Effects of enhanced UVB radiation on a marine benthic diatom mat

In order to study the ecophysiological response of a natural diatom-dominated microbial mat to an enhanced level of ultraviolet-B radiation (UVBR), intact sediment cores from a shallow microtidal bay on the Swedish west coast were incubated in an outdoor flow-through system and exposed to either no UVBR or to an artificially enhanced level of UVBR. The microbial mat was cohesive and dominated by the large (≈ 400 μm) motile diatom Gyrosigma balticum. Functional response to UVBR was assessed by measuring carbon fixation (¹⁴C) and allocation of photosynthetic products. Sediment oxygen microprofiles were measured as indicators of the balance between the photosynthetic and respiratory activity of the community. Structural variables included biomass and composition of microalgae, pigment composition (HPLC), content of UV-absorbing compounds, and composition of fatty acids. An enhanced level of UVBR resulted in significant functional changes in the microalgal community. Significantly decreased carbon fixation and lower net oxygen production (as calculated from oxygen microprofiles) suggest that primary productivity in the type of microbial mat studied is potentially sensitive to an enhanced level of UVBR. The pattern of carbon allocation hinted a change as to the photosynthetically active part of the community when exposed to UVBR, indicating a differential sensitivity among algal cells. Despite significant functional effects, pigment or algal composition were not significantly affected by enhanced UVBR. The concentration of UV-absorbing compounds was low and did not increase at UVBR exposure. Due to the short duration of the experiment (4 d), a change in algal biomass or composition was not to be expected. Moreover, the thickness of the sampled sediment layer, may have contributed to the lack of observed structural effects of enhanced UVBR. Visual observations suggested that UVBR affected the motility of G. balticum. This study, as well as other experiments with a similar diatom mat, suggest that vertical migration is a key mechanism to be further studied in relation to UVBR exposure of diatom-dominated microbial mats. Received: 7 September 1996 / Accepted: 8 October 1996     

Low levels of persistent organic pollutants (POPs) in New Zealand eels reflect isolation from atmospheric sources

Polychlorinated biphenyls (PCBs) and organic pesticides (i.e., DDTs) were measured in long finned eels (Anguilla dieffenbachii) in 17 streams on the west coast of South Island, New Zealand. Very low levels of PCBs and low levels of ppDDE were found. The concentrations of PCBs and ppDDE were not correlated within sites indicating that different processes determined the levels of the two pollutants in New Zealand eels. The PCBs probably originate from atmospheric transport, ppDDE levels are determined by land use and are higher in agriculture areas. The low contamination level of these aquatic systems seems to be a function of a low input from both long and short-range transport as well as few local point sources. No correlation could be found between lipid content and persistent organic pollutants (POPs) concentration (as shown in previous studies) in the eels which could be explained by low and irregular intake of the pollutants.     

Fluids and jellies of the acusticolateralis system in relation to body fluids in Coryphaenoides rupestris and other fishes

The marine deep-water fish Coryphaenoides rupestris has a lymph-like fluid in its large cranial lateral-line canals. A similar canal endolymph is also found in a few other fishes possessing closed lateral-line canals. We have analysed, chemically, the canal endolymph from 3 species of teleosts. In C. rupestris, the ionic composition resembles that of blood plasma, but the content of potassium is slightly lower. In Lota lota, the canal endolymph has a high potassium concentration, as does the inner-ear endolymph. In Glyptocephalus cynoglossus, the ionic composition of the canal endolymph resembles sea water. In all species, the concentrations of glucose and protein are much lower than in the blood plasma. Analyses were further made on endolymph and perilymph of the inner ear, on jelly-like material from the acusticolateralis system, and on body fluids from a small number of fish species, even elasmobranchs and a holocephalan. The water phase of the cupulae of the lateral-line system of C. rupestris had an ionic composition similar to that of the endolymph surrounding the cupulae. High potassium and low values for glucose and protein were found in the inner-ear endolymph of all species investigated. No carbonic anhydrase activity was found in the lateral-line system of C. rupestris, whereas a low activity of this enzyme was found in the inner ear of Gadus morrhua. The investigation shows that the composition of the fluids in contact with the mechano-receptors of the lateral-line system differs between different species of fishes. A few observations were made on the structural organization of the cranial lateral-line system in C. rupestris.     

Estimating reduction of nitrogen leaching from arable land and the related costs

The EU Water Framework Directive will require river-basin management plans in order to achieve good ecological status and find the most cost-efficient nitrogen (N) leaching abatement measures. Detailed scenario calculations based on modeling methods will be valuable in this regard. This paper describes the approach and an application with a coefficient method based on the simulation model SOILNDB for quantification of N leaching from arable land and for prediction of the effect of abatement scenarios for the R?nne? catchment (1900 km2) in southern Sweden. Cost calculations for the different measures were also performed. The results indicate that the individual measures-cover crop and spring plowing, late termination of ley and fallow, and spring application of manure-would only reduce N leaching by between 5% and 8%. If all measures were combined and winter crops replaced by their corresponding spring variants, a 21% reduction in N leaching would be possible. However, this would require total fulfillment of the suggested measures.     

Increased levels of bacterial markers and CO2 in occupied school rooms

Our group previously demonstrated that carbon dioxide (CO2) levels in heavily occupied schools correlate with the levels of airborne bacterial markers. Since CO2 is derived from the room occupants, it was hypothesized that in schools, bacterial markers may be primarily increased in indoor air because of the presence of children; directly from skin microflora or indirectly, by stirring up dust from carpets and other sources. The purpose of this project was to test the hypothesis. Muramic acid (Mur) is found in almost all bacteria whereas 3-hydroxy fatty acids (3-OH FAs) are found only in Gram-negative bacteria. Thus Mur and 3-OH FA serve as markers to assess bacterial levels in indoor air (pmol m(-3)). In our previous school studies, airborne dust was collected only from occupied rooms. However, in the present study, additional dust samples were collected from the same rooms each weekend when unoccupied. Samples were also collected from outside air. The levels of dust, Mur and C10:0, C12:0, C14:0, and C16:0 3-OH FAs were each much higher (range 5-50 fold) in occupied rooms than in unoccupied school rooms. Levels in outdoor air were much lower than that of indoor air from occupied classrooms and higher than the levels in the same rooms when unoccupied. The mean CO2 concentrations were around 420 parts per million (ppm) in unoccupied rooms and outside air; and they ranged from 1017 to 1736 ppm in occupied rooms, regularly exceeding 800-1000 ppm, which are the maximum levels indicative of adequate indoor ventilation. This indicates that the children were responsible for the increased levels of bacterial markers. However, the concentration of Mur in dust was also 6 fold higher in occupied rooms (115.5 versus 18.2 pmole mg(-1)). This further suggests that airborne dust present in occupied and unoccupied rooms is quite distinct. In conclusion in unoccupied rooms, the dust was of environmental origin but the children were the primary source in occupied rooms.     

Prenatal diagnosis of glutathione synthase deficiency

Prenatal diagnosis for glutathione synthase (EC 6·3.2·3) deficiency in two pregnancies of an at-risk couple was performed on amniotic fluid taken at 16 weeks' gestation. 5-Oxoproline (pyroglutamic acid) levels were 970 and 790 μmol/l compared with the normal mean value of 29 μmol/l (range 13–51 μmol/l). The pregnancies were terminated and the diagnosis in one case was subsequently confirmed by assay of glutathione synthase in cultured fetal fibroblasts. In the other, post-mortem tissue samples failed to grow.