Teeth of the red fox Vulpes vulpes (L., 1758) as a bioindicator in studies on fluoride pollution

An examination was made of fluoride content in the mandibular first molars of the permanent teeth of the red fox Vulpes vulpes living in north-west (NW) Poland. The teeth were first dried to a constant weight at 105°C and then ashed. Fluorides were determined potentiometrically, and their concentrations were expressed in dry weight (DW) and ash. The results were used to perform an indirect estimation of fluoride pollution in the examined region of Poland. The collected specimens (n = 35) were classified into one of the three age categories: immature (im, 6–12 months), subadult (subad, from 12 to 20 months) and adult (ad, >20 months). The mean concentrations (geometric mean) of fluoride were similar in the im and subad groups (230 and 296 mg/kg DW and 297 and 385 mg/kg ash, respectively), and significantly smaller than in the ad group (504 and 654 mg/kg, respectively, in DW and ash). Basing on other reports that the ∼400 mg/kg DW concentration of fluoride in bones in the long-lived wild mammals generally reflects the geochemical background, it was found that 57% of the foxes in NW Poland exceeded this value by 9% to 170%. This indirectly reflects a moderate fluoride contamination in the tested region

The effects of sex, age, season and habitat on diet of the red fox Vulpes vulpes in northeastern Poland

The diet of the red fox Vulpes vulpes was investigated in five regions of northeastern Poland by stomach content analysis of 224 foxes collected from hunters. The red fox is expected to show the opportunistic feeding habits. Our study showed that foxes preyed mainly on wild prey, with strong domination of Microtus rodents, regardless of sex, age, month and habitat. Voles Microtus spp. were found in 73% of stomachs and constituted 47% of food volume consumed. Other food items were ungulate carrion (27% of volume), other mammals (11%), birds (9%), and plant material (4%). Sex- and age-specific differences in dietary diversity were found. Adult males and juvenile foxes had larger food niche breadths than adult females and their diets highly overlapped. Proportion of Microtus voles increased from autumn to late winter. Significant habitat differences between studied regions were found. There was a tendency among foxes to decrease consumption of voles with increasing percentage of forest cover. Based on our findings, red foxes in northeastern Poland can be recognized as a generalist predators, consuming easily accessible and abundant prey. However, high percentage of voles consumed regardless of age, sex, month, or habitats may indicate red fox specialization in preying on Microtus rodents

Sezonowe zmiany uwalniania fosforu z osadów dennych w jeziorze Rusałka w trakcie zabiegów rekultywacyjnych

Paper presents a comparative study of phosphorus (P) internal loading from bottom sediments in Rusalka Lake in years 2006 and 2007, when restoration measures were conducted and in 2005, a year before restoration. Internal loading of P decreased as an effect of applied treatment. The mean loading in 2005 was 9.07 mg P m–2 d–1, whilst in next two years it was 4.36 mg P m–2 d–1 and 2.28 mg P m–2 d–1, respectively. The reduction reached 51 % in 2006 and 75 % in 2007. A domination of P release was noted in 2005 and 2006, amounting in summer to 38.1 mg P m–2 d–1 in the deepest place of the lake and 15.6 mg P m–2 d–1 in the littoral zone. A period of accumulation supremacy was observed in spring 2007, reaching 4.9 mg P m–2 d–1 in the littoral and 2.8 mg P m–2 d–1 in the profundal.Praca prezentuje zmiany uwalniania fosforu z osadów dennych w jeziorze Rusałka w latach 2006–2007, kiedy prowadzono rekultywację zbiornika z użyciem siarczanu(VI) żelaza(III). W wyniku przeprowadzonych zabiegów rekultywacyjnych zasilanie wewnętrzne w fosfor z osadów dennych wyraźnie zmniejszyło się. Średnie zasilanie wewnętrzne przed wykonaniem zabiegów rekultywacyjnych wynosiło 9,07 mg P m–2 d–1, w kolejnym zmniejszyło się do 4,36 mg P m–2 d–1 (redukcja o 51 %), a w ostatnim roku do 2,28 mg P m–2 d–1 (redukcja o 75 %). W latach 2005 i 2006 stwierdzano wydzielanie fosforu z osadów dennych, dochodzące w okresie letnim do 38,1 mg P m–2 d–1 w obrębie głęboczka i do 15,6 mg P m–2 d–1 w litoralu. W ostatnim roku badań wiosną, nie następowało wydzielanie P z osadów, a kumulacja P osiągnęła 4,9 mg P m–2 d–1 w litoralu i 2,8 mg P m–2 d–1 na głęboczku