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Selle valdkonna püsiv URIhttp://hdl.handle.net/10492/3061

Sirvi

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Black and white, day and night – fish diurnal movements in two different Amazonian lakes : [presentation]
(2021) Zingel, Priit; Tuvikene, Arvo; Feldmann, Tõnu; Agasild, Helen
The presentation took place at the 10th International Conference on Shallow Lakes in 2021.
Causal networks of phytoplankton diversity and biomass are modulated by environmental context
(Nature Research, 2022) Chang, Chun-Wei; Miki, Takeshi; Ye, Hao; Souissi, Sami; Adrian, Rita; Anneville, Orlane; Agasild, Helen; Ban, Syuhei; Be’eri-Shlevin, Yaron; Chiang, Yin-Ru; Feuchtmayr, Heidrun; Gal, Gideon; Ichise, Satoshi; Kagami, Maiko; Kumagai, Michio; Liu, Xin; Matsuzaki, Shin-Ichiro S.; Manca, Marina M.; Nõges, Peeter; Piscia, Roberta; Rogora, Michela; Shiah, Fuh-Kwo; Thackeray, Stephen J.; Widdicombe, Claire E.; Wu, Jiunn-Tzong; Zohary, Tamar; Hsieh, Chih-hao
Untangling causal links and feedbacks among biodiversity, ecosystem functioning, and environmental factors is challenging due to their complex and context-dependent interactions (e.g., a nutrient-dependent relationship between diversity and biomass). Consequently, studies that only consider separable, unidirectional effects can produce divergent conclusions and equivocal ecological implications. To address this complexity, we use empirical dynamic modeling to assemble causal networks for 19 natural aquatic ecosystems (N24°~N58°) and quantified strengths of feedbacks among phytoplankton diversity, phytoplankton biomass, and environmental factors. Through a cross-system comparison, we identify macroecological patterns; in more diverse, oligotrophic ecosystems, biodiversity effects are more important than environmental effects (nutrients and temperature) as drivers of biomass. Furthermore, feedback strengths vary with productivity. In warm, productive systems, strong nitratemediated feedbacks usually prevail, whereas there are strong, phosphate-mediated feedbacks in cold, less productive systems. Our findings, based on recovered feedbacks, highlight the importance of a network view in future ecosystem management.
Changes in nutrient concentration and water level affect the microbial loop: a 6‑month mesocosm experiment
(Springer, 2023) Zingel, Priit; Jeppesen, Erik; Nõges, Tiina; Hejzlar, Josef; Tavşanoğlu, Ülkü Nihan; Papastergiadou, Eva; Scharfenberger, Ulrike; Agasild, Helen
Eutrophication and lake depth are of key importance in structuring lake ecosystems. To elucidate the effect of contrasting nutrient concentrations and water levels on the microbial community in fully mixed shallow lakes, we manipulated water depth and nutrients in a lake mesocosm experiment in north temperate Estonia and followed the microbial community dynamics over a 6-month period. The experiment was carried out in Lake Võrtsjärv—a large, shallow eutrophic lake. We used two nutrient levels crossed with two water depths, each represented by four replicates. We found treatment effects on the microbial food web structure, with nutrients having a positive and water depth a negative effect on the biomasses of bacterial and heterotrophic nanoflagellates (HNF) (RM-ANOVA, p < 0.05). Nutrients affected positively and depth negatively the mean size of individual HNF and ciliate cells (RM-ANOVA; p < 0.05). The interactions of depth and nutrients affected positively the biomass of bacterivorous and bacteriherbivorous ciliates and negatively the biomass of predaceous ciliates (RM-ANOVA; p < 0.05). Bacterivorous ciliates had lowest biomass in shallow and nutrient-rich mesocosms, whilst predaceous ciliates had highest biomass here, influencing trophic interactions in the microbial loop. Overall, increased nutrient concentrations and decreased water level resulted in an enhanced bacterial biomass and a decrease in their main grazers. These differences appeared to reflect distinctive regulation mechanisms inside the protozoan community and in the trophic interactions in the microbial loop community.
