Lorenzo Bramanti | Centre National de la Recherche Scientifique / French National Centre for Scientific Research (original) (raw)
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Papers by Lorenzo Bramanti
Ecological Modelling, 2016
Octocorals are marine modular organisms with high ecological and economic importance. Mediterrane... more Octocorals are marine modular organisms with high ecological and economic importance. Mediterranean Red Coral (Corallium rubrum), is endemic to the Mediterranean sea and neighboring Atlantic rocky shores and has been exploited for jewelry since ancient times. Despite the lack of photosynthetic symbionts (Symbiodinium spp.), red coral growth and survival do depend on sea water temperature, as well as on trophic conditions and other physico-chemical parameters. We developed and applied a mechanistic numerical model to describe the growth of a C. rubrum colony (polyps number, polyp and gametes biomass, skeletal inorganic and organic matter) as a function of food availability and seawater temperature. The model follows a bioenergetic approach and is calibrated vs available experimental observations. Model results highlight that larger colonies are more sensitive to high temperature and actual limits of the ecological niche also depend on food availability, hydrodynamic condition and coral morphology. Bioenergetic considerations also support the conclusion that, though a modular organism, red coral exhibits constrained growth, because of the competition for available food between polyps from the same colony.
Initially, we asked whether it was possible to identify corals that are resistant or sensitive to... more Initially, we asked whether it was possible to identify corals that are resistant or sensitive to such conditions by compiling quantitative measures of their phenotypic traits determined through empirical studies, but we found only weak phenotypic discrimination between ecological winners and losers, or among taxa. To reconcile this outcome with ecological evidence demonstrating that coral taxa are functionally unequal, we looked beyond the notion that phenotypic homogeneity arose through limitations of empirical data. Instead, we examined the validity of contemporary means of categorizing corals based on ecological success. As an alternative means to distinguish among functional groups of corals, we present a demographic approach using integral projection models (IPMs) that link organismal performance to demographic outcomes, such as the rates of population Abstract Many tropical corals have declined in abundance in the last few decades, and evaluating the causal basis of these losses is critical to understanding how coral reefs will change in response to ongoing environmental challenges. Motivated by the likelihood that marine environments will become increasingly unfavorable for coral growth as they warm and become more acidic (i.e., ocean acidification), it is reasonable to evaluate whether specific phenotypic traits of the coral holobiont are associated with ecological success (or failure) under varying environmental conditions including those that are adverse to survival. Communicated by M. Byrne. Electronic supplementary material The online version of this article (
precious corals have been commercially exploited for many centuries all over the world. Their ske... more precious corals have been commercially exploited for many centuries all over the world. Their skeletons have been used as amulets or jewellery since antiquity and are one of the most valuable living marine resources. precious coral fisheries are generally characterized by the 'boomand-bust' principle, quickly depleting a discovered stock and then moving on to the next one. Most known stocks are overexploited today, and populations are in decline. The unsustainable nature of most fisheries is clearly revealed by analyzing all available data. precious corals belong to the functional group of deep corals and are important structure-forming organisms, so called ecosystem engineers, that provide shelter for other organisms, increasing biodiversity. Yet, their management is usually focused on single species rather than a holistic habitat management approach. This review compares the biology of precious corals as well as the historical ecology and the socioeconomy of their fisheries to improve precious coral management and conservation. The analysis demonstrates that a paradigm shift is necessary in precious coral exploitation, not only to conserve habitats of high biodiversity but also to achieve sustainable fisheries and stabilize a specialized jewellery industry.
Gorgonian corals are slow growing, long lived species whose three dimensional colonies form dense... more Gorgonian corals are slow growing, long lived species whose three dimensional colonies form dense canopies on Mediterranean reefs. As they are habitat forming, the ecology of the reef community depends in a large part on their survival. The red coral Corallium rubrum is a precious gorgonian whose heavily harvested populations have changed their size and age structure in shallow waters. In general gorgonians show low recruitment and low population growth rates. In 1999 and 2003 two mortality events, putatively linked to Global Climate Change, (GCC) affected a population of the red gorgonian Paramuricea clavata at the Western edge of the Gulf of La Spezia (NE Ligurian Sea Italy). The availability of pre and post mortality demographic data allowed us to follow the trajectory of this population over 12 years. In the first years population density decreased drastically and 90%, of the colonies died or suffered partial mortality; moreover recruitment decreased to 40% and the dominant size classes shifted towards a smaller size. In the subsequent years population density increased, damaged colonies recovered and recruitment reached six times that of 1998. While the populations of both species recovered, an increased frequency of mortality events with GCC could lead to local extinction (C. rubrum) or to a new stable structure reached at a lower density (P. clavata).
