Long-Term Toxicity of Gadolinium to the Freshwater Crustacean Daphnia magna.

The lanthanides are considered emerging contaminants but information on their long-term toxicity to aquatic species under environmentally relevant conditions is scarce. We aimed to fill this gap by evaluating the long-term adverse effects of gadolinium on the freshwater model-crustacean Daphnia magna. The exposure of D. magna for up to 39 days to 0.1 mg Gd/L (a 21-days chronic toxicity NOEC value derived by us formerly) in the lake water had no negative effect (p > 0.05) on vitality, size and reproduction of parent animals as well as their offspring. Thus, assumingly the current Gd contamination levels of surface waters pose no hazard to aquatic crustaceans that in general are very sensitive to various pollutants. Moreover, presence of 0.1 mg Gd/L in the lake water even mitigated the long-term toxic effect of 0.2 mg Ni/L (studied as a model co-contaminant) to D. magna's vitality and productivity.

Biotic threats for 23 major non-native tree species in Europe.

For non-native tree species with an origin outside of Europe a detailed compilation of enemy species including the severity of their attack is lacking up to now. We collected information on native and non-native species attacking non-native trees, i.e. type, extent and time of first observation of damage for 23 important non-native trees in 27 European countries. Our database includes about 2300 synthesised attack records (synthesised per biotic threat, tree and country) from over 800 species. Insects (49%) and fungi (45%) are the main observed biotic threats, but also arachnids, bacteria including phytoplasmas, mammals, nematodes, plants and viruses have been recorded. This information will be valuable to identify patterns and drivers of attacks, and trees with a lower current health risk to be considered for planting. In addition, our database will provide a baseline to which future impacts on non-native tree species could be compared with and thus will allow to analyse temporal trends of impacts.

Potential Hazard of Lanthanides and Lanthanide-Based Nanoparticles to Aquatic Ecosystems: Data Gaps, Challenges and Future Research Needs Derived from Bibliometric Analysis.

Lanthanides (Ln), applied mostly in the form of nanoparticles (NPs), are critical to emerging high-tech and green energy industries due to their distinct physicochemical properties. The resulting anthropogenic input of Ln and Ln-based NPs into aquatic environment might create a problem of emerging contaminants. Thus, information on the biological effects of Ln and Ln-based NPs is urgently needed for relevant environmental risk assessment. In this mini-review, we made a bibliometric survey on existing scientific literature with the main aim of identifying the most important data gaps on Ln and Ln-based nanoparticles' toxicity to aquatic biota. We report that the most studied Ln for ecotoxicity are Ce and Ln, whereas practically no information was found for Nd, Tb, Tm, and Yb. We also discuss the challenges of the research on Ln ecotoxicity, such as relevance of nominal versus bioavailable concentrations of Ln, and point out future research needs (long-term toxicity to aquatic biota and toxic effects of Ln to bottom-dwelling species).

Hazard evaluation of polystyrene nanoplastic with nine bioassays did not show particle-specific acute toxicity.

Plastic is a wide-spread pollutant and must be evaluated for potential adverse effects of its breakdown product, microplastic (≤5 mm) along with its subfraction, nanoplastic (1-100 nm). Risk assessment of pollutants cannot be conducted without their toxicity (dose-response) data. In this study, toxicity of polystyrene nanoplastics (PS-NPL) was evaluated using 8 acute and 1 subchronic toxicity assays with 10 organisms of different biological complexity (bacteria, yeast, algae, protozoans, mammalian cells in vitro, crustaceans, midge larvae). Commercial 26 and 100 nm carboxylated PS-NPL spheres were chosen as model and tested in nominal concentrations up to 100 mg/L (1.025·1016 26 nm and 1.83·1014 100 nm particles/L). In most of the assays, both PS-NPL proved non-toxic (L(E)C50 > 100 mg/L) but three tests (V. fischeri, R. subcapitata, D. magna) flagged toxicity in 'as received' 26 nm PS-NPL and D. magna also in 100 nm PS-NPL (EC50 ranging from 13 to 71 mg/L). As, according to manufacturers, both PS-NPL suspensions contained additives (surfactants and biocidal NaN3), the three toxicity tests were repeated also on dialysed PS-NPL and on NaN3. Non-toxicity of dialysed PS-NPL indicated that the toxicity of 'as-received' PS-NPL was not particle-specific but false positive due to water-soluble additives in the PS-NPL preparations. NaN3 was very toxic to D. magna (48 h EC50 = 0.05 ± 0.03 mg NaN3/L), toxic to R. subcapitata (72 h EC50 = 4.97 ± 3.7 mg NaN3/L) and non-toxic to V. fischeri. Toxicity of 'as-received' PS-NPL was not fully explainable by NaN3 but also attributable to other additives in the suspensions. Toxicity research of microplastic using commercial model particles must always consider the potential influence of additives, e.g. test the toxicity of dialysed NPL for comparison. In our study, D. magna, R. subcapitata and V. fischeri were the most sensitive to PS-NPL water-soluble additives and flagged their presence in NPL preparations.