Changes in nutrient concentration and water level affect the microbial loop: a multi-seasonal mesocosm experiment : [submitted version]
(Springer, 2023) Zingel, Priit; Jeppesen, Erik; Nõges, Tiina; Hejzlar, Josef; Tavşanoğlu, Ülkü Nihan; Papastergiadou, Eva; Scharfenberger, Ulrike; Agasild, Helen; Centre for Limnology
Eutrophication and lake depth are of key importance in structuring lake ecosystems. To elucidate the effect of contrasting nutrient concentrations and water levels on the microbial community, we manipulated water depth and nutrients in a mesocosm experiment in north temperate Estonia and followed the microbial community dynamics during a 6-month period. We used two nutrient levels crossed with two water depths, each represented by four replicates. We found treatment effects on the microbial food web structure, with nutrients having a positive and water depth a negative effect on bacterial biomass, heterotrophic nanoflagellates (HNF) and metazooplankton biomass. Nutrients and water depth had both positive impacts on phytoplankton biomass. Bacterivorous ciliates had lowest biomass in shallow and nutrient rich mesocosms, whilst predaceous ciliates had highest biomass here, influencing trophic interactions in the microbial loop. Overall, increased nutrient concentrations and decreased water level resulted in an enhanced bacterial biomass and a decrease in their main grazers. These differences appeared to reflect distinctive regulation mechanisms inside the protozoan community and in the trophic interactions in the microbial loop community.
Comparison of larval perch feeding between littoral and open-water sites of the lakes : [presentation]
(Estonian University of Life Sciences, 2021) Karus, Katrit; Žagars, Matiss; Zingel, Priit; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Medne-Peipere, Madara; Puncule, Linda
The presentation took place at the 10th International Conference on Shallow Lakes in 2021.
The comparison of the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of northern temperate lakes
(Estonian Academy Publishers, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Puncule, Linda; Zingel, Priit; Chair of Hydrobiology and Fishery; Centre for Limnology
We studied the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of four different lakes – one Latvian (Auciema) and three Estonian (Akste, Kaiavere, and Prossa). Altogether, 162 perch larvae (81 from both habitats) were collected to estimate the diet composition of gathered larval specimens in spring (2019) using gut content analysis via epifluorescence microscopy. Attention was paid particularly to the question how does the larval perch food composition differ in pelagic and littoral habitats. We hypothesized that the consumption of zooplankton is higher and the larval condition is better in littoral habitats. We assessed the feeding on both protozoo- (ciliates) and metazooplankton and applied multiple indices (Hurlbert’s standardized niche breadth, Ivlev’s selectivity and relative importance index) to evaluate, respectively, the larval fish prey importance, feeding homogeneity and strategies. The results showed that larval length and weight were slightly higher and body condition was slightly better in the lakes’ littoral habitats. The feeding niche of perch larvae was narrower in the littoral, which can indicate more favourable feeding conditions in littoral than lake pelagic habitats. While the small cladocerans (Bosmina longirostris Müller) were generally the preferred and important food objects, ciliates were avoided and consumed only when their share in the total zooplankton biomass was >40%. However, in shortage of cladocerans, ciliates could be vitally important food objects for perch larvae.
The diet of Eurasian perch larvae in lakes with different zooplankton assemblages
(2023) Zingel, Priit; Agasild, Helen; Zagars, Matiss; Feldmann, Tõnu; Tuvikene, Arvo; Zingel, Tiina; Puncule, Linda; Karus, Katrit; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Chair of Hydrobiology and Fishery. Estonian University of Life Sciences
Eurasian perch has a great ecological importance in freshwaters as it is often a dominating predatory fish in ecosystems. The knowledge of perch feeding patterns, strategies, and adaptivity to food environment in their early life stages is essential to understand its population development and dynamics. It has been demonstrated that there exists a positive relationships between preferred prey availability and larval feeding success. We examined the diet of larval perch in their natural habitats of different zooplankton assemblages in three small lakes with varying ecological status. In each lake, both pelagial and littoral were studied. We found significant relation between zooplankton biomass in the lake and zooplankton biomass consumed by fish larvae. The most important food objects were crus- taceans (Bosmina longirostris, Chydorus sphaericus). Ciliates were consumed only in one lake. Our results show that perch larvae are flexible in their choice of food and can adapt to different food environments.
