Iskanje po repozitoriju

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Ključne besede: reka Vipava, kakovost vode, onesnaževanje, namembnost zemljišča, invazivne vrste
Objavljeno v RUNG: 17.09.2019; Ogledov: 4745; Prenosov: 0
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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.
Ključne besede: hyporheic zone, ecosystem functioning, land use, biofilm characteristics, invertebrates
Objavljeno v RUNG: 02.07.2018; Ogledov: 5391; Prenosov: 169
Celotno besedilo (5,31 MB)

Opis: In this study, realised and fundamental niches were combined between studied ICS (Austropotamobius torrentium (Schrank, 1803), Austropotamobius pallipes (Lereboullet, 1858), Astacus astacus (Linnaeus, 1758)) and NICS (Pacifastacus leniusculus (Dana, 1852), Orconectes limosus (Rafinesque, 1817), Cherax quadricarinatus (von Martens, 1868)). The realised niche was described by population characteristics. P. leniusculus showed similar annual cycle than ICS, but on the other hand it showed higher population density, shorter breeding period, and better individual condition (estimated with SMI) comparing to the ICS. These are its advantages over ICS, which increase its potential for the invasiveness. The most pronounced this threat is to A. astacus, with which it has the most similar/ overlapping realised niche. Similar was observed comparing the ICS and NICS fundamental niches presented by selected physiological measurements (maximal food (Cmax) and oxygen consumption (Rn), concentration of haemocyanin in haemolymph (Hc), electron transport system (ETS) activity and potential growth scope (PGS). As a result of higher plasticity and adaptation to varied environmental conditions, NICS expressed different physiological response to temperature at cellular (ETS activity) and organism (Cmax, Rn, PGS) level. Similar fundamental characteristics (expressed with thermal optimums) were found between P. leniusculus and ICS, while optima for O. limosus and C. quadricarinatus were more narrow and higher (above 22 °C and 30 °C). Modelling of thermal niches showed differences mostly among species on cellular level (in ETS activity). This was a new approach and support for better estimation of success and proliferation of new invaders. Furthermore, C. Quadricarinatus, found for the first time as established population in temperate climate of Europe (in Slovenia in 2009), was used in this study, as a model organism, to show that the combination of fundamental and realised thermal niche, as well as ecophysiological and field research can constitute an important input to the model for estimating the risk associated with C. quadricarinatus. It is rarely possible to observe the development of new invaders in the new environment, therefore monitoring of the C. quadricarinatus through the three growth period (1-lag phase, 2-log phase, 3-stable phase), was unique example in the invasive biology. After extremely increasing the population in 2011 and 2012 (for 7.7 - 10.1 % per month) the population developed and stabilised in March 2012. Based on these high numbers of field and lab data, the TIRI (Thermal Invasive Risk Index) was developed to produce instant results that may be satisfactory for evaluation of different degrees of invasiveness. We found that the oxbow lake Topla had no lethal days (no. of days when water temperature is below or above temperature of death) in comparison with the adjacent rivers where the number of lethal days probably constitutes an important barrier for species spreading. Therefore, we concluded that C. quadricarinatus could potentially reproduce in the adjacent rivers, but survival of the brood is doubtful, especially due to previous results concerning critical min/max temperatures.
Ključne besede: potočni raki, jelševec, koščak, koščenec, signali rak, trnavec, rdečeškarjevec, sezonska dinamika, termalna toleranca, temeljna ekološka niša, realizirana niša, potencialna invazivnost
Objavljeno v RUNG: 24.11.2016; Ogledov: 7255; Prenosov: 363
Celotno besedilo (4,73 MB)

