STRUCTURE AND FUNCTIONING OF THE HYPORHEIC ZONES IN THE GRAVEL-BEDS OF FIVE RIVERS IN RELATION TO CATCHMENT LAND USEBarbara Debeljak
, 2018, doktorska disertacija
Opis: The hyporheic zone has been recognised as a functionally important component of streams and rivers. Due to increasing human impact on ecosystems, studies that assess ecological responses of the hyporheic zone are of great importance. The objectives of the thesis are to study the responses of abiotic parameters, sediment biofilm characteristics (the in situ respiration (R), potential respiratory activity (ETSA), protein content), and invertebrate assemblages (analysed as total assemblages, EPT assemblages and Copepoda assemblages) in the hyporheic zones related to different land use patterns (forest, agricultural and urban areas). The focus of study also includes the impact of clogging. This research is comprised of three sampling campaigns conducted in summer (2013), winter (2013) and spring (2014) in five pre-Alpine Slovenian rivers. For each river, three or six sampling locations were chosen in the downwelling hyporheic sections of three dominant land uses (forest, agriculture and urban) within a 250 m wide impact zone. Three sampling points per location were sampled from two depths (5 –15 cm and 20 – 40 cm) using PVC tube and Bou-Rouch method. The results indicate a significant spatial and temporal heterogeneity of measured hyporheic zone components. Physical and chemical parameters of water revealed moderate response to land use. The effect of land use on the amounts of suspendable fine sediments in the hyporheic zone was observed only in the spring season. The effect of land use was significant for in situ R during summer and spring and for ETSA and protein content in all seasons, indicating that land use, such as agriculture, near a stream can affect biogeochemical processes. A relatively high diversity of invertebrates was recognised in the hyporheic zone. Groups such as Nematoda, Oligochaeta, Copepoda and Chironomidae were found in all samples. Within EPT taxa as representatives of occasional hyporheic invertebrates, 35 taxa were identified. Within Copepoda, as representatives of permanent hyporheic invertebrates, 14 Cyclopoida and 19 Harpacticida taxa were identified. Both assemblages were characterised by high abundance of widespread taxa, such as Baetis sp., Leuctra sp., Diacylops cladestinus and Acanthocyclops hispanicus. Statistically significant differences were observed among land uses in Copopoda assemblages but not for EPT assemblages. Calculated metrics on EPT assemblages showed statistically significant differences in land use in the number of EPT taxa, Simpson index and Shannon-Wiener index. Within Copepoda assemblages, the numbers of Copepoda taxa were significantly higher at forest sites. The hyporheic assemblages were relatively well explained by environmental parameters. This thesis presents a comprehensive study of the hyporheic zone, where both structural and functional measures reflected the ecological integrity of the hyporheic zone. The in situ R and ETSA were generally higher in agriculture stream reaches, indicating that hyporheic functioning responded to nutrients and carbon runoff-derived inputs from agricultural activities within the 250 m impact zone. Thus functional parameters in situ R and ETSA were more efficient indicators of land use impacts in the hyporheic zone than physical and chemical parameters. The potential of using hyporheic invertebrates as bioindicators of environmental conditions was confirmed but should be tested with wider gradients of environmental parameters. The results obtained by this study underlined that the hyporheic zone should be integrated as an additional ecological element by assessing the ecological conditions of surface water bodies.
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Povzetek najdenega: ...study the responses of abiotic parameters, sediment biofilm characteristics (the in situ respiration (R), potential...
Ključne besede: hyporheic zone, ecosystem functioning, land use, biofilm characteristics, invertebrates
Objavljeno: 02.07.2018; Ogledov: 2776; Prenosov: 116
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