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

Zooplankton structure as a measure of the ecological status of lakes

Rozprawa doktorska powstała na podstawie cyklu czterech publikacji naukowych: P1. Ochocka A., Pasztaleniec A., 2016. Sensitivity of plankton indices to lake trophic conditions. Environmental Monitoring and Assessment volume 188: 622, https://doi.org/10.1007/s10661-021-09390-7; P2. Karpowicz M., Sługocki Ł., Kozłowska J. Ochocka A., López C., 2020. Body size of Daphnia cucullata as an indicator of the ecological status of temperate lake. Ecological Indicators 117: 106585, https://doi.org/10.1016/j.ecolind.2020.106585; P3. Ochocka A., 2021., ZIPLAS: Zooplankton Index for Polish Lakes’ Assessment - A new method to assess the ecological status of stratified lakes. Environmental Monitoring and Assessment 193: 664, https://doi.org/10.1007/s10661-021-09390-7; P4. Ochocka A., Karpowicz M., 2022. Assessment potential of zooplankton to establish reference conditions in lowland temperate lakes. Diversity 14: 501, https://doi.org/10.3390/d14060501Cele pracy obejmowały: (i) przetestowanie wskaźników bazujących na strukturze zespołu zooplanktonu jezior stratyfikowanych, w celu wytypowania najbardziej wrażliwych na eutrofizację, (ii) charakterystykę struktury zooplanktonu w warunkach referencyjnych oraz (iii) opracowanie metody oceny stanu ekologicznego bazującej na strukturze zooplanktonu. W pracy przetestowano wrażliwość wskaźników zooplanktonowych na nasilenie eutrofizacji. Testowane wskaźniki wykazały zróżnicowane typy reakcji na wzrost koncentracji biogenów. W kolejnym etapem prac wyznaczone zostały jeziora referencyjne oraz opracowana została struktura zasiedlających je zespołów zooplanktonu. Wyniki badań wykazały również, że Daphnia cucullata osiąga większe rozmiary ciała w jeziorach o niskiej trofii. Na podstawie otrzymanych wyników zaproponowany został wskaźnik BSI (Body Size Index). Wyróżniono gatunki charakterystyczne dla jezior referencyjnych, w tym Bosmina (Eubosmina) coregoni, Ascomorpha ecaudis, Collotheca pelagica i Gastropus stylifer. W ostatnim etapie prac opracowano metodę oceny stanu ekologicznego jezior stratyfikowanych, indeks ZIPLAS (Zooplankton Index for Polish Lakes’ Assessment). Indeks ZIPLAS silnie koreluje (korelacja rang Spearmana) ze wszystkimi parametrami eutrofizacji – najsilniej z widzialnością krążka Secchiego (r = 0,86), nieco słabiej z fosforem ogólnym (r = -0,74) i azotem ogólnym (r = 0,68). Uzyskane wyniki pokazują, że indeks ZIPLAS może być wykorzystany jako wiarygodne narzędzie w monitoringu stanu ekologicznego jezior stratyfikowanych.The aims of the dissertation included: (i) testing the zooplankton indices calculated based on the structure of the zooplankton community from stratified lakes in order to select the most sensitive indices of eutrophication pressure, (ii) the characteristics of the zooplankton structure in reference conditions, (iii) the development of a zooplankton based-method for assessing the ecological status of lakes. The first stage of the work was to test sensitivity of zooplankton indicators to the eutrophication parameters. The next stage was to determine lakes meeting the criteria of reference conditions and to analyze the structure of the zooplankton communities inhabiting them. The tested zooplankton indices showed three types of responses to the increases in nutrient concentration. The results showed that Daphnia cucullata grows larger in low trophic conditions. The new simple Body Size Index (BSI) has been proposed. The characteristic species for reference lakes were identified, including Bosmina (Eubosmina) coregoni, Ascomorpha ecaudis, Collotheca pelagica and Gastropus stylifer. Then zooplankton indices were calculated and tested against eutrophication parameters. Finally, the ZIPLAS multimetric index (Zooplankton Index for Polish Lakes' Assessment) was developed to assessment of the ecological status of stratified lakes. ZIPLAS responds clearly to eutrophication indicators - Secchi disc visibility (Spearman’s rank correlation r = 0.86), total phosphorus (r = -0.74) and total nitrogen (r = 0.68). The ZIPLAs index can be used as a valuable tool in the monitoring the ecological status of lakes.Dane wykorzystane do przygotowania rozprawy doktorskiej zostały zgromadzone w ramach grantu o numerze 2012/07/N/NZ9/01396, finansowanego przez Narodowe Centrum Nauki oraz w ramach działalności statutowej Instytutu Ochrony Środowiska – Państwowego Instytutu Badawczego, finansowanej z dotacji Ministerstwa Nauki i Szkolnictwa Wyższego.Uniwersytet w Białymstoku. Wydział Biologi

Assessment Potential of Zooplankton to Establish Reference Conditions in Lowland Temperate Lakes

Zooplankton community data from 45 dimictic lakes, representing homogenous abiotic conditions, were used to distinguish indicator taxa of near-pristine, reference lakes with low anthropopression. Reference conditions were selected based on natural land use in the catchment, lack of or low human activity, and the absence of point sources of pollution, as well as good water quality. According to these criteria, six lakes were designated references and all represent mesotrophic conditions. Reference lakes had a low abundance of Cyclopoida and Rotifera, and significantly lower biomass compared to non-reference lakes. We have found that species characteristic of the reference lake were: Bosmina (Eubosmina) coregoni, Ascomorpha ecaudis, Collotheca pelagica, and Gastropus stylifer. The species responsible for differences among reference and non-reference lakes were Keratella tecta, Pompholyx sulcata, and Ascomorpha saltans, which are considered typical for eutrophic waters

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

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

Data Descriptor: A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment