Nils Ekelund

Effects of Cu2+, Ni2+, Pb2+, Zn2+ and pentachlorophenol on photosynthesis and motility in Chlamydomonas reinhardtii in short-term exposure experiments

BackgroundHeavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulp- and paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies.ResultsThe concentrations studied ranged from 0.1 to 2.0 mg l-1 for copper, nickel, lead and zinc, and from 0.1 to 10.0 mg l-1 for pentachlorophenol. Exposure time was set to 24 h. Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii.ConclusionCopper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii. Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE. Because of high variance, motility was not considered a reliable physiological parameter when assessing toxicity of the substances using C. reinhardtii.

Comparison of usefulness of three types of artificial substrata (glass, wood and plastic) when studying settlement patterns of periphyton in lakes of different trophic status.

Usefulness of three types of artificial substrata (glass, wood and plastic) was tested when studying settlement patterns of periphyton in lakes of different trophic status. Strictly eu-, meso- and oligotrophic lakes in central Sweden were chosen as objects of the study. Glass slides, glass tubes, pieces of plastic (PVC) and pieces of wood of similar dimensions were placed for 9 weeks in July-August vertically 3 cm above bottom at a total depth of ca. 30 cm. Substrata were located at well-illuminated places without any other submerged objects (like macrophytes and stones), which could potentially affect colonisation patterns by algae. Periphyton communities, which colonised both the glass tubes and the pieces of wood tested, were specific enough to enable a clear classification of the lakes studied in eu-, meso- and oligotrophic. Glass tubes turned out to be the most favourable substratum when investigating settlement patterns of periphyton in this study. Although also colonised by periphytic species, wood did not support the same diversity and abundance of species as glass did. No algae were detected on the plastics studied. The plastics were covered entirely by a slime layer of bacteria. It is discussed if the nature of plastics could have some inhibitory effects on algal growth or the slime layer itself may have prevented settlement of algal spores.

The efficiency of seven diversity and one similarity indices based on phytoplankton data for assessing the level of eutrophication in lakes in central Sweden

Abstract Seven diversity and one similarity indices calculated on the basis of phytoplankton data were studied for their usefulness for eutrophication studies in lakes in central Sweden. The lakes of different eutrophication levels (eutrophic, mesotrophic and eutrophic) were investigated monthly during autumn 1998. All of the diversity indices calculated (Hurlbert’s, Margalef’s, Menhinick’s, Shannon’s, Simpson’s, McNaughton’s and Species Number) failed to distinguish between different levels of eutrophication. However, the use of similarity index based on presence–absence matrices of phytoplankton species proved its high efficiency for eutrophication studies in the lakes in central Sweden. The consideration of abundance, additionally to presence–absence data, was concluded not to be as efficient as only presence–absence matrices. We recommend the use of similarity index based on presence–absence matrices of phytoplankton species as a good tool for the assessment of the level of eutrophication in the lakes studied.

Photosynthesis and UV-B Tolerance of the Marine Alga Fucus vesiculosus at Different Sea Water Salinities

The marine algal species in the Baltic Sea are few due to the low sea water salinity. One of the few species that can be found is Fucus vesiculosus. Even this species is affected by the low salinity and becomes smaller in size in the Baltic. In present work the photosynthesis of F. vesiculosus in the northern Baltic (Bothnian Sea) was compared to the photosynthesis of F. vesiculosus in the Atlantic. Oxygen evolution was measured before and after exposure to 2.3 W of UV-B (280–320 nm) radiation for 5 h, as well as after 48 h recovery in low light. The plants were kept in their own sea water salinity as well as in a changed salinity, this to examine possible correlations between salinity and photosynthesis. The results show a significant higher initial maximal photosynthesis (Pmax) for Atlantic plants (10.3 nmol O2 g−1 FW s−1) compared to Baltic plants (4.0 nmol O2 g−1 FW s−1). The Baltic plants were found more sensitive to UV-B with a 40–50% decrease of Pmax as well as a lower degree of recovery (60–70% compared to 75–95% for the Atlantic plants). The higher salinity (35 psu) had a positive effect on the Baltic F. vesiculosus with increased Pmax as well as increased tolerance to UV-B. The lower salinity (5 psu) had a negative effect on the Atlantic plants with a decreased Pmax as well as a lower tolerance to UV-B. Pigment content was found higher in Atlantic F. vesiculosus. The pigment content decreased then the Atlantic plants were transferred to 5 psu. The concentration of Chl a as well as the total content of violaxanthin, diadinoxanthin and zeaxanthin in Baltic plants increased when transferred to 35 psu. The Atlantic F. vesiculosus can not survive the low salinity in the northern Baltic (died within 8 weeks). It is likely that a long time acclimation or adaptation to low salinity has taken place for F. vesiculosus in northern Baltic. If this is an ecotypic or genotypic development it is too early to say.

