Melliferous flora and pollen characterization of honey from Požega area

Melisopalinološkom analizom uzoraka meda s područja Požeške kotline utvrđen je peludni spektar koji ukazuje na botaničko podrijetlo meda. Najzastupljeniji je bio pelud vrsta iz porodica Asteraceae (6 svojti), Fabaceae (5 svojti), Rosaceae (4 svojte) i Fagaceae (3 svojte), dok je u najvećem broju uzoraka bio prisutan pelud svojti Brassica spp., Robinia pseudoacacia, Prunus spp. i Populus spp. Utvrđena su dva monoflorna repičina meda te po jedan kestenov i bagremov med, dok su ostali pripadali poliflornim vrstama meda. Tri poliflorna meda imala su značajan udio peluda svojti Brassica spp., a dva meda visok udjel peluda amorfe. Razdoblje cvatnje medonosnih biljaka ukazuje na to da su najznačajnije pčelinje paše Požeške kotline u travnju, svibnju i lipnju.Melissopalynological analysis of honey samples from Požega valley was used to determine the botanical origin of honey. The analysis showed the presence of 34 different pollen types, derived from plant taxa belonging to 18 families. The most represented plant families were Asteraceae (6 taxa), Fabaceae (5 taxa), Rosaceae (4 taxa) and Fagaceae (3 taxa), while the pollen types that appeared in most samples derived from Brassica spp., Robinia pseudoacacia, Prunus spp. and Populus spp. According to pollen spectra, two monofloral brassica honeys, as well as one chestnut and black locust honey, were determined, while other samples were considered as polyfloral. Three polyfloral honeys had a large portion of Brassica spp. pollen, while two had a high amount of Amorpha fruticosa pollen. Flowering period of melliferous plants in Požega valley suggests that the main foraging period for bees is during April, May and June

Rasprostranjenost pajasena (Ailanthus altissima (Mill.) Swingle), invazivne biljne vrste, na području grada Osijeka

The research on the tree of heaven (Ailanthus altissima (Mill.) Swingle) distribution within the Osijek city area was carried out in the summer period of 2017. In total of 589 individuals of the tree of heaven on 130 locations were recorded. The trees grew individually or in groups, mostly on abandoned places, and were rarely found in well-maintained areas. In the vicinity of the tree of heaven, mostly perennial herbaceous weeds were found. These plants thrive in different types of habitats. In order to prevent the uncontrolled spread of this invasive plant in the urban environment, it is necessary to continuously monitor and timely remove the tree of heaven individuals. Moreover, it is important to continuously educate the general public about the adverse impact of this species on the environment and biological diversity.Istraživanje prisutnosti pajasena (Ailanthus altissima (Mill.) Swingle) na području grada Osijeka provedeno je u ljetnom razdoblju 2017. godine. Na 130 lokaliteta zabilježeno je ukupno 589 jedinki stabala pajasena. Pajasen je rastao pojedinačno ili u skupinama, uglavnom na napuštenim područjima, dok je na uređenim i održavanim površinama bio rijetko prisutan. U neposrednoj blizini pajasena zabilježene su korovne, višegodišnje zeljaste biljke koje uspijevaju na različitim tipovima staništa. U svrhu sprječavanja nekontroliranog širenja ove invazivne biljke u gradskoj sredini potrebno je kontinuirano provoditi praćenje i pravovremeno uklanjanje pajasena, kao i kontinuiranu edukaciju šire javnosti o nepovoljnom utjecaju ove vrste na okoliš i biološku raznolikost

Early spring flora of the Sub-Pannonic steppic grassland (NATURA 2000 site) in Bilje, northeast Croatia

The diversity of early spring vascular flora was studied in the Sub- pannonic steppic grassland in the village of Bilje, north eastern Croatia. In all, 109 plant taxa within 35 families were found. The highest number of taxa belongs to the families Poaceae, Fabaceae, Asteraceae, Caryophyllaceae, Lamiaceae and Rosaceae. Specific habitat conditions, characterized by moderately wet and moderately acidic soil with intermediate fertility and the effects of the continental climate favour the development of different plant life forms. Out of the total recorded plant taxa, hemicryptophytes make up 59.6%, followed by therophytes (22.0%) and geophytes (13.8%). Chorological analysis shows that the most numerous are plants of Eurasian (33.9%), Pontic-Central-Asian (21.1%) and Central European (21.1%) floral elements. According to their status in the Red List, three critically endangered (CR), one vulnerable (VU) and three nearly threatened (NT) plant species were found. Altogether, the steppe-like grassland in Bilje is a unique habitat rich in valuable plants of the Croatian flora, including the critically endangered Doronicum hungaricum, therefore it is of great importance to preserve it. Important management tools include mowing and controlling the spreading of cultivated and invasive plant species

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Melliferous flora and pollen characterization of honey from Požega area

Melissopalynological analysis of honey samples from Požega valley was used to determine the botanical origin of honey. The analysis showed the presence of 34 different pollen types, derived from plant taxa belonging to 18 families. The most represented plant families were Asteraceae (6 taxa), Fabaceae (5 taxa), Rosaceae (4 taxa) and Fagaceae (3 taxa), while the pollen types that appeared in most samples derived from Brassica spp., Robinia pseudoacacia, Prunus spp. and Populus spp. According to pollen spectra, two monofloral brassica honeys, as well as one chestnut and black locust honey, were determined, while other samples were considered as polyfloral. Three polyfloral honeys had a large portion of Brassica spp. pollen, while two had a high amount of Amorpha fruticosa pollen. Flowering period of melliferous plants in Požega valley suggests that the main foraging period for bees is during April, May and June

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains

Harmful blooms across a longitudinal gradient in central Europe during heatwave: Cyanobacteria biomass, cyanotoxins, and nutrients

Climate change has increased the frequency, duration and intensity of heatwaves in Europe. These extreme events result in alterations of physical, chemical, and biological properties of lakes that may synergistically promote cyanobacterial dominance. In our study we focused on cyanobacterial blooms in lakes distributed over a longitudinal gradient in Central Europe during one of the “top ten European heat waves” in summer 2015. 92 lakes were included in the study, located across three climatic subregions: cool northern lakes, situated in Lithuania, temperate northern lakes in Poland, and warm northern lakes in Croatia. The objective of the study was to determine if cyanobacterial biomass, predominant species, and cyanotoxin concentration differed, across the south-north gradient, as a function of water temperature, total phosphorus, and total nitrogen. Statistical significance of observed patterns was tested using the Kruskal-Wallis rank sum test and the generalized linear model. We found the lowest average epilimnion temperature, but the highest average cyanobacterial biomass in the northern, ‘cool’ lakes while the highest average temperature with the lowest average cyanobacterial biomass in the southern, ‘warm’ lakes. The concentration of cyanotoxins was also the highest in the ‘cool’ lakes. Total phosphorus and total nitrogen correlated significantly with cyanobacterial biomass, cyanotoxins concentration and biomass of some cyanobacterial species (mainly Planktothrix agardhii), regardless of the latitude. Only in the ‘cool’ lakes concentration of cyanotoxins (microcystins and anatoxin-a) correlated significantly with cyanobacterial biomass and the biomass of some dominant cyanobacterial species (P. agardhii). Our results emphasized the differences of heat weaves impact on lakes of various latitudes, with the strongest increase in toxic cyanobacterial blooms in northern ‘cool’ lakes, situated in high latitudes. On the other hand, nutrients directly enhanced blooms across all the studied latitudes of Central Europe. The cyanobacteria species dominating in blooms might be recognized as ecological indicators of climate change, especially in the north-eastern part of Europe

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature.Peer reviewe

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature