Bioindicators Of Stress Research Articles

Assessment of hydrogen peroxide as a bioindicator of stress in seaweed aquaculture

The rapid expansion in commercial seaweed farming has highlighted the need for more effective monitoring methods, and health diagnostics. The production of the reactive oxygen species (ROS) hydrogen peroxide (H2O2) is a trait that is tied to all major macroalgal groups and holds significance both for its involvement in the oxidative stress response and in the production of climatically relevant gases such as halocarbons. Observations of increased production of H2O2 by plants as a stress response, along with its comparative stability and ease of quantification in seawater in comparison to other ROS, suggest that H2O2 could be used as an indicator of health. In this study we characterized aqueous H2O2 dynamics across a diel cycle, in response to small shifts in light and temperature, as well as when exposed to acute stress. Our results reveal that exposure to acute stressors leads to rapid and sustained concentrations of H2O2 that are orders of magnitude higher than changes in H2O2 concentrations observed throughout the day. These findings provide tantalizing evidence that monitoring H2O2 could be used as a health indicator in seaweed aquaculture and serve as an early warning sign of stress.

Season-dependent impact of forage quality on stress in alpine chamois.

Chronically heightened stress levels in wildlife species may have detrimental effects on individual life history traits, for example, through the increased likelihood of disease, parasitic infections, and overall reduced fitness. Understanding the drivers of stress may thus have great potential for informing wildlife conservation. Although the role of climate and individual status is well studied in stress ecology, the impact of related stressors such as dietary quality is of increasing interest to wildlife research and conservation. In this study, fecal cortisol metabolites (FCMs) in Alpine chamois Rupicapra r. rupicapra used as bioindicators of stress, and their relationship with forage quality-measured as the percentage of fecal crude protein (CP)-were investigated. Data collection took place in 2011 and 2012 in the Gran Paradiso National Park (Western Italian Alps), on 22 individually marked adult males. The relationship between FCMs and CPs was analyzed through linear models and separated between winter and summer months, accounting for the effect of potentially confounding exogenous and endogenous variables. After AICc-based model selection, we found that forage quality was negatively related to FCM levels in Alpine chamois during the summer months, meaning that higher quality forage was associated with the decreased expression of stress hormones. However, during the winter months, we did not find a significant relationship, potentially as a result of forage quality being ubiquitously poor. Although the mechanisms through which dietary variations impact FCM concentrations in wildlife populations are largely unknown, the occurrence of significant relationships between forage quality and stress levels supports potentially important implications for the long-term effect of climatic changes on the fitness of wildlife populations.

EFFECT OF AMLODIPINE ON MONOSODIUM GLUTAMATE-INDUCED CARDIAC OXIDATIVE STRESS IN RATS

Monosodium glutamate, MSG, induces oxidative stress which underlies many ailments including inflammation and heart dysfunctions. Amlodipine, AML, an anti-hypertensive could result to unknown effects on the cardiac oxidative function when co-taken with MSG. This study evaluated the effect of AML against experimental MSG-induced cardiac oxidative stress. Thus, rats orally and for 14 consecutive days received MSG (8000 mg/Kg/day). Cardiac oxidative stress bio-indicators: malondialdehyde, MDA, nitric oxide, NOX, glutathione peroxidase, GPX, superoxide dismutase, SOD, catalase, CAT, albumin, ALB, total protein, TP, magnesium, Mg, and zinc, Zn were determined. MSG significantly (p < 0.05) increased MDA and Zn but decreased others without altering NOX content compared to control rats in consistency with induction of cardiac oxidative stress in the rats. AML dose-dependently mitigated these MSG-induced oxidative effects. Thus, AML can protect against MSG-induced cardiac oxidative stress in the rats. Keywords: Monosodium glutamate, Amlodipine, Oxidative stress, Heart, Nitric oxide

Evaluation of Histopathological and Hematological Effects of Neonicotinoid (Acetamiprid 20% SP) on Grass Carp (Ctenopharyngodon idella)

