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Sökning: WFRF:(Gorokhova Elena)

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1.
  • Gorokhova, Elena, et al. (författare)
  • Nucleic acid levels in copepods : dynamic response to phytoplankton blooms in the northern Baltic proper
  • 2007
  • Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 349, s. 213-225
  • Tidskriftsartikel (refereegranskat)abstract
    • We examined changes in nucleic acids and concomitant population development of the copepods Acartia bifilosa and Eurytemora affinis in relation to the progress of the phytoplankton spring bloom in the northern Baltic proper. Individual RNA and DNA concentrations and their ratios in female copepods as well as copepod abundance and population structure were analyzed in 2 coastal areas that differed in the degree of eutrophication and phytoplankton development. During the study period (February to June 2002), bloom conditions were evident, with chlorophyll (chl) a values being 42% higher in the eutrophic area than in the reference area. In both areas, diatoms dominated; in the reference area, they were replaced by dinoflagellates toward the end of the bloom. Copepod RNA-DNA concentrations increased rapidly at the onset of the bloom and gradually decreased thereafter. Moreover, in the eutrophic area, both copepods had higher RNA content and RNA:DNA ratios throughout the study period, suggesting higher productivity in this area. In both species, we found positive correlations between RNA-based indices and chl a. Thus, as suggested by RNA dynamics, growth rates of A. bifilosa and E. affinis appear to respond rapidly to both temporal variation in spring phytoplankton stock and spatial variation due to the magnitude of the bloom. In addition, we found that species-specific RNA dynamics and RNA-chl a relationships differed between species, indicating possible differences in feeding preferences and growth potential.
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2.
  • Abel, Sebastian, 1988-, et al. (författare)
  • Chemical Activity-Based Loading of Artificial Sediments with Organic Pollutants for Bioassays : A Proof of Concept
  • 2024
  • Ingår i: Environmental Toxicology and Chemistry. - 0730-7268 .- 1552-8618. ; 43:2, s. 279-287
  • Tidskriftsartikel (refereegranskat)abstract
    • Persistent organic pollutants (POPs) pose a risk in aquatic environments. In sediment, this risk is frequently evaluated using total or organic carbon-normalized concentrations. However, complex physicochemical sediment characteristics affect POP bioavailability in sediment, making its prediction a challenging task. This task can be addressed using chemical activity, which describes a compound's environmentally effective concentration and can generally be approximated by the degree of saturation for each POP in its matrix. We present a proof of concept to load artificial sediments with POPs to reach a target chemical activity. This approach is envisioned to make laboratory ecotoxicological bioassays more reproducible and reduce the impact of sediment characteristics on the risk assessment. The approach uses a constantly replenished, saturated, aqueous POP solution to equilibrate the organic carbon fraction (e.g., peat) of an artificial sediment, which can be further adjusted to target chemical activities by mixing with clean peat. We demonstrate the applicability of this approach using four polycyclic aromatic hydrocarbons (acenaphthene, fluorene, phenanthrene, and fluoranthene). Within 5 to 17 weeks, the peat slurry reached a chemical equilibrium with the saturated loading solution. We used two different peat batches (subsamples from the same source) to evaluate the approach. Variations in loading kinetics and eventual equilibrium concentrations were evident between the batches, which highlights the impact of even minor disparities in organic carbon properties within two samples of peat originating from the same source. This finding underlines the importance of moving away from sediment risk assessments based on total concentrations. The value of the chemical activity-based loading approach lies in its ability to anticipate similar environmental impacts, even with varying contaminant concentrations. 
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3.
  • Andersson, Agneta, et al. (författare)
  • Microbial food web changes induced by terrestrial organic matter and elevated temperature in the coastal northern Baltic Sea
  • 2023
  • Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change has been projected to cause increased temperature and amplified inflows of terrestrial organic matter to coastal areas in northern Europe. Consequently, changes at the base of the food web favoring heterotrophic bacteria over phytoplankton are expected, affecting the food web structure. We tested this hypothesis using an outdoor shallow mesocosm system in the northern Baltic Sea in early summer, where the effects of increased temperature (+ 3°C) and terrestrial matter inputs were studied following the system dynamics and conducting grazing experiments. Juvenile perch constituted the highest trophic level in the system, which exerted strong predation on the zooplankton community. Perch subsequently released the microbial food web from heavy grazing by mesozooplankton. Addition of terrestrial matter had a stronger effect on the microbial food web than the temperature increase, because terrestrial organic matter and accompanying nutrients promoted both heterotrophic bacterial production and phytoplankton primary production. Moreover, due to the shallow water column in the experiment, terrestrial matter addition did not reduce the light below the photosynthesis saturation level, and in these conditions, the net-autotrophy was strengthened by terrestrial matter enrichment. In combination with elevated temperature, the terrestrial matter addition effects were intensified, further shifting the size distribution of the microbial food web base from picoplankton to microphytoplankton. These changes up the food web led to increase in the biomass and proportion of large-sized ciliates (>60 µm) and rotifers. Despite the shifts in the microbial food web size structure, grazing experiments suggested that the pathway from picoplankton to nano- and microzooplankton constituted the major energy flow in all treatments. The study implies that the microbial food web compartments in shallow coastal waters will adjust to climate induced increased inputs of terrestrial matter and elevated temperature, and that the major energy path will flow from picoplankton to large-sized ciliates during the summer period. 
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4.
  • Andriukonis, Eivydas, et al. (författare)
  • Kinetic N-15-isotope effects on algal growth
  • 2017
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Stable isotope labeling is a standard technique for tracing material transfer in molecular, ecological and biogeochemical studies. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism metabolism and growth, which is not consistent with current theoretical and empirical knowledge on kinetic isotope effects. Here, we demonstrate profound changes in growth dynamics of the green alga Raphidocelis subcapitata grown in N-15-enriched media. With increasing N-15 concentration (0.37 to 50 at%), the lag phase increased, whereas maximal growth rate and total yield decreased; moreover, there was a negative relationship between the growth and the lag phase across the treatments. The latter suggests that a trade-off between growth rate and the ability to adapt to the high N-15 environment may exist. Remarkably, the lag-phase response at 3.5 at% N-15 was the shortest and deviated from the overall trend, thus providing partial support to the recently proposed Isotopic Resonance hypothesis, which predicts that certain isotopic composition is particularly favorable for living organisms. These findings confirm the occurrence of KIE in isotopically enriched algae and underline the importance of considering these effects when using stable isotope labeling in field and experimental studies.
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5.
  • Berglund, Åsa M. M., 1978-, et al. (författare)
  • Effects on the food-web structure and bioaccumulation patterns of organic contaminants in a climate-altered Bothnian Sea mesocosms
  • 2023
  • Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change is expected to alter global temperature and precipitation patterns resulting in complex environmental impacts. The proposed higher precipitation in northern Scandinavia would increase runoff from land, hence increase the inflow of terrestrial dissolved organic matter (tDOM) in coastal regions. This could promote heterotrophic bacterial production and shift the food web structure, by favoring the microbial food web. The altered climate is also expected to affect transport and availability of organic micropollutants (MPs), with downstream effects on exposure and accumulation in biota. This study aimed to assess climate-induced changes in a Bothnian Sea food web structure as well as bioaccumulation patterns of MPs. We performed a mesocosms-study, focusing on aquatic food webs with fish as top predator. Alongside increased temperature, mesocosm treatments included tDOM and MP addition. The tDOM addition affected nutrient availability and boosted both phytoplankton and heterotrophic bacteria in our fairly shallow mesocosms. The increased tDOM further benefitted flagellates, ciliates and mesozooplankton, while the temperature increase and MP addition had minor effect on those organism groups. Temperature, on the other hand, had a negative impact on fish growth and survival, whereas tDOM and MP addition only had minor impact on fish. Moreover, there were indications that bioaccumulation of MPs in fish either increased with tDOM addition or decreased at higher temperatures. If there was an impact on bioaccumulation, moderately lipophilic MPs (log Kow 3.6 - 4.6) were generally affected by tDOM addition and more lipophilic MPs (log Kow 3.8 to 6.4) were generally affected by increased temperature. This study suggest that both increased temperatures and addition of tDOM likely will affect bioaccumulation patterns of MPs in shallow coastal regions, albeit with counteracting effects.
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6.