Assessment of the hazard of nine (doped) lanthanides-based ceramic oxides to four aquatic species.

The risk of environmental pollution with rare earth oxides rises in line with increasing application of these compounds in different sectors. However, data on potential environmental hazard of lanthanides is scarce and concerns mostly Ce and Gd. In this work, the aquatic toxicity of eight doped lanthanide-based ceramic oxides (Ce0.9Gd0.1O2, LaFeO3, Gd0.97CoO3, LaCoO3, (La0.5Sr0.5)0.99MnO3, Ce0.8Pr0.2O2, (La0.6Sr0.4)0.95CoO3, LaNiO4) and one non-doped oxide (CeO2) with primary size from 23 to 590nm were evaluated in four short-term laboratory assays with freshwater crustaceans and duckweeds. Results showed no acute toxicity (EC50>100mg/L) or very low acute toxicity for most studied oxides. Observed toxicity was probably due to bioavailable fraction of dopant metals (Ni and Co) but in the case of aquatic plants, decrease of nutrient availability (complexing of phosphorus by lanthanides) was also presumed. Studied oxides/metals accumulated in the aquatic plant tissue and in the gut of crustaceans and thus may be further transferred via the aquatic food chain. Accumulation of metals in the duckweed Lemna minor may be recommended as a cost-effective screening bioassay for assessment of potential hazard of poorly soluble oxides to aquatic ecosystems.

Effect of wood ash on leaf and shoot anatomy, photosynthesis and carbohydrate concentrations in birch on a cutaway peatland.

Trees in cutaway peatland are growing in difficult conditions. Fertilization with nutrient-rich wood ash helps improve growth conditions. Photosynthesis and carbohydrate concentration along leaf anatomy were studied on plots treated with 10 and 5 t ha(-1) wood ash (WA10 and WA5) and on untreated (Control) plot to explain the physiological background of the differences in tree growth. The leaves from WA10 had the largest leaf area, total thickness, the thickest mesophyll and also significantly larger average values of all anatomical parameters of the shoots. The photosynthetic assimilation was significantly higher on treated plots at 200 and 400 ppm CO2 levels. In leaves on the treated plots, the sucrose concentration was lower while that of starch was higher than in trees on untreated soil. The differences in the maximum photosynthesis were relatively small. At unit ground, the leaf area provided for a wood ash-treated tree an efficient surface for CO2 assimilation, light interception and some starch storage during the growing period.

Growth, aboveground biomass, and nutrient concentration of young Scots pine and lodgepole pine in oil shale post-mining landscapes in Estonia.

The investigation was carried out in 8-year-old Scots pine (Pinus sylvestris L.) and lodgepole pine (Pinus contorta var. latifolia Engelm.) plantations on post-mining area, Northeast Estonia. The aim of the study was to assess the suitability of lodgepole pine for restoration of degraded lands by comparing the growth, biomass, and nutrient concentration of studied species. The height growth of trees was greater in the Scots pine stand, but the tree aboveground biomass was slightly larger in the lodgepole pine stand. The aboveground biomass allocation to the compartments did not differ significantly between species. The vertical distribution of compartments showed that 43.2% of the Scots pine needles were located in the middle layer of the crown, while 58.5% of the lodgepole pine needles were in the lowest layer of the crown. The largest share of the shoots and stem of both species was allocated to the lowest layer of the crown. For both species, the highest NPK concentrations were found in the needles and the lowest in the stems. On the basis of the present study results, it can be concluded that the early growth of Scots pine and lodgepole pine on oil shale post-mining landscapes is similar.

Plasticity in mesophyll volume fraction modulates light-acclimation in needle photosynthesis in two pines.

Acclimation potential of needle photosynthetic capacity varies greatly among pine species, but the underlying chemical, anatomical and morphological controls are not entirely understood. We investigated the light-dependent variation in needle characteristics in individuals of Pinus patula Schlect. & Cham., which has 19-31-cm long pendulous needles, and individuals of P. radiata D. Don., which has shorter (8-17-cm-long) stiffer needles. Needle nitrogen and carbon contents, mesophyll and structural tissue volume fractions, needle dry mass per unit total area (M(A)) and its components, volume to total area ratio (V/A(T)) and needle density (D = M(A)/(V/A(T))), and maximum carboxylase activity of Rubisco (V(cmax)) and capacity of photosynthetic electron transport (J(max)) were investigated in relation to seasonal mean integrated irradiance (Q(int)). Increases in Q(int) from canopy bottom to top resulted in proportional increases in both needle thickness and width such that needle total to projected surface area ratio, characterizing the efficiency of light interception, was independent of Q(int). Increased light availability also led to larger M(A) and nitrogen content per unit area (N(A)). Light-dependent modifications in M(A) resulted from increases in both V/A(T) and D, whereas N(A) changed because of increases in both M(A) and mass-based nitrogen content (N(M)) (N(A) = N(M)M(A)). Overall, the volume fraction of mesophyll cells increased with increasing irradiance and V/A(T) as the fraction of hypodermis and epidermis decreased with increasing needle thickness. Increases in M(A) and N(A) resulted in enhanced J(max) and V(cmax) per unit area in both species, but mass-based photosynthetic capacity increased only in P. patula. In addition, J(max) and V(cmax) showed greater plasticity in response to light in P. patula. Species differences in mesophyll volume fraction explained most of the variation in mass-based needle photosynthetic capacity between species, demonstrating that differences in plastic adjustments in mass-based photosynthetic activities among these representative individuals were mainly associated with contrasting investments in mesophyll cells. Greater area-based photosynthetic plasticity in P. patula relative to P. radiata was associated with larger increases in M(A) and mesophyll volume fraction with increasing irradiance. These data collectively demonstrate that light-dependent increases in mass-based nitrogen contents and photosynthetic activities were associated with an increased mesophyll volume fraction in needles at higher irradiances. They also emphasize the importance of light-dependent anatomical modifications in determining needle photosynthetic capacity.