Pesticides are usually used as an effective tool to control pests in agriculture; however, these chemicals may be a threat to nontarget organisms, especially aquatic organisms, because aquatic environments are the last station of pollutants. The present study evaluated the toxicity of a commercial formulation of neonicotinoid (acetamiprid 20% SP) as a systematic pesticide on the survival, hematology, and histology of the grass carp (Ctenopharyngodon idella). For these purposes, 105 fingerlings of the grass carp with an average body weight of 30 ± 2 g were exposed to 0, 50, 100, 150, and 200 mg·L−1 of acetamiprid for 96 h. According to the data, a clear mortality was observed as the concentration of acetamiprid elevated ( P < 0.01 ). The LC50 96 h of acetamiprid was 121.146 mg·L−1. The hematological parameters in fish changed, following exposure to acetamiprid ( P < 0.05 ). Also, a strong correlation was found between acetamiprid concentrations and stress bioindicators such as glucose, total protein, albumin, and cholesterol ( P < 0.01 ). There was not significant tissue damage in the control group (0 mg·L−1 of acetamiprid); however, acetamiprid led to tissues lesions such as hypertrophy, hyperplasia, uplifting of gill filaments, necrosis of gill epithelial cells, pyknosis and karyorrhexis of liver cells, and hemorrhage and necrosis of liver cell. Finally, acetamiprid-exposed fish exhibited some clinical signs including unbalanced swimming near the water surface, increasing operculum movement, and deaths with open-mouthed. The results of the present study clearly showed the survival-reducing effects of acetamiprid in C. Idella, which may return to tissue damage and stress induced by the pesticide. The results of the present study can be used as a base for future studies and environmental management.

The use of fecal cortisol for enrolment of free-roaming dogs in Singapore to a national rehabilitation-rehoming program: A possible indicator of allostasis

Singapore's trap-neuter-release-management program strives to rehome as many free-roaming dogs as possible. However, before rehoming, most free-roaming dogs require rehabilitation and this requires sheltering them for some time. Therefore, an individual's suitability for rehoming hinges on his or her adaptability to shelter conditions. Currently, this is being assessed qualitatively across behavioral contexts. Augmenting the current assessment with a known bioindicator of stress, such as cortisol, would increase its robustness. However, the serum measurement of cortisol can be invasive. Canine fecal samples have presented an attractive alternative for measuring cortisol indirectly in various contexts. Nevertheless, it is unclear whether the resolution of fecal cortisol metabolites (FCM) is sufficient for evaluating Singapore free-roaming dogs’ adaptability to shelter conditions. To elucidate this, we performed linear mixed-effects model on 27 candidate models to compare FCM between pet and recently sheltered dogs, with sex, state of the feces, and time as covariates. Subsequently, we ran generalized mixed-effected model on 12 candidate models to examine the influence of between- and within-subject variations in FCM on the prognosis of sheltered dogs—based on our current assessment. Our analyses showed that FCM levels of recently sheltered dogs were higher than pet individuals. However, unlike several studies, FCM concentrations of recently sheltered dogs continued to rise, indicating that individuals have yet to adapt. Furthermore, the difference in FCM levels between newly sheltered individuals and pet dogs was moderated by sex. Unexpectedly, we found the average FCM levels of dogs with a good prognosis to be higher than those that received a poor prognosis, with sex and state of the fecal samples as important covariates. This may be due to the difference in allostasis between the 2 groups of dogs. Thus, our results showed FCM not only has sufficient resolution but is useful in evaluating dogs’ adaptability to shelter conditions.

Characterizing the stress response in juvenile Delta smelt exposed to multiple stressors

The Delta Smelt (Hypomesus transpacificus), once an abundant fish endemic to the Sacramento-San Joaquin Estuary, is now on the brink of extinction. Due to the high sensitivity of this species, knowledge of their stress response will be vital to their future survival and sustainability. Understanding the magnitude and kinetics of cortisol induction in Delta Smelt will provide valuable information when interpreting the degree of environmentally relevant stressors, such as warming and predator exposure. As little is known about the primary stress response and cortisol dynamics in Delta Smelt, the first aim of this study was to measure basal and maximal whole-body cortisol prior to and following exposure to a sublethal and significant netting stress at 17 and 21 °C. Our findings reveal that juvenile Delta Smelt held at 21 °C display an exacerbated stress response and a reduction in available energy compared to fish held at 17 °C. There was no evidence of the secondary stress response to the netting stress as whole-body glucose and lactate levels in treatment groups remained similar to basal values. The second aim of this study was to investigate the effect of a largemouth bass (Micropterus salmoides) predator cue, which was found to induce a significant increase in cortisol relative to control levels in juvenile Delta Smelt. Indices such as cortisol can be used as bioindicators of stress in the field and results from this study suggest that moderate temperatures and reduced predation are optimal release conditions during hatchery-based supplementation to minimize stress to this highly sensitive species.

