Freshwater reefs as mesohabitats for the assessment of diel invertebrate drift patterns

Freshwater reefs (known as tufa barriers) are special karst features recognized for highly heterogeneous habitat structures, complex hydrogeological features, and unique macrozoobenthos drift (downstream dispersal) patterns. Our study objective was to investigate diel and seasonal drift patterns between barriers and pools, both composed of moss-rich and fishless mesohabitat types, aligned on a small spatial scale within the karst, tufa-precipitating Plitvice Lakes hydrosystem. We monthly sampled drift at the two mesohabitat types (barriers and pools) during midday and dusk and examined quantitative and qualitative drift compositions, including drifting invertebrates, moss, and associated particulate organic and inorganic matter (APOIM). Barriers displayed higher invertebrate drift densities than those of pools. The same pattern was observed for moss and APOIM. At both mesohabitat types, invertebrate drift showed peak but highly variable densities during late spring and summer (mean >100 individuals m-3), whereas during late winter and early spring the drift densities were 5-fold lower than those densities. The nonmetric multidimensional scaling analysis revealed that invertebrate drift seasonality was influenced by seasonal drift patterns of aquatic moss and moss-dwelling invertebrate taxa. Adult and/or larval Riolus spp. and larval Hemerodromia spp. were found to be the most significant for the separation of midday and dusk within the NMDS ordination of barriers and pools. At barriers, midday drift densities of invertebrates, moss, and APOIM were higher than the respective dusk records. Within pools, invertebrate drift was largely aperiodic. We suggest that increased midday and/or aperiodic drift are a consequence of the lack of fish between barrier- and pool-mesohabitats. Our results further indicated that aquatic invertebrates inhabiting fast-flowing barriers and slow-flowing pools mostly exhibit “passive drift” mediated by transport agents such as water flow and dislodged aquatic vegetation. The observed spatio-temporal drift patterns are also likely influenced by ontogenetic shifts in drift periodicity (i.e., shifts depending on the development stage and morphological characteristics of the individual taxa) as well as benthic distribution of moss-dwelling invertebrate taxa. We can conclude that biotic (vs. abiotic) controls of drift are likely minimized in the fishless case of the freshwater reefs and associated barrier–pool sequences within Plitvice Lakes hydrosystem.

Effect of Current Velocity on Cd Accumulation in the Aquatic Moss Fontinalis antipyretica

With the aim of further standardizing biomonitoring techniques with aquatic mosses, the relationship between the velocity of water flow and cadmium (Cd) accumulation in transplants of the moss Fontinalis antipyretica was investigated. For this purpose, moss transplants were exposed in a controlled aquatic environment to different concentrations of Cd (0, 4, 16 and 36 ng g−1) and different water velocities (10, 30, 50, 70 and 90 cm s−1). The Cd concentrations in the moss transplants mainly depended on the Cd concentration in the water, but a small fraction of the variance was explained by water velocity. The Cd concentrations in moss were standardized to remove the effect of the concentration in the water so all the data could be analyzed together. The regression model for the standardized concentrations explained 23% of the variance in Cd accumulation in F. antipyretica and water velocity proved to be a significant predictor of Cd accumulation.

Draft genome of the aquatic moss Fontinalis antipyretica (Fontinalaceae, Bryophyta)

Mosses comprise one of three lineages forming a sister group to extant vascular plants. Having emerged from an early split in the diversification of embryophytes, mosses may offer complementary insights into the evolution of traits following the transition to, and colonization of, land. Here, we report the draft nuclear genome of Fontinalis antipyretica (Fontinalaceae, Hypnales), a charismatic aquatic moss that is widespread in temperate regions of the Northern Hemisphere. We sequenced and de novo-assembled its genome using the 10X Genomics method. The genome comprises 385.2 Mbp, with a scaffold N50 of 45.8 Kbp. The assembly captured 87.2% of the 430 genes in the BUSCO Viridiplantae odb10 dataset. The newly generated F. antipyretica genome is the third moss genome, and the second seedless aquatic plant genome, to be sequenced and assembled to date.

