Joanna Lenarczyk

Diatoms are regarded as reliable bioindicators for assessing heavy metal contamination in marine ecosystem including mercury. In the present study diatoms were used as bioindicators to reconstruct changes in the concentration of total mercury and its fractions in the Middle and Late-Holocene in the southern Baltic based on a 450 cm long sediment core. The goal of the study was to reconstruct changes in the concentration of Hg _tot and its fractions in relation to biodiversity of the diatom flora, climatic fluctuations occurring inferred from pollen and Pediastrum records and in relative abundance of sediment fractions. Hg _tot concentration increased from 4.6 ng g ⁻¹ (6300 cal. yr BP) to 353 ng g ⁻¹ (2021). Among the analyzed fractions HgS (⩽86.6%) dominated until ca. 4200 cal. yr BP after which a gradual increase in the proportion of Hg _F2 (⩽69.8%), was observed. The current study showed that over the last 6300 cal. yr BP the increase in Hg concentrations in the sediments of the Puck Bay has been influenced by human activities in addition to natural sources (atmospheric input, climatic fluctuations, storm events, diatoms productivity). About 4200–200 cal. yr BP the diatoms Schionodiscus oestrupii and Rhizosolenia hebetata f. hebetata enabled the identification eight time intervals during which climatic fluctuations influenced changes in sedimentary Hg _tot concentrations. Over the last ca. 200 cal. yr BP the highest Hg concentrations were associated with intensive human activity as evidenced by the anthropogenic diatom flora present at that time ( Cyclotella choctawhatcheeana , Thalassiosira levanderi ).

Sixteen monoclonal strains classified into six morphotypes typical of, or close to, intraspecific taxa of Pseudopediastum boryanum, including P. alternans (ALT), P. boryanum var. boryanum (BOR), P. boryanum var. cornutum (COR), P. boryanum var. forcipatum (FOR), P. boryanum var. longicorne (LON), and P. boryanum var. perforatum (PER), were simultaneously subjected to phylogenetic (26S rDNA and rbcL cpDNA) and morphometric analyses. Marginal cell shape, coenobium and cell size, and granule density on the cell surface were analyzed statistically. The shapes of some morphotypes (BOR, COR, FOR, and PER) were also compared to the shapes of corresponding type illustrations. Pseudopediastrum boryanum var. boryanum, without any reliable morphological and phylogenetic data, appeared to be a questionable taxon that needs a neotype. The variety longicorne proved to be a complex taxon that should be split after morphometric data of more strains and of the corresponding lectotype are included in the statistical analysis. A new species, Pseudopediastrum oblongum, was described, and four varieties were elevated to the species level, which resulted in establishing new combinations, P. cornutum, P. forcipatum, P. perforatum, and P. subgranulatum. Reference sequences for the new species and combinations were obtained. The paleoecological value of P. boryanum sensu lato appeared to be limited by the relatively low percentage of marginal cells typical of particular varieties and a high risk of their misidentification in the light microscope. The shape of marginal cells seemed to be the best diagnostic feature. Granule density could be helpful to discriminate between certain taxa.

The chrysophyte genus Dinobryon Ehrenberg consists of 44 taxa, which occur in freshwaters, rarely marine waters, mostly in temperate regions of the world. The taxa of Dinobryon produce characteristic solitary or dendroid colonies and resting stages called stomatocysts. Only 20 Dinobryon taxa have information on produced stomatocysts and only four stomatocysts are reliably linked with vegetative stages using modern identification standards employing scanning electron microscopy (SEM) analyses. In this study, an encysted material of Dinobryon pediforme (Lemmermann) Steinecke was collected in two lakes in contrasting regions of Poland. Light microscopy (LM) and scanning electron microscopy (SEM) analyses revealed that Dinobryon pediforme produces stomatocyst #61, Piątek J. that is described here as new morphotype following the International Statospore Working Group (ISWG) guidelines. This raises to five the number of reliable links between vegetative stages of Dinobryon species and corresponding stomatocysts. Phenotypic similarities between Dinobryon species and their stomatocysts, analysed for five reliably established links, showed no relationships in size and shape between loricas and stomatocysts belonging to the same species. The morphological characters of loricas and stomatocysts mapped onto the phylogenetic tree of the five Dinobryon species revealed only little congruence between their morphology and phylogenetic relationships.

A study of green and charophytic algae diversity in two high-mountain lakes in the Eastern Carpathians (Ukraine) identified 99 species (109 taxa at species and intraspecific rank) in 35 genera from different ecotopes of the studied lakes. Algal species composition was characterized, and the ecological parameters of the lakes were determined from monitoring data recorded over the last century. Environmental analyses using bioindication methods based only on data on the composition of green and charophytic algae confirmed that the environmental inferences were accurate. Degradation of the Nesamovyte and Brebeneskul lake ecosystems, as compared with their earlier states, was noted.

The present study is the first to investigate the evolution of morphological variability and modularity of single (marginal) cells in two-dimensional colonial (coenobial) microscopic algae. Geometric morphometric methods were applied to eight monoclonal strains forming a common phylogenetic lineage, composed primarily of Pseudopediastrum boryanum varieties. Both cell parts, the cell body and projections, exhibited great morphological variability, which was impacted more or less by allometry in six strains. A relationship between phylogeny and morphology was not found. Asymmetry was concentrated in the projections. The pressure of neighbouring cells in a coenobium might have stabilised the symmetry of the cell body and prevented its asymmetric fluctuations. Both cell parts were separate modules, but a strain with distinct perforations in coenobia, resulting in less contact with the neighbouring cells, exhibited stronger cell integration, generally regarded as a possible constraint for evolutionary changes. This suggested that the pressure of neighbouring cells can also act as a factor favouring cell modularity and, thus, the morphological evolution of the marginal cells.

The infraspecific relationships of the two most variable species, Pediastrum boryanum and P. duplex s.l. identified on the basis of morphological criteria, have been poorly studied so far. The present study focused on 12 original strains isola...