Assessing the effects of nickel on, e.g., Medicago sativa L. nodules using multidisciplinary approach.

Industrial wastes and fertilizers can introduce excessive levels of nickel (Ni) into the environment, potentially causing threats to plants, animals, as well as human beings. However, the number of studies on the effects of Ni toxicity on nodules is fairly limited. To address this issue, the effects of increasing Ni concentration on alfalfa nodules were assessed at chemical, biochemical, and transcriptomic levels. For this purpose, plants were grown in soils supplied with Ni (control, 0 mg/kg; C1, 50 mg/kg; C2, 150 mg/kg; C3, 250 mg/kg; and C4, 500 mg/kg) for 90 days. Ni loads in leaves, roots, and nodules were monitored after the exposure period. A set of biochemical biomarkers of oxidative stress was determined in nodules including antioxidants and metal homeostasis as well as lipid peroxidation. Gene expression levels of the main targets involved in oxidative stress and metal homeostasis were assessed. Our data indicated a high concentration of Ni in leaves, roots, and nodules where values reached 25.64 ± 3.04 mg/kg, 83.23 ± 5.16 mg/kg, and 125.71 ± 4.53 mg/kg in dry weight, respectively. Moreover, a significant increase in nodule biomass was observed in plants exposed to C4 in comparison to control treatment and percentage increased by 63%. Then, lipid peroxidation increased with a rate of 95% in nodules exposed to C4. Enzymatic activities were enhanced remarkably, suggesting the occurrence of oxidative stress, with increased superoxide dismutase (SOD), glutathione reductase (GR), and ascorbate peroxidase (APX). Our results showed also a significant upregulation of SOD, GR and APX genes in nodules. Nodule homoglutathione (HGSH) levels increased with the different Ni concentrations, with a remarkable decrease of glutathione S-transferase (GST) activity and glutathione (GSH) content for the highest Ni concentration with 43% and 52% reduction, respectively. The phytochelatin (PC) and metallothionein (MT) concentrations increased in nodules, which implied the triggering of a cellular protection mechanism for coping with Ni toxicity. The results suggested that Ni promotes a drastic oxidative stress in alfalfa nodules, yet the expression of MT and PC to reduce Ni toxicity could be used as Ni stress bioindicators. Our findings provide new insights into the central role of alfalfa nodules in limiting the harmful effects of soil pollution. Therefore, nodules co-expressing antioxidant enzymes may have high phytoremediation potential.

Context dependent variation in corticosterone and phenotypic divergence of Rana arvalis populations along an acidification gradient

BackgroundPhysiological processes, as immediate responses to the environment, are important mechanisms of phenotypic plasticity and can influence evolution at ecological time scales. In stressful environments, physiological stress responses of individuals are initiated and integrated via the release of hormones, such as corticosterone (CORT). In vertebrates, CORT influences energy metabolism and resource allocation to multiple fitness traits (e.g. growth and morphology) and can be an important mediator of rapid adaptation to environmental stress, such as acidification. The moor frog, Rana arvalis, shows adaptive divergence in larval life-histories and predator defense traits along an acidification gradient in Sweden. Here we take a first step to understanding the role of CORT in this adaptive divergence. We conducted a fully factorial laboratory experiment and reared tadpoles from three populations (one acidic, one neutral and one intermediate pH origin) in two pH treatments (Acid versus Neutral pH) from hatching to metamorphosis. We tested how the populations differ in tadpole CORT profiles and how CORT is associated with tadpole life-history and morphological traits.ResultsWe found clear differences among the populations in CORT profiles across different developmental stages, but only weak effects of pH treatment on CORT. Tadpoles from the acid origin population had, on average, lower CORT levels than tadpoles from the neutral origin population, and the intermediate pH origin population had intermediate CORT levels. Overall, tadpoles with higher CORT levels developed faster and had shorter and shallower tails, as well as shallower tail muscles.ConclusionsOur common garden results indicate among population divergence in CORT levels, likely reflecting acidification mediated divergent selection on tadpole physiology, concomitant to selection on larval life-histories and morphology. However, CORT levels were highly environmental context dependent. Jointly these results indicate a potential role for CORT as a mediator of multi-trait divergence along environmental stress gradients in natural populations. At the same time, the population level differences and high context dependency in CORT levels suggest that snapshot assessment of CORT in nature may not be reliable bioindicators of stress.