Light-acclimation of cladode photosynthetic potentials in Casuarina glauca: trade-offs between physiological and structural investments.

Many arid and saline habitat species possess sparse canopies with cylindrical foliage that is considered relatively invariable along environmental gradients. However, even in sparse canopies strong gradients of light develop between the canopy top and bottom. We studied structural and photosynthetic acclimation to within-canopy light gradient in Casuarina glauca Sieb. ex Spreng., the photosynthetic organs of which are cylindrical cladodes. Seasonal average integrated quantum flux density (Qint) varied 25-fold between the canopy top and the canopy bottom. Cladode cross-sectional shape was unaffected by irradiance, but cladode dry mass per unit total area (MA) varied 2-fold within the canopy light gradient. This resulted primarily from light-dependent changes in cladode thickness (volume to total area ratio,V / AT) and to a lesser extent from changes in cladode density (D, MA = DV / AT). Nitrogen content, and the volume of mesophyll per unit surface area increased with increasing Qint and V / AT, resulting in positive scaling of foliage photosynthetic potential (capacity of photosynthetic electron transport and maximum Rubisco carboxylase activity per unit area) with light. However, nitrogen content per unit dry mass and the volume fraction of mesophyll decreased with increasing irradiance. This was explained by greater fractional investment in mechanical tissues in cladodes with greater volume to surface area ratio. This trade-off between photosynthetic and support investments reduced the cladode photosynthetic plasticity. Our study demonstrates a significant acclimation potential of species with cylindrical foliage that should be included in larger-scale carbon balance estimations of arid and saline communities.

Dependence of needle architecture and chemical composition on canopy light availability in three North American Pinus species with contrasting needle length.

Morphology and chemical composition of needles of shade-intolerant southern conifers (Pinus palustris Mill. (mean needle length +/- SD = 29.1 +/- 4.1 cm), P. taeda L. (12.3 +/- 2.9 cm) and P. virginiana Mill. (5.1 +/- 0.8 cm)) were studied to test the hypothesis that foliage acclimation potential to canopy light gradients is generally low for shade-intolerant species, and in particular, because of mechanical limitations, in species with longer needles. Plasticity for each needle variable was defined as the slope of the foliar characteristic versus irradiance relationship. A novel geometrical model for needle area and volume calculation was employed for the three-needled species P. palustris and P. taeda. Needle thickness (T) strongly increased, but width (W) was less variable with increasing daily integrated quantum flux density averaged over the season (Q(int)), resulting in changes in cross-sectional needle shape that were manifested in a positive relationship between the total to projected needle area ratio (A(T)/A(P)) and Q(int) in the three-needled species. In contrast, cross-sectional needle geometry was only slightly modified by irradiance in the two-needled conifer P. virginiana. Needle dry mass per unit total needle area (M(T)) was positively related to Q(int) in all species, leading to greater foliar nitrogen contents per unit area at higher irradiances. Separate examination of the components of M(T) (density (D) and the volume (V) to A(T) ratio; M(T) = DV/A(T)) indicated that the positive effect of light on M(T) resulted solely from increases in V/A(T), i.e., from increases in the thickness of foliage elements. Foliar chlorophyll content per unit mass increased with increasing Q(int), allowing an improvement in light-harvesting efficiency in low light. The variables characterizing needle material properties (D, the dry to fresh mass ratio, and needle carbon content per unit mass) were generally independent of Q(int), suggesting that needles were less stiff and had greater tip deflections under their own weight at lower irradiances because of smaller W and T. Comparisons with the literature revealed that plasticity in foliar characteristics tended to be lower in the studied shade- intolerant species than in shade-tolerant conifers, but plasticity among the investigated species was unaffected by needle length. However, we argue that, because of mechanical limitations, plastic changes in needle cross section in response to low irradiance may decrease rather than increase light-interception efficiency in long-needled species.