From microscopy to genes – tracing toxic cyanobacteria in a shallow eutrophic lake
(Estonian University of Life Sciences, 2022) Panksep, Kristel; Kisand, Veljo; Agasild, Helen; Sivonen, Kaarina; Institute of Agricultural and Environmental Sciences; Vasas, Gabor (opponent)
Global warming paired with eutrophication processes is shifting phytoplankton communities towards the dominance of bloom-forming and potentially toxic cyanobacteria. Cyanobacterial blooms are considered an increasing threat in freshwater. Traditional monitoring predominantly relies on cyanobacterial biomass as an indicator of potential toxin presence, disregarding that toxin concentrations can rapidly increase even when cyanobacterial biomass is low. The concentration of toxins in the water is related to the abundance of toxin-producing species and the amount of toxin per cell – toxin quota. My research provides valuable information about the cyanobacterial community composition, the abundance of toxic genotypes, microcystin concentrations, microcystin quota and the environmental factors that promote toxic cyanobacterial blooms in the large and shallow freshwater lake Peipsi. This is the first study to utilise molecular methods as complementary to routine monitoring to determine cyanobacterial toxicity potential in lake Peipsi. In situ studies on zooplankton taxon-specific ingestion of potentially toxic cyanobacteria are still limited. My study focused on the importance of cyanobacteria as a food source for the dominant crustacean grazers. Among the first studies using qPCR targeting cyanobacterial genus-specific mcyE synthase genes in zooplankton gut content analysis, we show that potentially toxic strains of Microcystis can be ingested directly or indirectly by different zooplankton grazers. Information gathered from this study expanded our knowledge on the ecology of toxic cyanobacteria, provided an indication of how molecular methods can improve traditional risk assessment concerning the abundance of cyanobacteria and their cyanotoxins and broadened our knowledge of how target specific molecular tools could be further used in aquatic food-web studies. In the current thesis, I present a synthesis of spatial and temporal variability of potentially toxic cyanobacteria and the importance of cyanobacteria as a food source for crustacean zooplankton in large and shallow lake. The thesis is based on three published papers each dedicated to a different aspect of the whole. This thesis improves our knowledge of potentially toxic cyanobacteria and cyanotoxins in large and shallow eutrophic lakes and also provides the first insight into the in-situ consumption of toxic Microcystis by cladoceran and copepod grazers dominating in the lake. The knowledge gained from this study will guide us to further important questions that should be addressed in future research regarding the functioning of the food web of lake Peipsi. Phytoplankton community through high throughput sequencing would allow analysing the relation of cyanobacterial community composition along with concentration and diversity of cyanotoxins. This would include small-sized cyanobacteria in analysis, which are now excluded from the research. To elucidate the processes underlying cyanotoxin dynamics in more detail, further exploration focusing on the expression of toxin genes along with toxin concentration would be beneficial. Toxin gene expression could better indicate potential risks, especially in water bodies comprising mixed assemblages of toxic and non-toxic cyanobacteria.