The effects of UV-B radiation on dinoflagellates

Summary Ultraviolet radiation, UV-B (280-320 nm), has harmful effects on marine phytoplankton. The presentexperiments were done to determine the effects of UV-B radiation on motility and growth of four marine motile dinoflagellates, Gyrodinium aureolum, Prorocentrum minimum, Heterocapsa triquetra and Scrippsiella trochoidea . The specific growth rate of the dinoflagellates showed an inhibition after 1 hour UV-B (1.5 kj m(su-2}day -1 ) daily during 1 week. The motility of H. triquetra showed a pronounced inhibition after 12 kJ m -2 day -1 , the motility of S. trochoidea did not show the same sensitivity to UV-B radiation. The photosynthetic inhibitor DCMU (10 -5 M) inhibited the motility of S. trochoidea but not the motility of H. triquetra . Action spectra (UV-B, 280-320 nm) for inhibition of motility of G. aureolum showed the maximum sensitivity at 280 and 290 nm.

CHROMOPHORE ROTATION IN 124‐kD ALTON A vena sativa PHYTOCHROME AS MEASURED BY LIGHT‐INDUCED CHANGES IN LINEAR DICHROISM

Abstract— From light‐induced changes in linear dichroism, we have calculated the rotation of the long‐wavelength‐absorbing transition moment that occurs during phototransformation of 124‐kilodalton Avena sativa phytochrome. Phytochrome was purified to homogeneity and immobilized onto Sepharose beads covalently coated with antibodies against A. sativa phytochrome. Changes in linear dichroism were induced by plane‐polarized red or far‐red light and measured by the absorbance differences at 660 and 730 nm using a dual‐wavelength spectrophotometer equipped with polarizing filters in the measuring beams. From such measurements, we calculate a rotation angle of 31o (or 149o) during photoconversion of Pr to Pfr and 30o (or 150o) during photoconversion of Pfr to Pr. These values are similar to the value of 32o (or 148o) reported earlier for the rotation of the transition moment of “large”A. sativa phytochrome (? 120 kilodalton) isolated under conditions that did not preclude post homogenization proteolysis of the 124 kilodalton molecule.

Comparative studies on the usefulness of seven ecological indices for the marine coastal monitoring close to the shore on the swedish east coast

The simultaneous behaviour of seven ecological indices(Hurlbert’s, Margalef’s, Menhinick’s, Shannon’s,species number, Jaccard’s and saprobic index) wasstudied based on phytoplankton data close to the shoreon the East coast of Sweden during the summer 1998.The sampling stations had a similar eutrophicationlevel and were located in bays. Standard phytoplanktondatabases were used in calculating the indices, whichwere later compared using cluster analysis.Hurlbert’s, Margalef’s, Menhinick’s, Shannon’s andspecies number indices, as measure of communitydiversity, produced similar trends which oftendiffered from those based on Jaccard’s index ofsimilarity. However, the simultaneous use of theseindices was found meaningful as a possible part of themonitoring close to the shore. The application of asaprobic index lead to erroneous conclusions in thestudied case.

Desiccation and salinity effects on marine and brackhish Fucus vesiculosus L. (Phaeophyceae).

