The effects of contaminants in European eel: a review

River networks as biodiversity hotlines

For several years, measures to insure healthy river functions and to protect biodiversity have focused on management at the scale of drainage basins. Indeed, rivers bear witness to the health of their drainage basins, which justifies integrated basin management. However, this vision should not mask two other aspects of the protection of aquatic and riparian biodiversity as well as services provided by rivers. First, although largely depending on the ecological properties of the surrounding terrestrial environment, rivers are ecological systems by themselves, characterized by their linearity: they are organized in connected networks, complex and ever changing, open to the sea. Second, the structure and functions of river networks respond to manipulations of their hydrology, and are particularly vulnerable to climatic variations. Whatever the scale considered, river networks represent "hotlines" for sharing water between ecological and societal systems, as well as for preserving both systems in the face of global change. River hotlines are characterized by spatial as well as temporal legacies: every human impact to a river network may be transmitted far downstream from its point of origin, and may produce effects only after a more or less prolonged latency period. Here, I review some of the current issues of river ecology in light of the linear character of river networks.

Spatial variations in the levels and isomeric patterns of PBDEs and HBCDs in the European eel in Flanders

Pooled yellow eel (Anguilla anguilla L.) samples, consisting of 3-10 eels, from 50 locations collected in the period 2000-2006 were used to assess the pollution with PBDEs and HBCDs in Flemish waters (Belgium). Results from this monitoring network are presented and the spatial aspect throughout Flanders is included, linking POP levels to the industrial characteristics of the different sampling locations. The following PBDE congeners were measured using GC/MS: 28, 47, 49, 66, 85, 99, 100, 153, 154, 183 and 209. Concentrations of summation sigmaPBDE ranged between 10 and 5811 ng/g lipid weight (lw) with a median value of 81 ng/glw. BDE 47 dominated the PBDE profile in the majority of the eel samples, except for six samples, in which BDE 209 was the dominating congener. These latter samples are probably associated with recent exposure to the Deca-BDE mixture. Three HBCD diastereoisomers (alpha-, beta- and gamma-HBCD) were measured using LC/MS-MS. summation sigmaHBCDs ranged between 16 and 4397 ng/glw, with a median value of 73 ng/glw. alpha-HBCD was the dominant isomer in all eel samples. Sediment concentrations of PBDEs were available from four locations and were used to compare the PBDE profile with those in eel. An important shift in the profile was observed, especially for BDE 209. While BDE 209 was only found in 12 eel samples, it was the dominant congener in all sediment samples. This could be due to its metabolisation or degradation in biota combined with the poor uptake of BDE 209 from sediments and its very low water solubility. No HBCDs were detected in any of the sediment samples. No significant correlation could be found between concentrations of PBDEs in eel and sediment from the same location. Comparison with previous studies shows that PBDE and HBCD levels in Flemish eels have decreased rapidly between 2000 and 2006 at particular sites, but alarming concentrations can still be found at industrialized hot spots. This finding is reflected in the human exposure to PBDEs and HBCDs through eel consumption. For average consumers (2.9 geel/day), intakes ranged between 3 and 2295 ng/day for summation sigmaPBDEs (with a median value of 16 ng/day) and between 3 and 1110 ng/day for summation sigmaHBCDs (with a median value of 18 ng/day), respectively. Additionally, human intakes were calculated for recreational fishermen, eating up to 12 g or 86 geel/day. Intakes of those risk groups were higher in comparison with average consumers and were above reference doses described in literature which may induce adverse effects.