The significance of water ionic strength on aluminium toxicity in brown trout (Salmo trutta L.)

The toxicity of aluminium to fish is related to interactions between aluminium and the gill surface. We investigated the possible effect of water ionic strength on this interaction. The mortality of brown trout (Salmo trutta L.) exposed to three different degrees of Al polymerisation was compared in water with increased ionic strength (mean 7.31 x 10(-4) M) after additions of the base cations Ca2+, Mg2+, Na+ or K+, and in water with no such addition (mean ionic strength 5.58 x 10(-4) M). Only a very slight ameliorating effect of increased ionic strength was observed, while the degree of Al polymerisation was of major importance in fish mortality. In addition, it was observed that smaller fish survived the Al exposures for a longer time than larger fish. We hypothesise that this is because larger fish are more susceptible to hypoxia than smaller fish.     

Pastoral ecosystems and the issue of scale

This paper uses examples from Kenya and the Sudan to argue that the scale at which we pitch our analysis when trying to identify the basic properties of pastoral ecosystems may not be appropriate when it comes to recommending policy measures to secure the continued viability of pastoral herding. Pastoral households are always parts of large-scale economic and social structures. In many cases, such integration has provided the basis for the continued viability of pastoral adaptations. In other cases, the changing nature of local economies and social relations following from integration into large systems, has threatened the viability of pastoral herding or led to increasing differentiation within and between local communities. This paper raises the issue of how we most fruitfully define and delimit ecological and social systems in different local settings. It also questions conventional approaches to community-based natural resource management, which are now attracting widespread international attention.     

Organochlorine residues in harbour porpoises from Southwest Greenland

During the 1995 hunting season, 75 harbour porpoises (Phocoena phocoena) were sampled in three locations in West Greenland: Maniitsoq, Nuuk, and Paamiut. Sex, age, morphometrics, reproductive condition, and organochlorine compound (OC) levels in blubber were determined for each individual. OC levels were extremely low and, therefore considered unlikely to affect the population adversely: mean blubber concentrations, expressed on lipid weight basis were 1.98 (S.D.=1.1) mg/kg for PCBs, 2.76 (S.D.=1.66) mg/kg for tDDT and 0.21 (S.D.=0.11) mg/kg for HCB. No statistical differences were observed among individuals caught in the various locations. OC concentrations showed statistically significant positive associations with age in males but negative in females; consequently, mature females presented lower pollutant loads than their male counterparts. Juveniles did not show differences between sexes. A higher proportion of less chlorinated and more metabolizable polychlorinated biphenyls (PCBs) compared to tPCBs was found in calves (age< or =1) than in mature females, indicating that the feeding habits of these two groups differ and that a greater transfer of less chlorinated compounds is passed from females to their pups through lactation and parturition. Harbour porpoises significantly contribute to the dietary intake of OCs by local Inuit populations. This contribution could be reduced if mature males were selectively avoided; however, current hunting procedures make this selection impracticable.     

Dissipation of oxytetracycline, chlortetracycline, tetracycline and doxycycline using HPLC-UV and LC/MS/MS under aquatic semi-field microcosm conditions

A mixture of four tetracyclines; oxytetracycline (OTC), chlortetracycline (CTC), tetracycline (TC), and doxycycline (DC) was applied in fifteen 12000l outdoor microcosms at four treatment levels plus controls each with three replicates (n = 3). The dissipation times of parent compounds were monitored and half-lives (DT50) of 1-4 days, depending on treatment level were recorded. This is in accordance with half-lives from previous findings in bench-top experiments. Parent compound DT50, were determined using HPLC-UV. Furthermore, the samples were analyzed for ten different tetracycline products using LC/MS/MS. Two products were found for chlortetracycline; 4-epi-anh-chlortetracyline and the iso-chlortetracycline. Iso-forms were only found for CTC and only at the highest treatment (300 microg l(-1)). The half-lives, trajectories, and relative amounts of the products were analogous for all four tetracyclines. DT50 for products were less than 1.2 days. Formation of 4-epi-anh-tetracyclines, occurred at neutral to weak alkaline conditions.     

Preparation and certification of a reference material on PCBs in pig fat and its application in quality control in monitoring laboratories during the Belgian "PCB-crisis"

In this article, the production and validation of a new certified reference material "PCBs in animal fat" for the control of the maximum level of 200 ng/g setup by the European Communities for veterinary products from Belgium is described. Three materials are established: a blank, one material with about 100 ng/g and one with about 200 ng/g (sum of seven PCBs). Data on the production and certification are given. Additionally, this material was used as an unknown test material in the quality assurance program of the Belgium meat monitoring system (before the certification of the material). While the certification was performed with an uncertainty of less than 10%, the round robin exhibited larger deviations. However, these deviations were less than 20% for most of the 30 participating laboratories. Only two had significantly higher deviations.     

