https://doi.org/10.22364/eeb.17.06 ABSTRACTS OF THE 77th SCIENTIFIC CONFERENCE OF THE UNIVERSITY OF LATVIA January – February 2019 Gruberts D., Paidere J., Druvietis I. Downstream transformation of the phytoplankton communities along the Middle Daugava River at different flood-flow discharges 29 Purvina S., Medne R., Bajinskis J., Kondratjeva N. Success of long-term salmonid restocking in Latvia 31 Poppela D., Poppels A., Druvietis I. Limnological characteristics of small shallow lakes situated in Garkalne County, Latvia 33 Pentjuss A. Biomass objective function and its role in metabolism modelling 35 Seņkovs M., Nikolajeva V., Petriņa Z. Trichoderma asperellum, Bacillus subtilis, Botrytis cinerea and their consortium effects on soil microbiota 36 Paiders M., Makarenkova G., Kleperis J., Nikolajeva V. Microbial population dynamics of freshwater sludge during fermentation of crude glycerol 37 Karlsons A., Osvalde A. Effect of foliar fertilization of microelements on yield and quality of highbush blueberries (Vaccinium corumbosum) in cutover peatlands 39 Gailīte A., Ruņģis D.E. Investigation of bilberry (Vaccinium myrtillus) genetic diversity and population structure 40 Mihailova (Magomedova) E., Melecis V. Traditional beekeeping and its sustainable development in eastern Latvia 41 Kokrīte I., Druvietis I., Ozoliņa L. Uzule L. Ozoliņš D., Jēkabsone J. Algae as indicators of the ecological quality of Latvian rivers 42 Abersons K. Efficiency of stocking of river lamprey ammocoetes – first results 43 Laizāne L., Eglīte L., Cibrovska A., Avsejenko J., Grantiņa-Ieviņa L. Detection of Salmonella spp. presence in food and samples from primary steps of food production chain using microbiological and molecular biology methods 45 Mališevs A., Bergšpica I., Cibrovska A., Avsejenko J., Makarova S., Grantiņa-Ieviņa L. 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Shape variation in taxonomically problematic genus Phthiracarus Perty, 1841 of armoured mites (Acari: Oribatida) investigated by using methods of geometric morphometrics: preliminary results 55 Environmental and Experimental Biology ISSN 2255-9582 27 Žorža L., Rapoport A., Muter O. Activated sludge stimulation by adding yeast biomass 57 Ažēna E., Apermane L., Grigāne I., Makarenkova G. Effects of Lentinula edodes extract on melanization reaction un hydrogen peroxide resistance in Drosophila melanogaster 59 Kalneniece K., Mazkalniņa L., Švirksts K., Grūbe M., Kalniņa Z., Ķizāne G., Bankovskis V., Grīnbergs A., Muter O. Effect of nutrient amendments on the growth and dehydrogenase activity of lactic acid bacteria under oxidative stress conditions 61 Ievinsh G., Ieviņa S., Samsone I., Andersone-Ozola U. Functional chemistry of coastal plant species: towards a definition of Na and K metallophytes (electrolytophytes) 63 Landorfa-Svalbe Z., Andersone-Ozola U., Miesniece E., Ievinsh G. 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Alien species of legume family in the flora of Latvia 69 Environmental and Experimental Biology (2019) 17: 29–30 Abstract of the 77th Scientific Conference of the University of Latvia Downstream transformation of the phytoplankton communities along the Middle Daugava River at different flood-flow discharges Dāvis Gruberts1*, Ivars Druvietis2 1Department of Geography and Chemistry, Daugavpils University, Parādes 1, Daugavpils LV–5400, Latvia 2Department of Hydrobiology, Faculty of Biology, University of Latvia, Jelgavas 1, Rīga LV–1004, Latvia * Corresponding author, E-mail: [email protected] Key words: chlorophyll a, Daugava River, discharge, Lagrangian sampling, phytoplankton, spring floods. This study is based on the results obtained during annual all drift experiments included regular measurements of the Lagrangian drift expeditions conducted by Daugavpils average drift speed, the channel’s depth and the chlorophyll University in the upper part of the Naujene-Jēkabpils a concentration near the water surface (Gruberts, Paidere stretch of the Daugava River in 2007 – 2017. 