Andmebaasi logo

Sirvi Autor "Teesalu, Paul" järgi

Nüüd näidatakse 1 - 10 10
  • Pisipilt
    Kirje
    Behavioural responses of invasive (Gmelinoides faciatus) and native (Gammarus lacustris) amphipods to predators on different bottom substrates : [poster]
    (Estonian University of Life Sciences, 2023) Teesalu, Paul; Ercoli, Fabio; Tuvikene, Arvo
    The amphipod Gmelinoides fasciatus has invaded and established in numerous large lakes in Eurasia and, in the process, has displaced the native amphipod, Gammarus lacustris. In Lake Peipsi, G. fasciatus dominates the shoreline macroinvertebrate fauna, forming up to 99% of macroinvertebrate individuals (Fig. 1). The mechanism behind its invasion success is unclear and remains an important topic for invasion ecology. In order to determine if different bottom substrates and predator avoidance behaviour contribute to the invasion success of G. fasciatus we conducted two laboratory experiments.
  • Pisipilt
    Kirje
    Behavioural responses of invasive (Gmelinoides fasciatus) and native (Gammarus lacustris) amphipods to predators on different bottom substrates
    (Springer Nature, 2023) Teesalu, Paul; Ercoli, Fabio; Tuvikene, Arvo
    The amphipod Gmelinoides fasciatus has invaded and established in numerous large lakes in Eurasia and, in the process, has displaced the native amphipod, Gammarus lacustris. The mechanism behind its invasion success is unclear and remains an important topic for invasion ecology. Three labo- ratory experiments were conducted to determine if superior predator avoidance and different types of bottom substrate could be important factors contrib- uting to the invasion success of G. fasciatus. Our results indicate that, on gravel and sand substrates, G. fasciatus exhibited superior digging behaviour to avoid predation by fishes (perch and common roach), contrary to G. lacustris. On sandy substrate, only 9% of G. fasciatus individuals were consumed, whereas G. lacustris were consumed much more intensively at 74%. In addition, G. fasciatus exhibited a more sub- stantial reduction in activity, where the time spent in motion reduced from 37.6 to 20.8% compared to G. lacustris (from 21.8 to 17.4%) when in the presence of predatory fish kairomones. G. fasciatus movement speed was also reduced in the presence of kairomones (from 57.1 to 39.3 mm/s). However, the presence of kairomones had little effect on digging behaviour of G. fasciatus. G. fasciatus consistently demonstrated superior predator avoidance abilities over G. lacus- tris, suggesting that this mechanism might play an important role in the invasion success of G. fasciatus.
  • Pisipilt
    Kirje
    Effects of environmentally relevant concentrations of microplastics on amphipods
    (Elsevier, 2022) Rani-Borges, Barbara; Meitern, Richard; Teesalu, Paul; Raudna-Kristoffersen, Merilin; Kreitsberg, Randel; Heinlaan, Margit; Tuvikene, Arvo; Ivask, Angela
    Lack of microplastics (MP) toxicity studies involving environmentally relevant concentrations and exposure times is concerning. Here we analyzed the potential adverse effects of low density polyethylene (LDPE) MP at environmentally relevant concentration in sub-chronic exposure to two amphipods Gmelinoides fasciatus and Gammarus lacustris, species that naturally compete with each other for their habitats. 14-day exposure to 2 μg/L (8 particles/L corresponding to low exposure) and 2 mg/L (~8400 particles/L, corresponding to high exposure) of 53–100 μm LDPE MP were used to assess ingestion and egestion of MP, evaluate its effects on amphipod mortality, swimming ability and oxidative stress level. Both amphipod species were effectively ingesting and egesting LDPE MP. On the average, 0.8 and 2.5 MP particles were identified in the intestines of each amphipod exposed to 2 μg/L and 2 mg/L LDPE MP, respectively. Therefore, intestinal MP after 14-day exposure did not fully reflect the differences in LDPE MP exposure concentrations. Increased mortality of both amphipods was observed at 2 mg/L LDPE MP and in case of G. lacustris also at 2 μg/L exposure. The effect of LDPE on swimming activity was observed only in case of G. fasciatus. Oxidative stress marker enzymes SOD, GPx and reduced glutathione GSH varied according to amphipod species and LDPE MP concentration. In general G. lacustris was more sensitive towards LDPE MP induced oxidative stress. Overall, the results suggested that in MP polluted environments, G. lacustris may lose its already naturally low competitiveness and become overcompeted by other more resistant species. The fact that in the sub-chronic foodborne exposure to environmentally relevant and higher LDPE MP concentrations all the observed toxicological endpoints were affected refers to the potential of MP to affect and disrupt aquatic communities in the longer perspective.