  • Bighiu, Maria Alexandra, et al. (författare)
  • Metal contamination in harbours impacts life-history traits and metallothionein levels in snails
  • 2017
  • Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 12:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Harbours with limited water exchange are hotspots of contaminant accumulation. Antifouling paints (AF) contribute to this accumulation by leaching biocides that may affect non-target species. In several leisure boat harbours and reference areas in the Baltic Sea, chronic exposure effects were evaluated using caging experiments with the snail Theodoxus fluviatilis. We analysed variations in ecologically relevant endpoints (mortality, growth and reproduction) in concert with variation in metallothionein-like proteins (MTLP) levels. The latter is a biomarker of exposure to metals, such as copper (Cu) and zinc (Zn), which are used in AF paints as active ingredient and stabilizer, respectively. In addition, environmental samples (water, sediment) were analysed for metal (Cu and Zn) and nutrient (total phosphorous and nitrogen) concentrations. All life-history endpoints were negatively affected by the exposure, with higher mortality, reduced growth and lower fecundity in the harbours compared to the reference sites. Metal concentrations were the key explanatory variables for all observed adverse effects, suggesting that metal-driven toxicity, which is likely to stem from AF paints, is a source of anthropogenic stress for biota in the harbours.
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8.
  • Breitholtz, Magnus, et al. (författare)
  • Calmodulin inhibition as a mode of action of antifungal imidazole pharmaceuticals in non-target organisms
  • 2020
  • Ingår i: Toxicology Research. - : Oxford University Press (OUP). - 2045-452X .- 2045-4538. ; 9:4, s. 425-430
  • Tidskriftsartikel (refereegranskat)abstract
    • To improve assessment of risks associated with pharmaceutical contamination of the environment, it is crucial to understand effects and mode of action of drugs in non-target species. The evidence is accumulating that species with well-conserved drug targets are prone to be at risk when exposed to pharmaceuticals. An interesting group of pharmaceuticals released into the environment is imidazoles, antifungal agents with inhibition of ergosterol synthesis as a primary mode of action in fungi. However, imidazoles have also been identified as competitive antagonists of calmodulin (CaM), a calcium-binding protein with phylogenetically conserved structure and function. Therefore, imidazoles would act as CaM inhibitors in various organisms, including those with limited capacity to synthesize sterols, such as arthropods. We hypothesized that effects observed in crustaceans exposed to imidazoles are related to the CaM inhibition and CaM-dependent nitric oxide (NO) synthesis. To test this hypothesis, we measured (i) CaM levels and its gene expression, (ii) NO accumulation and (iii) gene expression of NO synthase (NOS1 and NOS2), in the cladoceran Daphnia magna exposed to miconazole, a model imidazole drug. Whereas significantly increased CaM gene expression and its cellular allocation were observed, supporting the hypothesized mode of action, no changes occurred in either NO synthase expression or NO levels in the exposed animals. These findings suggest that CaM inhibition by miconazole leads to protein overexpression that compensates for the loss in the protein activity, with no measurable downstream effects on NO pathways. The inhibition of CaM in D. magna may have implications for effect assessment of exposure to mixtures of imidazoles in aquatic non-target species.
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9.
  • Brutemark, Andreas, et al. (författare)
  • Growth, toxicity and oxidative stress of a cultured cyanobacterium (Dolichospermum sp.) under different CO2/pH and temperature conditions
  • 2015
  • Ingår i: Phycological Research. - : Wiley. - 1322-0829 .- 1440-1835. ; 63:1, s. 56-63
  • Tidskriftsartikel (refereegranskat)abstract
    • Cyanobacteria blooms are a worldwide nuisance in fresh, brackish and marine waters. Changing environmental conditions due to upwelling, changed mixing conditions or climate change are likely to influence cyanobacteria growth and toxicity. In this study, the response of the toxic cyanobacterium Dolichospermum sp. to lowered pH (-0.4 units by adding CO2) and elevated temperature (+4 degrees C) in an experimental set-up was examined. Growth rate, microcystin concentration and oxidative stress were measured. The growth rate and intracellular toxin concentration increased significantly as a response to temperature. When Dolichospermum was exposed to the combination of elevated temperature and high CO2/low pH, lipid peroxidation increased and antioxidant levels decreased. Microcystin concentrations were significantly correlated with growth rates. Our results show, although oxidative stress increases when exposed to a combination of high CO2/low pH and high temperature, that growth and toxicity increase at high temperature, suggesting that the cyanobacterium in general seems to be fairly tolerant to changes in pH and temperature. Further progress in identifying biological responses and predicting climate change consequences in estuaries experiencing cyanobacteria blooms requires a better understanding of the interplay between stressors such as pH and temperature.
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10.
  • Calliari, Danilo, 1969, et al. (författare)
  • Instantaneous salinity reductions affect the survival and feeding rates of the co-occurring copepods Acartia tonsa Dana and A-clausi Giesbrecht differently
  • 2008
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 362:1, s. 18-25
  • Tidskriftsartikel (refereegranskat)abstract
    • Salinity variability at short time scales constitutes a severe restriction to marine life in coastal and estuarine ecosystems. In these environments zooplankters may experience rapid salinity variations due to diverse processes, yet lethal or sub-lethal responses to such changes have been scarcely studied. We assessed short-term (12 h) survival and time-integrated clearance (F; mL ind(-1) h(-1)) and ingestion rates (1, mu gC ind(-1) h(-1)) after 1, 2, 4, 8 and 12 h of two widespread and abundant coastal copepods, Acartia tonsa and A. clausi, subjected to instant salinity changes from 32 PSU to 26, 20,14, 8 and 4 PSU (A. tonsa) and from 32 to 26, 20 and 14 PSU (A. clausi). We expected that A. tonsa, which occur naturally in environments where sharp salinity gradients are common would tolerate wider salinity changes than A. clausi, which less frequently encounter sharp gradients in nature. For A. tonsa mortality for the extreme haline shock (change from 32 to 4 PSU) was 31%, whereas A. clausi reached 22% Mortality already at a change from 32 to 14 PSU; in comparison, mortality for A. tonsa at the 32/14 PSU treatment was only 3%. F and I decreased significantly at extreme treatments, and the total clearance in experimental bottles with salinity shocked animals (F-tot, mL h(-1)) was only 5% of rates measured in non-shocked control bottles for A. tonsa (32/4 PSU change) and 20% for A. clausi (32/14 PSU change); corresponding total ingestion (I-tot, mu gC h(-1)) represented 9.5% of that in control bottles for A. tonsa and 24% for A. clausi. In comparison, the 32/14 PSU treatment did not affect either clearance or ingestion rates in A. tonsa. Results suggest that in the field A. tonsa is not likely to suffer significant mortalities due to sudden salinity reductions in the Surrounding medium - except under extreme circumstances- while A. clausi cannot tolerate changes > 18 PSU. However, in both species feeding activity could be severely compromised by salinity reductions. The decreased feeding rate may have direct implications for processes ranging from energy acquisition at individual level to organic matter transfers at ecosystem level and thus deserves more attention in experimental studies and population modelling. (C) 2008 Elsevier B.V. All rights reserved.
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12.
  • Castro, Mafalda (författare)
  • Chlorinated Paraffins: improved understanding of their bioaccumulation and toxicity in Daphnia magna
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Chlorinated paraffins (CPs) are industrial chemicals, mainly used as flame retardants, plasticizers and metal cutting fluids. Their production has reached historically high levels in the last decade, with an annual production exceeding one million tonnes. In 2017, short chain chlorinated paraffins (SCCPs) were regulated due to their Persistent, Bioaccumulative and Toxic (PBT) properties, while medium and long chain chlorinated paraffins (MC and LCCPs) were suggested as alternatives. The high hydrophobicity of CPs, which complicates bioaccumulation and aquatic toxicity testing, has hindered proper hazard identification by regulatory authorities. This project was initiated in response to the insufficient understanding of bioaccumulative and toxicological properties of these chemicals, which have even surpassed the environmental levels of legacy Persistent Organic Pollutants (POPs) in certain regions.The research presented in this thesis, contributes to filling these knowledge gaps by adapting methods for reliable bioaccumulation and aquatic toxicity assessment. In Paper I, passive dosing, traditionally used for other highly hydrophobic compounds, was adapted and validated for CPs. SC, MC and LCCPs partitioned from silicone into water and, when the crustacean Daphnia magna was introduced into the test system, the CPs were observed to be effectively taken up by the test organism. This passive-dosing approach was further used in Paper II, to investigate the bioconcentration and bioaccumulation potential in D. magna. All tested CPs were found to bioaccumulate in daphnids, including highly hydrophobic, long chained CP congeners. The two most bioaccumulative CPs in Paper II (CP-52 and Huels70C) were thereafter used in a chronic toxicity study (Paper III) and significantly decreased population growth and disrupted fatty acid metabolism of D. magna. Finally, in Paper IV, liposome-mediated delivery of chemicals to aquatic biota was adapted for the first time for organic contaminants, including CPs. This approach yielded stable body burdens of the tested chemicals in D. magna and allowed for kinetic and toxicity assessments.Overall, two alternative bioaccumulation and aquatic toxicity testing methods were successfully adapted for technically challenging (industrial) chemicals. These methods allowed the determination of endpoints of scientific and regulatory interest, such as the high bioaccumulation and toxicity potential of CPs, but were also used to demonstrate their metabolic disruption potential in small crustaceans. 
