Bioaccumulation of 137Cs and 60Co in freshwater plants

Contamination of the aquatic environment by the heavy metals and radionuclides has become a serious concern in the world. In our study, gamma-spectrometry of freshwater plants Bacopa monnieri and Egeria densa growing in cultivation media spiked with 137CsCl and 60CoCl2 was used for quantitative determination of bioaccumulation kinetic and distribution Cs+ and Co2+ ions in plant tissues. We found, that bioaccumulation of Cs and Co by fully immersed B. monnieri in Hoagland media (HM) was dependent on ion concentration in medium. Approx. 5-times lower Cs uptake 2.9 nmol/g (d.w.) was obtained in plants cultivated in 20% HM than from deionized water. The maximal Co uptake was 4-times higher than cesium uptake at the same conditions. Both Cs and Co were localized mainly in roots. The highest immobilization from roots to shoots was found in the case of Co uptake from deionized water with concentration ratio [Co]leaves : [Co]stem : [Co]root = 1.00 : 5.33 : 56.8. Cesium uptake by submerged plant E. densa was also strongly dependent on nutrients concentration in medium. However, in the case of cobalt uptake this dependence was less pronounced. Nutrients concentration also had a significant influence on distribution of Cs between stems and leaves of E. densa. Cesium was localized in leaves, however with increasing of nutrients concentration in cultivation media Cs was localized for account of stem. On the other hand, cobalt was immobilized mainly in leaves in whole range of nutrients concentration. Obtained data can serve as a models for understanding of phytoaccumulation of radionuclides from open water ponds and water channels in the vicinity of nuclear power plants and monovalent and bivalent metals from industrial sources of contamination.

Known but not called by name: recreational fishers’ ecological knowledge of freshwater plants in Hungary

Background Documenting local ecological knowledge (LEK) has recently become a topic of considerable interest. LEK can contribute to various areas of ecology, including habitat management and conservation biology. It has been recently revealed that recreational fishers’ ecological knowledge (FEK) can also provide valuable information about different organisms and habitats, while recreational fishers’ ecological knowledge is understudied in many aspects and regions of the world. Methods We aimed to record Hungarian recreational FEK on plant species related to freshwater habitats. Our research was conducted in three regularly fished water bodies in Hungary, namely Lake Velence, Keleti Main Canal, and Lake Látóképi, where a total of 72 interviews were conducted with recreational anglers. During interviews, 24 plant species occurring at freshwater habitats with common or sporadic distribution were shown to anglers as single species or in congeneric pairs. Miscellaneous plant-related knowledge of anglers was also collected. Results Anglers identified a total of 16 plant species. They used 45 botanical or folk names. An angler knew the name of 4.6 plants on average and recognized 7.4 other species without naming it. According to our detailed analysis, anglers were able to name or at least recognize those plant species which are somehow related to fishing activities, are salient, and/or common. Moreover, anglers at Lake Velence recognized less plant species; however, they also had less years of fishing experience compared to anglers of the other two locations. Conclusion We found that recreational FEK exists even in the case of freshwater plants which are not the main focus of anglers. It is highly presumable that recreational fishers would be able to provide reliable ecologically related data for scientific research establishing future citizen science projects of nature conservation.

The importance of intraspecific diversity on duckweed growth with and without salt stress

