Comparison between the Nereis diversicolor and Nereis virens marine worms in the transformation of ingested hydrocarbons

A feeding experiment was conducted on the marine worm Nereis diversicolor to compare the fate of a hydrocarbon mixture during the gut passage in this species with the hydrocarbon breakdown process demonstrated for Nereis virens. Hydrocarbon dissolution/solubilization processes in the gut of N. diversicolor were found to have similar qualitative and quantitative importance in the hydrocarbon transformation as those observed in N. virens

L'introduction de l'enseignement de l'hygiène au Québec

Au Québec, bien que les trois premières facultés de médecine aient été créées dans la première moitié du xixe siècle, l'enseignement de l'hygiène n'a été inclus dans le cursus des études médicales que beaucoup plus tardivement. L'étude dont nous présentons les résultats confirme qu'il ne suffit pas qu'il y ait un savoir disponible pour qu'une matière appartenant au champ de la médecine soit reconnue officiellement et enseignée dans les facultés de médecine. Il faut qu'un certain nombre de méd..

Alteration and release of aliphatic compounds by the polychaete Nereis virens (Sars) experimentally fed with hydrocarbons

In the laboratory, marine worms were fed with a mixture of algae and several aliphatic hydrocarbons for 15 days. After ingestion by the worms, 34.9% of hydrocarbons are found in the faeces and only 3.1% accumulated in the gut. The comparison between the initial mixture and the faeces shows that the worm’s digestive process lead to changes in the distribution of the n-alkane mixture. These changes are different from those only due to physical processes in the experimental conditions. In our experiment, no variation in the distribution of hydrocarbons in faeces with time and no microbial hydrocarbon biodegradation were evidenced. Our results suggest that marine worm feeding can substantially affect the fate of hydrocarbons in the sedimentary marine ecosystem by predominantly stimulating dissolution processes

Effects of temperature on in vitro sediment reworking processes by a gallery biodiffusor, the polychaete Neanthes virens

Temperature-induced variations in bioturbation could affect sediment mixing processes in the marine benthic environment. In this study, sediment reworking by Neanthes virens (Sars), a widely distributed polychaete in muddy sand communities of northern temperate latitudes, was studied under different temperature conditions representing winter (1°C), spring and fall (6°C), summer(13°C), and tide pool (18°C) temperatures in the lower St. Lawrence Estuary, Québec, Canada. Sediment reworking was quantified using inert fluorescent particles (luminophores) deposited at the sediment surface. Based on the 1-D luminophore distributions obtained after 5 and 30 d, the use of the specific ‘gallery-biodiffusor’ model allowed us to quantify both biodiffusion (Db) and biotransport (Vb) due to the organisms. Our results showed temperature effects on sediment transport. The lowest biotransport and biodiffusion coefficients were measured at 1 and 6°C and did not change with time. The highest biodiffusion occurred at 13°C for both sampling periods. At 18°C, biodiffusion was intermediate while biotransport was maximal. Differences between the 13°C biodiffusive transport and the other temperatures increased with time. Low transport values at 1 and 6°C suggest that a quiescent stage exists for this species at these temperatures, with sediment mixing occurring mostly during burrow construction. On the other hand, sediment mixing resulted from both the burrow construction and maintenance phases at higher temperatures (13 and 18°C)

Sediment reworking by marine benthic species from the Gullmar Fjord (Western Sweden): Importance of faunal biovolume

In order to compare and quantify sediment reworking activities by different species/functional groups of macrofauna, a laboratory experiment was carried out with species from the Gullmarsfjord (Western Sweden). Monospecific communities of Amphiura filiformis, Echinocardium cordatum, Scalibregma inflatum and Abra nitida were introduced in experimental mesocosms, with identical densities (795 ind. m−2), for 10 days. Sediment reworking was studied by quantifying downward and upward movements of fluorescent inert tracers (luminophores). Luminophores with different colour were initially deposited both at the sediment surface and within the sediments. Population biomass and biovolume were also determined. Surface tracers reworking coefficients ranged from 0.6 to 2.2 cm2 y−1 and 0.9 to 4.1 y−1, respectively for the biodiffusive-like and non-local transports. Calculated biodiffusive-like coefficient was between 1.0 and 2.3 cm2 y−1 for the deep tracers. For both tracers, the E. cordatum population presented the highest reworking coefficients. Among the morphological and/or ethological parameters that could determine overall patterns of reworking and differences between species, results have shown a direct relationship between the apparent biodiffusive mixing and the biovolume of the individuals (Db=0.35 ⁎ Biovolume). This suggests that the biovolume of macrofauna may allow a rough estimate of the biodiffusive-like reworking intensity of particles deposited on the sediment surface

