argopecten purpuratus</i> (Lamarck, 1819), in La Rinconada Marine Reserve, Antofagasta, Chile

Scientia Marina, Mar 30, 2007

has in the past been noted for the retention of scallop larvae by local gyres, in which their num... more has in the past been noted for the retention of scallop larvae by local gyres, in which their numbers can vary between 89 and 34175 larvae m-3 , producing larval sets of 400 to 15340 post-larvae (spat) per collector. The results showed no quantitative relationship between larval abundance in the water and the spat density collected per day in the collectors, although high settlement rates were associated with high numbers of umboned larvae in the water. Allowing collectors to remain in situ for extended periods of 88 and 159 days resulted in a severe loss of seed which had settled in the collectors during the first 28 to 40 days of immersion. These losses varied between 50.9 and 99.6% of the spat collected, and were more prejudicial for the smaller cohorts that had settled in the collectors at the end of the first immersion period. The growth rates measured among different cohorts for each immersion period varied between 81.3 and 235.2 μm/day for the first cohort (C 1) and between 64.0 and 167.4 μm/day for the second cohort (C 2). The highest growth rates occurred in collectors containing the lowest numbers of spat after the occurrence of spat losses during the long periods of immersion. Occurrence of intraspecific competition within the collectors is discussed as potentially responsible for the decreases in spat numbers and the variations observed in their growth rates.

Research paper thumbnail of Estimate of state variables of a trophic web model in the Bay of Brest

HAL (Le Centre pour la Communication Scientifique Directe), 1995

International audienceWinter biomasses of the benthic fauna in the Bay of Brest were estimated to... more International audienceWinter biomasses of the benthic fauna in the Bay of Brest were estimated to model carbon fluxes through the benthic food web. Total biomass (9.59 g C m(-2)) is dominated by macrofaunal suspension feeders (53%) and carnivores (25%). Macrofaunal deposit feeders and herbivores, meiofauna, bacteria and demersal fishes accounted for 22% of total biomass. Most of the biomass was found on coarse coralline algae bottoms, in relation to environmental and biotic factors. Mean macrofaunal biomass is significantly higher in the Bay of Brest than in many other temperate coastal ecosystems. The proliferation of suspension feeders in the Bay would correspond to the first perturbation level of the ecosystem, due to organic enrichment. Suspension feeders would prevent eutrophication by controlling phytoplankton biomass

Research paper thumbnail of Determination of Pecten maximus (L.) pre-recruitment in the Bay of Saint-Brieuc: processes regulating the abundance, survival and growth of post-larvae and juveniles

Research paper thumbnail of Déterminisme du pré-recrutement de Pecten maximus L. En baie de Saint-Brieuc

Research paper thumbnail of Reproduction of the invasive slipper limpet, Crepidula fornicata, in the Bay of Brest, France

Marine Biology, Mar 28, 2006

Research paper thumbnail of Les flux de CO2 face à la marée : avec ou sans eau ?

HAL (Le Centre pour la Communication Scientifique Directe), 2018

Il est difficile d'admettre que, dans ses angoisses de racines, d'ombres moussues, la man... more Il est difficile d'admettre que, dans ses angoisses de racines, d'ombres moussues, la mangrove puisse etre un tel berceau de vie (...) Elle ne semble appartenir ni a la terre, ni a la mer. " Patrick Chamoiseau La mangrove, cette foret entre terre et mer qui borde les littoraux tropicaux, a longtemps ete percue comme un milieu hostile ou inutile... Elle renvoie aussi a un puissant imaginaire des tropiques qui a inspire bon nombre de nos plus grands ecrivains. Cet ecosysteme, complexe, abrite les paletuviers capables de vivre les pieds dans l'eau salee, des poissons pouvant respirer hors de l'eau, des crabes ingenieurs et une multitude de bacteries indispensables au recyclage de la matiere organique. Aujourd'hui, confrontee a la crevetticulture, aux coupes de bois, a la pollution mais aussi sous l'emprise directe des changements climatiques, cette mangrove, grignotee de toute part, est en danger. Cet ouvrage, redige par des chercheurs specialistes du milieu, nous montre combien sa preservation devient un enjeu ecologique mondial tant cet ecosysteme contribue a l'equilibre des littoraux tropicaux et a ceux de la planete tout entiere. Sait-on par exemple que ces forets maritimes jouent le role de puits de carbone en absorbant de grandes quantites de CO2 ? Qu'elles peuvent servir de filtres ou d'eponges face aux pollutions humaines ? Qu'elles constituent un rempart contre les tempetes ou les tsunamis ? Un livre qui nous invite a poser un regard nouveau sur cette foret si secrete au coeur des enjeux ecologiques tropicaux. Un ouvrage collectif illustre sous la direction de Francois Fromard, Emma Michaud, Martine Hossaert-McKey, Institut ecologie et environnement (INEE) du CNRS.

