New records of Chara connivens P. Salzmann ex A. Braun 1835 – an extremely rare and protected species in Polish brackish waters

The stonewort Chara connivens was rediscovered in the Vistula Lagoon in 2011, almost 35 years after its last record. In 2012, the species was recorded for the first time in the Szczecin Lagoon. Chara connivens occurred at shallow (0.5–1.2 m) sandy-muddy and muddy bottoms of small embayments. In the Vistula Lagoon, the stonewort was represented by single small specimens, while in the Szczecin Lagoon, it formed dense and extensive patches

Ecology of charophytes – permanent pioneers and ecosystem engineers

For almost a century, charophytes have been regarded as a group that is confined to low-nutrient-clear water conditions. In light of recent research, this generalisation of the ecological niche dimensions of charophytes has changed and now includes more facets of ecological existence. In this review, the current knowledge with respect to species-specificity as well as temporal aspects – ontogenetic and successional ones – of the ecological requirements of charophytes are presented and discussed. This review identifies new directions for ecological research on charophytes as well as knowledge gaps to be filled, not just for reasons of academic curiosity, but also for applied purposes such as lake restoration, bioremediation and bioindication of water quality and water regime

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

New records of Chara connivens P. Salzmann ex A. Braun 1835 – an extremely rare and protected species in Polish brackish waters

The stonewort Chara connivens was rediscovered in the Vistula Lagoon in 2011, almost 35 years after its last record. In 2012, the species was recorded for the first time in the Szczecin Lagoon. Chara connivens occurred at shallow (0.5–1.2 m) sandy-muddy and muddy bottoms of small embayments. In the Vistula Lagoon, the stonewort was represented by single small specimens, while in the Szczecin Lagoon, it formed dense and extensive patches

Lychnothamnus barbatus (Meyen) Leonhardi 1863, A New Species to the Flora of Montenegro

This study presents a newly discovered site of Lychnothamnus barbatus, one of the rarest charophytes worldwide of a disjunctive, Euro-Australasian-American distribution. The species is the only representative of the genus Lychnothamnus on a global scale, hence its threat poses a risk of extinction to the entire lineage. In June 2019, Lychnothamnus barbatus was discovered in Lake Malo Blato, a north-western bay of Lake Shkodra/Skadar, to be a new element to the flora of Montenegro. Lychnothamnus barbatus was recorded at a depth of 3 m, in nutrient-poor but calcium-rich water and on a muddy substrate in the zone of submerged vegetation composed of charophytes and angiosperms. The collected thalli of L. barbatus were young and sterile, green, slightly calcified, and up to 15 cm high. Except for gametangia, all features which are diagnostic for this rare charophyte were well developed. Based on the synthesis of the current state of knowledge, the new site of L. barbatus is presented in the context of the species’ ecological requirements and climatic plasticity, current distribution, and history in the Balkans

Preliminary evidence of an endangered species benefiting from moderate climate warming: A palaeolimnological study of the charophyte Lychnothamnus barbatus

1. In a time of rapid environmental changes, identification of the effects of climate warming on charophytes (Characeae, Charophyta) will enable the optimization of conservation measures, especially for extremely rare species. Lychnothamnus barbatus is one of the rarest charophytes worldwide, which has decreased in the number of occupied sites over the last century. However, the recolonization of former sites has been observed in recent years (e.g. Lake Ku znickie, Poland). The study aimed to analyse the effects of climatic changes and human pressure on the L. barbatus population. 2. Three 30 cm sediment cores were collected from minimum, average, and maximum depths of L. barbatus occurrence to determine the past vegetation composition. Sediment cores were dated using the radioisotopes lead-210, caesium-137, and carbon-14. A spatial analysis of the lake catchment changes during the last 120 years was also conducted. 3. The study demonstrated L. barbatus presence in Lake Kuźnickie at the beginning of the 16th century. However, a sharp increase in the proportion of this species in the vegetation community occurred in the 19th century and during climate warming at the end of the Little Ice Age. Factors that significantly influenced the present occurrence of the L. barbatus population included improvement in water quality and the oospore bank deposited in the bottom sediments. 4. This study is the first palaeoreconstruction in a modern lake dominated by L. barbatus. Based on the history of L. barbatus in Lake Kuźnickie after the end of the Little Ice Age, the positive effect of climate warming on the contemporary recovery of this charophyte is postulated. 5. The reaction of L. barbatus to climate warming appears to differ from commonly accepted scenarios for aquatic macrophytes because its recovery in the past and at present coincided with increases in air temperature. This research indicated the appropriate management and conservation practices for lakes with L. barbatus populations

Seasonality of Water Chemistry, Carbonate Production, and Biometric Features of Two Species of Chara in a Shallow Clear Water Lake

The objective of this study was to analyze the temporal variability of biometric features and the carbonate production of two charophytes: Chara polyacantha A. Braun and Chara rudis A. Braun against the background of the physical-chemical properties of water. The investigation was carried out in a small, mid-forest Lake Jasne (western Poland). It is a polymictic, mesotrophic, hardwater ecosystem dominated by charophyte vegetation. Each month, 10 individuals of each species were characterized in terms of morphometric features, fresh and dry weight, and the percentage of calcium carbonate. Additionally, physical-chemical parameters of the water were studied. The results of physical-chemical analyses indicated similar habitat conditions for both species. Despite smaller dry weight C. polyacantha was characterized by greater morphological variability and higher rates of growth and percentage share of calcium carbonate in dry mass than C. rudis. The percentage of calcium carbonates in dry mass did not differ significantly between the species and exceeded 60%, reaching the maximum (76% in C. polyacantha) in July and August. For both species, distinct correlations between the structure of biomass and morphological features were found. The obtained results show the great importance of charophyte vegetation in carbon cycling and functioning of lake ecosystems

Climate features or the composition of submerged vegetation? Which factor has a greater impact on the phytoplankton structure in temperate lakes?

This study compares the composition and biomass of phytoplankton assemblages of lakes with abundant vegetation dominated by (1) charophytes (Chara-lakes) and (2) angiosperms (Potamogeton-lakes). These two groups of submerged macrophytes effectively control the phytoplankton development in lakes, but differ in the feedback mechanisms involved. Despite increasing interest, the phytoplankton development in charophyte- and angiosperm-dominated lakes under different climatic circumstances remains poorly recognized. Each type of lakes was studied in two distant (>500 km apart) regions of Poland, characterized by distinctly different climate features (western – warmer, and north-eastern – cooler), with temperature differences corresponding to the predicted magnitude of the global warming-related temperature rise in the near future. Twelve lakes were selected for this study, three Chara- and three Potamogeton-lakes in each region. In addition to phytoplankton analysis, macrophytes and climatic conditions, water chemistry, and the use of land in the catchment area were studied. Although we expected that climatic differences would have greater impact on the structure of phytoplankton assemblage than that expected due to higher macrophyte biomass and lower nutrient availability in Chara- than in Potamogeton-lakes, multidimensional statistical analyses clearly distinguished between the two macrophyte types of lakes. Significantly lower values of the total phytoplankton biomass, and the biomass of diatoms and cyanobacteria occurred in Chara- vs Potamogeton-lakes. We therefore postulate that not only abundantly developed submerged macrophytes, but also the type of vegetation are important factors structuring phytoplankton development and by interacting with the physical and chemical characteristics of water show potential in mitigating the effects of climate change