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Marseille, France

Bensoussan N.,IPSO FACTO | Pairaud I.,French Research Institute for Exploitation of the Sea | Garreau P.,French Research Institute for Exploitation of the Sea | Somot S.,French National Center of Weather Research | And 2 more authors.
OCEANS 2013 MTS/IEEE - San Diego: An Ocean in Common | Year: 2013

Climate change by the end of the 21st century is expected to induce great changes of coastal benthic ecosystems at the sub-regional scale in the North Western Mediterranean Sea. In order to assess the impact of the expected warming, we developed a strategy for the definition of warming scenarios in coastal habitats and their potential sub-lethal to lethal impacts on key benthic species. This was achieved by combining numerical simulations under IPCC-A2 scenario with field observations and thermo-tolerance experiments. First, a model validation was conducted for the period 2001-2008 in contrasted coastal areas. Then, scenarios forecast run temperature outputs were analyzed in order to explore the expected changes in the stratification by the end of the 21st century. These simulations were used together with species spatial distribution and thermo-tolerance functions to explore the potential risk of temperature induced mortality for the red gorgonian Paramuricea clavata, considered a key-species in coastal Mediterranean ecosystems, by the end of the century. © 2013 MTS. Source


Teixido N.,CSIC - Institute of Marine Sciences | Teixido N.,Stazione Zoologica Anton Dohrn | Bensoussan N.,IPSO FACTO | Gori A.,CSIC - Institute of Marine Sciences | And 2 more authors.
Marine Ecology | Year: 2016

Understanding processes that contribute to a better comprehension of the population dynamics of long-lived species is critical for the maintenance and potential recovery of such species. Despite the abundance of soft corals in Mediterranean rocky reefs, little information exists on their life histories and reproductive patterns. In this study, we assessed the main reproductive characteristics and early life-history traits of the long-lived soft coral Alcyonium acaule. The sex ratio was 1:1; the smallest fertile colonies were one finger in size (2.1 ± 0.6 cm in height), and both colony and polyp fertility increased with colony size. Likewise, the number of eggs and spermary sacs per polyp increased significantly with colony size, whereas the diameter of the female and male sexual products did not. Over 6 years of observations (2007-2012), spawning occurred primarily in July, after the seawater reached 20 °C, in a single spawning episode per year. Approximately 80% of female colonies released eggs, which were retained on the surface of the mother colony by mucous strings for up to a few days. High fertilization rates were observed during spawning in 2008 and 2009 (94.9% and 87.0%, respectively). The timing of development was ~24 h for the blastulae, ~48-72 h for the planulae and 8-22 days for metamorphosis into primary polyps. Survivorship of planulae was relatively high (~50% at 45 days after release), but only 24% of larvae metamorphosed into primary polyps, and their survivorship was moderate after 2 months (65% in 2008 and 74% in 2009). Asexual reproduction was negligible, indicating that sexual reproduction is the main mechanism supporting the maintenance and recovery of populations. © 2016 Blackwell Verlag GmbH. Source


Teixido N.,Stazione Zoologica Anton Dohrn | Bensoussan N.,IPSO FACTO | Gori A.,CSIC - Institute of Marine Sciences | Fiorillo I.,CSIC - Institute of Marine Sciences | Viladrich N.,Institute of Environmental Science and Technology ICTA Edifici Z s n Cerdanyola del Valles Spain
Marine Ecology | Year: 2015