A biomonitoring study: Using the biomarkers in Cyprinus carpio for the evaluation of water pollution in Sapanca lake (Sakarya, Turkey)

This study aims to determine the toxic effects of heavy metal pollution on carp (Cyprinus carpio) in Sapanca Lake by biochemical and histological analyses. For this reason, fish and water samples were taken from the lake in 2015. Heavy metal (Cu, Fe, Zn, Pb, Cd) analyzes in the water column and tissues (muscle, liver, gill) were determined by ICP-OES. CAT, GSH and MDA levels, which are oxidative stress bioindicators in tissues, were measured by spectrophotometric methods. Histopathological findings in tissues were determined by Hematoxylin-Eosin staining. As a result, heavy metal concentrations in water were determined as Fe > Zn > Pb > Cu > Cd. The accumulation of Cu, Fe and Cd in the tissues of the fish were liver > gill > muscle, and the accumulation of Zn was gill > liver > muscle. CAT activity, MDA and GSH level of the tissues changed with the water temperature. General signs of destruction were observed in the gill tissues of the fish. Necrotic conditions in hepatocytes were observed. In conclusion, the presence of biochemical and histopathological findings in tissues suggests that the lake is not only affected by heavy metals but also by other pollutants.

Harmful effects of metal(loid) oxide nanoparticles.

The incorporation of nanomaterials (NMs), including metal(loid) oxide (MOx) nanoparticles (NPs), in the most diversified consumer products, has grown enormously in recent decades. Consequently, the contact between humans and these materials increased, as well as their presence in the environment. This fact has raised concerns and uncertainties about the possible risks of NMs to human health and the adverse effects on the environment. These concerns underline the need and importance of assessing its nanosecurity. The present review focuses on the main mechanisms underlying the MOx NPs toxicity, illustrated with different biological models: release of toxic ions, cellular uptake of NPs, oxidative stress, shading effect on photosynthetic microorganisms, physical restrain and damage of cell wall. Additionally, the biological models used to evaluate the potential hazardous of nanomaterials are briefly presented, with particular emphasis on the yeast Saccharomyces cerevisiae, as an alternative model in nanotoxicology. An overview containing recent scientific advances on cellular responses (toxic symptoms exhibited by yeasts) resulting from the interaction with MOx NPs (inhibition of cell proliferation, cell wall damage, alteration of function and morphology of organelles, presence of oxidative stress bio-indicators, gene expression changes, genotoxicity and cell dead) is critically presented. The elucidation of the toxic modes of action of MOx NPs in yeast cells can be very useful in providing additional clues about the impact of NPs on the physiology and metabolism of the eukaryotic cell. Current and future trends of MOx NPs toxicity, regarding their possible impacts on the environment and human health, are discussed.Key points• The potential hazardous effects of MOx NPs are critically reviewed.• An overview of the main mechanisms associated with MOx NPs toxicity is presented.• Scientific advances about yeast cell responses to MOx NPs are updated and discussed.

Drosophila melanogaster Response to Feeding with Neomycin-Based Medium Expressed in Fluctuating Asymmetry.

The fruit fly Drosophila melanogaster is a model species used for a wide range of studies. Contamination of Drosophila cultures with bacterial infection is common and is readily eradicated by antibiotics. Neomycin antibiotics can cause stress to D. melanogaster’s larvae and imagoes, which may affect the interpretation of the results of research using culture from neomycin-based medium. In the present study, fluctuating asymmetry (FA), one of the important bioindicators of stress, was measured. Larvae and imagoes of a wild-type D. melanogaster strain were exposed to various concentrations of neomycin. The size of anal papillae and selected wing veins were measured using scanning electron and light microscopy, respectively. Next, the FA was checked. The values obtained for larval anal papillae appeared to be concentration-dependant; the FA indices increased with the concentration of neomycin. The wing FA presented a large but variable correlation, depending on the measured vein. However, the mean length of veins was the highest for the control group, with neomycin-exposed groups showing lower values. The research showed that neomycin may cause sublethal stress in D. melanogaster, which manifests in increased FA indices. This suggests that neomycin can cause physiological and developmental stress in insects, which should be taken into account when interpreting the results of studies using these model organisms.