Research paper thumbnail of Experimental collection of postlarvae of Pecten maximus (L.) and other benthic macrofaunal species in the Bay of Saint-Brieuc, France. II. Reproduction patterns and postlarval growth of five mollusc species

Journal of Experimental Marine Biology and Ecology, Jun 1, 1991

Settlement patterns ofPecten maximus (L.) postlarvae and 105 other species of benthic macrofauna ... more Settlement patterns ofPecten maximus (L.) postlarvae and 105 other species of benthic macrofauna in the Bay of Saint-Brieuc were studied from spat collectors in order to clarify biotic interactions at the postlarval stage. Between-sites differences in taxonomic group abundances reflected the bottom sediment type beneath the collectors and were partly explained by hydrographic mechanisms; larval retention occurred in the collection areas. Other factors regulating settlement process were the water turbulence and trophic resources. Temporal variability in collection occurred between and within the taxonomic groups. Optimal collection for all the species was within 2 m above the seabed for an immersion period of < 1 month. Anomia ephippium L., Crepidulafornicata L. and Chlamys varia L. were the main spatio-trophic competitors ofP. maximus collected in the bay while brachyuran crustaceans accounted for 96 % of the potential scallop predators. Possible ways of improving scallop spat collection and cultivation in the bay are discussed.

Research paper thumbnail of Experimental collection of post-larvae of Pecten maximus (L.) and other benthic macrofaunal species, in the Bay of Saint-Brieuc. II - Reproduction patterns and post-larval growth of 5 mollusc species

HAL (Le Centre pour la Communication Scientifique Directe), 1991

... Temperature and trophic resources were the main factors determining these variations, in P.ma... more ... Temperature and trophic resources were the main factors determining these variations, in P.maximus, another source of growth variation, the gamete quality, is ... 1976; Buestel et al., 1977, 1979; Pickett, 1978; Brand et al., 1980; Paul et al., 1981; Wallace, 1982; Richardson et al ...

Research paper thumbnail of Variabilité saisonnière de la structure trophique et de la biodiversité du macrobenthos en Manche occidentale

HAL (Le Centre pour la Communication Scientifique Directe), Nov 24, 1994

National audienc

Research paper thumbnail of Corals adapted to extreme and fluctuating seawater <scp>pH</scp> increase calcification rates and have unique symbiont communities

Ecology and Evolution, May 1, 2023

Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification... more Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification rate. Identifying the resilience factors of corals to decreasing seawater pH is of paramount importance to predict the survivability of coral reefs in the future. This study compared corals adapted to variable pHT (i.e., 7.23–8.06) from the semi‐enclosed lagoon of Bouraké, New Caledonia, to corals adapted to more stable seawater pHT (i.e., 7.90–8.18). In a 100‐day aquarium experiment, we examined the physiological response and genetic diversity of Symbiodiniaceae from three coral species (Acropora tenuis, Montipora digitata, and Porites sp.) from both sites under three stable pHNBS conditions (8.11, 7.76, 7.54) and one fluctuating pHNBS regime (between 7.56 and 8.07). Bouraké corals consistently exhibited higher growth rates than corals from the stable pH environment. Interestingly, A. tenuis from Bouraké showed the highest growth rate under the 7.76 pHNBS condition, whereas for M. digitata, and Porites sp. from Bouraké, growth was highest under the fluctuating regime and the 8.11 pHNBS conditions, respectively. While OA generally decreased coral calcification by ca. 16%, Bouraké corals showed higher growth rates than corals from the stable pH environment (21% increase for A. tenuis to 93% for M. digitata, with all pH conditions pooled). This superior performance coincided with divergent symbiont communities that were more homogenous for Bouraké corals. Corals adapted to variable pH conditions appear to have a better capacity to calcify under reduced pH compared to corals native to more stable pH condition. This response was not gained by corals from the more stable environment exposed to variable pH during the 100‐day experiment, suggesting that long‐term exposure to pH fluctuations and/or differences in symbiont communities benefit calcification under OA.

Research paper thumbnail of Size‐based survival of cultured <i>Argopecten purpuratus</i> (L, 1819) under severe hypoxia

Journal of the World Aquaculture Society, May 3, 2021

During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays.... more During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays. One of the main drivers related to these mortalities was hypoxic events. This study was designed to understand the hypoxia phenomenon in these bays and to assess how the Peruvian scallop, Argopecten purpuratus, can cope with reduced oxygen levels in seawater based on individual size. First, we analyzed the relationships between dissolved oxygen saturation and other environmental parameters (the Coastal El Niño Index, temperature, salinity and pH) in bottom seawater, the frequency and intensity of hypoxic events in two main culture areas (Sechura and Paracas Bays), and their relationship with scallop mass mortalities. Then, we performed experiments with two size groups of A. purpuratus (31 and 80 mm shell height; seed and commercial size, respectively) to assess their respective survival time under severe hypoxia (1% oxygen saturation) at 16 C and a salinity of 35. Finally, the results of the field records and the experimental data are used to suggest ways to improve scallop cultivation along the Peruvian coast.

