Past and present: changes in the Odonata fauna of small lowland watercourses.

Small lowland watercourses, strongly exposed to anthropogenic activities and climate change, have received negligible odonatological attention. This study provides a revised checklist of three typical lowland small watercourses (Kállai-fofolyás, Konyári-Kálló and Ölyvös) within the Pannonian Lowland and presents the changes in their diversity over the past decades. Results revealed a significant biodiversity loss, with a 31.6% decline in Odonata fauna over the last 53 years. The upper and middle sections degraded the most, where the habitats have dried out or become intermittent. However, a diverse Odonata assemblage (1,277 individuals of 27 species) was observed at the 14 sampling sites of the three watercourses, containing protected and sensitive species (Somatochloraflavomaculata, Orthetrumbrunneum, Aeshnaisoceles, Libellulafulva). However, the low abundance of larval and exuvial forms (59 individuals of 13 species) suggests that the majority of the observed adults were developed in other watercourses. While recolonisation from nearby habitats is still possible, a parallel degradation of adjecent waterbodies could lead to an irreversible biodiversity loss.

Landscape-scale terrestrial factors are also vital in shaping Odonata assemblages of watercourses.

Habitat loss and fragmentation causes a decline in insect populations. Odonata (both dragonflies and damselflies) are especially threatened by the destruction of both aquatic and terrestrial environment. Moreover, effects of large-scale habitat heterogeneity on Odonata assemblages are poorly studied. In a two years study along East-European lowland watercourses both aquatic and terrestrial environment were studied to reveal the importance of local (e.g. water depth, macrovegetation cover, etc.) and landscape-scale (e.g. farmland patch size, forest patch proportion, etc.) variables to Odonata (as well as to dragonflies and damselflies separately) through increasing spatial sampling scales. The specimens were sampled using 500 m long transects from May to September. Results, both on local and landscape scales emphasized the importance of terrestrial environment on Odonata. Local variables influence damselflies, while dragonflies are more sensitive to landscape variables. Damselfly's diversity decreased with increasing macrovegetation cover, while dragonfly's diversity decreased with the increasing degree of land use intensification, but increased with the length of watercourses. It is thus vital to stress the importance of partial watercourse clearing, and moderate maintenance of traditional farm management based on small parcel farming near watercourses to maintain diverse and healthy Odonata assemblages.

Characterization of mercury and other heavy metals in sediment of an ecological important backwater area of River Tisza (Hungary).

Sediment from a representative and ecologically important backwater wetland under the influence of River Tisza (Hungary) was chemically characterized for sediment pollutants. Phosphine production potential, methyl mercury, mercury, and other heavy metals were determined along with other sediment chemical and physical properties. The wetland site, which is relatively isolated, represents an important bird reserve and nature conservation area. Methyl mercury and total mercury content was also low reflecting little mercury pollution in the sediment. Results of heavy metal analysis showed that only copper was elevated with concentration slightly above the reported levels considered excessive in soils and sediments. Other sediment properties were in normal range except boron content, which was high. Results show sediment were relatively unpolluted but should be routinely monitored to insure that this ecologically important area remains environmentally safe for future generation.