The effect of dimethoate and cypermethrin on soil-dwelling beetles under semi-field conditions

The effect of cypermethrin and dimethoate exposure on soil-dwelling beetles, in spring barley at different growth stages, of doses of up to eight times maximum field application rate has been investigated. Doses up to eight times maximum field application rate of cypermethrin did not have any acute effects on larger beetles, such as P. melanarius and C. erratus. Small beetles (A. bilineata, A. dorsale, B. lanpros, B. obtusum) were not harmed by doses up to two times maximum field application rate. T. hypnorum was affected at maximum field rate. Dimethoate at maximum field application rate harmed all species, but in particular the smaller species. When dimethoate was applied in high foliage density fields in the summer, very severe acute effects on spring breeding beetles were found. In the autumn, when only a low crop cover existed, this very high effect was not observed. The severe effect in the summer may be explained by the mode of action of dimethoate on 'old beetles'. The observed high toxic effect of dimethoate on spring breeders in the summer is expected only to have limited effect on the population, because the spring breeders at this time of the year have finished their egg depositing in the soil.     

Assessment of the importance of sorption for steroid estrogens removal during activated sludge treatment

Distribution coefficients (K(d)) between water and activated sludge particles (f(oc)=27.7+/-0.1%) were measured for the steroid estrogens (SE), estrone (E1), 17beta-estradiol (E2) and 17alpha-ethinylestradiol (EE2) in batch experiments. Experimental concentration levels ranged from environmentally realistic low ng/l to the high microg/l. In this range K(d)s were independent of their water concentration. The experimentally obtained K(d)s (with 95% confidence intervals) were 402+/-126 l/kg, 476+/-192 l/kg and 584+/-136 l/kg for E1, E2 and EE2, respectively. K(d)s were used to estimate the fraction of the total SE concentration that is expected to be sorbed in the activated sludge treatment tanks of a typical STP assuming equilibrium conditions. Assuming a suspended solids concentration of 4 g/l dissolved solids (ds), it was estimated that 61+/-9%, 66+/-13% and 70+/-6% of the total concentration of E1, E2 and EE2, respectively, would be sorbed during activated sludge treatment. The fraction of the SEs that was expected to be sorbed to suspended sludge particles in the effluents from a typical Danish STP was estimated to be only 0.20+/-0.06%, 0.24+/-0.10% and 0.29+/-0.07% of the total concentration of E1, E2 and EE2, respectively, at a suspended solids concentration of 5 mg/lds. For a typical STP the removal of steroid estrogens with excess sludge was estimated to be only 1.5-1.8% of the total loading if equilibrium conditions exists. Sorption is therefore not important for the fate of SEs in STPs compared to biodegradation.     

Reproduction and larval development in three scalpellid barnacles, Scalpellum scalpellum (Linnaeus 1767), Ornatoscalpellum stroemii (M. Sars 1859) and Arcoscalpellum michelottianum (Seguenza 1876), Crustacea: Cirripedia: Thoracica): implications for reproduction and dispersal in the deep sea

We studied reproduction and larval development in three species of pedunculated barnacles with different depth distribution, that is, Scalpellum scalpellum (30–200 m), Ornatoscalpellum stroemii (100–1,600 m) and Arcoscalpellum michelottianum (64–5,190 m). Morphology, position and number of males in the female/hermaphrodite, type of larval development and the number and size of eggs were recorded. All three species have a pair of pocket-like receptacles, each of which can host only a single male in O. stroemii, up to five males in S. scalpellum and up to 12 males in A. michelottianum. Eggs and larvae were smallest in S. scalpellum, intermediately sized in O. stroemii and largest in A. michelottianum. Brood size was comparable for S. scalpellum and O. stroemii, but five times higher in A. michelottianum. The ratio for body/egg size is almost similar in S. scalpellum and A. michelottianum, but much smaller in O. stroemii. Both S. scalpellum and A. michelottianum have nauplii that spend upwards of 10 days in the plankton while the larvae of O. stroemii hatch as cyprids that settle soon after release. All these reproductive data indicate that O. stroemii invests considerably more in each propagule than the other two species. We hypothesize that the observed differences in reproductive system and mode of development in the three species represent adaptations to their different habitats. S. scalpellum are mainly transported by currents in the coastal sublittoral zone. O. stroemii is presumably spread by intermediate deep currents along the shelf and shelf-slope, while A. michelottianum occurs on seamounts and is probably transported by demersal currents over wide areas of inhospitable soft-bottoms. Our observations are in accordance with the general pattern that, egg-size and propagule-size are positively correlated to bathymetric and geographic distribution, and that the continental slope environment represents a high disturbance environment, where a short larval stage is an advantage.