Über Mytilus edulis L. und seine Formen

Von Dr. Richard Hilbert

John Sims Reeves, Brustbild

Signatur des Originals: S 36/F09605

John Sims Reeves, Brustbild

Signatur des Originals: S 36/G03542

John Sims Reeves, Brustbild

Signatur des Originals: S 36/G03543

John Sims Reeves, Kniestück

Signatur des Originals: S 36/G04323

Crecimiento inicial bajo cultivo de Chrysolaena flexuosa (Sims) H. Rob., Asteraceae nativa de valor ornamental potencial

Se realizó un estudio para conocer características relacionadas con el crecimiento inicial de la especie Chysolaena flexuosa (Sims) H. Rob., Asteraceae nativa de las sierras bonaerenses con potencial ornamental gracias al colorido de sus capítulos durante la floración y a su inflorescencia. Se empleó para el ensayo simiente de C. flexuosa recolectada en la Sierra La Barrosa (Partido de Balcarce) y se analizó la evolución de las plantas en invernáculo durante un ciclo de crecimiento. Los estadios reproductivos de C. flexuosa comprendieron las estaciones de primavera, verano e inicios de otoño. En todas las plantas se observaron, a mediados de la etapa reproductiva, capítulos con flores violáceas conjuntamente con capítulos fructificados. A principios de otoño todas las plantas poseían capítulos fructificados que exhibían sus papus de color blanco, situación que entrega a la planta otro interesante atributo. Por su rusticidad, establecida sobre la base de la germinación y supervivencia de sus plántulas, y por el atractivo de la especie desde primavera a inicios del otoño, C. flexuosa se destaca como promisoria para la obtención de cultivares ornamentales para uso como ejemplar aislado, en macetas, borduras o como flor de corte para la realización de arreglos florales secos.

Effects of various pollutant mixtures on immune responses of the blue mussel (Mytilus edulis) collected at a salinity gradient in Danish coastal waters, links to supplementary material

The Baltic Sea is a semi-enclosed sea with a steady salinity gradient (3 per mil-30 per mil). Organisms have adapted to such low salinities, but are suspected to be more susceptible to stress. Within the frame of the integrated environmental monitoring BONUS + project "BEAST" the applicability of immune responses of the blue mussel was investigated in Danish coastal waters. The sampling sites were characterised by a salinity range (11-19 per mil) and different mixtures of contaminants (metals, PAHs and POPs), according to chemical analysis of mussel tissues. Variation partitioning (redundancy analysis) was applied to decompose salinity and contamination effects. The results indicated that cellular immune responses (total and differential haemocyte count, phagocytic activity and apoptosis) were mainly influenced by contaminants, whereas humoral factors (haemolytic activity) were mainly impacted by salinity. Hence, cellular immune functions may be suitable as biomarkers in monitoring programmes for the Baltic Sea and other geographic regions with salinity variances of the studied range.

Impact of ocean acidification and warming on respiration, heart rate and acid-base status of Mytilus edulis from the North Sea

Anthropogenic climate change confronts marine organisms with rapid trends of concomitant warming and CO2 induced ocean acidification. The survival and distribution of species partly depend on their ability to exploit their physiological plasticity during acclimatization. Therefore, in laboratory studies the effects of simulated future ocean acidification on thermal tolerance, energy metabolism and acid-base regulation capacity of the North Sea population of the blue mussel Mytilus edulis were examined. Following one month of pre-acclimation to 10 °C and control CO2 levels, mussels were exposed for two weeks to control and projected oceanic CO2 levels (390, 750 and 1120 µatm) before being subjected to a stepwise warming protocol between 10 °C and 31 °C (+ 3 °C each night). Oxygen consumption and heart rates, anaerobic metabolite levels and haemolymph acid-base status were determined at each temperature. CO2 exposure left oxygen consumption rate unchanged at acclimation temperature but caused a somewhat stronger increase during acute warming and thus mildly higher Q10-values than seen in controls. Interestingly, the thermally induced limitation of oxygen consumption rate set in earlier in normocapnic than in hypercapnic (1120 µatm CO2) mussels (25.2 °C vs. 28.8 °C), likely due to an onset of metabolic depression in the control group following warming. However, the temperature induced increase in heart rate became limited above 25 °C in both groups indicating an unchanged pejus temperature regardless of CO2 treatment. An upper critical temperature was reached above 28 °C in both treatments indicated by the accumulation of anaerobic metabolites in the mantle tissue, paralleled by a strong increase in haemolymph PCO2 at 31 °C. Ocean acidification caused a decrease in haemolymph pH. The extracellular acidosis remained largely uncompensated despite some bicarbonate accumulation. In all treatments animals developed a progressive warming-induced extracellular acidosis. A stronger pH drop at around 25 °C was followed by stagnating heart rates. However, normocapnic mussels enhanced bicarbonate accumulation at the critical limit, a strategy no longer available to hypercapnic mussels. In conclusion, CO2 has small effects on the response patterns of mussels to warming, leaving thermal thresholds largely unaffected. High resilience of adult North Sea mussels to future ocean acidification indicates that sensitivity to thermal stress is more relevant in shaping the response to future climate change.