L'Estuaire (65)

Éditorial: La relance de la revue de l'Estuaire: 15 ans déjà! -- Le chemin de fer et le tourisme au Bas-Saint-Laurent -- Les dames Drapeau -- Histoire oubliée: Une étrange odyssée...des Madelinots s'établissent sur l'Île Nepawa (Abitibi) en 1941 -- Étude démographique de la population de Rimouski 1701-1750 -- Sur la piste des forêts du passé -- Mgr Courchesne: la récupération des forêts pour la colonisation -- Joseph-Pierre Ouellet, 2e architecte de l'église de Trois-Pistoles -- La seigneurie de l'Anse-aux-Coques ou de Lepage-Thivierge -- Nouvelles brèves -- Livres à lir

Le service de santé de Montréal de l'établissement au démantèlement (1865-1975)

Au cours de la décennie 1970, le Québec entreprend une vaste réforme de son système de santé qui aboutit au démantèlement des anciennes structures de santé publique mises en place à partir de 1926 comme les unités sanitaires de comté ou de la fin du xixe siècle comme le service de santé de la ville de Montréal. Cette étude, en cours et partie d'une enquête plus vaste sur les conditions d'institutionnalisation des pratiques de santé publique au Québec du milieu du xixe s. à nos jours, analyse ..

L'Estuaire, vol. 25 (1)

Éditorial -- Sainte-Luce: refuge d'un incorruptible -- Le "Vocabulaire micmac" de Joseph Hamel. L'histoire d'une cueillette de données linguistiques. Partie 2: qui est Joseph Hamel? -- La famille Desrosiers dans la région de Rimouski au XVIIIe siècle. Partie 1: implantation dans la seigneurie de Rimouski -- Les trésors du grenier -- L'année des Français -- Un grand marin gaspésien. Le capitaine Paul M. Fournier -- Matane dans les relations de voyage de Champlain: un 375e anniversaire -- La naissance d'une petite paroisse au coeur de La Mitis: le cas de Sainte-Flavie -- Nouvelles brèves -- Des livres à lire

Use of axial tomography to follow temporal changes of benthic communities in an unstable sedimentary environment (Baie des Ha! Ha!, Saguenay Fjord)

In the upper layer of the sediment column, organic matter recycling is greatly influenced by bioturbation. However, there are many physical changes in the nature of the sediment that may disturb benthic communities and create a biogeochemical imbalance. Following a very heavy rainfall between 26 and 29 July 1996, an intense flash flood in the Saguenay Fjord caused discharges of 6 million cubic metres of sediments into Baie des Ha! Ha!. Unstable sediment deposits located at the top of the delta of the Rivie`re des Ha! Ha! were sporadically exported to the deep basin. After this physical disturbance, meiobenthic and macrobenthic organisms progressively re-colonised the sediment column. To determine the impacts of such sedimentary depositions on benthic fauna, two stations, one at the head and one at the mouth of the Baie des Ha! Ha!, have been monitored since 1996. During this survey, we developed a new method for the quantification of biogenic structures using computer axial tomography (CAT-Scan). Benthic fauna analysis showed that the two stations were characterised by different temporal changes in the benthic dynamics according to their geographic location. Using CAT-Scan analysis of sediment cores, we were able to characterise the stability of the sediment column for the two stations in 1999 and 2000. Scan results suggest that colonisation processes were closely linked with the stability of the sediment column. Erosion and redeposition of surficial sediments caused a succession in the formation of biogenic structures. These variations were characterised for the first time using CAT-Scan, which is a nondestructive, rapid, and precise method. Tomographic analysis showed the importance of the production and destruction rates of biogenic structures and the sedimentation rate for the preservation of burrows and potentially reactive components. This study finally demonstrated that each erosional event could be followed by a rapid formation of biogenic structures, allowing the re-oxidation of old deposits