Marine Ecology Progress Series, 2003
This study provides the first description of the reproductive features of a red coral Corallium r... more This study provides the first description of the reproductive features of a red coral Corallium rubrum population. This circum-Mediterranean octocoral has been over-harvested and commercial stocks are depleted. The population we studied was gonochoric at both the colony and polyp levels, and its sex ratio was significantly biased toward females. The minimum age at first reproduction was 2 yr. The percentage of fertile colonies increased with age, reaching 100% fertility for those over 5 yr. Due to the low frequency of older colonies, 2 /3 of the population was unreproductive. The seasonal cycle of oocyte maturation resulted in a rapid increase in diameter after March, corresponding to a significant reduction in fecundity and fertility. Larval release occurred between late July and August, and settlement ended by mid-September. No significant difference was found in fecundity or fertility between colonies living at different depths (25 and 35 m). Both reproductive parameters depended on polyp position on the colony branches, being significantly lower in the tips of 1st order and proximal parts of 2nd order branches. Due to these opposing trends, no significant overall difference was found between branches of different orders. Female polyp fecundity (0.87 gonads per polyp) was considerably lower than fecundity measured in other octocorals, and the larval production depends on the size/age of the colony: while reproductive colonies in Class 2 (diameter 1.82 mm) produce on average 24 planulae, the larger, older colonies in Class 6 (diameter > 4.6 mm) produce 157 planulae on average. This clearly indicates large differences in larval production between populations with different size and/or age structures. A better understanding of red coral reproduction will help to match harvesting levels to recovery rates in overexploited populations.
Ecological Modelling, 2016
Octocorals are marine modular organisms with high ecological and economic importance. Mediterrane... more Octocorals are marine modular organisms with high ecological and economic importance. Mediterranean Red Coral (Corallium rubrum), is endemic to the Mediterranean sea and neighboring Atlantic rocky shores and has been exploited for jewelry since ancient times. Despite the lack of photosynthetic symbionts (Symbiodinium spp.), red coral growth and survival do depend on sea water temperature, as well as on trophic conditions and other physico-chemical parameters. We developed and applied a mechanistic numerical model to describe the growth of a C. rubrum colony (polyps number, polyp and gametes biomass, skeletal inorganic and organic matter) as a function of food availability and seawater temperature. The model follows a bioenergetic approach and is calibrated vs available experimental observations. Model results highlight that larger colonies are more sensitive to high temperature and actual limits of the ecological niche also depend on food availability, hydrodynamic condition and coral morphology. Bioenergetic considerations also support the conclusion that, though a modular organism, red coral exhibits constrained growth, because of the competition for available food between polyps from the same colony.
