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Ultraviolet B modulates gamma radiation-induced stress responses in Lemna minor at multiple levels of biological organisation
Get PDFElevated levels of ionizing and non-ionizing radiation may co-occur and pose cumulative hazards to biota. However, the combined effects and underlying toxicity mechanisms of different types of radiation in aquatic plants remain poorly understood. The present study aims to demonstrate how different combined toxicity prediction approaches can collectively characterise how chronic (7 days) exposure to ultraviolet B (UVB) radiation (0.5 W m−2) modulates gamma (γ) radiation (14.9, 19.5, 43.6 mGy h−1) induced stress responses in the macrophyte Lemna minor. A suite of bioassays was applied to quantify stress responses at multiple levels of biological organisation. The combined effects (no-enhancement, additivity, synergism, antagonism) were determined by two-way analysis of variance (2 W-ANOVA) and a modified Independent Action (IA) model. The toxicological responses and the potential causality between stressors were further visualised by a network of toxicity pathways. The results showed that γ-radiation or UVB alone induced oxidative stress and programmed cell death (PCD) as well as impaired oxidative phosphorylation (OXPHOS) and photosystem II (PSII) activity in L. minor. γ-radiation also activated antioxidant responses, DNA damage repair and chlorophyll metabolism, and inhibited growth at higher dose rates (≥20 mGy h−1). When co-exposed, UVB predominantly caused non-interaction (no-enhancement or additive) effects on γ-radiation-induced antioxidant gene expression, energy quenching in PSII and growth for all dose rates, whereas antagonistic effects were observed for lipid peroxidation, OXPHOS, PCD, oxidative stress, chlorophyll metabolism and genes involved in DNA damage responses. Synergistic effects were observed for changes in photochemical quenching and non-photochemical quenching, and up-regulation of antioxidant enzyme genes (GST) at one or more dose rates, while synergistic reproductive inhibition occurred at all three γ-radiation dose rates. The present study provides mechanistic knowledge, quantitative understanding and novel analytical strategies to decipher combined effects across levels of biological organisation, which should facilitate future cumulative hazard assessments of multiple stressors.publishedVersio
Nitrate respiration occurs throughout the depth of mucoid and non-mucoid Pseudomonas aeruginosa submerged agar colony biofilms including the oxic zone
Get PDFPseudomonas aeruginosa is an opportunistic pathogen and well characterized biofilm former. P. aeruginosa forms strong oxygen gradients inside biofilms due to rapid oxygen respiration in the top layers and the poor solubility of oxygen coupled with diffusion limited transport. Transcriptomic evidence from in vitro and ex vivo sampling suggests that denitrification is occurring in biofilms in ostensibly oxic environments. It is hypothesized that in the presence of nitrate there is stratification with aerobic respiration occurring in the outer oxic layer and denitrification in the lower anoxic zone. We used submerged agar colony biofilms grown from mucoid (FRD1) and non-mucoid (PAO1) strains to simultaneously measure depth microprofiles of oxygen and nitrous oxide in the same colony with microelectrodes. Oxygen respiration occurred at the top of the colony as expected but denitrification occurred throughout the entire depth, even in the oxic region. Local denitrification rates were highly variable suggesting heterogenous metabolic activity within the colony. We also assessed the short-term influence of tobramycin on aerobic respiration within a PAO1 colony. Although there was an immediate reduction in respiration it was never completely arrested over a 2 h period. On tobramycin removal the oxygen gradient steadily reestablished, demonstrating immediate recovery of metabolic activity.publishedVersio
Short-term effects of macrophyte removal on emission of CO2 and CH4 in shallow lakes
Get PDFMass development of macrophytes in freshwater ecosystems is today considered a worldwide problem and substantial resources are spent on macrophyte removal each year. By removing the dominant primary producer, however, this management practice radically changes the ecosystem overnight. Here, we studied short-term effects of the removal of a mass development of free-floating (Pontederia crassipes), submerged (Elodea nuttallii) and emergent (mix of Ludwigia grandiflora and L. peploides) macrophytes on fluxes of CH4 and CO2 in three lakes. In our field experiment, we assigned an impact site where macrophytes were removed, and a control site where vegetation remained. Before and after removal, diffusive fluxes of CO2 and CH4 were determined in lakes dominated by P. crassipes and E. nuttallii, whereas total emission of CH4 was determined in all three case study lakes. Additionally, plant biomass, and physical and chemical parameters were measured before and after removal. While removal of emergent Ludwigia spp. showed no clear effect on total CH4 emission, removal of submerged E. nuttallii reduced both CO2 fixation and total CH4 emission. Removal of free-floating P. crassipes, on the other hand, increased CH4 fluxes and stimulated phytoplankton blooms. The lack of a universal response across our case study lakes suggests that both macrophyte life forms and environmental parameters can be important factors determining effects of removal. Additionally, indirect effects of macrophyte removal on temperature and dissolved oxygen can help to explain carbon emissions. Long-term effects should be studied to allow development of sustainable management practices.publishedVersio
