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Seasonal variation of gas exchange and pigmentation in branches of three grafted clones of mature ponderosa pine exposed to ozone and acid rain
1997
Anderson, P.D. | Houpis, J.L.J. | Helms, J.A. | Momen, B. (USDA Forest Service, Forestry Sciences Laboratory, Rhinelander, Wisconsin (USA))
Seasonal variability of total and easily leachable element contents in topsoils (0-5 cm) from eight catchments in the European Arctic (Finland, Norway and Russia)
1997
Niskavaara, H. | Reimann, C. | Chekushin, V. | Kashulina, G. (Geological Survey of Finland, PO Box 77, FIN-96101 Rovaniemi (Finland))
Composting of spent pig litter at different seasonal temperatures in subtropical climate
1997
Tiquia, S.M. | Tam, N.F.Y. | Hodgkiss, I.J. (Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China))
The seasonal changes of keratinolytic fungi in sediments of Catalonian Rivers (Spain)
1997
Ulfig, K. | Łukasik, W. | Guarro, J. | Cano, J. | Gené Badía, Joan | Vidal, P. | Figueras, M. J.
The Catalonian river sediments were found to be rich in keratinolytic fungi. The keratinolytic fungal populations showed clear seasonal changes in the river sediments. The main factors ‘regulating’ these populations in such habitat were temperature, dissolved oxygen concentration, pH, ammonium, nitrates, total fungal number, BOD₅, water poisons (cyanides, detergents, phenols), salinity and, presumably, strong insolation associated with low water levels. The last was probably of special importance in the deterioration of the fungal populations in the spring/summer season. A toxic effect on keratinolytic fungi in sediments was observed.Chrysosporium keratinophilum was found to be most resistant to industrial contaminants and salinity. Therefore, this species could be used as an indicator of water pollution.
Show more [+] Less [-]Total mercury and methylmercury in sediments and in the polychaeteNereis diversicolor at Groot Buitenschoor (Scheldt estuary, Belgium)
1997
Muhaya, B. B. M. | Leermakers, M. | Baeyens, W.
Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete wormNereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g⁻¹ dw and from 0.8 to 6 ng g⁻¹ dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation byN. diversicolor was significantly (p<0.05) higher at stations with sandy sediments (mean value: 125 ng g⁻¹ dw) than at stations with muddy sediments (mean value, 80 ng g⁻¹), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg inN. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg inN. diversicolor. Total Hg concentrations in sediments were significantly (p<0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p<0.01) higher in spring and summer than in autumn and winter.
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