Optimization of the Biomonitoring Technique with the Aquatic Moss Fontinalis antipyretica Hedw.: Selection of Shoot Segment Length for Determining Trace Element Concentrations

Bryophytes, including Fontinalis antipyretica Hedw., are widely used for biomonitoring aquatic environments. However, some methodological aspects, such as the fraction of shoot analysed, have not yet been standardized. The main objective of this study was to establish the length of segments of F. antipyretica shoots that should be used for trace element determination in monitoring studies. For this purpose, we determined the concentrations of 12 different trace elements (11 metals and one metalloid) in five successive 1 cm-long segments of the shoots of F. antipyretica collected from four different locations. We found that the concentrations of most elements increased steadily towards the basal part of the shoots without becoming stable. Sometimes, these increasing trends were concealed by another underlying trend of increasing dry/fresh weight ratios, caused by morphological changes (leaf density, shoot thickness) related with shoot development. The concentration trends were due to factors such as the deposition of Mn oxides on the moss surface. This element showed the largest increases in concentration towards the basal part of the shoot and its concentrations were closely correlated with those of most of the other elements. Considering the results obtained, we recommend the use of 3 cm-long apical segments for determining trace element concentrations in F. antipyretica. This recommendation is based on the following: (1) The change in dry weight beyond this length of segment is small; (2) the workload and the quantity of material to collect in the river is acceptable; (3) Most previous studies have used shoot segments of similar lengths.

Welcome to the Czech Republic again! Rare northern mosses Calliergon megalophyllum and Drepanocladus sordidus (Amblystegiaceae) in South Bohemia in light of their European distribution and habitat preferences

Two aquatic moss species, Calliergon megalophyllum and Drepanocladus sordidus (Amblystegiaceae, Bryophyta), which had been considered extinct in the Czech Republic, were found in the Třeboň Basin, South Bohemia, in 2016–2017. They co-occurred in extensive reed- and sedge-dominated fen pools with humic water on the shore of an old fishpond and the former species was also discovered in a small humic pool in an old shallow sand-pit. The new Czech sites of these rare boreal species represent one of the southernmost known outposts within their entire European range. Previously, the two species were only known from single records in the Czech Republic from the late 19th and early 20th centuries. To confirm our morphological observations, we used phylogenetic analyses of DNA sequence variation in four chloroplast loci (atpB-rbcL, trnL-trnF, rpl16, trnG) and one nuclear region, the internal transcribed spacers of ribosomal DNA (ITS). We found (1) monophyly of all Calliergon megalophyllum specimens tested; (2) based on chloroplast DNA sequences, monophyly among all Drepanocladus sordidus specimens and representatives of Pseudocalliergon turgescens and P. lycopodioides moss species; (3) based on nuclear ITS sequences, monophyly of all original D. sordidus specimens. These results corroborate morphological studies and thus confirm the existence of natural sites for the studied moss species in the Třeboň Basin, South Bohemia, Czech Republic.

Aquatic Mosses as Adaptable Bio-Filters for Heavy Metal Removal from Contaminated Water

Heavy metals (HMs) are released into the environment by many human activities and persist in water even after remediation. The efficient filtration of solubilized HMs is extremely difficult. Phytoremediation appears a convenient tool to remove HMs from polluted water, but it is limited by the choice of plants able to adapt to filtration of polluted water in terms of space and physiological needs. Biomasses are often preferred. Aquatic moss biomasses, thanks to gametophyte characteristics, can act as live filtering material. The potential for phytoremediation of Hypnales aquatic mosses has been poorly investigated compared to aquatic macrophytes. Their potential is usually indicated as a tool for bioindication and environmental monitoring more than for pollutant removal. When phytoremediation has been considered, insufficient attention has been paid to the adaptability of biomasses to different needs. In this study the heavy metal uptake of moss Taxiphyllum barbieri grown in two different light conditions, was tested with high concentrations of elements such as Pb, Cd, Zn, Cu, As, and Cr. This moss produces dense mats with few culture needs. The experimental design confirmed the capacity of the moss to accumulate HMs accordingly to their physiology and then demonstrated that a significant proportion of HMs was accumulated within a few hours. In addition to the biosorption effect, an evident contribution of the active simplistic mass can be evidenced. These reports of HM accumulation within short time intervals, show how this moss is particularly suitable as an adaptable bio-filter, representing a new opportunity for water eco-sustainable remediation.

Draft genome of the aquatic moss Fontinalis antipyretica (Fontinalaceae, Bryophyta)

BackgroundMosses compose one of the three lineages that form the sister group to extant vascular plants. Having emerged from an early split in the diversification of embryophytes, mosses may offer complementary insights into the evolution of traits following the transition to and colonization of land. Here, we report the draft nuclear genome of Fontinalis antipyretica (Fontinalaceae, Hypnales), a charismatic aquatic moss widespread in temperate regions of the Northern Hemisphere. We sequenced and de novo assembled its genome using the 10 × genomics method. The genome comprises 486.3 Mb, with a scaffold N50 of 38.8 kb. The assembly captured 89.4% of the 303 genes in the BUSCO eukaryote dataset. The newly generated F. antipyretica genome is the third genome of mosses, and the second genome for a seedless aquatic plant.