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13.
  • Christiansen, Sigurd, et al. (författare)
  • Influence of Arctic Microlayers and Algal Cultures on Sea Spray Hygroscopicity and the Possible Implications for Mixed-Phase Clouds
  • 2020
  • Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-8996 .- 2169-897X. ; 125:19
  • Tidskriftsartikel (refereegranskat)abstract
    • As Arctic sea ice cover diminishes, sea spray aerosols (SSA) have a larger potential to be emitted into the Arctic atmosphere. Emitted SSA can contain organic material, but how it affects the ability of particles to act as cloud condensation nuclei (CCN) is still not well understood. Here we measure the CCN-derived hygroscopicity of three different types of aerosol particles: (1) Sea salt aerosols made from artificial seawater, (2) aerosol generated from artificial seawater spiked with diatom species cultured in the laboratory, and (3) aerosols made from samples of sea surface microlayer (SML) collected during field campaigns in the North Atlantic and Arctic Ocean. Samples are aerosolized using a sea spray simulation tank (plunging jet) or an atomizer. We show that SSA containing diatom and microlayer exhibit similar CCN activity to inorganic sea salt with a κ value of ∼1.0. Large-eddy simulation (LES) is then used to evaluate the general role of aerosol hygroscopicity in governing mixed-phase low-level cloud properties in the high Arctic. For accumulation mode aerosol, the simulated mixed-phase cloud properties do not depend strongly on κ, unless the values are lower than 0.4. For Aitken mode aerosol, the hygroscopicity is more important; the particles can sustain the cloud if the hygroscopicity is equal to or higher than 0.4, but not otherwise. The experimental and model results combined suggest that the internal mixing of biogenic organic components in SSA does not have a substantial impact on the cloud droplet activation process and the cloud lifetime in Arctic mixed-phase clouds.
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14.
  • Christiansen, Sigurd, et al. (författare)
  • Sea Spray Aerosol Formation : Laboratory Results on the Role of Air Entrainment, Water Temperature, and Phytoplankton Biomass
  • 2019
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:22, s. 13107-13116
  • Tidskriftsartikel (refereegranskat)abstract
    • Sea spray aerosol (SSA) emission is a complex process affected by various controlling factors. This work seeks to deconvolute some of this complexity in a controlled laboratory setting using a plunging jet by varying three key parameters, one at a time: (1) air entrainment rate, (2) seawater temperature, and (3) biomass of phytoplankton. The production of SSA is found to vary linearly with air entrainment rate. By normalizing the production flux to air entrainment rate, we observe nonlinear variation of the production efficiency of SSA with seawater temperature with a minimum around 6-10 degrees C. For comparison, SSA was also generated by detraining air into artificial seawater using a diffuser demonstrating that the production efficiency of SSA generated using a diffuser decreases almost linearly with increasing seawater temperature, and the production efficiency is, significantly higher than that for SSA generated using a plunging jet. Finally, by varying the amount of phytoplankton biomass we demonstrate that SSA particle production varies nonlinearly with the amount of biomass in seawater.
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16.
  • Coll, Claudia, et al. (författare)
  • Association between Aquatic Micropollutant Dissipation and River Sediment Bacterial Communities
  • 2020
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:22, s. 14380-14392
  • Tidskriftsartikel (refereegranskat)abstract
    • Assessment of micropollutant biodegradation is essential to determine the persistence of potentially hazardous chemicals in aquatic ecosystems. We studied the dissipation half-lives of 10 micropollutants in sediment–water incubations (based on the OECD 308 standard) with sediment from two European rivers sampled upstream and downstream of wastewater treatment plant (WWTP) discharge. Dissipation half-lives (DT50s) were highly variable between the tested compounds, ranging from 1.5 to 772 days. Sediment from one river sampled downstream from the WWTP showed the fastest dissipation of all micropollutants after sediment RNA normalization. By characterizing sediment bacteria using 16S rRNA sequences, bacterial community composition of a sediment was associated with its capacity for dissipating micropollutants. Bacterial amplicon sequence variants of the genera Ralstonia, Pseudomonas, Hyphomicrobium, and Novosphingobium, which are known degraders of contaminants, were significantly more abundant in the sediment incubations where fast dissipation was observed. Our study illuminates the limitations of the OECD 308 standard to account for variation of dissipation rates of micropollutants due to differences in bacterial community composition. This limitation is problematic particularly for those compounds with DT50s close to regulatory persistence criteria. Thus, it is essential to consider bacterial community composition as a source of variability in regulatory biodegradation and persistence assessments.
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17.
  • Dahl, Ulrika, et al. (författare)
  • Food quality effects on copepod growth and development : Implications for bioassays in ecotoxicological testing
  • 2009
  • Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier Inc. - 0147-6513 .- 1090-2414. ; 72:2, s. 351-357
  • Tidskriftsartikel (refereegranskat)abstract
    • We evaluated effects of six algal species in 25 combinations on growth and reproduction of the harpacticoid copepod Nitocra spinipes. In the first lifecycle test, Rhodomonas salina, Phaeodactylum tricornutum, and Dunaliella tertiolecta were used. The results showed that R. salina was the best food, whereas P. tricornutum (0% development success) and D. tertiolecta (41.7% malformations) were poor food items. In the second lifecycle test, a mixture of R. salina, Tetraselmis suecica, and Thalassiosira weisflogii (selected from screening tests) was tested together with a mono-diet of R. salina. Also in this test, copepods fed R. salina performed better (i.e. had higher survival and reproductive success) compared with the other treatment. We conclude that R. salina is appropriate to use as food in toxicity testing with N. spinipes, whereas some of the algae commonly used as feed in ecotoxicological tests with other copepods had detrimental effects on the development, reproduction, and survival of N. spinipes.
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18.
  • Edlund, Anna, et al. (författare)
  • Antibiotic-Induced Change of Bacterial Communities Associated with the Copepod Nitocra spinipes
  • 2012
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:3, s. e33107-
  • Tidskriftsartikel (refereegranskat)abstract
    • Environmental pressures, such as physical factors, diet and contaminants may affect interactions between microbial symbionts and their multicellular hosts. Despite obvious relevance, effects of antimicrobial contaminants on host-symbiont relations in non-target aquatic organisms are largely unknown. We show that exposure to antibiotics had negative effects on survival and juvenile development of the copepod Nitocra spinipes and caused significant alterations in copepod-associated bacterial communities. The significant positive correlations between indices of copepod development and bacterial diversity indicate that disruption of the microflora was likely to be an important factor behind retarded juvenile development in the experimental animals. Moreover, as evidenced by ribotype distribution in the bacterial clone libraries, the exposure to antibiotics caused a shift in dominance from Betaproteobacteria to Cardinium bacteria; the latter have been shown to cause reproductive manipulations in various terrestrial arthropods. Thus, in addition to providing evidence that the antibiotic-induced perturbation of the microbial community associates with reductions in fitness-related traits of the host, this study is the first record of a copepod serving as a host for endosymbiotic Cardinium. Taken together, our results suggest that (1) antimicrobial substances and possibly other stressors can affect micobiome and symbiont-mediated interactions in copepods and other hosts, and (2) Cardinium endosymbionts may occur in other copepods and affect reproduction of their hosts.
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19.
  • Ek, Caroline, et al. (författare)
  • Growth Retardation and Altered Isotope Composition As Delayed Effects of PCB Exposure in Daphnia magna
  • 2016
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 50:15, s. 8296-8304
  • Tidskriftsartikel (refereegranskat)abstract
    • Trophic magnification factor (TMF) analysis employs stable isotope signatures to derive biomagnification potential for environmental contaminants. This approach relies on species delta N-15 values aligning with their trophic position (TP). This, however, may not always be true, because toxic exposure can alter growth and isotope allocation patterns. Here, effects of PCB exposure (mixture of PCB18, PCB40, PCB128, and PCB209) on delta N-15 and delta C-13 as well as processes driving these effects were explored using the cladoceran Daphnia magna. A two-part experiment assessed effects of toxic exposure during and after exposure; juvenile daphnids were exposed during 3 days (accumulation phase) and then allowed to depurate for 4 days (depuration phase). No effects on survival, growth, carbon and nitrogen content, and stable isotope composition were observed after the accumulation phase, whereas significant changes were detected in adults after the depuration phase. In particular, a significantly lower nitrogen content and a growth inhibition were observed, with a concomitant increase in delta N-15 (+0.1 parts per thousand) and decrease in delta C-13 (-0.1 parts per thousand). Although of low magnitude, these changes followed the predicted direction indicating that sublethal effects of contaminant exposure can lead to overestimation of TP and hence underestimated TMF.
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20.