Increased Bacterial Richness Associated With Lesions Within the Porites spp. of Vietnam

Coral reefs worldwide are rapidly declining due to increasing anthropogenic stressors and environmental changes, with large-scale mortalities of coral reefs observed in many locations across the globe. It has become clear that the microbiome of corals is important in understanding the causes of coral infections, although its exact role is yet to be fully understood. Here, we characterize the bacteria and fungi associated with the non-lesional and lesional (identified by discoloration and tissue loss) tissues of coral species from Vietnam. Metabarcoding of the bacterial 16S rRNA gene and the fungal ITS rRNA gene region were performed. We sampled across two Porites species with potentially multiple causes of stresses, yet the bacterial compositions of lesional regions were consistently different from non-lesional areas of the same coral. These differences were driven by a considerable and significant increase in OTU richness within the lesional region compared to the non-lesional region. While no single OTU was consistently associated with lesional tissue, indicator analysis revealed that nine OTUs were significantly more persistent in the lesional regions that could represent useful bioindicators of stress. Meanwhile, there were no indicator OTUs in the non-lesional region. Further investigations are needed to determine whether changing bacterial communities play a mechanistic role in inducing lesioning, or are opportunistically colonizing stressed corals.

Antioxidant enzyme cycling over reproductive lunar cycles in Pocillopora damicornis.

The impacts of continued degradation of watersheds on coastal coral reefs world-wide is alarming, and action addressing anthropogenic stressors and subsequent rehabilitation of watersheds and adjacent reefs is an urgent priority. The aim of this study is to develop and improve the use of antioxidant enzymes as bioindicators of stress in coral species. In order to fully develop such tools, it is necessary to first understand baseline cycling of these enzymes within coral tissues. Due to inherent links between reproduction and oxidative stress, these aims may be facilitated by sampling coral tissues over reproductively-linked lunar cycles to determine variations from baseline. By developing a greater understanding of biochemical markers of stress in corals, specifically antioxidant defense enzymes catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), and superoxide dismutase (SOD) in Hawaiian Pocillopora damicornis, we have provided molecular tools that identify thresholds of stress on coral reefs. Our results suggest that the coral reproductive state is a significant factor affecting the activity of antioxidant enzymes. Specifically, CAT and GR display maximum activity during peak reproductive state. Whereas significant maximal Se-independent GPx and SOD activity was measured during off-peak reproductive cycles. Such insight into the cyclical variation of the activity of these enzymes should be applied towards differentiating the influence of natural biological activity cycling in diagnostic tests identifying the effects of different physical environmental factors and chemical pollutants on coral health. Through the development and application of these molecular biomarkers of stress, we look to improve our ability to identify problems at the sub-lethal level, when action can be taken to mitigate a/biotic impacts.

Juvenile Oblada melanura (L. 1758) otolith shape variation as an early environmental indicator

Abstract Coasts are increasingly subject to the pressure of human activities, thus bioindicators of stress are also becoming necessary. We tested whether the otolith shape of Oblada melanura juveniles could be used as indicator of anthropic impacts. Otolith shapes, defined by Fourier elliptic analysis, were compared using canonical analysis of principal coordinates. In this three-year study, we compared two geographically close sites: one with low-level pollution and one near a recreational harbour. Determining the minimum fish standard length at which the influence of fish size on otolith shape does not occult other influences, 11 mm in this study, is a prerequisite for the study of otolith shape variation in juveniles. Inter-annual environmental variations interfere with local conditions and delays between samplings are also important considerations. We have demonstrated that the comparison of O. melanura juvenile otolith shape is an effective method to compare the short-term influence of different environmental conditions.

