Geographic and seasonal patterns and limits on the adaptive response to temperature of European Mytilus spp. and Macoma balthica populations

Seasonal variations in seawater temperature require extensive metabolic acclimatization in cold-blooded organisms inhabiting the coastal waters of Europe. Given the energetic costs of acclimatization, differences in adaptive capacity to climatic conditions are to be expected among distinct populations of species that are distributed over a wide geographic range. We studied seasonal variations in the metabolic adjustments of two very common bivalve taxa at European scale. To this end we sampled 16 populations of Mytilus spp. and 10 Macoma balthica populations distributed from 39° to 69°N. The results from this large-scale comprehensive comparison demonstrated seasonal cycles in metabolic rates which were maximized during winter and springtime, and often reduced in the summer and autumn. Studying the sensitivity of metabolic rates to thermal variations, we found that a broad range of Q10 values occurred under relatively cold conditions. As habitat temperatures increased the range of Q10 narrowed, reaching a bottleneck in southern marginal populations during summer. For Mytilus spp., genetic-group-specific clines and limits on Q10 values were observed at temperatures corresponding to the maximum climatic conditions these geographic populations presently experience. Such specific limitations indicate differential thermal adaptation among these divergent groups. They may explain currently observed migrations in mussel distributions and invasions. Our results provide a practical framework for the thermal ecophysiology of bivalves, the assessment of environmental changes due to climate change and its impact on (and consequences for) aquaculture

Calorific value, lipid content and radioactivity of common species from Hornsund, southwest Spitsbergen

In the summer of 1981 the common flora and fauna of 28 species from Hornsund were collected, and the energy value, lipid content and global activity determined. It was found that the plants had low energy values, varying from 12.26 2 0.42 kJ g-' dry weight to 15.45 +1.00 kJ-' dry weight. The highest values in animals were noted in Liparis liparis (Pisces) 22.15 2 0.89kJg-' dry weight, and Sagitta ekgans (Chaetognatha) 20.64 2 0.49 kJ g-', the lowest being in Orchomene minuta (Amphipoda) 11.30 2 0.74 kJ g-' d.w. The lipid contents in the species studied were mostly low, the mean range from lowest to highest being 1.37-8.60% for plants and 7.14-31.93% for animals, and they were proportional to the energy value. Both the energy values and lipid contents were comparable to those in similar species from other waters. The global ? activity in the organisms analysed was not high; at the same time plants had a higher content of radioactive isotopes, 1.97-61.9 pCi g-' d.w., than animals, 5.2-17.8pCi g-' d.w

Changes in the energy content of common species from Hornsund, southwest Spitsbergen

During the period August 1981 to July 1982, samples of six species of Amphipoda common to Hornsund were collected, and a study of their energy value changes was carried out. Only slight fluctuations of energy values were observed throughout the year, and no distinct seasonal changes as in the case of boreal organisms. Individuals of greater body size exhibit higher energy values. The lowest energy values 10.93 kJ g-' d.w. (SD = 3.01) and highest ash contents 29.8% (SD = 7.6) were found in small Amphipoda (e.g. Ischyrocerus anguipes), while species attaining greater body size were characterized by higher energy values and lower ash contents, for example Gammarellus homari 16.96 kJ g' d.w. (SD = OSO), and 22.9% (SD = 3.3%) ash

Genetic diversity of European populations of the invasive soft-shell clam Mya arenaria (Bivalvia

The genetic diversity of the soft-shell clam Mya arenaria from seven locations in Europe (two stations in the southern Baltic Sea (the Gulf of Gdansk) and two in the North Sea (Veerse Meer and Oosterschelde), and three additional stations in the Denmark Straits and Bay of Biscay) was determined using starch gel electrophoresis of allozymes. The results showed a low level of genetic variability and a lack of genetic di¡erentation among the populations studied. Basic polymorphism characteristics calculated for populations from the North Sea estuaries and the Gulf of Gdansk were: He 0.094^0.145, Ho 0.092^0.130, percentage of polymorphic loci 33 (0.95 criterion), mean number of alleles per locus 2.0^2.7. The mean value of F ST was 0.0133 and not signi¢cant. It is concluded that in spite of a low level of genetic polymorphism the soft-shell clam is a successful colonizer. The genetic homogeneity among the populations re£ects rapid population extension, alleles neutrality and a high gene £ow

Contribution de la méiofaune aux transferts des métaux dans le réseau trophique de la baie de Gdańsk (Baltique) et de la baie de Marennes-Oléron (Atlantique)