  • Pisipilt
    Kirje
    Effects of water temperature on marbled crayfish invasion ecology : [presentation]
    (Estonian University of Life Sciences, 2023) Teesalu, Paul
    The presentation took place at the CrayfIT 2023 Conference.
  • Pisipilt
    Kirje
    Lake Võrtsjärv past and present commercial fishery and ichthyology : [presentation]
    (Estonian University of Life Sciences, 2023) Teesalu, Paul
    The presentation took place at the 11th International Shallow Lakes Conference.
  • Pisipilt
    Kirje
    Niche partitioning of invasive Amur sleeper (Perccottus glenii) amongst native fish communities in three different freshwater ecosystems
    (Pensoft Publishers, 2024) Ercoli, Fabio; Kiljunen, Mikko; Teesalu, Paul; Tuvikene, Arvo; Tambets, Meelis; Kärgenberg, Einar; Nõges, Tiina
    The invasive fish, Amur sleeper, poses a significant and growing threat to Central European freshwater ecosystems. Despite its rapid spread, the ecological implications of its invasion have been poorly explored. Recent findings confirm its presence in various Estonian freshwater systems, raising concerns about its imminent expansion into larger lakes. To better understand its potential ecological impacts, we explored the isotopic niche of the Amur sleeper in comparison with native fish species co-existing in three Estonian freshwater ecosystems. We employed carbon and nitrogen stable isotope analyses alongside gut content analyses. Our findings show that the Amur sleeper’s diet in newly-invaded Estonian water bodies predominantly comprises benthic macroinvertebrates, although it may also include fish, confirming its role as a predator in the local food web. Notably, Amur sleeper populations exhibited clear isotopic niche partitioning in three invaded ecosystems. A logistic regression model, based on stomach content analyses, revealed an ontogenetic diet shift from benthivorous to piscivorous feeding habits from small to large specimens. Amur sleeper exhibits voracious, non-selective feeding habits, which can negatively impact native freshwater communities. The ability to occupy a distinct isotopic niche, with minimal overlap with native fish populations, may reduce interspecific competition, facilitating the spread and establishment of Amur sleeper in newly-invaded habitats. Managing the spread of this invasive species thus becomes even more critical to safeguard the integrity of native aquatic ecosystems.
  • Pisipilt
    Kirje
    Non-native species invasion strategies and effects on freshwater native communities
    (Estonian University of Life Sciences, 2025) Teesalu, Paul; Ercoli, Fabio (advisor); Tuvikene, Arvo (advisor); Institute of Agricultural and Environmental Sciences; Tricarico, Elena (opponent)
    ABSTRACT. The spread of invasive species has been forecasted to increase, particularly in freshwater ecosystems due to anthropogenic and environmental changes taking place at increasing rates. Invasive species generally adapt quickly to new environments, have high reproductive rates and can tolerate a wide range of conditions. This thesis studied three invasive species in the Narva reservoir area and found that their success is linked to dietary flexibility, behaviour, and tolerance to temperature changes. The Amur sleeper fish (Percottus glenii) can inhabit various waterbodies, for example, we found it in a warm-water channel, a large reservoir and a small pond. The Amur sleeper demonstrated great dietary plasticity, or the ability to consume a wide range of prey items. As Amur sleeper individuals grew, their diet shifted from a benthivorous diet to a piscivorous diet. The small amphipod Gmelinoides fasciatus, which has outcompeted and displaced native gammarid Gammarus lacustris in Lake Peipsi, exhibits superior predator avoidance and shows a more pronounced behavioural response to predators than its native counterpart, increasing its survivability. Marbled crayfish (Procambarus fallax virginalis) can shift from a protein rich macroinvertebrate based diet to a macrophyte based diet, indicating great dietary plasticity. Additionally, marbled crayfish, despite being considered a warm-water species, could withstand a wide range of water temperatures ranging from 0-30 °C over an extended period at our study site. During the implementation of invasive species management programs, it is important to consider their environmental tolerance, dietary adaptability and behavioural traits. As conditions change in our freshwater lakes and reservoirs, it is likely that invasive species will continue to be a problem, highlighting the need to understand and manage their spread to protect native freshwater ecosystems.