Short-term temporal variation of coastal marine eDNA
Get PDFTemporal variation in eDNA signals is increasingly explored for understanding community ecology in aquatic habitats. Seasonal changes have been addressed using eDNA sampling, but very little is known regarding short-term temporal variation that spans hours to days. To address this, we filtered marine water samples from a single coastal site in Denmark every hour for 32 h. We used metabarcoding to target both fish and broader eukaryote diversity and evaluated temporal changes in this marine community. Results revealed variation in fish species richness (15–27) and eukaryote class richness (35–64) across the 32 h of sampling, and we further evaluated sampling efforts needed to reach different levels of diversity saturation. Relative read frequency data for both fish and eukaryotes indicated a clear diel change in community composition, with different communities detected during daylight versus dark hours. The abundance signals in our data reflected biological variation rather than stochastic variation, since replicates taken at the same hour were more similar to each other than those taken at different hours. Our compositional results indicated a dynamic community, rather than a static pool of eDNA—even across a few hours. The fish data showed a daily pattern of relative species abundances, and the uncoupling of fish and broader eukaryote data suggest that variation in eDNA profiles across a single day can provide valuable information reflecting diel changes, at least for highly mobile organism groups. However, our results also point to several pitfalls in current eDNA experimental design, in which samples are taken over large areas without relative time-consistency or short-term replication. Our findings shed new light on short-term variation in coastal eDNA and have wide implications for experimental study design and for incorporating temporality into project conceptualization for future aquatic biodiversity monitoring.publishedVersio
Investigation of the effect of microplastics on the UV inactivation of antibiotic-resistant bacteria in water
Get PDFThis study investigated the effect of polyethylene and polyvinyl chloride microplastics on the UV fluence response curve for the inactivation of multidrug-resistant E. coli and enterococci in ultrapure water at pH 6.0 ± 0.1. In the absence of microplastics, the UV inactivation of the studied bacteria exhibited an initial resistance followed by a faster inactivation of free (dispersed) bacteria, while in the presence of microplastics, these 2 regimes were followed by an additional regime of slower or no inactivation related to microplastic-associated bacteria (i.e., bacteria aggregated with microplastics resulting in shielding bacteria from UV indicated by tailing at higher UV fluences). The magnitude of the negative effect of microplastics varied with different microplastics (type/particle size) and bacteria (Gram-negative and Gram-positive). Results showed that when the UV transmittance of the microplastic-containing water was not taken into account in calculating UV fluences, the effect of microplastics as protectors of bacteria was overestimated. A UV fluence-based double-exponential microbial inactivation model accounting for both free and microplastic-associated bacteria could describe well the disinfection data. The present study elucidated the effect of microplastics on the performance of UV disinfection, and the approach used herein to prove this concept may guide future research on the investigation of the possible effect of other particles including nanoplastics with different characteristics on the exposure response curve for the inactivation of various microorganisms by physical and chemical disinfection processes in different water and wastewater matrices.publishedVersio
Invasion impacts and dynamics of a European-wide introduced species
Get PDFGlobalization has led to the introduction of thousands of alien species worldwide. With growing impacts by invasive species, understanding the invasion process remains critical for predicting adverse effects and informing efficient management. Theoretically, invasion dynamics have been assumed to follow an “invasion curve” (S-shaped curve of available area invaded over time), but this dynamic has lacked empirical testing using large-scale data and neglects to consider invader abundances. We propose an “impact curve” describing the impacts generated by invasive species over time based on cumulative abundances. To test this curve's large-scale applicability, we used the data-rich New Zealand mud snail Potamopyrgus antipodarum, one of the most damaging freshwater invaders that has invaded almost all of Europe. Using long-term (1979–2020) abundance and environmental data collected across 306 European sites, we observed that P. antipodarum abundance generally increased through time, with slower population growth at higher latitudes and with lower runoff depth. Fifty-nine percent of these populations followed the impact curve, characterized by first occurrence, exponential growth, then long-term saturation. This behaviour is consistent with boom-bust dynamics, as saturation occurs due to a rapid decline in abundance over time. Across sites, we estimated that impact peaked approximately two decades after first detection, but the rate of progression along the invasion process was influenced by local abiotic conditions. The S-shaped impact curve may be common among many invasive species that undergo complex invasion dynamics. This provides a potentially unifying approach to advance understanding of large-scale invasion dynamics and could inform timely management actions to mitigate impacts on ecosystems and economies.publishedVersio