  • Ek, Caroline, et al. (författare)
  • Increase in stable isotope ratios driven by metabolic alterations in amphipods exposed to the beta-blocker propranolol
  • 2019
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Anthropogenic pressures, such as contaminant exposure, may affect stable isotope ratios in biota. These changes are driven by alterations in the nutrient allocation and metabolic pathways induced by specific stressors. In a controlled microcosm study with the amphipod Gammarus spp., we studied effects of the beta-blocker propranolol on stable isotope signatures (delta N-15 and delta C-13), elemental composition (%C and %N), and growth (protein content and body size) as well as biomarkers of oxidative status (antioxidant capacity, ORAC; lipid peroxidation, TBARS) and neurological activity (acetylcholinesterase, AChE). Based on the known effects of propranolol exposure on cellular functions, i.e., its mode of action (MOA), we expected to observe a lower scope for growth, accompanied by a decrease in protein deposition, oxidative processes and AChE inhibition, with a resulting increase in the isotopic signatures. The observed responses in growth, biochemical and elemental variables supported most of these predictions. In particular, an increase in %N was observed in the propranolol exposures, whereas both protein allocation and body size declined. Moreover, both ORAC and TBARS levels decreased with increasing propranolol concentration, with the decrease being more pronounced for TBARS, which indicates the prevalence of the antioxidative processes. These changes resulted in a significant increase of the delta N-15 and delta C-13 values in the propranolol-exposed animals compared to the control. These findings suggest that MOA of beta-blockers may be used to predict sublethal effects in non-target species, including inhibited AChE activity, improved oxidative balance, and elevated stable isotope ratios. The latter also indicates that metabolism-driven responses to environmental contaminants can alter stable isotope signatures, which should be taken into account when interpreting trophic interactions in the food webs.
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22.
  • Ek, Caroline, et al. (författare)
  • Stable Isotope Composition in Daphnia Is Modulated by Growth, Temperature, and Toxic Exposure : Implications for Trophic Magnification Factor Assessment
  • 2015
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:11, s. 6934-6942
  • Tidskriftsartikel (refereegranskat)abstract
    • The potential for using stable isotope analysis in risk assessment of environmental contaminants is crucially dependent on the predictability of the trophic transfer of isotopes in food webs. The relationship between contaminant levels and trophic position of consumers is widely used to assess biomagnification properties of various pollutants by establishing trophic magnification factors (TMF). However, contaminant-induced variability of the isotopic composition in biota is poorly understood. Here, we investigated effects of toxic exposure on delta N-15 and delta C-13 values in a consumer, with a main hypothesis that these effects would be largely mediated via growth rate and metabolic turnover of the test animals. The cladoceran Daphnia magna was used in two experiments that were conducted to manipulate growth and body condition (assayed as C:N ratio) by food availability and temperature (Experiment 1) and by toxic exposure to the pesticide lindane (Experiment 2). We found a significant negative effect of growth rate and a positive effect of temperature on the consumer-diet discrimination factor for delta N-15 and delta C-13, with no effects on the C:N ratio (Experiment 1). In lindane-exposed daphnids, a significant growth inhibition was observed, with concomitant increase in metabolic costs and significantly elevated size-specific delta N-15 and delta C-13 values. Moreover, a significantly higher incorporation of carbon relative to nitrogen, yet a concomitant decrease in C:N ratio was observed in the exposed animals. Together, these results have methodological implications for determining trophic positions and TMF in polluted environments, where elevated delta N-15 values would translate into overestimated trophic positions and underestimated TMF. Furthermore, altered delta C-13 values may lead to erroneous food-chain assignment of the consumer in question.
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23.
  • Ek, Caroline, 1985- (författare)
  • Towards understanding stable isotope signatures in stressed systems
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Stable isotope analysis (SIA) is a valuable tool in ecotoxicology because δ13C and δ15N may provide insights into the trophic transfer of contaminants in a food web. The relationship between a species’ trophic position (TP, determined from δ15N) and internal concentration of biomagnifying contaminants can be established and used for regulatory purposes. However, the exposure of organisms to xenobiotics incurs physiological costs, and the stable isotope signature of a consumer reflects not only diet but also a physiological state. The latter raises questions regarding the interpretation of stable isotope signatures in contaminated areas. Therefore, the aim of this Thesis was to evaluate the behaviour of consumers’ stable isotope signatures in stressed systems, with a primary focus on the effects of environmental contaminants.In paper I, the physiological costs of chemical exposure were found to alter incorporation rates of dietary nitrogen and carbon in a consumer by influencing both growth and metabolic turnover, with resulting changes in isotope signatures relative to a control system. In paper II, the diet-consumer discrimination factors for 15N and 13C were confirmed to increase under chemical exposure mediated via increased metabolic costs. However, the physiological response was low and translated into only minor shifts in the δ13C and δ15N. The predictability of exposure effects on the stable isotope signature was demonstrated in paper III, in which animals exposed to a chemical with a known mode of action presented expected effects on elemental composition, body size, biomarkers of oxidative stress and the stable isotope signatures. Moreover, consumers’ oxidative balance was found to be related to their δ15N values, thus providing evidence of the kinetic isotope effect on the oxidative status. However, despite the alterations in stable isotope signatures observed in laboratory settings (papers I-III), the effect of xenobiotics on the TP estimates was nil or minor in the field-collected animals. Moreover, the TP values were not significantly different between the animals in the contaminated and the reference habitats because of the high overall uncertainties in the TP estimates (paper IV). Also, the TP estimates based on δ15N in bulk material were more similar between the contaminated and the reference systems than TP estimates based on δ15N values in amino acids. Therefore, the latter method appears more sensitive towards xenobiotics (and, possibly, other environmental stressors) and thus less suitable for TP assessment in contaminated areas.This Thesis improved the overall understanding of the applicability of SIA in stressed systems by establishing relationships between various exposure regimes, physiological responses and the stable isotope signatures in consumers. In model species at low trophic levels, the exposure to xenobiotics was found to significantly affect δ13C and δ15N values, which can be expected whenever physiological responses are detected. However, because of the overall high uncertainty in TP estimates, no significant differences between contaminated and control systems were detected, although the estimated TP were consistently higher in the contaminated systems. Future research should focus on higher trophic levels, in which effects of a greater magnitude can be expected. Moreover, the effects in entire food webs should be addressed rather than single prey–consumer relationships as well as other environmental variables that may contribute to the stable isotope variability in and among systems under various environmental pressures.
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24.
  • Ek, Caroline, et al. (författare)
  • Using Compound-Specific and Bulk Stable Isotope Analysis for Trophic Positioning of Bivalves in Contaminated Baltic Sea Sediments
  • 2018
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:8, s. 4861-4868
  • Tidskriftsartikel (refereegranskat)abstract
    • Stable nitrogen isotopes (delta N-15) are used as indicators of trophic position (TP) of consumers. Deriving TP from delta N-15 of individual amino acids (AAs) is becoming popular in ecological studies, because of lower uncertainty than TP based on bulk delta N-15 (TPbulk). This method would also facilitate biomagnification studies provided that isotope fractionation is unaffected by toxic exposure. We compared TPAA and TPbulk estimates for a sediment-dwelling bivalve from two coastal sites, a pristine and a contaminated. Chemical analysis of PCB levels in mussels, sediments, and pore water confirmed the expected difference between sites. Both methods, but in particular the TPAA underestimated the actual TP of bivalves. Using error propagation, the total uncertainty related to the analytical precision and assumptions in the TP calculations was found to be similar between the two methods. Interestingly, the significantly higher intercept for the regression between T-AA, and TPbulk in the contaminated site compared to the pristine site indicates a higher deamination rate due to detoxification as a result of chronic exposure and a higher N-15 fractionation. Hence, there is a need for controlled experiments on assumptions underlying amino acid-specific stable isotope methods in food web and bimagnification studies.
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25.
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26.
  • El-Shehawy, Rehab, et al. (författare)
  • Global warming and hepatotoxin production by cyanobacteria : What can we learn from experiments?
  • 2012
  • Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 46:5, s. 1420-1429
  • Tidskriftsartikel (refereegranskat)abstract
    • Global temperature is expected to rise throughout this century, and blooms of cyanobacteria in lakes and estuaries are predicted to increase with the current level of global warming. The potential environmental, economic and sanitation repercussions of these blooms have attracted considerable attention among the world's scientific communities, water management agencies and general public. Of particular concern is the worldwide occurrence of hepatotoxic cyanobacteria posing a serious threat to global public health. Here, we highlight plausible effects of global warming on physiological and molecular changes in these cyanobacteria and resulting effects on hepatotoxin production. We also emphasize the importance of understanding the natural biological function(s) of hepatotoxins, various mechanisms governing their synthesis, and climate-driven changes in food-web interactions, if we are to predict consequences of the current and projected levels of global warming for production and accumulation of hepatotoxins in aquatic ecosystems.
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27.
