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

The State and the Role of Peatlands in Poland

Peatlands, as other wetlands, became recently objects of ecological and environmental studies. In past few years there are great interest in them, because of their significance both in natural landscape and environment protection. In this paper the role and the state of peat ecosystems in Poland is presented. The role of peatlands in landscape is significant in its hydrology and biogeochemical cycles. It is connected with such environmental problems as eutrophication of waters and greenhouse effect. Peatlands are also important as places of great biodiversity. Poland has big ammount of peat ecosystems (12nd place in the world) but the majority of them are under influence of human management. Up to the present management of them brought to great transformations, which reduce the role of peatlands in Polish landscape

(Ehr.) Diesing bloom formation in nine lakes of Polesie region (Central–Eastern Poland)

Using data from nine lakes, sampled between 2002 and 2010, as well as literature we have analysed blooms of Gonyostomum semen (Ehr.) Diesing in a new spreading area (Polesie region, Central–Eastern Poland). We tried to determine habitat suitability for high biomass of the species, including both physicochemical and morphometric features. High biomass of Gonyostomum (>1.4 mg.L−1) was found in three groups of coloured water bodies: (a) very small (<0.002 km2) peat pits with low pH values and mineral content; (b) larger ponds with neutral pH values and intermediate conductivity; (c) natural lakes with intermediate parameters in terms of area, pH and mineral content. There were no statistical differences regarding the values of the species biomass among the groups of lakes. Gonyostomum biomass was closely positively correlated with water colour, whereas it was weakly negatively correlated with lake area and depth. The results show that G. semen in a new spreading area bloomed in a broad spectrum of freshwater habitats

Does Water Brownification Affect Duckweeds in Freshwaters? Results from a Laboratory Experiment

The influence of water brownification (an increase in water color) on floating-leaved macrophytes appears to be an important issue in predicting the consequences of climate change in freshwater ecosystems. To fill the gap in the knowledge in this area, we performed a laboratory experiment aiming to test the impact of humic acid (HA) on Lemna minor sampled from an oxbow lake. Plants were exposed over seven days to four different additions of pure HA (resulting in DOC concentrations between 5.0 ± 0.1 mg dm−3 and 36.5 ± 0.4 mg dm−3). Changes in duckweed total fresh biomass, leaf area and the root length were measured, as well as the concentrations of total phosphorus, phosphates and nitrates in the water. The study did not find any significant decrease in either the biomass or leaf area of L. minor under conditions of enhanced HA content. However, we found that a moderate increase in HA in water promoted the growth of duckweed roots, thus, increasing the biomass but not the leaf area. In contrast, a large increase in HA in the water suppressed the growth of roots in L. minor, which was also in coincidence with less nutrient depletion in the water

Distribution of planktonic crustaceans and its diurnal changes in a hypertrophic shallow lake: does the switch from turbid-water state to clear-water state matters?

The paper presents results of post hoc analysis of diurnal changes in the crustacean distribution along the horizontal transect in the shallow hypertrophic lake, which undergone a switch from turbid-water, phytoplankton-dominated state (chl-a: 257.8 ± 100.2 µg dm−3, Secchi depth: 0.17 ± 0.02 m) to clear-water plant-dominated state (chl-a: 26.8 ± 4.8 µg dm−3, Secchi depth: 1.03 ± 0.29 m). Changes in crustacean biomass were observed in two consecutive years during two July days (every sixth hour, starting with the noon) in three sampling sites (emergent macrophytes, submerged macrophytes and center), situated along the horizontal transect between the lake shore and the center of the lake. Analysis revealed that: (a) in turbid-water conditions crustaceans aggregated at night-time near the water surface, both in the littoral zone and the lake center; (b) in clear-water state a nocturnal increase in crustacean biomass was noted only in submerged macrophyte site, but concerned only cladocerans. In conclusion, we hypothesized that switch from phytoplankton-dominated to plant-dominated state effects in change of predator-avoidance strategy showed by planktonic crustaceans.The paper presents results of post hoc analysis of diurnal changes in the crustacean distribution along the horizontal transect in the shallow hypertrophic lake, which undergone a switch from turbid-water, phytoplankton-dominated state (chl-a: 257.8 ± 100.2 µg dm−3, Secchi depth: 0.17 ± 0.02 m) to clear-water plant-dominated state (chl-a: 26.8 ± 4.8 µg dm−3, Secchi depth: 1.03 ± 0.29 m). Changes in crustacean biomass were observed in two consecutive years during two July days (every sixth hour, starting with the noon) in three sampling sites (emergent macrophytes, submerged macrophytes and center), situated along the horizontal transect between the lake shore and the center of the lake. Analysis revealed that: (a) in turbid-water conditions crustaceans aggregated at night-time near the water surface, both in the littoral zone and the lake center; (b) in clear-water state a nocturnal increase in crustacean biomass was noted only in submerged macrophyte site, but concerned only cladocerans. In conclusion, we hypothesized that switch from phytoplankton-dominated to plant-dominated state effects in change of predator-avoidance strategy showed by planktonic crustaceans

Does Water Brownification Affect Duckweeds in Freshwaters? Results from a Laboratory Experiment