2014). The sub-surface phytoplankton samples were Within the Piedrujas-Naujenes stretch, the valley of the collected during five such drifts, and final results of three Middle Daugava River crosses the East Latvian Lowland. of them (conducted in 2007, 2011 and 2015, respectively) The depth of the valley and longitudinal gradient of its were selected for this study. riverbed is the smallest one while the width of the main All three Lagrangian drift experiments mentioned above channel and that of the adjacent floodplains the largest one were conducted by applying a manned drifting research when compared to other stretches of the Daugava River platform “Aventura” (constructed at Daugavpils University in Latvia (Eberhards 1972). Within this stretch significant in 2007), made of an inflatable boat and a maritime life-raft changes in main physical characteristics of the flood-flows attached to each other (Gruberts et al. 2012). The research occur: the current slows down and floodwaters spread platform was equipped with two floating anchors, a HACH across the adjacent floodplain area. Therefore, an active DS-5 multiprobe (with the chlorophyll a sensor), a GPS hydrological connection between the main channel of the receiver, an echo-sounding device and the phytoplankton Daugava River and various floodplain habitats (meadows, sampling equipment. At the beginning of the drift wetlands, standing water bodies etc.) is temporarily experiment, the platform was deployed and transported to established. Some of the largest floodplain lakes in Latvia the middle of the main channel (usually at Krauja village are located here, and their ecosystems clearly benefit from 10 km upstream from Daugavpils), then left to drift freely such natural exchange of the fresh water masses, suspended along the current and used by the crew as a constantly matter, nutrients and living organisms (phytoplankton, moving sampling station. zooplankton, fish populations etc.) with the Daugava River The Lagrangian sampling strategy was followed by flowing nearby (Gruberts et al. 2007). drifting continuously along with the Daugava’s current To understand how (and where) such interaction occurs during daytime (for about 10 to 12 h) and by conducting in real-time regime regarding the water mass dynamics, repeated probing and sampling of the selected water masses chemistry and plankton communities, the first Lagrangian- for their chlorophyll α concentration and phytoplankton type field study in Latvia (the real-time Lagrangian drift composition. The sub-surface phytoplankton sampling was experiment) was conducted on the Middle Daugava on repeated each 60 min during the whole drift resulting in 11 March 28, 2007, at the peak of the spring floods (Gruberts to 13 samples per drift collected en route. The phytoplankton et al. 2012). Since then, there were nine additional drift samples were conserved in situ and analysed for their experiments conducted by Daugavpils University within composition, abundance and biomass later by an inverted the upper part of the Naujenes-Jēkabpils stretch (i.e. from microscope method at the Department of Hydrobiology, Krauja to Dunava, about 60 km long distance), usually in University of Latvia (Gruberts et al. 2012; 2018). late March, mid-April, at the peak of the spring floods. Each To obtain direct insight in the real-time physical drift experiment was focused on different hydrological, processes of downstream transformation of the physical, chemical and biological characteristics of the phytoplankton transported by the Daugava’s floodwaters, selected flood water masses that were tracked for many biological data records (the chlorophyll a concentration, hours and sampled repeatedly en route. For example, almost number of phytoplankton taxa, its abundance and biomass) 29 were plotted on the distance axis (i.e. the Lagrangian the filamenous Oscillatoria sp. (Gruberts et al. 2018). reference system) and compared to main hydrological Downstream trends in the number of phytoplankton characteristics of each sampling site (the average drift taxa, its abundance and total biomass also depends on the speed, the channel’s depth and active cross-section area). extent (magnitude) of the spring floods. Thus, during the The average values of main biological parameters for each large floods of 2011 the number of phytoplankton taxa drift were also calculated and compared to the peak flood and its total abundance gradually decreased downstream. discharges of the Daugava River at Daugavpils recorded on In contrast, during the low floods of