  • Pisipilt
    Kirje
    Rändvähi (Gmelinoides fasciatus) kui ohtliku invasiivse liigi levikupotentsiaal ning tähtsus kalade toiduobjektina
    (2021) Tuvikene, Arvo; Timm, Henn; Teesalu, Paul; Seller, Siim; Voode, Margus; Timm, Tarmo
    Rändvähk siirati Peipsisse 1970. aastate alguses Venemaa kalateadlaste soovitusel, et suurendada kalade toiduvarusid. Paraku muutus ta seal kiiresti invasiivseks ning põhjustab tänapäeval halba bioseisundit Euroopa Veepoliitika Raamdirektiivi (2000) mõttes, sest alandab oluliselt taksonirikkust. Võrtsjärves asustab kohalik liik järve-kirpvähk endiselt sarnaseid elupaiku, mille Peipsis on hõivanud rändvähk. Ta aga ei moodusta kuskil samasugust "monokultuuri". Peipsist on rändvähk seni levinud nii pärivoolu Narva jõkke kui ka suubuvaid jõgesid mööda vastuvoolu, eriti piki Emajõge (Panov et al. 2000, Timm & Tuvikene 2019). Tema kõrge arvukus ning depressiivne mõju teistele liikidele on tõenäoliselt üks põhjus, miks ka Emajõe bioloogilist seisundit mõnedes lõikudes pole hea. Emajões allpool Tartut kuni Peipsini on rändvähk kõikjal levinud. Võrtsjärve elustikule on ta potentsiaalselt väga ohtlik. Loomulikult harvendab rändvähk ka Emajõe enda loomi, kuid et jõepõhi on mitmekesisem ja taimerikkam kui järvepõhi, ei suuda ta seda sama edukalt muudest liikidest puhastada. Keskkonnatingimuste suhtes on rändvähk võrreldes järve-kirpvähiga laiema amplituudiga. Ta talub paremini hüpoksiat ja madalat pH-d. Kalad küll tarvitavad rändvähki toiduks, kuid tabavad teda võrreldes järve-kirpvähiga oluliselt halvemini, sest ta peitub ohu korral liiva või kruusa sisse. Rändvähile meeldib asustada võrkpüüniseid. Katseliselt ulatus nende asustustihedus 5-7 isendini/100 cm2 kohta. Ca 50-60% võrgule kinnitunud vähkidest tuleb võrguga veest väljatõstmisel kaasa. Seega peitub oht rändvähkide sattumiseks Võrtsjärve või mõnda teise veekogusse, kui Peipsist võetud püünised asetatakse kiiresti püügile, ilma et neid oleks vahepeal kuivatatud või kuuma veega töödeldud.
  • Pisipilt
    Kirje
    The role of trophic niche in eel head dimorphism : [presentation]
    (Estonian University of Life Sciences, 2022) Teesalu, Paul
    The presentation took place at the 12th ISOECOL, June 2022 in Gaming, Austria.
  • Pisipilt
    Kirje
    The Role of trophic niche in eel head shape dimorphism
    (Eesti Maaülikool, 2019) Teesalu, Paul; Ercoli, Fabio (juhendaja); Silm, Maidu (juhendaja); Vesiviljelus
    The European eel is a critically endangered fish species with a complex life cycle. Many aspects of eel ecology are poorly investigated; therefore, it is crucial to have a thorough understanding of this fish species for better stock management practices and conservation actions. In this thesis we caught and measured the head width of eels from the Estonian lakes of Saadjärv and Võrtsjärv. We hypothesised that individuals with narrow heads would be primarily benthivorous, whereas broad-headed individuals were likely to be piscivorous. Lake ecosystems and the subsequent difference in food availability could play a role in the formation of either head morph. Thus, our second hypothesis is that Lake Saadjärv, with an average macroinvertebrate biomass of 2.5 g/m2 would have more broad-headed eels than Lake Võrtsjärv, which has a higher macroinvertebrate biomass of 6.6 g/m2 . We combined gut content analyses and stable isotopes of δ 15N and δ 13C to determine and compare trophic niches of eel populations. Gut content analyses results confirm that eels in Saadjärv are affected by head shape in their feeding habits, with narrow-headed eels consuming proportionally more macroinvertebrates and broad-headed eels consuming more fish. This was confirmed with stable isotope analyses- broad-headed eels were significantly more enriched in δ 15N and therefore had a higher trophic position than narrow-headed eels. In Lake Võrtsjärv nearly all eels (95%) displayed a narrow head shape, suggesting a diet based mainly on macroinvertebrates, particularly chironomids. In line with our expectations stable isotope analyses indicated that the eel population in Võrtsjärv rely mostly on Chironomus plumosus and marginally on other benthic macroinvertebrates. The occurance of broad-headed eels was indeed higher in Saadjärv (31%) than in Võrtsjärv (2.3%) indicating that food availability plays a crucial role in eel head morphology