Research paper thumbnail of Predicting the energy budget of the scallop Argopecten purpuratus in an oxygen–limiting environment

Journal of Sea Research, 2019

Low concentrations of oxygen determine marine species distribution and abundance along the Peruvi... more Low concentrations of oxygen determine marine species distribution and abundance along the Peruvian coast with consequences for human activity such as fishing and aquaculture. In order to assess bioenergetic consequences of oxygen limitation on the Peruvian scallop Argopecten purpuratus, we first developed a Dynamic Energy Budget (DEB) model of growth and reproduction calibrated on field experimental datasets. Then, we included oxygen availability as an additional forcing variable using a simple rule based on the ability of the scallop to regulate oxygen consumption. The resulting model was tested using growth/reproduction monitoring and simultaneous high frequency environmental records in Paracas Bay (Peru) at two different depths: suspended in the water column and on the sea bottom. Simulations indicated that scallops growth and reproduction was not food-limited. The negative observed effects of hypoxia on growth and reproduction could be explained by a decrease in both assimilation and reserve mobilization. However, hypoxic conditions in summer were not sufficient to explain the observed losses in somatic tissue weights and the disruption of reproduction. The latter two patterns were better simulated when assuming increased somatic maintenance costs due to the presence of H 2 S during milky turquoise water discolouration events observed during summer.

Research paper thumbnail of Feeding behaviour and growth of the Peruvian scallop ( Argopecten purpuratus ) under daily cyclic hypoxia conditions

Journal of Sea Research, 2018

As a secondary consequence of the high productivity of the upwelling system, organisms inhabiting... more As a secondary consequence of the high productivity of the upwelling system, organisms inhabiting Peruvian coastal bays are frequently exposed to hypoxic conditions. The aim of the present paper was to investigate the effects of daily-cyclic-severe hypoxia on energetics of a species presenting little escape ability when facing hypoxia. For this purpose, juvenile Peruvian scallops (Argopecten purpuratus) were exposed to four experimental conditions: fed and starved, combined or not to nightly severe hypoxia (5% oxygen saturation) for ≈ 12 hours over a 21-day experiment. In both fed conditions, clearance rate was measured by the mean of an open-flow system. Our results indicate that the Peruvian scallop is able to maintain an active filtration even at low oxygen saturation, at least during expositions up to 12 hours. During the first phase of exposure to hypoxia, clearance rate decreased abruptly when oxygen saturation dropped below 10%, but rapidly recovered to values close to those found under normoxia. As a consequence of this ability to feed during hypoxia, no difference in soft tissue dry weight (digestive gland not included) was observed at the end of the experimental period between oxic conditions among fed scallops. However, shell growth was negatively affected by hypoxic condition. Starved individuals exhibited similar weight loss between hypoxic and normoxic conditions indicating no or little effect of oxic condition on maintenance costs. Considering the observed responses for feeding, growth and maintenance, we can hypothesize that this species presents metabolic/bioenergetic efficient adaptations to deal with hypoxic conditions that are recurrent in Peruvian coastal bays. We hypothesize that the small observed effects might be modeled in the context of the Dynamic Energy Budget theory as a restriction of reserve mobilization under hypoxic conditions.

Research paper thumbnail of Marine Species Introduced on the French Channel-Atlantic Coasts: A Review of Main Biological Invasions and Impacts

Open Journal of Ecology, 2015

The impacts of anthropogenisation modify permanently the distribution patterns of brackish and ma... more The impacts of anthropogenisation modify permanently the distribution patterns of brackish and marine species. Globalization leads to a rapid increase of the numbers of introduced species anywhere in the world. Biological invasions often result in significant losses in the economic value, biological diversity and function of invaded ecosystems. This review presents the main pathways of introduction of non-indigenous species and the main benthic taxonomic groups being established and/or invasive along the French Channel-Atlantic coasts. A focus is put on main invasive marine species in the intertidal and subtidal zones of Brittany (France), among macroalgae (Sargassum muticum, Grateloupia turuturu, Undaria pinnatifida, Codium fragile and Gracilaria vermiculophylla), halophytes (Spartina alterniflora) and benthic invertebrates (Mollusks: Crepidula fornicata, Crassostrea gigas and Venerupis philippinarum). The species biology, introduction vectors, reproductive and dispersal capacities are considered, together with proliferation patterns along the Channel-Atlantic coasts. The ecological impacts of these species on the environment are also described, as well as the European regulations existing to limit alien species introduction and some examples of struggle against the invaders including eradication trials and biomass valorization. Last, the ongoing impacts of global changes on alien species invasiveness along the Channel-Atlantic coasts are discussed.

Research paper thumbnail of Les espèces marines introduites sur la façade Manche-Atlantique : invasions biologiques ou immigration contrôlée ?

HAL (Le Centre pour la Communication Scientifique Directe), 2015

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