Initially, we asked whether it was possible to identify corals that are resistant or sensitive to... more Initially, we asked whether it was possible to identify corals that are resistant or sensitive to such conditions by compiling quantitative measures of their phenotypic traits determined through empirical studies, but we found only weak phenotypic discrimination between ecological winners and losers, or among taxa. To reconcile this outcome with ecological evidence demonstrating that coral taxa are functionally unequal, we looked beyond the notion that phenotypic homogeneity arose through limitations of empirical data. Instead, we examined the validity of contemporary means of categorizing corals based on ecological success. As an alternative means to distinguish among functional groups of corals, we present a demographic approach using integral projection models (IPMs) that link organismal performance to demographic outcomes, such as the rates of population Abstract Many tropical corals have declined in abundance in the last few decades, and evaluating the causal basis of these losses is critical to understanding how coral reefs will change in response to ongoing environmental challenges. Motivated by the likelihood that marine environments will become increasingly unfavorable for coral growth as they warm and become more acidic (i.e., ocean acidification), it is reasonable to evaluate whether specific phenotypic traits of the coral holobiont are associated with ecological success (or failure) under varying environmental conditions including those that are adverse to survival. Communicated by M. Byrne. Electronic supplementary material The online version of this article (
precious corals have been commercially exploited for many centuries all over the world. Their ske... more precious corals have been commercially exploited for many centuries all over the world. Their skeletons have been used as amulets or jewellery since antiquity and are one of the most valuable living marine resources. precious coral fisheries are generally characterized by the 'boomand-bust' principle, quickly depleting a discovered stock and then moving on to the next one. Most known stocks are overexploited today, and populations are in decline. The unsustainable nature of most fisheries is clearly revealed by analyzing all available data. precious corals belong to the functional group of deep corals and are important structure-forming organisms, so called ecosystem engineers, that provide shelter for other organisms, increasing biodiversity. Yet, their management is usually focused on single species rather than a holistic habitat management approach. This review compares the biology of precious corals as well as the historical ecology and the socioeconomy of their fisheries to improve precious coral management and conservation. The analysis demonstrates that a paradigm shift is necessary in precious coral exploitation, not only to conserve habitats of high biodiversity but also to achieve sustainable fisheries and stabilize a specialized jewellery industry.
Gorgonian corals are slow growing, long lived species whose three dimensional colonies form dense... more Gorgonian corals are slow growing, long lived species whose three dimensional colonies form dense canopies on Mediterranean reefs. As they are habitat forming, the ecology of the reef community depends in a large part on their survival. The red coral Corallium rubrum is a precious gorgonian whose heavily harvested populations have changed their size and age structure in shallow waters. In general gorgonians show low recruitment and low population growth rates. In 1999 and 2003 two mortality events, putatively linked to Global Climate Change, (GCC) affected a population of the red gorgonian Paramuricea clavata at the Western edge of the Gulf of La Spezia (NE Ligurian Sea Italy). The availability of pre and post mortality demographic data allowed us to follow the trajectory of this population over 12 years. In the first years population density decreased drastically and 90%, of the colonies died or suffered partial mortality; moreover recruitment decreased to 40% and the dominant size classes shifted towards a smaller size. In the subsequent years population density increased, damaged colonies recovered and recruitment reached six times that of 1998. While the populations of both species recovered, an increased frequency of mortality events with GCC could lead to local extinction (C. rubrum) or to a new stable structure reached at a lower density (P. clavata).
Marine Ecology Progress Series, 2003
This study provides the first description of the reproductive features of a red coral Corallium r... more This study provides the first description of the reproductive features of a red coral Corallium rubrum population. This circum-Mediterranean octocoral has been over-harvested and commercial stocks are depleted. The population we studied was gonochoric at both the colony and polyp levels, and its sex ratio was significantly biased toward females. The minimum age at first reproduction was 2 yr. The percentage of fertile colonies increased with age, reaching 100% fertility for those over 5 yr. Due to the low frequency of older colonies, 2 /3 of the population was unreproductive. The seasonal cycle of oocyte maturation resulted in a rapid increase in diameter after March, corresponding to a significant reduction in fecundity and fertility. Larval release occurred between late July and August, and settlement ended by mid-September. No significant difference was found in fecundity or fertility between colonies living at different depths (25 and 35 m). Both reproductive parameters depended on polyp position on the colony branches, being significantly lower in the tips of 1st order and proximal parts of 2nd order branches. Due to these opposing trends, no significant overall difference was found between branches of different orders. Female polyp fecundity (0.87 gonads per polyp) was considerably lower than fecundity measured in other octocorals, and the larval production depends on the size/age of the colony: while reproductive colonies in Class 2 (diameter 1.82 mm) produce on average 24 planulae, the larger, older colonies in Class 6 (diameter > 4.6 mm) produce 157 planulae on average. This clearly indicates large differences in larval production between populations with different size and/or age structures. A better understanding of red coral reproduction will help to match harvesting levels to recovery rates in overexploited populations.