A.M. Gylle, C.A. Nygård and N.G.A. Ekelund. 2009. Desiccation and salinity effects on marine and brackish Fucus vesiculosus L. (Phaeophyceae). Phycologia 48: 156–164. DOI: 10.2216/08-45.1. Ecotypes of Fucus vesiculosus L. from the Norwegian Sea (34 psu, marine ecotype) and Bothnian Sea (5 psu, brackish ecotype) have been compared with respect to the ability to withstand desiccation at different temperatures (0, 10, and 20°C). The aim was also to investigate the importance of salinity and light for the availably energy reserves, osmotic adjustment, and pigment content. The maximum quantum yield of photosystem II photochemistry (Fv/Fm) values revealed that the marine ecotype was more able to resist desiccation. The brackish algae showed a decrease in Fv/Fm as a response to desiccation at all temperatures, but the decrease was most pronounced at 20°C. The brackish ecotype recovered from desiccation within 5 h only when treated at 0°C. When the two ecotypes were treated at different levels of salinity in darkness and light, the results suggested that both salinity and irradiance are main factors in the differences in mannitol content between the two ecotypes. Chlorophyll (Chl) measurements showed 25% higher Chl α and 60% higher Chl c in the brackish ecotype in comparison to the marine ecotype. Darkness had a more pronounced effect on the Chl content than the salinity and initiated an increase in the amount of Chl, especially Chl c in the brackish ecotype.

Influence of waste water from the paper industry and UV-B radiation on the photosynthetic efficiency of Euglena gracilis

The green flagellate Euglena gracilis has been used as a model organism to elucidate the possible large-scale and short-term effects of waste substances from the pulp and paper industry on photosynthetic efficiency (PE). Different concentrations of waste substances before and after treatment in a cleaning system were studied. The uncleaned sample at concentrations up to 1:10 and the cleaned sample at concentrations up to 1:5 showed stimulating effects on the PE after 7 days of incubation compared to the control. The effects of waste substances on the PE of E. gracilis were also studied in combination with short-term studies (20 and 40 min) of ultraviolet-B radiation (UV-B, 280–320 nm). It was shown that increasing concentrations of the uncleaned sample had continuously stimulating effects on the PE and worked protectively against UV-B radiation. The cleaned sample exhibited no effects, or negative effects, on the PE of E. gracilis together with UV-B radiation compared to the experiments with only UV-B radiation. At the concentration 1:1 of the cleaned sample an increase in the PE was detected due to the high concentration of the coloured substances and a decrease in the UV-B penetration. PE revealed itself to be highly sensitive for detecting toxic effects on E. gracilis and is thus very promising for use in regular toxicity tests of waste water from pulp and paper industry.

Applicability of growth rate, cell shape, and motility of Euglena gracilis as physiological parameters for bioassessment at lower concentrations of toxic substances: An experimental approach

The responses of the growth rate, motility, and cell shape in the green flagellate Euglena gracilis to different concentrations of waste water substances from the pulp and paper industry were tested in a long‐term study (7 days). Samples before (uncleaned sample) and after (cleaned sample) the treatment in a cleaning system were studied. The influence of different doses of UV‐B radiation on cell shape and motility was also investigated. No statistically significant effects of increasing concentrations of the waste substances both before and after the cleaning process (except inhibition by the undiluted uncleaned effluent) on the growth rate in E. gracilis were observed. Cell shape turned out to be an unreliable physiological parameter for assessing the toxicity at lower concentrations of waste water substances. No significant patterns could be observed in the response of the cell shape to the different concentrations of the waste water substances or to UV‐B radiation. Motility has been concluded to be a more sensitive parameter than cell shape. However, no clear patterns were observed in the response of the motility to the different concentrations of the waste water substances studied. Increasing concentrations of the uncleaned sample demonstrated a defense against UV‐B radiation, due to the high absorbance in the UV‐B range, when effects on motility were examined. We conclude that contrary to the results reported in the literature earlier, cell shape and motility of E. gracilis are not universal physiological parameters for bioassessment at lower concentrations of toxic substances, including metals such as copper and zinc from the pulp and paper industry. The long‐duration tests had, in general, higher significance than those of short duration. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 78–83, 2001