  • El-Shehawy, Rehab, et al. (författare)
  • Microbiota-Dependent and -Independent Production of L-Dopa in the Gut of Daphnia magna
  • 2021
  • Ingår i: mSystems. - 2379-5077. ; 6:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Host-microbiome interactions are essential for the physiological and ecological performance of the host, yet these interactions are challenging to identify. Neurotransmitters are commonly implicated in these interactions, but we know very little about the mechanisms of their involvement, especially in invertebrates. Here, we report a peripheral catecholamine (CA) pathway involving the gut microbiome of the model species Daphnia magna. We demonstrate the following: (i) tyrosine hydroxylase and Dopa (3,4-dihydroxyphenylalanine) decarboxylase enzymes are present in the gut wall; (ii) Dopa decarboxylase gene is expressed in the gut by the host, and its expression follows the molt cycle peaking after ecdysis; (iii) biologically active L-Dopa, but not dopamine, is present in the gut lumen; (iv) gut bacteria produce L-Dopa in a concentration-dependent manner when provided l-tyrosine as a substrate. Impinging on gut bacteria involvement in host physiology and ecologically relevant traits, we suggest L-Dopa as a communication agent in the host-microbiome interactions in daphnids and, possibly, other crustaceans.IMPORTANCE Neurotransmitters are commonly implicated in host-microbiome communication, yet the molecular mechanisms of this communication remain largely elusive. We present novel evidence linking the gut microbiome to host development and growth via neurotransmitter L-Dopa in Daphnia, the established model species in ecology and evolution. We found that both Daphnia and its gut microbiome contribute to the synthesis of the L-Dopa in the gut. We also identified a peripheral pathway in the gut wall, with a molt stage-dependent dopamine synthesis, linking the gut microbiome to the daphnid development and growth. These findings suggest a central role of L-Dopa in the bidirectional communication between the animal host and its gut bacteria and translating into the ecologically important host traits suitable for subsequent testing of causality by experimental studies.
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28.
  • Engström-Öst, Jonna, et al. (författare)
  • The effects of short-term pH decrease on the reproductive output of the copepod Acartia bifilosa - a laboratory study
  • 2014
  • Ingår i: Marine and Freshwater Behaviour & Physiology. - : Informa UK Limited. - 1023-6244 .- 1029-0362. ; 47:3, s. 173-183
  • Tidskriftsartikel (refereegranskat)abstract
    • This laboratory study reports some reproductive responses of the copepod Acartia bifilosa to rapid variations in pH. The imposed changes mimic those that copepods could experience due to coastal upwelling, changed mixing conditions or vertical migration. We measured effects of low pH on egg production, hatching and early nauplii development (H-0: no effects on response variables between low and ambient pH). On treatment with low pH, we found positive effects on egg production rate and nauplii development time. The positive response to low pH could be an initial stress response or show that A. bifilosa is tolerant to the experimental pH values. The result suggests that A. bifilosa is adapted to pH changes as it performs daily migrations between the depths with differing pH. It could also be advantageous for population development if eggs hatch at high speed and so reduce the possibility that they will sink into anoxic and low pH waters.
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29.
  • Engström-Öst, Jonna, et al. (författare)
  • Toxin-producing cyanobacterium Nodularia spumigena, potential competitors and grazers : testing mechanisms of reciprocal interactions
  • 2011
  • Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 62:1, s. 39-48
  • Tidskriftsartikel (refereegranskat)abstract
    • Interactions among toxic cyanobacteria, sympatric algae and planktivorous grazers are key processes governing plankton dynamics and cyanobacterial blooms. We studied interactions between the cyanobacterium Nodularia spumigena and microalgae (Rhodomonas salina and Tetraselmis suecica) as well as effects of zooplankton (copepod Eurytemora affinis) grazing on these interactions. N. spumigena was incubated without algae or with algae at different concentrations and with or without copepods. Following similar to 24 h incubation, we assayed changes in N. spumigena and algae abundance, concentration of intracellular (IC) and dissolved nodularin (toxin produced by N. spumigena) and quantity of Nodularia DNA in copepod guts (as a proxy for grazing pressure on the cyanobacterium). In the presence of algae, IC nodularin levels increased in a concentration-dependent manner; however, when copepods were present in the mixtures of algae and cyanobacterium, this increase was significantly less. The presence of T. suecica negatively affected the growth rate of N. spumigena, whereas the presence of the cyanobacterium strongly impeded growth of R. salina, but not of T. suecica. The IC nodularin quota correlated negatively with growth of R. salina, implicating the toxin's involvement in the observed growth suppression of the eukaryotic alga. Copepods actively ingested N. spumigena, even when the alternative food was plentiful, and neither N. spumigena quantity nor its toxin concentrations influenced copepod feeding rates and survival. These findings suggest complex allelopathic interactions between the autotrophs, whereas mesozooplankton grazers have an indirect negative effect on the nodularin concentrations by suppressing the competitors. These findings underscore the need to study ecologically important interactions among toxic cyanobacteria, sympatric algae and grazers, if we are to understand mechanisms regulating cyanobacterial blooms.
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30.
  • Eriksson Wiklund, Ann-Kristin, et al. (författare)
  • Cardiotoxic and neurobehavioral effects of sucralose and acesulfame in Daphnia : Toward understanding ecological impacts of artificial sweeteners
  • 2023
  • Ingår i: Comparative Biochemistry and Physiology - Part C. - 1532-0456 .- 1878-1659. ; 273
  • Tidskriftsartikel (refereegranskat)abstract
    • Artificial sweeteners are widely used in food and pharmaceuticals, but their stability and persistence raise concerns about their impact on aquatic life. Although standard toxicity tests do not reveal lethal effects, recent studies suggest a potential neurotoxic mode of action. Using environmentally relevant concentrations, we assessed the effects of sucralose and acesulfame, common sugar substitutes, on Daphnia magna focusing on biochemical (acetylcholinesterase activity; AChE), physiological (heart rate), and behavioural (swimming) endpoints. We found dose-dependent increases in AChE and inhibitory effects on heart rate and behaviour for both substances. Moreover, acesulfame induced a biphasic response in AChE activity, inhibiting it at lower concentrations and stimulating at higher ones. For all endpoints, the EC50 values were lower for acesulfame than for sucralose. Additionally, the relationship between acetylcholinesterase and heart rate differed depending on the substance, suggesting possible differences in the mode of action between sucralose and acesulfame. All observed EC50 values were at μg/l levels, i.e., within the levels reported for wastewater, with adverse effects observed at as low as 0.1 μg acesulfame /l. Our findings emphasise the need to re-evaluate risk assessment thresholds for artificial sweeteners and provide evidence for the neurotoxic effects of artificial sweeteners in the environment, informing international regulatory standards.
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31.
  • Furuhagen, Sara, 1985- (författare)
  • Application and interpretation of biomarkers in ecotoxicology - from molecular to individual level responses
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The use of biomarkers is considered a promising alternative, or complement, to traditional ecotoxicological assays. Toxic effects are often initially manifested at the molecular or biochemical level, biomarkers are therefore used as sensitive indicators of toxic exposure. Ideally, biomarkers would also indicate reduced fitness and possible later effects at the individual or population levels. However, implementing biomarkers in ecotoxicology is challenging and few biomarkers have an established connection to reduced individual fitness. The aim of this thesis was to increase the value and improve the interpretation of biomarker responses in ecotoxicological studies by examining the impact of confounding factors and the relationship between oxidative biomarkers and reproductive effects in crustaceans.The sensitivity of biomarkers was confirmed in paper I as toxic effects of pharmaceuticals with conserved drug target orthologs were observed at the molecular and biochemical levels both earlier and at lower concentrations than effects on mortality and reproduction. No toxic effects were observed for the pharmaceutical without identified drug target orthologs, thus stressing the importance of considering toxic mechanisms and being aware of the most likely target when evaluating toxic effects also in non-target species. Many xenobiotics and environmental stressors interfere with oxidative processes, making oxidative biomarkers interesting to study in ecotoxicology and stress ecology. Still, feeding rate was identified as a confounding factor for antioxidant capacity (assayed as oxygen radical absorbance capacity, ORAC) and lipid peroxidation in ecotoxicological studies (paper II). However, ORAC normalized to protein was independent of altered feeding rates, hence it can be applied as a suitable exposure biomarker without considering alterations and effects of feeding rate. The connection between reproduction and oxidative stress is dual, as reproduction both can be inhibited by oxidative stress and induce pro-oxidative processes. Further, a positive association was found between ORAC and the occurrence of embryo aberrations in the benthic amphipod Monoporeia affinis (paper III). An association between antioxidant defense and reproduction was also observed for Daphnia magna (paper IV). Threshold values for identification of exposed individuals and prediction of possible later reproductive effects were established for ORAC.This thesis has contributed to diminishing some of the knowledge gaps limiting the use of oxidative biomarkers in ecotoxicology, by contributing to increased understanding of how oxidative biomarkers relate to important life-traits. Moreover, ORAC has been identified as a suitable biomarker of not only exposure, but also reproductive effects. Future research should continue to establish connections between biomarker responses and effects at higher levels, and focus on providing defined threshold values to enable predictions about later effects.   
