Immunomodulating effects of environmentally realistic copper concentrations in Mytilus edulis adapted to naturally low salinities.

The monitoring of organisms' health conditions by the assessment of their immunocompetence may serve as an important criterion for the achievement of the Good Environmental Status (GES) as defined in the Marine Strategy Framework Directive (EU). In this context, the complex role of natural environmental stressors, e.g. salinity, and interfering or superimposing effects of anthropogenic chemicals, should be carefully considered, especially in scenarios of low to moderate contamination. Organisms from the Baltic Sea have adapted to the ambient salinity regime, however energetically costly osmoregulating processes may have an impact on the capability to respond to additional stress such as contamination. The assessment of multiple stressors, encompassing natural and anthropogenic factors, influencing an organisms' health was the main aim of the present study. Immune responses of Mytilus edulis, collected and kept at natural salinities of 12‰ (LS) and 20‰ (MS), respectively, were compared after short-term exposure (1, 7 and 13 days) to low copper concentrations (5, 9 and 16 µg/L Cu). A significant interaction of salinity and copper exposure was observed in copper accumulation. LS mussels accumulated markedly more copper than MS mussels. No combined effects were detected in cellular responses. Bacterial clearance was mostly achieved by phagocytosis, as revealed by a strong positive correlation between bacterial counts and phagocytic activity, which was particularly pronounced in LS mussels. MS mussels, on the other hand, seemingly accomplished bacterial clearance by employing additional humoral factors (16 µg/L Cu). The greatest separating factor in the PCA biplot between LS and MS mussels was the proportion of granulocytes and hyalinocytes while functional parameters (phagocytic activity and bacterial clearance) were hardly affected by salinity, but rather by copper exposure. In conclusion, immune responses of the blue mussel may be suitable and sensitive biomarkers for the assessment of ecosystem health in brackish waters (10-20‰S).

Oxygen-dependent niche formation of a pyrite-dependent acidophilic consortium built by archaea and bacteria.

Biofilms can provide a number of different ecological niches for microorganisms. Here, a multispecies biofilm was studied in which pyrite-oxidizing microbes are the primary producers. Its stability allowed not only detailed fluorescence in situ hybridization (FISH)-based characterization of the microbial population in different areas of the biofilm but also to integrate these results with oxygen and pH microsensor measurements conducted before. The O2 concentration declined rapidly from the outside to the inside of the biofilm. Hence, part of the population lives under microoxic or anoxic conditions. Leptospirillum ferrooxidans strains dominate the microbial population but are only located in the oxic periphery of the snottite structure. Interestingly, archaea were identified only in the anoxic parts of the biofilm. The archaeal community consists mainly of so far uncultured Thermoplasmatales as well as novel ARMAN (Archaeal Richmond Mine Acidophilic Nanoorganism) species. Inductively coupled plasma analysis and X-ray absorption near edge structure spectra provide further insight in the biofilm characteristics but revealed no other major factors than oxygen affecting the distribution of bacteria and archaea. In addition to catalyzed reporter deposition FISH and oxygen microsensor measurements, microautoradiographic FISH was used to identify areas in which active CO2 fixation takes place. Leptospirilla as well as acidithiobacilli were identified as primary producers. Fixation of gaseous CO2 seems to proceed only in the outer rim of the snottite. Archaea inhabiting the snottite core do not seem to contribute to the primary production. This work gives insight in the ecological niches of acidophilic microorganisms and their role in a consortium. The data provided the basis for the enrichment of uncultured archaea.

Antioxidant system efficiently protects goldfish gills from Ni(2+)-induced oxidative stress.

Fish gills are target organs for waterborne metal ions and this work aimed to investigate the effects of waterborne Ni(2+) (10, 25 and 50 mg L(-1)) on goldfish gills. A special focus was on the relationship between Ni uptake and the homeostasis of reactive oxygen species (ROS) in the gills, the tissue, in direct contact with the metal pollutant. Ni-accumulation in the gills occurred as a function of exposure concentration (R(2)=0.98). The main indices of oxidative stress, namely carbonyl proteins (CP) and lipid peroxides (LOOH), decreased by 21-33% and 21-24%, as well as the activities of principal antioxidant enzymes superoxide dismutase and glutathione-dependent peroxidase, by 29-47% and 41-46%, respectively, in gills of Ni-exposed fish. One of the main players in the antioxidant defense of gills seems to be catalase, which increased by 23-53% in Ni-treated fish, and low molecular mass thiol-containing compounds (L-SH), exceeding untreated controls by 73-105% after fish exposure to 10-50 mg L(-1) of Ni(2+). The increased level of L-SH, mainly represented by reduced glutathione, was supported by enhanced activities of glutathione reductase (by 27-38%), glutathione-S-transferase (56-141%) and glucose-6-phosphate dehydrogenase (by 96-117%) and demonstrates the ability of the antioxidant system of gills to resist Ni-induced oxidative stress.

Tissue specificity in nickel uptake and induction of oxidative stress in kidney and spleen of goldfish Carassius auratus, exposed to waterborne nickel.

Toxic and carcinogenic effects of nickel compounds are suggested to result from nickel-mediated oxidative damage to macromolecules and/or inhibition of cellular antioxidant defenses. We investigated the effects of waterborne Ni(2+) (10, 25 and 50 mg/L) on the blood and blood-producing tissues (kidney and spleen) of goldfish to identify relationships between Ni accumulation and oxidative stress. Whereas the main hematological parameters (total hemoglobin and hematocrit) were unaffected, Ni(2+) exposure had substantial influence on goldfish immune system, causing lymphopenia. Ni accumulation increased renal iron content (by 49-78%) and resulted in elevated lipid peroxide (by 29%) and protein carbonyl content (by 274-278%), accompanied by suppression of the activities of superoxide dismutase (by 50-53%), glutathione peroxidase (15-45%), glutathione reductase (31-37%) and glucose-6-phosphate dehydrogenase (20-44%), indicating development of oxidative stress in kidney. In contrast to kidney, in spleen the activation of glutathione peroxidase (by 34-118%), glutathione-S-transferase (by 41-216%) and glutathione reductase (by 47%), as well as constant levels of low molecular mass thiols and metals together with enhanced activity of glucose-6-phosphate dehydrogenase (by 41-94%) speaks for a powerful antioxidant potential that counteracts Ni-induced ROS production. Further, as Ni accumulation in this organ was negligible, Ni-toxicity in spleen may be minimized by efficient exclusion of this otherwise toxic metal.

Differences in heavy metal concentrations and in the response of the antioxidant system to hypoxia and air exposure in the Antarctic limpet Nacella concinna.

During the austral spring and summer months, the Antarctic limpet Nacella concinna colonizes intertidal environments in the Western Antarctica Peninsula region. The species is divided into a permanently sub-littoral and a seasonally intertidal, migratory subpopulation. We investigate the physiological differentiation between the two limpet groups to identify cellular and molecular changes that accompany adaptation of stenothermal Antarctic invertebrates to life under more stressful intertidal habitat conditions. A major difference between the two groups is the significantly higher concentrations of heavy metals (Fe, Al, Zn) from ingested sediments in sub-littoral limpet digestive glands (DG), associated with higher rates of reactive oxygen species (ROS) formation in this organ. ROS formation is accompanied by significantly higher SOD activity in sub-littoral limpet DG. These high SOD activities are, however, not conserved during either air exposure or hypoxic stress exposure of the sub-littoral limpets, when ROS production is slowed due to the absence of oxygen. The intertidal animals maintain higher levels of SOD and also conserve catalase activity at higher levels during hypoxia or air exposure compared to sub-littoral individuals under the same exposure conditions. More oxidized redox potential in gills and foot muscle and higher antioxidant enzyme activities in gills indicate that intertidal limpets maintain more oxygenated tissues during air exposure, in keeping with shell-lifting for oxygen up-take by the gills of intertidal limpets which migrate up the shore in the spring and down in the autumn. An increase of the redox ratio (GSSG/GSH) and accumulation of the lipid oxidation derived malonedialdehyde in intertidal limpet foot muscle during 12h of exposure to air shows that indeed this tissue becomes more oxidized before the limpets eventually contract their shells tightly to minimize water loss and eventually become anaerobic. Intertidal limpets obviously avoid early onset of anaerobic energy production seen in their sub-littoral congeners when exposed to air and are still able to maintain tissue redox ratio balance when exposed to air.