Seawater carbonate chemistry and biological processes of Mytilus edulis during experiments, 2010

Marine organisms are exposed to increasingly acidic oceans, as a result of equilibration of surface ocean water with rising atmospheric CO2 concentrations. In this study, we examined the physiological response of Mytilus edulis from the Baltic Sea, grown for 2 months at 4 seawater pCO2 levels (39, 113, 243 and 405 Pa/385, 1,120, 2,400 and 4,000 µatm). Shell and somatic growth, calcification, oxygen consumption and excretion rates were measured in order to test the hypothesis whether exposure to elevated seawater pCO2 is causally related to metabolic depression. During the experimental period, mussel shell mass and shell-free dry mass (SFDM) increased at least by a factor of two and three, respectively. However, shell length and shell mass growth decreased linearly with increasing pCO2 by 6-20 and 10-34%, while SFDM growth was not significantly affected by hypercapnia. We observed a parabolic change in routine metabolic rates with increasing pCO2 and the highest rates (+60%) at 243 Pa. excretion rose linearly with increasing pCO2. Decreased O:N ratios at the highest seawater pCO2 indicate enhanced protein metabolism which may contribute to intracellular pH regulation. We suggest that reduced shell growth under severe acidification is not caused by (global) metabolic depression but is potentially due to synergistic effects of increased cellular energy demand and nitrogen loss.

Element ratio (Sr/Ca, Ba/Ca, B/Ca, and Mg/Ca) profiles throughout the larval life stage of Mytilus edulis, 2011

Rising anthropogenic CO2 in the surface ocean has raised serious concerns for the ability of calcifying organisms to secrete their shells and skeletons. Previous mollusc carbonate perturbation experiments report deleterious effects at lowered pH (7.8-7.4 pH units), including reduced shell length and thickness and deformed shell morphology. It is not clear whether the reduced shell growth results from a decrease in calcification rate due to lowered aragonite saturation or from an indirect effect on mollusc metabolism. We take a novel approach to discerning between these two processes by examining the impact of lowered pH on the 'vital-effect' associated with element ratios. Reported herein are the first element ratio (Sr/Ca, Ba/Ca, B/Ca, Mg/Ca and Mn/Ca) profiles throughout the larval life stage of Mytilus edulis. Element ratio data for individuals reared in ambient conditions provide new insights into biomineralization during larval development. Sr/Ca ratios are consistent with Sr incorporation in the mineral phase. Mg and Mn are likely hosted in an organic phase. The Ba partition coefficient of early larval shells is one of the highest reported in biogenic aragonite. The reason for the high Ba concentrations is unknown, but may reflect the assimilation of Ba from food and/or Ba concentration in an organic or amorphous carbonate phase. There is no observable difference in the way the studied elements are incorporated into the shells of individuals reared in ambient and lowered pH conditions. The reduced growth rate at lower pH may be a consequence of a disruption to the larval mollusc metabolism.

Seawater carbonate chemistry during experiments with Mytilus edulis, 2008

The effects of medium term (32 d) hypercapnia on the immune response of Mytilus edulis were investigated in mussels exposed to acidified (using CO2) sea water (pH 7.7, 7.5 or 6.7; control: pH 7.8). Levels of phagocytosis increased significantly during the exposure period, suggesting an immune response induced by the experimental set-up. However, this induced stress response was suppressed when mussels were exposed to acidified sea water. Acidified sea water did not have any significant effects on other immuno-surveillance parameters measured (superoxide anion production, total and differential cell counts). These results suggest that ocean acidification may impact the physiological condition and functionality of the haemocytes and could have a significant effect on cellular signalling pathways, particularly those pathways that rely on specific concentrations of calcium, and so may be disrupted by calcium carbonate shell dissolution.