Analyse av mikroplast i marine sedimentprøver
Get PDFProsjektleder Cecilie Singdahl-LarsenSedimentprøver, både overflateprøver fra det øverste laget (0-2 cm) av sedimentet og kjerneprøver (fra 0 til 30 cm), ble analysert for mikroplast på NIVA. Prøvene ble opparbeidet ved tetthetsseparasjon med natriumjodid (NaI, ρ=1,5-1,6 g/cm3) og behandlet med 10 % eddiksyre. Etter opparbeiding ble prøvene analysert med stereomikroskop for å bestemme lengde (μm), form (fiber, fragment, kule), og farge til mikroplastpartiklene. Deretter ble mikroplastpartiklene analysert med FTIR (Fourier-Transform infrarød spektrometri) for å bestemme polymertype. Resultatene er presentert i denne rapporten.Norges geologiske undersøkelse, NGUpublishedVersio
Restaurering av ålegrasenger: En praktisk veileder utviklet for Oslo kommune
Get PDFProsjektleder Kristina Øie KvileÅlegrasenger er marine undervannsenger som finnes på grunne bløtbunnsområder langs Norskekysten, inkludert i Oslofjorden. De utgjør en viktig naturtype som huser et rikt biologisk mangfold og produserer en rekke økosystemtjenester. Klimaetaten i Oslo kommune ønsket en utredning av kunnskapsgrunnlaget og kartlegging av muligheter for restaurering eller reintroduksjon av ålegrasenger, og hvordan det vil påvirke karbonopptak og klimatilpasning i Oslofjorden. I tillegg ønsket de en praktisk veileder om reintroduksjon og restaurering av ålegras. Denne veilederen inneholder en detaljert steg-for-steg beskrivelse av hvordan restaurering kan gjennomføres i praksis, og dekker i) valg av område for restaurering, ii) planting og iii) overvåking. Kunnskap om ålegrasenger og deres rolle for karbonopptak og klimatilpasning er presentert i en egen rapport (Kvile et al. 2022).publishedVersio
Integrated biological effects assessment of the discharge water into the Sunndals fjord from an aluminium smelter
Get PDFProsjektleder: Ailbhe MackenAndre reviderte versjon av rapport 7537-2020. Første revisjon: 7543-2020.The following study describes an integrated biological effects monitoring programme using field transplanted mussels to determine the potential biological effects of the effluent discharge from Hydro’s aluminium smelter in the Sunndals fjord. Chemical body burden (PAH and metals) and a suite of biological effects markers were measured in mussels positioned at known distances (1, 2, 5, 10 and 20 km) from the aluminium smelter for 6 weeks. Overall, the biological responses observed where greater in the mussels positioned closest to the smelters discharge (1 – 5 km), although the chemical concentrations in mussel tissues were low and below the expected threshold levels. The lowest chemical accumulation and biomarker responses were observed in mussels positioned 10 km from the smelter. Mussels located furthest from the smelter exhibited significant biomarker responses, probably associated with a different contaminant source. The integrated biological response index (IBR) reflected the expected level of exposure to the smelters discharge and the Principal component analysis (PCA) differentiated between the mussel groups, with the most impacted located closest to the smelters discharge. Not one chemical factor explained the biological responses in mussels, correlations were found between certain measured contaminants (i.e. PAH, Mn, Ni and Cr) and distance from the smelter, although the concentrations of these contaminants were low and unlikely to have caused the biological effects observed in the mussels (1 and 5 km).Aluminiumindustriens Miljøsekretariat (AMS)publishedVersio
Microplastics in Norwegian coastal areas, rivers, lakes and air (MIKRONOR1)
Get PDFProsjektleder Bert van BavelThe Norwegian Environment Agency (Miljødirektoratet, NEA) tasked the Norwegian Institute for Water Research (NIVA) to initiate Norway’s National microplastic monitoring program. The program “Microplastics in Norwegian coastal areas, rivers, lakes and air (MIKRONOR)”, was designed to target the multitude of environments in the Norwegian coastal, freshwater and terrestrial ecosystems. The primary aim is to provide information on levels and types of microplastics in aquatic environments as well as in air and build on the baseline data already generated for a number of these environments on previous assignments by NEA. This report contains the first results of coastal sites, open marine waters, lakes, rivers and air including high-volume water samples (freshwater and marine, n=48), Ferrybox samples (marine, n=20), blue mussels (marine, n=71), vertical plankton net samples (marine, n=29) and 24 air samples (precipitation n= 12 and active air sampling n = 12).Norwegian Environment AgencypublishedVersio