Journal of Experimental Marine Biology and Ecology, 2010
... Shells of mollusks provide high-resolution and temporally aligned records of past climate cha... more ... Shells of mollusks provide high-resolution and temporally aligned records of past climate change ([Jones et al., 1989], [Andreasson and Schmitz, 1996] and [Kobashi et al., 2001]), as well as seasonality and weather ([Kaandorp et al., 2003], [Surge et al., 2003] and [Dettman et al ...
ABSTRACT Cockle (Cerastoderma edule) growth has not been studied a lot yet and the current approa... more ABSTRACT Cockle (Cerastoderma edule) growth has not been studied a lot yet and the current approach of counting external ridges in order to make age estimation is limited. Nevertheless, growth is a key parameter for monitoring bivalves populations, which are heavily exploited in French estuaries. The Bay of Somme which is located in the eastern Channel in the north of France, is the first French field of cockles (Cerastoderma edule). In order to improve stock management, it is necessary to increase our knowledge of this species. This study is looking at the growth of the common cockle. In this way, recapture of shells previously marked under calcein marker and then breed in natural conditions in the Bay of Somme, was performed in order to determine the shell growth patterns. In a methodological point of view, calcein marking has showed a fluorescent increment in shells stayed for only 30 min immersion time at 150 mg.L-1, but also for shells immersed 3 hours at 50 mg.L-1. High-resolution pictures analysis with the TNPC software (Digital Processing for Calcified Structures) dedicated by Noesis society and Ifremer, performed on several marked cockles permitted to count 23 increments on average between the mark and the ventral edge of the valves, corresponding to the 12 days experience during which 23 tides happened. The periodicity of increment formation is validated for a tidal frequency. This preliminary study give a clue to the understanding of the cockle growth and could be completed by cockles age monitoring, but also by chemical analysis to learn more about biomineralization process of this species.
Compared to oxygen isotopes, the carbon isotope composition of biogenic carbonates is less common... more Compared to oxygen isotopes, the carbon isotope composition of biogenic carbonates is less commonly used as proxy for palaeoenvironmental reconstructions because shell δ 13 C is derived from both dissolved inorganic (seawater) and organic carbon sources (food), and interactions between these two pools make it difficult to unambiguously identify any independent effect of either. The main purpose of this study was to demonstrate any direct impact of variable food supply on bivalve shell δ 13 C signatures, using low/high rations of a 13 C-light mixed algal diet fed to 14-month-old (adult) cultured Japanese Crassostrea gigas under otherwise essentially identical in vitro conditions during 3 summer months (May, June and July 2003, seawater temperature means at 16, 18 and 20°C respectively) in experimental tanks at the Argenton laboratory along the Brittany Atlantic coast of France. At a daily ration of 12% (versus 4%) oyster dry weight, the newly grown part of the shells (hinge region) showed significantly lower δ 13 C values, by 3.5‰ (high ration: mean of −5.8±1.1‰, n=10; low ration: mean of −2.3±0.7‰, n=6; ANOVA Scheffe's test, p<0.0001). This can be explained by an enhanced metabolic activity at higher food supply, raising 13 C-depleted respiratory CO 2 in the extrapallial cavity. Based on these δ 13 C values and data extracted from the literature, and assuming no carbon isotope fractionation between food and shell, the proportion of shell metabolic carbon would be 26±7 and 5±5% for the high-and low-ration C. gigas shells respectively; with carbon isotope fractionation (arguably more realistic), the corresponding values would be 69±14 and 24±9%. Both groups of cultured shells exhibited lower δ 13 C values than did wild oysters from Marennes-Oléron Bay in the study region, which is not inconsistent with an independent influence of diet type. Although there was no significant difference between the two food regimes in terms of δ 18 O shell values (means of 0.1±0.3 and 0.4±0.2‰ at high and low rations respectively, non-significant Scheffe's test), a positive δ 13 C vs. δ 18 O relationship recorded at high rations supports the interpretation of a progressive temperature-mediated rise in metabolic activity fuelled by higher food supply (in this case reflecting increased energy investment in reproduction), in terms not only of δ 13 C (metabolic signal) but also of δ 18 O (seawater temperature signal). Overall, whole-shell δ 18 O trends faithfully recorded summer/winter variations in seawater temperature experienced by the 17-month-old cultured oysters.
Proceedings of the National Academy of Sciences of the United States of America, Jan 10, 2011
Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-... more Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-Atlantic Ridge (MAR) is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids. Despite high concentrations of reduced chemicals in the fluids, this unique example of a serpentinite-hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high-temperature vent sites. Here we report abundant specimens of chemosymbiotic mussels, associated with gastropods and chemosymbiotic clams, in approximately 100 kyr old Lost City-like carbonates from the MAR close to the Rainbow site (36 °N). Our finding shows that serpentinization-related fluids, unaffected by high-temperature hydrothermal circulation, can occur on-axis and are able to sustain high-biomass communities. The widespread occurrence of seafloor ultramafic rocks linked to likely long-...