The influence of macrophyte ecological groups on food web components of temperate freshwater lakes
(Elsevier, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Tuvikene, Arvo; Zingel, Priit; Puncule, Linda; Medne-Peipere, Madara; Feldmann, Tõnu
Aquatic macrophyte taxonomic composition, species abundance and cover determine the physical structure, complexity and heterogeneity of aquatic habitats – the structuring role of macrophytes. These traits influence richness, distribution, feeding and strength of the relationships between food web communities in lakes. The aim of this study was to determine how lakes with different dominating macrophyte ecological groups affect planktonic food web components, emphasising the influence on young of year (YOY) fish and large (≥1 +) fish community. We hypothesised that different dominating macrophyte ecological groups have different structural effects on food web components and YOY fish growth, abundance and feeding. Studied lakes categorised into three different macrophyte ecological groups – lakes dominated by emergent, floating+floating-leaved or submerged vegetation. We found that all dominating ecological groups had a strong influence on plankton communities (except heterotrophic bacterioplankton and nanoflagellates), YOY fish and large fish. Floating-leaved plant dominance was positively related to planktonic food web structure and YOY fish weight, length, abundance and the consumption of zooplankton as a prey of all major species of YOY fishes. Larger fish tended to favour the presence of emergent vegetation. This conclusion has important implications for local managers and conservationists in respect to the maintenance and protection of littoral habitats and fish resources.
Keystone species Chydorus sphaericus in shallow eutrophic Lake Võrtsjärv (Estonia) – 56 years of continuous zooplankton monitoring and research : [poster]
(Estonian University of Life Sciences, 2023) Blank, Kätlin; Haberman, Juta; Agasild, Helen; Tuvikene, Lea; Zingel, Priit; Nõges, Peeter; Bernotas, Priit; Cremona, Fabien
Presentation at the 11th International Shallow Lakes Conference, Estonia 11.-16.06.2023.
Lake food webs and C metabolism across gradients of catchment alkalinity and climate : [presentation]
(Estonian University of Life Sciences, 2021) Nõges, Tiina; Agasild, Helen; Cremona, Fabien; Laas, Alo; Nõges, Peeter; Tõnno, Ilmar; Zingel, Priit
The presentation took place at the 10th International Conference on Shallow Lakes in 2021.
Larval and juvenile perch feeding in some Estonian and Latvian study lakes : [poster]
(Estonian University of Life Sciences, 2021) Karus, Katrit; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Medne-Peipere, Madara; Žagars, Matiss; Puncule, Linda; Zingel, Priit
The presentation took place at the Lahti Lakes 2021 Symposium.
Predicting multiple stressor effect on zooplankton abundance, biomass and community composition in two large eutrophic lakes : [presentation]
(Estonian University of Life Sciences, 2022) Cremona, Fabien; Agasild, Helen; Blank, Kätlin; Haberman, Juta; Zingel, Priit; Nõges, Peeter; Nõges, Tiina; Laas, Alo
Presentation at the BIOGEOMON 2022, 10th International Symposium on Ecosystem Behavior, June 26–30, 2022, Tartu, Estonia.
Prey selection and growth in 0+ Eurasian perch Perca fluviatilis L. in littoral zones of seven temperate lakes
(Wiley, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Puncule, Linda; Zingel, Priit
We studied the relationships between the planktonic food base and feeding patterns of juvenile mid-summer/ early autumn Eurasian perch Perca fluviatilis L., a common predatory freshwater fish in large parts of Europe and Asia. The feeding of 0+ perch was studied during summer and autumn in littoral habitats of seven lakes with different environmental conditions –four Latvian (Auciema, Riebinu, Vārzgūnes, Laukezers) and three Estonian (Kaiavere, Prossa and Akste) lakes. Simultaneously, the abundance, biomass and structure of zooplankton communities were examined. We focused on the littoral areas because many studies in lakes suggest that littoral habitats are particularly important for 0+ fish growth and survival. We were interested in the question: can the diet and growth of 0+ perch be explained by zooplankton community structure? We also presumed that if the amount of zooplankton is low, more benthic invertebrates will be consumed by 0+ perch. Opposite to expectations, we found that zooplankton always counted for over 90% of diet biomass in perch. There were also clear correlations between the zooplankton biomass in a given lake, the zooplankton biomass in 0+ perch stomachs, and the fish growth rate. The study also suggested that nutrient enrichment can positively impact the 0+ perch feeding conditions in lakes.

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