Les nématodes (groupe principal de la méiofaune) sont étudiés sous deux aspects: l un, écologique, vise à déterminer la structure taxonomique/trophique du peuplement et évaluer sa contribution au flux de carbone au sein du système benthique dans les Baies de Marennes-Oléron et Gdańsk. Les résultats des expériences de traçage radioactif (14C) ont permis de quantifier le flux de carbone des diatomées benthiques vers les nématodes et confirment l importance des nématodes dans le transfert du C au sein du réseau trophique benthique. L autre, écotoxicologique, s intéresse au compartiment comme réacteur biologique potentiel susceptible d accumuler, biotransformer et transférer les métaux aux maillons supérieurs du réseau trophique. Le compartiment des nématodes aux concentrations de métaux supérieures à celles de la macrofaune constituerait une voie importante de transfert des métaux dans la chaîne alimentaire et jouerait un rôle majeur dans le recyclage des métaux fixés par les diatomées.LA ROCHELLE-BU (173002101) / SudocSudocFranceF

Conséquences de l'aménagement agricole des marais de la région Poitou-Charentes sur la qualité des eaux conchylicoles

La campagne d'essai 1985-86 a donné lieu à un suivi de la qualité des eaux dans des situations parcellaires très diversifiées, crées expérimentalement à cet effet. Elle permet de hiérarchiser les risques d'entrainement en particules et en solutés. Il apparait que la couverture prairiale pérenne limite tous les entraînements solides et solubles. De même la mise en culture est particulièrement sensible aux entraînements en particules. Dans tous les cas, les quantités exportées s'accroissent considérablement lorsque la stabilité structurale est faible. En outre le mode d'assainissement par rigoles et mise en ados est très nettement le plus sensible à l'érosion. Cependant il est possible, suivant des caractéristiques liées à la parcelle, de modéliser ces entraînements en fonction du débit.Le drainage enterré favorise les entraînements nitrique et phosphorique, notamment lorsque le fonctionnement hydraulique de la parcelle est satisfaisant. Compte tenu de la pratique agricole, les entraînements constatés concernent, pour l'essentiel, les reliquats du cycle cultural précédent.Par ailleurs, les tentatives d'acclimatation de coques comme organismes concentrateurs des solutés dans les eaux de drainage, ont abouti à des taux de survie satisfaisants

Application of a micro-respirometric volumetric method to respiratory measurements of larvae of the Pacific oyster

The application of a simple, fast and reliable volumetric microrespirometric method to assess respiration of bivalve larvae is discussed. As a model, C. gigas larvae of various sizes were used. Metabolic activity of veliger larvae was assessed by measuring respiratory rate for use in ecophysiological modelling. As an example of the application of this approach, additional measurements of veliger respiratory rates were carried out to assess the effect on larval metabolism of different concentrations of leachate from wood treated with chromated copper-arsenate (CCA). Veligers of Crassostrea gigas (length from 95 to 331 µm) were fed with a mixture of Isochrysis galbana and Chaetoceros pumilum cells. Experiments were performed in a 20 °C constant seawater temperature. The wet and dry weight of four length (L, in µm) classes of larvae were obtained from which the relationship between total dry weight and veliger length was derived {DW = e(3.27+L×0.0154)} (R2 = 99%). Moreover, tissue dry weight (TDW; in ng) was calculated according to Gerdes (1983). Since the mathematical model between larval length and respiratory rate explained 88% of the total variability, a more conservative approach using oyster larval dry meat weight (in ng) and respiratory rate (in µl O2 h−1) was developed to establish a linear model explaining 94.5% of the variability: Resp. = -3.849 × 10-4 + 5.211 × 10-6 × TDW. These experiments provided updated figures of C. gigas larval respiratory rates for use in ecophysiological models. The relationship between tissue dry weight and respiratory rate was close to previous estimates obtained by Gerdes (1983) and Hoegh-Guldberg and Manahan (1995) at 25 °C and 20 °C respectively. Our experiments demonstrate that volumetric microrespirometry is suitable for assessing larval respiratory rate and therefore can be used to assess impacts of pollutants on an early larval stage. Oysters exposed to leachates from chromated copper arsenate (CCA) treated timber at 5 kg m−3 showed initially highly variable respiratory rates while those rates decreased drastically for a 15 kg m−3 CCA treatment exposure. Among bioindicators using physiological response to assess pollutant effects, swimming activity and respiratory rates can be compared, the later showing a significant response at a lower pollutant concentration

Matrix of RAD loci from pyRAD analysis

NEXUS file used for SVDquartet analysi

Population assignments

File with population assignments for the samples: a two column text file with the sample ids in the first column and the ids of the populations in the second column