Green Alga Raphidocelis Subcapitata Research Articles

The effects of graphene oxide on green algae Raphidocelis subcapitata

Graphene represents a new class of nanomaterials that has attracted great interest due to its unique electrical, thermal, and mechanical properties. Once disposed in the environment, graphene can interact with biological systems and is expected to exhibit toxicological effects. The ecotoxicity of graphene and its derivatives, viz.: graphene oxide (GO) depends on their physicochemical properties, including purity, diameter, length, surface charge, functionalization and aggregation state. In this study we evaluated the effects of graphene oxide (GO) on green algae Raphidocelis subcapitata. The algae were exposed to different concentrations of GO pre-equilibrated for 24h with oligotrophic freshwater medium (20ml) during incubation in a growth chamber under controlled conditions: 120μEm−2s−1 illumination; 12:12h light dark cycle and constant temperature of 22±2°C. Algal growth was monitored daily for 96h by direct cell counting. Reactive oxygen species level (ROS), membrane damage (cell viability) and autofluorescence (chl-a fluorescence) were evaluated using fluorescent staining and further analyzed by flow cytometry. The toxic effects from GO, as observed in algal density and autofluorescence, started at concentrations from 20 and 10μgmL−1, respectively. Such toxicity is probably the result of ROS generation and membrane damage (cell viability). The shading effect caused by GO agglomeration in culture medium may also contribute to reduce algal density. The results reported here provide knowledge regarding the GO toxicity on green algae, contributing to a better understanding of its environmental behavior and impacts.

Age-dependent shift in response to food element composition in Collembola: contrasting effects of dietary nitrogen

We examined the effect of different food qualities, in terms of the C:N:P content, on the collembolan Hypogastrura viatica. We hypothesised that (faster growing) juveniles would have higher demands for P and N than adults; this, however, was rejected by our experiments. There was no difference between the elemental compositions of juveniles and adults. In food preference experiments, juveniles and adults were offered green algae Raphidocelis subcapitata with three different C:N:P ratios. There was a strong shift in dietary response with age; juveniles preferred algae with low or medium N contents over the most N-rich algae, whereas adults showed the opposite. No response was seen when the specific P content in the food was varied. Juveniles fed on algae with high N content showed lower growth rates and survival than those fed on algae with other food qualities. In contrast, adults had lowest growth rates when fed on algae with a low N content. The negative effect on juveniles of the most N-rich diet appeared to be a toxic response that was directly or indirectly related to the algal N content. Adults had higher tolerance for N-rich diets, but were also more likely to face dietary N-limitation. These animals face a stoichiometric trade-off scenario in the sense that adaptation to maximise retention of a limiting element may result in reduced physiological ability to cope with excessive elements when feeding on "richer" diets, and vice versa. This problem is partly solved in H. viatica by contrasting selective feeding and ontogenetic dietary shifts between juveniles and adults.

Occurrence and fate of corrosion-induced zinc in runoff water from external structures

This paper comprises data from an extensive cross-disciplinary research project aiming to elucidate the environmental fate of corrosion-induced zinc release from external structures. It includes an exposure assessment that provide long-term runoff rates, concentrations and chemical speciation of zinc, from 14 zinc-based materials exposed during 5 years in Stockholm, Sweden, and an effect assessment including bioavailability and ecotoxicity measurements, both at the immediate release situation and after soil interaction. Runoff rates of total zinc ranged from 0.07 to 2.5 g Zn m − 2 yr − 1 with zinc primarily released as the free ion for all materials investigated. The average effect concentration, causing a 50% growth reduction after 72 h to the green algae Raphidocelis subcapitata, was at the immediate release situation 69 μg Zn L − 1 . Upon interaction of runoff water with soil, which simulated 18 to 34 years of exposure, the total zinc concentration was significantly reduced, from milligram per litre to microgram per litre levels. Simultaneously, the most bioavailable fraction of zinc in runoff, the hydrated zinc(II)-ion, decreased from more than 95% to about 30%. The major fraction, 98–99%, of the introduced total zinc concentration in the runoff water was retained within the soil. As long as the soil retention capacity was not reached, this resulted in zinc concentrations in the percolate water transported through the soil layer, close to background values and below growth inhibition concentrations for the green algae investigated. Zinc retained in soil was to a large extent (85–99.9%) extractable with EDTA, and available for plant uptake after 5 to 7 months of ageing.

Toxicity assessment of 40 herbicides to the green alga Raphidocelis subcapitata

The effects of 40 herbicides with nine modes of action on the green alga Raphidocelis subcapitata were studied by 96-h acute toxicity tests. Results showed that the EC 50 of the herbicides with respect to the photosynthetic processes of R. subcapitata ranged from 0.0007 to 4.2286 mg L −1. Photosynthesis was the process of the green alga most sensitive to the tested herbicides. The most toxic herbicides were atrazine, ametryme, simazine, prometryne, cyanazine, isoproturon, chlorotoluron, diuron, methabenzthiazuron, and paraquat. The EC 50 of the protoporphyrinogen oxidase inhibitor oxadiargyl, which was the parameter least sensitive to the herbicides tested in this study, was 42.5 mg L −1. The descending order of the average acute toxicity to R. subcapitata of herbicides with regard to the nine modes of action was as follows: photosynthetic process>cell division>lipid synthesis, acetyl-coenzyme A carboxylase>acetolactate synthase> 5-enolpyruvyl-shikimate-3-phosphate synthase, glutamine synthase, hormone synthesis>protoporphyrinogen oxidase.

Abstracts from the 12th international symposium on pollutant responses in marine organisms - molecular markers

In this study an enzyme-linked immunosorbent assay (ELISA) was developed to detect the stress protein Hsp70 in the green alga Raphidocelis subcapitata. Using this ELISA, the response to a variety of pollutants, including ZnCl2, SeO2 (heavy metals), lindane (organochlorine pesticide), pentachlorophenol (PCP, chlorinated hydrocarbon insecticide and fungicide), carbaryl (carbamate pesticide) and sodium dodecyl sulphate (SDS; surfactant) was tested. Our results show that Hsp 70 is produced in a dose-dependent way in response to most chemicals investigated (except PCP) and at concentrations below the range of classical cytotoxicity testing (i.e. growth inhibition, lethality). Still, the potential to induce Hsp70 varied among the pollutants tested, the heavy metals ZnCl2 and SeO2 being the strongest inducers of Hsp70. Combined with the existing literature, these results indicate that Hsp70 in R. subcapitata is a sensitive biomarker for a wide range of environmental pollutants.

Cyst-based toxicity tests. XI. Influence of the type of food on the intrinsic growth rate of the rotifer Brachionus calyciflorus in short-chronic toxicity tests.

As important members of zooplankton communities worldwide, rotifers are used extensively in ecotoxicological research. Chronic rotifer tests are, however, dependent on live algal food which adds to the complexity, the variability and the costs of these bioassays. To bypass the former problem, experiments have been undertaken with the freshwater rotifer Brachionus calyciflorus, to determine their intrinsic growth rate (r) when fed for 48 h on a mixture of green algae (Raphidocelis subcapitata recently renamed Pseudokirchneriella subcapitata) obtained from algal beads stored for different periods of time, and other inert foods. All tests have been performed in disposable multiwells, in 1 ml cups each inoculated with 1 rotifer freshly hatched from dried cysts. The majority of the growth tests was performed in eight replicates. The investigations revealed that microalgae from algal beads stored for up to one year, in darkness, at 4 degrees C, supplemented with dried blue-green algae (Spirulina) gave satisfactory rotifer reproduction. The intrinsic growth rates of the rotifers, were, however, dependent on the storage time of the algal beads; the highests r's (0.7-0.8) were obtained with algae from beads not older than four months. Growth tests with combinations of P. subcapitata and other inert feeds revealed that the enrichment food Selco used in aquaculture, also gave the same reproductive output as the combination microalgae/Spirulina. A rotifer growth experiment with 18 replicates showed that the variation coefficient is below 20% when the tests comprise eight replicates. This study demonstrated that microalgae from beads, supplemented by other inert food, open the door for a practical and cost-effective short-chronic rotifer test, which is totally independent of the culturing of both the test species and its live food.

Runoff rates, chemical speciation and bioavailability of copper released from naturally patinated copper

The release of copper, induced by atmospheric corrosion, from naturally patinated copper of varying age (0 and 30 years) has been investigated together with its potential ecotoxic effect. Results were generated in an interdisciplinary research effort in which corrosion science and ecotoxicology aspects were combined. The aim of the investigation was to elucidate the situation when copper-containing rainwater leaves a roof in terms of runoff rate, chemical speciation, bioavailability and ecotoxicity effects. Data have been collected during a three-year field exposure conducted in the urban environment of Stockholm, Sweden. The potential environmental effects have been evaluated using a combination of a copper specific biosensor test with the bacterium Alcaligenes eutrophus and the conventional 72-h growth inhibition test with the green alga Raphidocelis subcapitata. The results show annual runoff rates between 1.0 and 1.5 g/m 2 year for naturally patinated copper of varying age. The runoff rate increased slightly with patina age, which mainly is attributed to the enhanced first flush effect observed on thicker patina layers. The total copper concentration in investigated runoff samplings ranged from 0.9 to 9.7 mg/l. Both computer modeling and experimental studies revealed that the majority (60–100%) of released copper was present as the free hydrated cupric ion, Cu(H 2O) 6 2+, the most bioavailable copper species. However, other copper species in the runoff water, such as, e.g. Cu(OH) + and Cu 2(OH) 2 2+, were also bioavailable. The copper-containing runoff water, sampled directly after release from the roof, caused significant reduction in growth rate of the green alga. It should be emphasized that the results describe the runoff situation immediately after release from the copper roof and not the real environmental ecotoxicity. Therefore the data should only be used as an initial assessment of the potential environmental effect of copper runoff from building applications. Future risk assessments should also consider dilution effects of copper, changes in its chemical speciation and bioavailability during environmental entry, and type and sensitivity of the receiving ecosystem.

Bioavailability of zinc in runoff water from roofing materials

Corrosion and runoff from zinc-coated materials and outdoor structures is an important source for the dispersion of zinc in the environment. Being part of a large inter-disciplinary research project, this study presents the bioavailability of zinc in runoff water immediately after release from the surface of 15 different commercially available zinc-based materials exposed to the urban environment of Stockholm, Sweden. Runoff water was analysed chemically and evaluated for its possible environmental impact, using both a biosensor test with the bacteria Alcaligenes eutrophus (Biomet ®) and the conventional 72 h growth inhibition test with the green alga Raphidocelis subcapitata. Chemical speciation modelling revealed that most zinc (94.3–99.9%) was present as the free Zn ion, the most bioavailable speciation form. These findings were confirmed by the results of the biosensor test (Biomet ®) which indicated that all zinc was indeed bioavailable. Analysis of the ecotoxicity data also suggested that the observed toxic effects were due to the presence of Zn 2+ ions. Finally, regression analysis showed that, for this type of runoff samples, the rapid screening biosensor was capable of predicting (a) the total amount of zinc present in the runoff samples ( R 2 of 0.93–0.98; p<0.05) and (b) the observed 72 h-EbC 50s ( R 2 of 0.69–0.97; p<0.05).

Dose-dependent induction of heat shock protein 70 synthesis in Raphidocelis subcapitata following exposure to different classes of environmental pollutants

In this study an enzyme-linked immunosorbent assay (ELISA) was developed to detect the stress protein Hsp70 in the green alga Raphidocelis subcapitata. Using this ELISA, the response to a variety of pollutants, including ZnCl 2, SeO 2 (heavy metals), lindane (organochlorine pesticide), pentachlorophenol (PCP, chlorinated hydrocarbon insecticide and fungicide), carbaryl (carbamate pesticide) and sodium dodecyl sulphate (SDS; surfactant) was tested. Our results show that Hsp 70 is produced in a dose-dependent way in response to most chemicals investigated (except PCP) and at concentrations below the range of classical cytotoxicity testing (i.e. growth inhibition, lethality). Still, the potential to induce Hsp70 varied among the pollutants tested, the heavy metals ZnCl 2 and SeO 2 being the strongest inducers of Hsp70. Combined with the existing literature, these results indicate that Hsp70 in R. subcapitata is a sensitive biomarker for a wide range of environmental pollutants.

The use of miniaturized algal bioassays in comparison to the standard flask assay

Plastic test tubes and microplates were used in two miniaturized algal bioassays for comparison with a standard algal operational procedure in glass flasks. All three methods used spectrophotometrical measurements of growth of the green alga Raphidocelis subcapitata after 72 h. The EC50 values were determined from growth inhibition results for three metal compounds (CuSO4˙5H2O, ZnSO4˙7H2O, KMnO4), one pesticide (trichlorphone), and eight pharmacological drugs (oxytetracycline hydrochloridum, peroxysulphate, toltrazuril, pyrrolidone, formaldehyde, sodium chloride, chloridochlornane, and benzensulphochloramidum). Good interprocedural concordance for chemicals were reported and the comparability of toxicity results was demonstrated also for the eight environmental samples. This comparative study describes and recommends two algal microbioassays that can be used as an alternative to the standard flask toxicity test with algae. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 235–241, 1998