Augmenting fish health usingEmblica officinalisagainst triarylmethane dye induced blood toxicity inCyprinus carpio

Blood is a sensitive bioindicator of stress observed by organisms in response to toxicants. Erythrocytic morphological abnormalities serve as a reliable determinant of fish health. Malachite green, a multifunctional dye was assessed for toxicity in Cyprinus carpio. Dye-induced blood toxicity has been determined through biochemical and ultra structural endpoints at 15, 30 and 60 days in the fish. Further, an attempt has been made to combat the adverse effects of the toxicant through supplementation with Emblica officinalis. Electron microscopic study depicted erythrocytic remodelling in form of surface blebbing, lobopodial projections and shrinkage; appearance of crenate, acanthocytes, echinocytes, dacrocytes, spherocytes and rhomboidal cells. Hepatic marker enzymes showed significantly (p < 0.05) elevated levels of biomarker enzymes, alkaline phosphatase, serum glutamate oxaloacetate transaminase and serum glutamate pyruvate transaminase. Contrarily feeding with E. officinalis extract (1,000 mg/kg feed) significantly attenuated biochemical and morphological alterations, indicating the protective efficacy of E. officinalis. Both toxicity and attenuation observed were in exposure-dependent manner.

Sublethal Effects of Solanum nigrum Fruit Extract and Its Pure Glycoalkaloids on the Physiology of Tenebrio molitor (Mealworm).

Background: Solanaceae plants produce glycoalkaloids (GAs) that affect various physiological processes of herbivorous insects and they are being tested as potential alternatives for synthetic pesticides. They cause lethal and sublethal effects. Nevertheless, their mode of action remains unclear. Therefore, we examined the effects of Solanum nigrum fruit extracts and pure glycoalkaloids on a model beetle, Tenebrio molitor. Methods: Plant extracts or pure alkaloids were added to the food of the larvae for three days. The lipid, glycogen, and protein content in the fat body and the midgut were determined, and the contractility of the heart, hindgut, and oviduct muscles was tested using the video-microscopy technique. Finally, the ultrastructure of the fat body and the midgut was observed using electron microscopy. Results: No lethal effects were noted. Sublethal changes were observed in the content of biomolecules, malformations of organelles, chromatin condensation, and heart and oviduct contractility. The observed effects differed between the tested glycoalkaloids and the extract. Conclusions: Both the extract and pure GAs have a wide range of effects that may result in impaired development, food intake, and reproduction. Some early effects may be used as bioindicators of stress. The effects of the extract and pure alkaloids suggest that the substances produced by the plant may act additively or synergistically.

Fecal cortisol metabolites under anonymized sampling: Robust estimates despite significant individual heterogeneity

The levels of fecal cortisol metabolites (FCMs) are widely used as bioindicators of stress in wildlife studies. Although FCMs allow to assess the impact of ecological and physiological stressors through anonymous scat sampling, recent studies have highlighted the importance of accounting for individual heterogeneity to deal with pseudoreplication and obtain robust parameter estimates. It has been suggested that repeatable among-individual differences in the levels of FCMs may be the result of selective pressures. If so, species-specific variations in the level of heterogeneity in glucocorticoid secretion may occur, possibly bearing contrasting consequences on parameter estimates when fecal sampling is carried out anonymously. I used data collected on individually identified male chamois Rupicapra rupicapra in Gran Paradiso National Park (Western Italian Alps) in 2011 and 2012, to study the importance of individual heterogeneity on the variation of FCM levels in response to several biotic and abiotic stressors over different periods, and to evaluate the robustness of parameter estimates under anonymized (pseudoreplicated) data collection. The importance of individual heterogeneity varied conspicuously with life history stages, with the highest individual variation in FCM values occurring in the mating season. Despite widespread significant individual heterogeneity, parameter estimates under different sampling designs were consistently similar, suggesting that the lack of individual information does not always preclude the possibility to obtain valuable indications of the impact of ecological stressors on populations using FCM levels. The consequences of neglecting pseudoreplication when evaluating FCM levels may thus vary with species- or study-specific features. While identifiable sampling is always desirable to obtain robust estimates of stressors’ impacts through FCMs, researchers should carefully evaluate the costs and benefits of retrieving individual information, possibly based on individual sampling frequency, variance explained by biotic and abiotic predictors, target species and period of sampling.

Use of earthworms Eisenia andrei on the bioremediation of contaminated area in north of Tunisia and microbial soil enzymes as bioindicator of change on heavy metals speciation

A better understanding is required of the potential of soil biota in controlling the availability and mobility of heavy metals and ascertaining their toxicity. The objectives of this work are to assess, first, the modification of heavy metal speciation induced by earthworms Eisenia andrei and, second, the consequence of this metal speciation change on soil enzyme activities as an easy bioindicator of stress. The experiment was conducted on six sites from Jebel Ressas Mines, which are characterized by a gradient heavy metal contamination (Pb, Zn, and Cd). Earthworms E. andrei were introduced in these six soils for 60 days. We had performed heavy metal speciation both in the presence and absence of worms. Modifications of activities of seven enzymes implicated in C, N, and P biochemical cycles were used as a bioindicator of metal stress. We had used the co-inertia statistical method to evaluate the correlation between change in heavy metal speciation induced by earthworms and the enzyme activities in soils. Our results suggested that earthworms modified the heavy metal dynamic and speciation. They decrease the amount of metal associated with the most available fraction, such as exchangeable one, and increase the amount of metal bound to the more stable fraction, like Mn and Fe oxide ones. On the same hand, enzyme activities increased in majority of the soils, following earthworm activity, but this effect is dependent on the amount of soil contamination. Moreover, the co-inertia results denote that change in heavy metal speciation significantly influences the soil enzyme activities in Jebel Ressas soils, especially β-glucosidase, urease, deshydrogenase, and fluorescein diacetate hydrolysis (FDA), and can be considered as bioindicators of metal toxicity and biological quality in the contaminated area. By reducing the availability of heavy metals, the earthworms are useful in the bioremediation of heavy metal contaminated soils. Soil enzymes β- glucosidase, urease, deshydrogenase, and FDA can be used to assess the changes in metal speciation and can let us, therefore, predict if the soils are bioremediated.

Fluctuating asymmetry as bioindicator of stress and developmental instability in Perna viridis (Asian Green Mussel) from the coastal areas in Northern Mindanao, Philippines

Fluctuating asymmetry as bioindicator of stress and developmental instability in Perna viridis (Asian Green Mussel) from the coastal areas in Northern Mindanao, Philippines

Dietary supplementation of heat-treated Gracilaria and Ulva seaweeds enhanced acute hypoxia tolerance in gilthead sea bream (Sparus aurata).

ABSTRACTIntensive aquaculture practices involve rearing fish at high densities. In these conditions, fish may be exposed to suboptimal dissolved O2 levels with an increased formation of reactive O2 species (ROS) in tissues. Seaweeds (SW) contain biologically active substances with efficient antioxidant capacities. This study evaluated the effects of dietary supplementation of heat-treated SW (5% Gracilaria vermiculophylla or 5% Ulva lactuca) on stress bioindicators in sea bream subjected to a hypoxic challenge. 168 fish (104.5 g average weight) were distributed in 24 tanks, in which eight tanks were fed one of three experimental diets for 34 days: (i) a control diet without SW supplementation, (ii) a control diet supplemented with Ulva, or (iii) a control diet with Gracilaria. Thereafter, fish from 12 tanks (n=4 tanks/dietary treatment) were subjected to 24 h hypoxia (1.3 mg O2 l−1) and subsequent recovery normoxia (8.6 mg O2 l−1). Hypoxic fish showed an increase in hematocrit values regardless of dietary treatment. Dietary modulation of the O2-carrying capacity was conspicuous during recovery, as fish fed SW supplemented diets displayed significantly higher haemoglobin concentration than fish fed the control diet. After the challenge, survival rates in both groups of fish fed SW were higher, which was consistent with a decrease in hepatic lipid peroxidation in these groups. Furthermore, the hepatic antioxidant enzyme activities were modulated differently by changes in environmental O2 condition, particularly in sea bream fed the Gracilaria diet. After being subjected to hypoxia, the gene expression of antioxidant enzymes and molecular chaperones in liver and heart were down regulated in sea bream fed SW diets. This study suggests that the antioxidant properties of heat-treated SW may have a protective role against oxidative stress. The nature of these compounds and possible mechanisms implied are currently being investigated.