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

The reproduction of Crepidula fornicata was studied in the Bay of Brest in order to characterise the first step of the reproductive cycle of this invasive species. The survey was carried out from 2000 to 2003 and different parameters were measured, namely, the percentage of the different sexual stages, the straight length of the shell and the percentage of brooding females using a survey of the embryonic development and the fecundity. The juvenile frequency increases generally from mid-June or mid-August, depending on the year. In 2001 and 2003, a first peak was observed as early as May, but it was followed by a rapid disappearance of the individuals. The sex-ratio female/male increased from 0.22 to 0.46 between 2001 and 2003. The sex change between intermediates and females took place mainly in summer and was well marked in 2001 and 2003. The survey of the embryonic development in the egg capsules brooded by the females provided an annual phenology of the laying and hatching processes. The laying period extends from February to September with three to four major periods of egg-laying per year and corresponding hatching periods about 1 month later. Each female lays two to four times per year on average. The first egg-laying concerned fewer females than subsequent ones, except in 2003, and exhibited a higher fecundity. The annual mean of the number of eggs for each stage was not significantly different, thus indicating no significant mortality rate during embryonic development. For the C. fornicata population in the Bay of Brest, several reproductive characteristics tend to highlight its invasive capacity: (1) a long reproductive period, (2) reproduction in a ‘multi-trials' process equivalent to a spreading out of the risks and (3) a relatively high fecundit

Captación artificial y crecimiento temprano de la semilla de Argopecten puppuratus (Lamarck, 1819) en la Reserva Marina La Rinconada, Antofagasta, Chile

Artificial collection of early juveniles (“spat”) of the scallop Argopecten purpuratus in Japanese-type collectors was evaluated between January 2001 and July 2002 in the La Rinconada Marine Reserve, Antofagasta, Chile. This area of Antofagasta Bay 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 mm/day for the first cohort (C1) and between 64.0 and 167.4 mm/day for the second cohort (C2). 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.Un programa mensual de captación de A. purpuratus, implementado en la reserva marina de La Rinconada, entre enero de 2001 y julio de 2002, la caracterizó como zona de retención larvaria, con densidades variando entre 89 y 34175 larvas m-3, y de fijaciones entre 400 y 15340 post-larvas por colector. No se encontró una relación directa entre abundancia larvaria y asentamiento, sin embargo, las mayores captaciones estuvieron asociadas a la presencia de un elevado número de estados umbonados. La mantenimiento prolongado de colectores in situ, por periodos que variaron entre 88 y 159 días, provocó una fuerte reducción en el número de semillas que se asentaron en ellos durante los primeros 28 a 40 días de inmersión Estas reducciones variaron entre el 99.6 y el 50.9% de la semilla fijada, siendo las más perjudicadas las cohortes más pequeñas, asentadas al final del primer periodo de inmersión. Las tasas de crecimiento registradas en estas cohortes, para cada periodo de inmersión, variaron entre 81.3 y 235.2 ìm/día para las cohortes C1 y entre 64.0 y 167.4 ìm/día para las cohortes C2. Las mayores tasas están directamente relacionadas con un menor número de semilla recuperada. Se discuten las competencias intraespecíficas ocurridas en los colectores, como responsables de la disminución del número de semilla y de las variaciones registradas en sus tasas de crecimiento

A review of potential impacts of submarine power cables on the marine environment:Knowledge gaps, recommendations and future directions

Submarine power cables (SPC) have been in use since the mid-19th century, but environmental concerns about them are much more recent. With the development of marine renewable energy technologies, it is vital to understand their potential impacts. The commissioning of SPC may temporarily or permanently impact the marine environment through habitat damage or loss, noise, chemical pollution, heat and electromagnetic field emissions, risk of entanglement, introduction of artificial substrates, and the creation of reserve effects. While growing numbers of scientific publications focus on impacts of the marine energy harnessing devices, data on impacts of associated power connections such as SPC are scarce and knowledge gaps persist. The present study (1) examines the different categories of potential ecological effects of SPC during installation, operation and decommissioning phases and hierarchizes these types of interactions according to their ecological relevance and existing scientific knowledge, (2) identifies the main knowledge gaps and needs for research, and (3) sets recommendations for better monitoring and mitigation of the most significant impacts. Overall, ecological impacts associated with SPC can be considered weak or moderate, although many uncertainties remain, particularly concerning electromagnetic effects

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

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Les flux de CO2 face à la marée : avec ou sans eau ?

International audienceIl est difficile d'admettre que, dans ses angoisses de racines, d'ombres moussues, la mangrove puisse être un tel berceau de vie (...) Elle ne semble appartenir ni à la terre, ni à la mer. " Patrick ChamoiseauLa mangrove, cette forêt entre terre et mer qui borde les littoraux tropicaux, a longtemps été perçue comme un milieu hostile ou inutile... Elle renvoie aussi à un puissant imaginaire des tropiques qui a inspiré bon nombre de nos plus grands écrivains. Cet écosystème, complexe, abrite les palétuviers capables de vivre les pieds dans l'eau salée, des poissons pouvant respirer hors de l'eau, des crabes ingénieurs et une multitude de bactéries indispensables au recyclage de la matière organique.Aujourd'hui, confrontée à la crevetticulture, aux coupes de bois, à la pollution mais aussi sous l'emprise directe des changements climatiques, cette mangrove, grignotée de toute part, est en danger.Cet ouvrage, rédigé par des chercheurs spécialistes du milieu, nous montre combien sa préservation devient un enjeu écologique mondial tant cet écosystème contribue à l'équilibre des littoraux tropicaux et à ceux de la planète tout entière.Sait-on par exemple que ces forêts maritimes jouent le rôle de puits de carbone en absorbant de grandes quantités de CO2 ? Qu'elles peuvent servir de filtres ou d'éponges face aux pollutions humaines ? Qu'elles constituent un rempart contre les tempêtes ou les tsunamis ? Un livre qui nous invite à poser un regard nouveau sur cette forêt si secrète au coeur des enjeux écologiques tropicaux.Un ouvrage collectif illustré sous la direction de François Fromard, Emma Michaud, Martine Hossaert-McKey, Institut écologie et environnement (INEE) du CNRS

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

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Déterminisme du pré-recrutement de Pecten maximus (L.) en baie de Saint-Brieuc : processus régulateurs de l'abondance, de la survie et de la croissance des post-larves et juvéniles

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

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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

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