Opis: Ena izmed invazivnejših tujerodnih vrst na svetu je školjka Dreissena polymorpha (Pallas, 1771), slovensko potujoča trikotničarka ali školjka trikotničarka (Remec–Rekar, Š., 2013). Naseljuje jezera, rezervoarje, bazene in lagune. Širjenje je opaženo predvsem v jezerih, kjer je velika številčnost fitoplanktona in je alkalna voda bogata s kalcijem in magnezijevimi solmi (Minchin, D. idr., 2002). Čeprav je stopnja rasti in številčnost školjke omejena z dejavniki, kot so pretok, razpoložljivost hrane in temperatura, se školjke brez trdne podlage ne morejo naseliti, razširiti ali razmnoževati (McLaughlan, C. in Aldridge, D. C., 2013). V jezerih školjke tvorijo velike populacije, kar pomeni tudi do 120.000 osebkov na kvadratni meter, to pa zaradi aktivne filtracije povzroča večjo prosojnost vode (Minchin, D. idr., 2002). Tako številčnost lahko dosežejo zaradi velike tolerance, saj se na različne življenjske razmere, kot so nihanja vodne gladine, povečana slanost in večja nihanja temperatur, hitro prilagodijo (Remec-Rekar, Š., 2013). Do 19. stoletja je bila školjka prisotna le v Črnem, Kaspijskem in Azovskem morju. Med letoma 1800 in 1900 se je razširjenost školjke po Evropi povečala za dvakrat. Glavne možnosti za širitev so bile plovbe po celinskih vodah, še posebej po odprtju novih plovnih poti med vzhodno in srednjo Evropo v začetku leta 1800 (Birnbaum, C., 2011). Izjemno hitro se je razširila tudi v Severni Ameriki, kjer so jo prvič opazili leta 1988 v jezeru St. Clair (Minchin, D. idr., 2002). V slovenskih vodah je bila trikotničarka prvič opažena v reki Dravi, leta 2010 pa so jo opazili tudi v Blejskem jezeru (Remec-Rekar, Š., 2013). Od leta 2012 potapljači iz Društva za podvodne dejavnosti (DPD) Bled spremljajo njeno širitev po jezeru ter jo poskušajo s fizičnim odstranjevanjem tudi omejiti (DPD Bled). V okolju, ki ga naseljujejo, povzročajo spremembe fizične in biološke strukture. Spremenijo obstoječe življenjske prostore in zagotovijo novo okolje za druge organizme, vplivajo na prehranjevalni splet in razpoložljivost hrane. Prav tako vplivajo na druge procese in stanja v ekosistemih, vključno z mineralizacijo hranil, razpoložljivostjo kisika in stopnjo sedimentacije (Karatayev, Y. A. idr., 2002). Zaradi hitre prilagodljivosti, nevarnosti širitve in njihovega vpliva je treba zagotoviti učinkovit monitoring stanja školjk v Blejskem jezeru in okoliških vodah, v katere se lahko naselijo. S pomočjo tuje in domače znanstvene literature sem se seznanila z invazivno vrsto školjke v jezeru. V analizo školjk, ki so bile nabrane v Blejskem jezeru, smo zajeli velikostno in starostno strukturo populacije školjk ter obseg in gostoto poselitve. Na trinajstih naključno izbranih lokacijah smo s potapljači iz Društva za podvodne dejavnosti Bled (DPD) od januarja do junija 2015 školjke nabirali tedensko. Z vsake lokacije smo podrobno analizirali okoli 250 gramov naključno nabranih školjk, katerim smo izmerili dolžino, širino in višino, namen pa je bilo ugotoviti intenzivnost rasti, glede na posamezne lokacije in starost. Narejena pa je bila tudi biološka analiza vode, s katero sem preverjala prisotnost ličink veliger. Rezultati velikostne in starostne sestave kažejo na stabilnost populacije v jezeru. Iz podatkov o velikosti populacij iz prejšnjih let lahko ocenimo, da do večjega izboljšanja v jezeru ni prišlo.
Ključne besede: Školjka trikotničarka, Blejsko jezero, tujerodna vrsta, vpliv na okolje, velikost populacije, starost osebkov
Objavljeno v RUNG: 30.09.2015; Ogledov: 7852; Prenosov: 297
Celotno besedilo (2,26 MB)

Ključne besede: ekologija, hidrologija, epikras, prenikla voda, dežne padavine, analiza recesije, topljenje snega, vadozni tok, disertacije
Objavljeno v RUNG: 22.01.2015; Ogledov: 6207; Prenosov: 404
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