The influence of water brownification (an increase in water color) on floating-leaved macrophytes appears to be an important issue in predicting the consequences of climate change in freshwater ecosystems. To fill the gap in the knowledge in this area, we performed a laboratory experiment aiming to test the impact of humic acid (HA) on Lemna minor sampled from an oxbow lake. Plants were exposed over seven days to four different additions of pure HA (resulting in DOC concentrations between 5.0 &plusmn; 0.1 mg dm&minus;3 and 36.5 &plusmn; 0.4 mg dm&minus;3). Changes in duckweed total fresh biomass, leaf area and the root length were measured, as well as the concentrations of total phosphorus, phosphates and nitrates in the water. The study did not find any significant decrease in either the biomass or leaf area of L. minor under conditions of enhanced HA content. However, we found that a moderate increase in HA in water promoted the growth of duckweed roots, thus, increasing the biomass but not the leaf area. In contrast, a large increase in HA in the water suppressed the growth of roots in L. minor, which was also in coincidence with less nutrient depletion in the water

An experimental study on the influence of the bloom-forming alga Gonyostomum semen (Raphidophyceae) on cladoceran species Daphnia magna

The effect of the unicellular, bloom-forming alga Gonyostomum semen (Raphidiophyceae) on the survival rate and body size of Daphnia magna was tested under experimental laboratory conditions. Using samples from four humic lakes with a long history of Gonyostomum blooms, we exposed D. magna for 72 h to various Gonyostomum treatments which included homogenized biomass (frozen and fresh), live cell populations as well as lake water separated from the concentrated biomass of live cells. Filtered lake water and the chlorophycean alga Stichococcus bacillaris population (homogenized biomass or live cells) we used as controls. Our study revealed that (1) frozen homogenized G. semen biomass in the concentrations typical for blooms was not harmful for Daphnia and appeared to have a nutritive effect because it supported its growth; however, Daphnia mortality occurred after exposure to fresh and highly concentrated cell homogenate containing high amount of mucilage; (2) it is unlikely that living Gonyostomum cells excrete extracellular substances harmful for Daphnia; however, dense live Gonyostomum population that formed mucilaginous aggregates immobilized Daphnia and increased its mortality. The results suggest that various interactions between G. semen and D. magna take place and may play an essential role in natural freshwater ecosystems

Diversity of the Rhopalodiaceae Diatoms (Bacillariophyta) on Macrophytes of Different Architecture in Small and Shallow Oxbow Lakes (SE Poland)

The research was conducted in July 2018 on six oxbow lakes of the San River. A total of 21 samples from various macrophyte species were collected. Over 400 species of diatoms were identified in the analyzed materials, 9 of which belonged to the Rhopalodiaceae family. Most of these Epithemia and Rhopalodia species developed as dominants in most of the studied samples. One of reported species – Epithemia selengaensis Vishnyakov, Kulikovskiy & Genkal was first time reported from Poland. The aim of the study was to present the taxonomic diversity of the representatives of the Rhopalodiaceae family growing different macrophyte species in oxbow lakes in the summer aspect

Vertical distribution of expansive, bloom-forming algae Gonyostomum semen vs. plankton community and water chemistry in four small humic lakes

One of the features of Gonyostomum semen, a bloom-forming and expansive flagellate, is uneven distribution in the vertical water column often observed in humic lakes. In this paper, we analysed vertical distribution of the algae in four small (0.9–2.5 ha) and humic (DOC: 7.4–16.5 mg dm−3) lakes with similar morphometric features with the aim to test the hypothesis that vertical distribution of G. semen may be shaped by zooplankton structure and abundance. In addition, we wanted to check whether high biomass of this flagellate has any influence on the chemical composition as well as on planktonic bacteria abundance of the water column. The results of the study showed that vertical distribution of the algae during the day varied among all studied lakes. Our most important finding was that (a) the abundance and structure of zooplankton community (especially in case of large bodied daphnids Daphnia pulicaria, D. longispina and copepod Eudiaptomus graciloides) may shape G. semen vertical distribution in studied lakes; (b) high G. semen biomass may decrease the content of ammonium ions in the water column by intense uptake, but has low effect on other water chemical parameters. The results of the study contribute to the understanding of the factors influencing this expansive algae behaviour as well as it shows interesting aspects of G. semen influence on some components of the lake ecosystem

An experimental study on the influence of the bloom-forming alga

The effect of the unicellular, bloom-forming alga Gonyostomum semen (Raphidiophyceae) on the survival rate and body size of Daphnia magna was tested under experimental laboratory conditions. Using samples from four humic lakes with a long history of Gonyostomum blooms, we exposed D. magna for 72 h to various Gonyostomum treatments which included homogenized biomass (frozen and fresh), live cell populations as well as lake water separated from the concentrated biomass of live cells. Filtered lake water and the chlorophycean alga Stichococcus bacillaris population (homogenized biomass or live cells) we used as controls. Our study revealed that (1) frozen homogenized G. semen biomass in the concentrations typical for blooms was not harmful for Daphnia and appeared to have a nutritive effect because it supported its growth; however, Daphnia mortality occurred after exposure to fresh and highly concentrated cell homogenate containing high amount of mucilage; (2) it is unlikely that living Gonyostomum cells excrete extracellular substances harmful for Daphnia; however, dense live Gonyostomum population that formed mucilaginous aggregates immobilized Daphnia and increased its mortality. The results suggest that various interactions between G. semen and D. magna take place and may play an essential role in natural freshwater ecosystems