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32.
  • Furuhagen, Sara, et al. (författare)
  • Are Pharmaceuticals with Evolutionary Conserved Molecular Drug Targets More Potent to Cause Toxic Effects in Non-Target Organisms?
  • 2014
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:8
  • Tidskriftsartikel (refereegranskat)abstract
    • The ubiquitous use of pharmaceuticals has resulted in a continuous discharge into wastewater and pharmaceuticals and their metabolites are found in the environment. Due to their design towards specific drug targets, pharmaceuticals may be therapeutically active already at low environmental concentrations. Several human drug targets are evolutionary conserved in aquatic organisms, raising concerns about effects of these pharmaceuticals in non-target organisms. In this study, we hypothesized that the toxicity of a pharmaceutical towards a non-target invertebrate depends on the presence of the human drug target orthologs in this species. This was tested by assessing toxicity of pharmaceuticals with (miconazole and promethazine) and without (levonorgestrel) identified drug target orthologs in the cladoceran Daphnia magna. The toxicity was evaluated using general toxicity endpoints at individual (immobility, reproduction and development), biochemical (RNA and DNA content) and molecular (gene expression) levels. The results provide evidence for higher toxicity of miconazole and promethazine, i.e. the drugs with identified drug target orthologs. At the individual level, miconazole had the lowest effect concentrations for immobility and reproduction (0.3 and 0.022 mg L-1, respectively) followed by promethazine (1.6 and 0.18 mg L-1, respectively). At the biochemical level, individual RNA content was affected by miconazole and promethazine already at 0.0023 and 0.059 mg L-1, respectively. At the molecular level, gene expression for cuticle protein was significantly suppressed by exposure to both miconazole and promethazine; moreover, daphnids exposed to miconazole had significantly lower vitellogenin expression. Levonorgestrel did not have any effects on any endpoints in the concentrations tested. These results highlight the importance of considering drug target conservation in environmental risk assessments of pharmaceuticals.
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33.
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34.
  • Furuhagen, Sara, et al. (författare)
  • Feeding Activity and Xenobiotics Modulate Oxidative Status in Daphnia magna : Implications for Ecotoxicological Testing
  • 2014
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:21, s. 12886-12892
  • Tidskriftsartikel (refereegranskat)abstract
    • To apply biomarkers of oxidative stress in laboratory and field settings, an understanding of their responses to changes in physiological rates is important. The evidence is accumulating that caloric intake can increase production of reactive oxygen species and thus affect background variability of oxidative stress biomarkers in ecotoxicological testing. This study aimed to delineate effects of food intake and xenobiotics on oxidative biomarkes in Daphnia magna. Antioxidant capacity measured as oxygen radical absorbance capacity (ORAC) and lipid peroxidation assayed as thiobarbituric acid reactive substances (TBARS) were measured. Food intake was manipulated by varying food densities or by exposing the animals to chemicals inhibiting feeding rate (pharmaceutical haloperidol and pesticide lindane). Feeding rate proved to affect both protein, ORAC, and TBARS in unexposed daphnids. However, there was no significant effect of feeding rate on the protein-specific ORAC values. Both substances affected individual protein and ORAC levels and changed their relationship to feeding rate. Our results show that inhibition of feeding rate influenced the interpretation of biomarker response and further emphasize the importance of understanding (1) baseline variability in potential biomarkers due to variations in metabolic state and (2) the contribution of feeding rate on toxic response of biomarkers.
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35.
  • Furuhagen, Sara (författare)
  • Integrative approaches in ecotoxicological testing: Implications for biomarker development and application
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Ecotoxicology aims to understand toxic effects of chemicals in the environment. Effects can be observed at different levels of the biological organization, from molecular to ecosystem level. Biomarkers on molecular and biochemical levels are used in ecotoxicology as early warning signals of chemical exposure, possible toxic effects and underlying mechanisms. As methods and technologies improve, more biomarkers are being implemented in ecotoxicological studies, due to the general interest in early detection and thus efficient prevention of environmental risks. However, to be of value in ecotoxicological assessment, a connection between biomarker response and effects at higher levels of biological organization should be established. Also, baseline variability for the biomarker in question as well as response to natural fluctuations of environmental factors should be evaluated.The aim of this thesis was to increase value and understanding of biomarkers in ecotoxicological assessment by (1) linking responses across different levels of biological organization, and (2) gaining better understanding of the relative importance of ecological and physiological factors affecting oxidative biomarkers.Paper I is focused on evolutionary conserved drug targets and the toxicity of pharmaceuticals for non-target organisms. The main conclusion from this study is that pharmaceuticals with conserved drug targets in non-target organisms have a higher toxicity than pharmaceuticals for which drug-targets have not been identified in the species. The effects were evaluated using end points at molecular, biochemical and individual levels. Consistent with the expected higher sensitivity of molecular and biochemical end points, the effects on the low-level biomarkers were observed at lower concentrations than at the individual level.  Paper II is focused on delineating effects of feeding and toxic exposure on oxidative biomarkers commonly used in ecotoxicology. The results are in agreement with the theory of caloric restriction that links enhanced caloric intake to increased pro-oxidative processes in animals. In our experiments with the cladoceran Daphnia magna, we observed positive effects for both antioxidant capacity and oxidized lipids in response to enhanced feeding rates. This have implications for the use of oxidative stress biomarkers in ecotoxicology as many substances have inhibitory effects on feeding rate and thus, changes in oxidative biomarkers can result from the altered feeding rate rather than other toxic mechanisms. Therefore, possible changes in feeding rate should be assessed when conducting exposure experiments or interpreting field data in studies employing oxidative stress biomarkers. However, it was concluded that the ratio between antioxidative capacity and protein content was independent of feeding rate. Thus, this biomarker is suitable for xenobiotic exposure in D. magna. This thesis have contributed to better understanding of molecular and biochemical biomarkers in ecotoxicological studies in regard to the connections between effects at different biological levels and confounding factors in biomarker response.
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36.
  • Furuhagen, Sara, et al. (författare)
  • Oxidative biomarkers as indicators of reproductive effects in Daphnia magna
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Oxidative stress can be induced by various stressors, and oxidative biomarkers are commonly used as indicators of xenobiotic exposure. However, the capacity of oxidative biomarkers to predict pro-oxidative exposure or indicate reproductive effects has not been evaluated. In this study, we hypothesized that biomarkers of oxidative stress (catalase, antioxidant capacity, and lipid peroxidation) can be used to diagnose pro-oxidative exposure, with concomitant reproductive penalties. We exposed Daphnia magna to UVB irradiation, a known agent inducing pro-oxidative processes in various organisms, from birth to adult stage. The biomarker responses were followed in different life-stages in concert with reproductive success and individual growth rate. The UVB exposure induced alterations in antioxidant capacity (measured as oxygen radical absorbance capacity, ORAC) in both juvenile and adult daphnids. Moreover, these effects were age-specific, with decreased and increased ORAC in juveniles and adults, respectively. These changes were associated with reproductive success, as increased number of offspring was negatively associated with antioxidant capacity. Also, a trans-generational effect was observed as exposed females allocated less antioxidants to their offspring. ORAC normalized to protein content (ORACp) was identified as a suitable biomarker of pro-oxidative exposure. For diagnostics of oxidative stress in field and laboratory settings, two logistic models employing ORACp in juvenile and adult D. magna were proposed; the classification accuracy of the models was about 80%. None of the other biomarkers contributed significantly to the models.
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37.
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38.
  • Förlin, Lars, et al. (författare)
  • Effektscreening – Biologisk effektövervakning i förorenade områden längs Sveriges kust 2017–2018
  • 2019
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Undersökningarna visar att samtliga metoder inklusive undersökningar av hälsotillståndet hos fisk, fortplantning och biomarkörer hos vitmärla, lysosomal membranstabilitet hos mussla och imposex hos snäckor med få undantag visade på tydliga effekter i de åtta undersökta och förorenade områdena längs Sveriges kuster. En jämförelse mellan de olika metoderna visar, med undantag för området i Uddevalla/Byfjorden, en tydlig påverkan i resterande undersökta områdena. I Byfjorden noterades mindre stressade musslor och endast låga stadier av imposex hos snäckor medan fiskhälsan kunde konstateras vara påverkad. Utöver Byfjorden gjordes undersökningar med mer än en av metoderna även i Sundsvallsfjärden, Norrsundet, Bråviken, Ronnebyåns mynning och Landskrona. I dessa områden visar jämförelsen mellan metoderna att samtliga indikerar en tydlig påverkan. Att samtliga metoder ger utslag beror sannolikt på att alla valda undersökningsområden har en mycket komplex och ganska påtaglig föroreningsbelastning vilket innebär att det kan förväntas att de flesta organismer som lever i dessa områden kan uppvisa effekter som kan härledas till påverkan av miljöstörande ämnen.I Sverige är den nationella effektbaserade miljöövervakningen i marin miljö väsentligen inriktad på att undersöka effekter av miljögifter i referensområden. Sådana områden karakteriseras av att de ska ligga på stort avstånd från större befolkningscentra och industrier, eller till exempel inte ligga nära stora flodmynningar. Resultaten från denna studie kompletterar den ordinarie miljöövervakningen i referensområden och visar med stor tydlighet att de undersökta områdena är källor för miljöstörande ämnen till vattenmiljön. Undersökningarna visar också att det är önskvärt att kontinuerlig biologisk effektövervakning kommer igång i något eller några påverkade områden inom ramen för den nationella miljöövervakningen för att parallellt följa förändringar i miljön nära eller en bit från påtagliga, mer eller mindre kontinuerliga föroreningskällor i vårt samhälle. Detta skulle också komplettera Sveriges internationella rapportering av miljödata genom att förutom att rapportera effektdata från referensområden även kunna rapportera data från påverkade/förorenade områden.
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39.
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40.
  • Gardeström, Johanna, et al. (författare)
  • A multilevel approach to predict toxicity in copepod populations : Assessment of growth, genetics, and population structure
  • 2006
  • Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 79:1, s. 41-48
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the goals of environmental risk assessment (ERA) is to understand effects of toxicant exposure on individual organisms and populations. We hypothesized that toxicant exposure can reduce genetic diversity and alter genotype composition, which may ultimately lead to a reduction in the average fitness of the exposed population. To test this hypothesis, we exposed a copepod, Nitocra psammophila, to a toxic reference compound and assayed resulting alterations in genetic structure, i.e. expected heterozygosity and percent polymorphic loci, as well as other population- and fitness-related measures, i.e. population abundance, demographic structure and juvenile growth. The copepods were exposed to 0.11-1.1 mu g of the pentabromo-substituted diphenyl ether (BDE-47) mg(-1) freeze-dried algae for 24 days (i.e. > 1 generation). There was no significant decline in total population abundance. However, there were significant alterations in population structure, manifested as diminished proportion of nauplii and increased proportion of copepodites. In addition, individual RNA content in copepodites decreased significantly in exposed individuals, indicating declined growth. Finally, in the exposed populations, heterozygosity was lower and genotype composition was altered compared to the controls. These results therefore confirm the hypothesized reduction in overall genetic variability resulting from toxicant exposure. Multilevel approaches, such as the one used in the present study, may help unravel subtle effects on the population level, thus increasing the predictive capacity of future ERA.
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41.
  • Gerdes, Zandra, et al. (författare)
  • A novel method for assessing microplastic effect in suspension through mixing test and reference materials
  • 2019
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • The occurrence of microplastic in the environment is of global concern. However, the microplastic hazard assessment is hampered by a lack of adequate ecotoxicological methods because of conceptual and practical problems with particle exposure. In the environment, suspended solids (e.g., clay and cellulose) in the same size range as microplastic, are ubiquitous. Therefore, it must be established whether the addition of microplastic to these background levels of particulate material represents a hazard. We present a novel approach employing a serial dilution of microplastic and reference particles, in mixtures, which allows disentangling the effect of the microplastic from that of the other particulates. We demonstrate the applicability of the method using an immobilization test with Daphnia magna exposed to polyethylene terephthalate (test microplastic; median particle diameter similar to 5 mu m) and kaolin clay (reference material; similar to 3 mu m). In the range of the suspended solids test concentrations (0-10 000 mg L-1), with microplastic contributing 0-100% of total mass, the Lc(50) values for the plastic mixtures were significantly lower compared to the kaolin exposure. Hence, the exposure to polyethylene terephthalate was more harmful to the daphnids than to the reference material alone. The estimated threshold for the relative contribution of the test microplastic to suspended matter above which significantly higher mortality was observed was 2.4% at 32 mg of the solids L-1. This approach has a potential for standardization of ecotoxicological testing of particulates, including microplastic.
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42.
  • Gerdes, Zandra, 1989- (författare)
  • Exploring the ecotoxicity of microparticle debris
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The global distribution and anticipated increase of environmental microplastic (MP) pollution are concerning. However, while the impacts of macroplastic litter on wildlife are apparent, we know relatively little about the MP hazard potential. Moreover, the current ecotoxicological methodology is inadequate for solid waste particles and MP hazard assessment because it fails to distinguish particle and chemical effects. This thesis improves our understanding of the particle effects of MP relative to other microparticles.First, a comparative analysis of effect studies on MP and mineral particulates across different biological organisation levels revealed high similarities in responses between these materials (Paper I). At the suborganismal levels, the similarity in the effect concentrations suggests shared particle effect mechanisms. At the higher levels, however, MP induced more severe impacts, possibly due to chemical leaching. Moreover, the highly variable MP effect concentrations motivated exploring the role of polymer properties and ageing status on MP effects; these aspects were addressed in Papers II-III.In Paper II, the possibility of MP acting as a vector of contaminants was evaluated, showing enhanced transport of highly hydrophobic organic contaminants (HOC) at very high HOC and MP concentrations. However, observing it at environmentally relevant contaminant levels would be unlikely. Paper III compared behavioural and physiological responses in benthic amphipods to MP exposure using different polymers (polystyrene and polyethylene terephthalate) and clay as a non-plastic reference particle. The amphipods avoided sediments with high concentrations of the added material regardless of the material type, including aged and virgin MP and clay. Solid waste, including MP, co-occur with various suspended solids in aquatic environments; therefore, the natural solids can serve as reference material when evaluating the MP particle effect. In Paper IV, a novel method for testing MP effects in mixtures with reference particles was proposed. In the exposure experiment with daphnids, the method was used to derive hazard thresholds for the MP contribution to suspended matter conditional on the total suspended solid concentration in the water. Together, these studies add to our understanding of MP-biota interactions and suggest that similarly sized MP and natural particulates share similar particle effects. However, MP might have a higher potential as vectors of chemical contaminants, which needs to be further evaluated in environmentally relevant settings.
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43.
  • Gerdes, Zandra, et al. (författare)
  • Insufficient evidence for behavioural and metabolic effects in a sediment-dwelling amphipod exposed to microplastics
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Microplastics (MP) are an emerging type of solid contaminants ubiquitous in aquatic environments. Coastal, soft bottom ecosystems are particularly susceptible to MP pollution because they are deposition areas for solid and soluble contaminants. The addition of MP or any other inert particles to the sediment may dilute its nutritional content and modify structural integrity, leading to adverse effects in sediment-living biota. Behavioural endpoints are sensitive but underutilized indicators of habitat quality linked to physiological responses, such as metabolism, which is essential for understanding the mechanisms behind the MP effects. We studied the behaviour of the benthic deposit-feeding amphipod Corophium volutator exposed to sediments enriched in MP and measured the Electron Transport System activity (ETS) as a proxy for respiration in the animals facing varying sediment quality. The natural sediments were manipulated by dilution with two common plastic polymers (polystyrene PS and polyethylene terephthalate PET — aged and virgin) and kaolin clay as reference material at 1 and 10% sediment dry weight. We did not find any significant effects of neither material type nor ageing status on the behavioural traits. However, a significant increase in erratic non-feeding movements in the 10% mixture treatments suggested a general stress response to the altered habitat quality. There was also a consistent preference for the natural sediment, as evidenced by a relatively higher burrowing frequency compared to mixed sediments. The ETS activity was positively correlated with the increased physical activity due to the non-feeding movements but not food acquisition behaviour. In conclusion, the effects of MP on the behaviour and metabolic state of deposit-feeding amphipods are similar to other nutritionally inert particles, and the adverse effects are more of a reaction to a general disturbance than being material specific. Nevertheless, compared to the published data on MP effect concentrations in benthic organisms, behavioural endpoints are sensitive and informative when studying alterations in sediment quality; thus, they may provide complementary information for developing sediment quality criteria.
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44.