Understanding processes that contribute to a better comprehension of the population dynamics of long-lived species is critical for the maintenance and potential recovery of such species. Despite the abundance of soft corals in Mediterranean rocky reefs, little information exists on their life histories and reproductive patterns. In this study, we assessed the main reproductive characteristics and early life-history traits of the long-lived soft coral Alcyonium acaule. The sex ratio was 1:1; the smallest fertile colonies were one finger in size (2.1 ± 0.6 cm in height), and both colony and polyp fertility increased with colony size. Likewise, the number of eggs and spermary sacs per polyp increased significantly with colony size, whereas the diameter of the female and male sexual products did not. Over 6 years of observations (2007-2012), spawning occurred primarily in July, after the seawater reached 20 °C, in a single spawning episode per year. Approximately 80% of female colonies released eggs, which were retained on the surface of the mother colony by mucous strings for up to a few days. High fertilization rates were observed during spawning in 2008 and 2009 (94.9% and 87.0%, respectively). The timing of development was ~24 h for the blastulae, ~48-72 h for the planulae and 8-22 days for metamorphosis into primary polyps. Survivorship of planulae was relatively high (~50% at 45 days after release), but only 24% of larvae metamorphosed into primary polyps, and their survivorship was moderate after 2 months (65% in 2008 and 74% in 2009). Asexual reproduction was negligible, indicating that sexual reproduction is the main mechanism supporting the maintenance and recovery of populations. © 2015 Blackwell Verlag GmbH. Source


Pairaud I.L.,French Research Institute for Exploitation of the Sea | Bensoussan N.,IPSO FACTO | Garreau P.,French Research Institute for Exploitation of the Sea | Faure V.,IPSO FACTO | And 2 more authors.
Ocean Dynamics | Year: 2014

In the framework of climate change, the increase in ocean heat wave frequency is expected to impact marine life. Large-scale positive temperature anomalies already occurred in the northwestern Mediterranean Sea in 1999, 2003 and 2006. These anomalies were associated with mass mortality events of macrobenthic species in coastal areas (0-40 m in depth). The anomalies were particularly severe in 1999 and 2003 when thousands of kilometres of coasts and about 30 species were affected. The aim of this study was to develop a methodology to assess the current risk of mass mortality associated with temperature increase along NW Mediterranean continental coasts. A 3D regional ocean model was used to obtain the temperature conditions for the period 2001-2010, for which the model outputs were validated by comparing them with in situ observations in affected areas. The model was globally satisfactory, although extremes were underestimated and required correction. Combined with information on the thermo-tolerance of a key species (the red gorgonian P. clavata) as well as its spatial distribution, the modelled temperature conditions were then used to assess the risk of mass mortality associated with thermal stress for the first time. Most of the known areas of observed mass mortality were found using the model, although the degree of risk in certain areas was underestimated. Using climatic IPCC scenarios, the methodology could be applied to explore the impacts of expected climate change in the NW Mediterranean. This is a key issue for the development of sound management and conservation plans to protect Mediterranean marine biodiversity in the face of climate change. © 2013 Springer-Verlag Berlin Heidelberg. Source


Escoffier N.,University Paris Diderot | Escoffier N.,Ecole Polytechnique Federale de Lausanne | Bensoussan N.,IPSO FACTO | Vilmin L.,MINES ParisTech | And 6 more authors.
Environmental Science and Pollution Research | Year: 2016

Large rivers are important components of the global C cycle. While they are facing an overall degradation of their water quality, little remains known about the dynamics of their metabolism. In the present study, we used continuous multi-sensors measurements to assess the temporal variability of gross primary production (GPP) and ecosystem respiration (ER) rates of the anthropized Seine River over an annual cycle. Downstream from the Paris urban area, the Seine River is net heterotrophic at the annual scale (−226 gO2 m−2 year−1 or −264 gC m−2 year−1). Yet, it displays a net autotrophy at the daily and seasonal scales during phytoplankton blooms occurring from late winter to early summer. Multivariate analyses were performed to identify the drivers of river metabolism. Daily GPP is best predicted by chlorophyll a (Chla), water temperature (T), light, and rainfalls, and the coupling of daily GPP and Chla allows for the estimation of the productivity rates of the different phytoplankton communities. ER rates are mainly controlled by T and, to a lesser extent, by Chla. The increase of combined sewer overflows related to storm events during the second half of the year stimulates ER and the net heterotrophy of the river. River metabolism is, thus, controlled at different timescales by factors that are affected by human pressures. Continuous monitoring of river metabolism must, therefore, be pursued to deepen our understanding about the responses of ecosystem processes to changing human pressures and climate. © 2016 Springer-Verlag Berlin Heidelberg Source

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