Journal of Experimental Marine Biology and Ecology, 2010
... Shells of mollusks provide high-resolution and temporally aligned records of past climate cha... more ... Shells of mollusks provide high-resolution and temporally aligned records of past climate change ([Jones et al., 1989], [Andreasson and Schmitz, 1996] and [Kobashi et al., 2001]), as well as seasonality and weather ([Kaandorp et al., 2003], [Surge et al., 2003] and [Dettman et al ...
ABSTRACT Cockle (Cerastoderma edule) growth has not been studied a lot yet and the current approa... more ABSTRACT Cockle (Cerastoderma edule) growth has not been studied a lot yet and the current approach of counting external ridges in order to make age estimation is limited. Nevertheless, growth is a key parameter for monitoring bivalves populations, which are heavily exploited in French estuaries. The Bay of Somme which is located in the eastern Channel in the north of France, is the first French field of cockles (Cerastoderma edule). In order to improve stock management, it is necessary to increase our knowledge of this species. This study is looking at the growth of the common cockle. In this way, recapture of shells previously marked under calcein marker and then breed in natural conditions in the Bay of Somme, was performed in order to determine the shell growth patterns. In a methodological point of view, calcein marking has showed a fluorescent increment in shells stayed for only 30 min immersion time at 150 mg.L-1, but also for shells immersed 3 hours at 50 mg.L-1. High-resolution pictures analysis with the TNPC software (Digital Processing for Calcified Structures) dedicated by Noesis society and Ifremer, performed on several marked cockles permitted to count 23 increments on average between the mark and the ventral edge of the valves, corresponding to the 12 days experience during which 23 tides happened. The periodicity of increment formation is validated for a tidal frequency. This preliminary study give a clue to the understanding of the cockle growth and could be completed by cockles age monitoring, but also by chemical analysis to learn more about biomineralization process of this species.
Compared to oxygen isotopes, the carbon isotope composition of biogenic carbonates is less common... more Compared to oxygen isotopes, the carbon isotope composition of biogenic carbonates is less commonly used as proxy for palaeoenvironmental reconstructions because shell δ 13 C is derived from both dissolved inorganic (seawater) and organic carbon sources (food), and interactions between these two pools make it difficult to unambiguously identify any independent effect of either. The main purpose of this study was to demonstrate any direct impact of variable food supply on bivalve shell δ 13 C signatures, using low/high rations of a 13 C-light mixed algal diet fed to 14-month-old (adult) cultured Japanese Crassostrea gigas under otherwise essentially identical in vitro conditions during 3 summer months (May, June and July 2003, seawater temperature means at 16, 18 and 20°C respectively) in experimental tanks at the Argenton laboratory along the Brittany Atlantic coast of France. At a daily ration of 12% (versus 4%) oyster dry weight, the newly grown part of the shells (hinge region) showed significantly lower δ 13 C values, by 3.5‰ (high ration: mean of −5.8±1.1‰, n=10; low ration: mean of −2.3±0.7‰, n=6; ANOVA Scheffe's test, p<0.0001). This can be explained by an enhanced metabolic activity at higher food supply, raising 13 C-depleted respiratory CO 2 in the extrapallial cavity. Based on these δ 13 C values and data extracted from the literature, and assuming no carbon isotope fractionation between food and shell, the proportion of shell metabolic carbon would be 26±7 and 5±5% for the high-and low-ration C. gigas shells respectively; with carbon isotope fractionation (arguably more realistic), the corresponding values would be 69±14 and 24±9%. Both groups of cultured shells exhibited lower δ 13 C values than did wild oysters from Marennes-Oléron Bay in the study region, which is not inconsistent with an independent influence of diet type. Although there was no significant difference between the two food regimes in terms of δ 18 O shell values (means of 0.1±0.3 and 0.4±0.2‰ at high and low rations respectively, non-significant Scheffe's test), a positive δ 13 C vs. δ 18 O relationship recorded at high rations supports the interpretation of a progressive temperature-mediated rise in metabolic activity fuelled by higher food supply (in this case reflecting increased energy investment in reproduction), in terms not only of δ 13 C (metabolic signal) but also of δ 18 O (seawater temperature signal). Overall, whole-shell δ 18 O trends faithfully recorded summer/winter variations in seawater temperature experienced by the 17-month-old cultured oysters.
Proceedings of the National Academy of Sciences of the United States of America, Jan 10, 2011
Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-... more Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-Atlantic Ridge (MAR) is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids. Despite high concentrations of reduced chemicals in the fluids, this unique example of a serpentinite-hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high-temperature vent sites. Here we report abundant specimens of chemosymbiotic mussels, associated with gastropods and chemosymbiotic clams, in approximately 100 kyr old Lost City-like carbonates from the MAR close to the Rainbow site (36 °N). Our finding shows that serpentinization-related fluids, unaffected by high-temperature hydrothermal circulation, can occur on-axis and are able to sustain high-biomass communities. The widespread occurrence of seafloor ultramafic rocks linked to likely long-...
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Papers by Franck Lartaud