  • Gerdes, Zandra, et al. (författare)
  • Microplastic-mediated transport of PCBs? A depuration study with Daphnia magna
  • 2019
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The role of microplastic (MP) as a carrier of persistent organic pollutants (POPs) to aquatic organisms has been a topic of debate. However, the reverse POP transport can occur if relative contaminant concentrations are higher in the organism than in the microplastic. We evaluated the effect of microplastic on the PCB removal in planktonic animals by exposing the cladoceran Daphnia magna with a high body burden of polychlorinated biphenyls (PCB 18, 40, 128 and 209) to a mixture of microplastic and algae; daphnids exposed to only algae served as the control. As the endpoints, we used PCB body burden, growth, fecundity and elemental composition (%C and %N) of the daphnids. In the daphnids fed with microplastic, PCB 209 was removed more efficiently, while there was no difference for any other congeners and Sigma PCBs between the microplastic-exposed and control animals. Also, higher size-specific egg production in the animals carrying PCB and receiving food mixed with micro-plastics was observed. However, the effects of the microplastic exposure on fecundity were of low biological significance, because the PCB body burden and the microplastic exposure concentrations were greatly exceeding environmentally relevant concentrations.
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45.
  •  
46.
  • Gorokhova, Elena, et al. (författare)
  • A comparison of TO-PRO-1 iodide and 5-CFDA-AM staining methods for assessing viability of planktonic algae with epifluorescence microscopy
  • 2012
  • Ingår i: Journal of Microbiological Methods. - : Elsevier BV. - 0167-7012 .- 1872-8359. ; 89:3, s. 216-221
  • Tidskriftsartikel (refereegranskat)abstract
    • Two fluorescent dyes, TO-PRO-1 iodide and 5-CFDA-AM, were evaluated for LIVE/DEAD assessment of unicellular marine algae Brachiomonas submarina and Tetraselmis suecica. Epifluorescence microscopy was used to estimate cell viability in predetermined mixtures of viable and non-viable algal cells and validated using microplate growth assay as reference measurements. On average, 5-CFDA-AM underestimated live cell abundance by similar to 25% compared with viability estimated by the growth assay, whereas TO-PRO-1 iodide provided accurate viability estimates. Furthermore, viability estimates based on staining with TO-PRO-1 iodide were not affected by a storage period of up to one month in -80 degrees C, making the assay a good candidate for routine assessment of phytoplankton populations in field and laboratory studies.
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47.
  • Gorokhova, Elena (författare)
  • A single-step staining method to evaluate egg viability in zooplankton
  • 2010
  • Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 8, s. 414-423
  • Tidskriftsartikel (refereegranskat)abstract
    • A simplified method for viability analysis of zooplankton eggs by staining of nonviable eggs with a fluorescent nucleic acid stain TO-PRO-1 iodide is proposed here as a further development of fluorescence-based egg viability assays. This is one-step analysis with no intermediate steps for chorion removal. The method was calibrated using predetermined mixtures of viable and nonviable eggs (rotifers and copepods), and validated using hatching experiments (copepods) and egg development assay (cladocerans) as reference measurements. In these tests, eggs of several zooplankton species, Brachionus plicatilis (Rotatoria), Daphnia magna (Cladocera), Nitocra spinipes (Harpacticoida), Acartia tonsa (Calanoida), were used. Moreover, staining efficiency was not affected by storage of samples for up to 1 month in -80 degrees C, making the assay suitable for egg viability assessment in field and laboratory studies. To illustrate usefulness of the method, it was applied to evaluate how absence of re-mating affects production of viable eggs in females of A. bifilosa (Calanoida). In females separated from males, proportion of sterile eggs increased in 3 d after the separation and no viable eggs were produced after 5 d. The effects of mating frequency on egg viability are important to understand when designing egg production experiments and interpreting field data on egg viability in populations with skewed sex ratios.
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48.
  • Gorokhova, Elena, et al. (författare)
  • Algal Growth at Environmentally Relevant Concentrations of Suspended Solids : Implications for Microplastic Hazard Assessment
  • 2020
  • Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • Hazard assessment of microplastic is challenging because standard toxicity testing is targeting soluble (at least partially) chemicals. Adverse effects can occur when test organisms are exposed to turbid environments in the presence of various particulate matter (PM), both natural, such as clay and cellulose, and anthropogenic, such as microplastic. It is, therefore, relevant to compare responses to PM exposure between the microplastic and other suspended solids present at ecologically relevant concentrations. This comparison is possible when reference materials are included in the testing of microplastic hazard potential. Here, we evaluated growth inhibition in unicellular alga Raphidocelis subcapitata exposed to different PM (microplastic, kaolin, and cellulose; 10, 100, and 1,000 mg/L); algae without added solids were used as a control. Also, aggregate formation in the exposure systems was analyzed using particle size distribution (PSD) data. At 10-100 mg/L, no adverse growth effects were observed in any treatments; moreover, algal growth was significantly stimulated in kaolin and cellulose treatments compared to the control. However, at 1,000 mg/L, all tested materials exerted growth inhibition, with no significant differences among the materials. Comparing PSD s across the treatments showed that both PM concentration and size of the particle aggregates were significant growth predictors for all materials tested. Therefore, at high concentrations, both natural and anthropogenic materials have a similar capacity to cause growth inhibition. Linking effects in unicellular organisms to microplastic fragments remains a challenge since plastics incorporate chemicals that may leach and elicit specific effects relative to the particulates. The use of reference materials in hazard assessment of plastic litter is needed to delineate these effects.
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49.
  • Gorokhova, Elena, et al. (författare)
  • Antioxidant Responses in Copepods Are Driven Primarily by Food Intake, Not by Toxin-Producing Cyanobacteria in the Diet
  • 2022
  • Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
  • Tidskriftsartikel (refereegranskat)abstract
    • The association between oxidative processes and physiological responses has received much attention in ecotoxicity assessment. In the Baltic Sea, bloom-forming cyanobacterium Nodularia spumigena is a significant producer of various bioactive compounds, and both positive and adverse effects on grazers feeding in cyanobacteria blooms are reported. To elucidate the effect mechanisms and species sensitivity to the cyanobacteria-dominating diet, we exposed two Baltic copepods, Acartia bifilosa and Eurytemora affinis, to a diet consisting of toxin-producing cyanobacteria N. spumigena and a high-quality food Rhodomonas salina at 0-300 mu g C L-1; the control food was R. salina provided as a monodiet at the same food levels. The subcellular responses to food type and availability were assayed using a suite of biomarkers - antioxidant enzymes [superoxide dismutases (SOD), catalase (CAT), and glutathione S-transferases (GST)] and acetylcholinesterase (AChE). In parallel, we measured feeding activity using gut content (GC) assayed by real-time PCR analysis that quantified amounts of the prey DNA in copepod stomachs. As growth and reproduction endpoints, individual RNA content (a proxy for protein synthesis capacity), egg production rate (EPR), and egg viability (EV%) were used. In both toxic and nontoxic foods, copepod GC, RNA content, and EPR increased with food availability. Antioxidant enzyme activities increased with food availability regardless of the diet type. Moreover, CAT (both copepods), SOD, and GST (A. bifilosa) were upregulated in the copepods receiving cyanobacteria; the response was detectable when adjusted for the feeding and/or growth responses. By contrast, the diet effects were not significant when food concentration was used as a co-variable. A bimodal response in AChE was observed in A. bifilosa feeding on cyanobacteria, with up to 52% increase at the lower levels (5-25 mu g C L-1) and 32% inhibition at the highest food concentrations. These findings contribute to the refinement of biomarker use for assessing environmental stress and mechanistic understanding of cyanobacteria effects in grazers. They also suggest that antioxidant and AChE responses to feeding activity and diet should be accounted for when using biomarker profiles in field-collected animals in the Baltic Sea and, perhaps other systems, where toxic cyanobacteria are common.
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50.
  • Gorokhova, Elena, et al. (författare)
  • Bacteria-Mediated Effects of Antibiotics on Daphnia Nutrition
  • 2015
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:9, s. 5779-5787
  • Tidskriftsartikel (refereegranskat)abstract
    • In polluted environments, contaminant effects may be manifested via both direct toxicity to the host and changes in its microbiota, affecting bacteria host interactions. In this context, particularly relevant is exposure to antibiotics released into environment. We examined effects of the antibiotic trimethoprim on microbiota of Daphnia magna and concomitant changes in the host feeding. In daphnids exposed to 0.25 mg L-1 trimethoprim for 24 h, the microbiota was strongly affected, with (1) up to 21-fold decrease in 16S rRNA gene abundance and (2) a shift from balanced communities dominated by Curvibacter, Aquabacterium, and Limnohabitans in controls to significantly lower diversity under dominance of Pelomonas in the exposed animals. Moreover, decreased feeding and digestion was observed in the animals exposed to 0.25-2 mg L-1 trimethoprim for 48 h and then fed C-14-labeled algae. Whereas the proportion of intact algal cells in the guts increased with increased trimethoprim concentration, ingestion and incorporation rates as well as digestion and incorporation efficiencies decreased significantly. Thus, antibiotics may impact nontarget species via changes in their microbiota leading to compromised nutrition and, ultimately, growth. These bacteria-mediated effects in nontarget organisms may not be unique for antibiotics, but also relevant for environmental pollutants of various nature.
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