The pollution of freshwater ecosystems is threatening freshwater plant species diversity worldwide. Freshwater plants, such as duckweed (Lemna minor), are potentially sensitive to novel stressful environments. To test if intraspecific diversity could increase resistance to stressful environments, I used seven L. minor populations and assessed their growth rates in the absence and presence of moderate salt stress across an intraspecific diversity gradient.I grew the populations (ecotypes) of L. minor over five months in 92 experimental mesocosms in a glasshouse either in ecotype monocultures or in polyculture with either one or three conspecific ecotypes (23 unique compositions). The experiment was conducted in semi-natural conditions, including a natural community of algae and microbes. After assessing the duckweed growth rate in unperturbed conditions, the cultures were subjected to moderate salt stress (50mM NaCl) for several weeks. Population abundances were assessed weekly, both on the ecotype level and the whole-population level.Throughout the experiment, the ecotypes differed in their growth rates, the fastest growing at twice the rate of others. Whether the ecotypes grew in monoculture or in polyculture with other conspecifics further shaped the ecotype growth rates. Ecotype polycultures showed higher abundances towards the end of the experiment, indicating that over time, as the environment deteriorated, intraspecific diversity gained in importance. These findings show that intraspecific variation in growth rates can translate to a positive effect of intraspecific diversity on whole-population abundance. Exposure of L. minor to moderate salt levels did not significantly impact growth rates.

Known But Not Called by name: Recreational Fishers’ Ecological Knowledge of Freshwater Plants in Hungary

Background: Documenting local ecological knowledge (LEK) has recently became a topic of considerable interest. LEK can contribute to various areas of ecology, including habitat management and conservation biology. It has been recently revealed that recreational fishers’ ecological knowledge (FEK) can also provide valuable information about different organisms and habitats, while recreational fishers’ ecological knowledge is understudied in many aspects and regions of the world. Methods: We aimed to record Hungarian recreational FEK on plant species related to freshwater habitats. Our research was conducted in three regularly fished water bodies in Hungary, namely Lake Velence, Keleti Main Canal, and Lake Látóképi, where a total of 72 interviews were conducted with recreational anglers. During interviews, 24 plant species occurring at freshwater habitats with common or sporadic distribution were shown to anglers as single species or in congeneric pairs. Miscellaneous plant related knowledge of anglers was also collected. Results: Anglers identified a total of 16 plant species. They used 45 botanical or folk names. An angler knew the name of 4.6 plants on average, and recognized 7.4 other species without naming it. According to our detailed analysis, anglers were able to name or at least recognise those plant species which are somehow related to fishing activities, are salient and/or common. Moreover, anglers at Lake Velence recognized less plant species, however, they also had less years of fishing experience compared to anglers of the other two locations. Conclusion: We found that recreational FEK exist even in the case of freshwater plants which are not the main focus of anglers. It is highly presumable that recreational fishers would be able to provide reliable ecologically related data for scientific research establishing future citizen science projects of nature conservation.

Patterns and mechanisms underlying ecoregion delineation in North American freshwater plants

Aim: Biogeographical regionalisations are actively studied in different ecosystems, because they increase our understanding on fundamental broad-scale patterns and can help us in the establishment of conservation areas. Thus, we studied how well existing freshwater ecoregions describe geographical delineation for inland water plants and which ecogeographical gradients explain them. Location: North America, excluding Mexico and remote islands. Taxon: Freshwater vascular plants of all taxa and different functional groups. Methods: Using newly available fine-grained data on freshwater plant distributions, we calculated internal homogeneity and cross-boundary heterogeneity among neighbouring ecoregions. We further integrated measures of community dissimilarity to assess whether the degree of within-ecoregion homogeneity and distinctness are driven by their relationships to species replacements and richness differences, and explored how a complex suite of ecogeographical mechanisms and plant life forms affect ecoregion delineation using spatially explicit regression routines. Results: We found a clear geographical patterning of ecoregion robustness for North American freshwater plants, with their communities being more internally homogeneous and more similar to one another in polar and subtropical inland waters. Surprisingly, the degree of internal homogeneity and ecoregion distinctness were almost equally driven by species replacements and richness differences. Considering different life forms, ecoregion delineation performed best for emergent and floating-leaved plants. Finally, within-ecoregion homogeneity and distinctness were best explained by annual mean temperature and terrain ruggedness, respectively, with mean water alkalinity, ecoregion area and Late Quaternary Ice Age legacies having supplementary effects. Main conclusions: Our findings emphasise that geographical regionalisations founded on a particular organismal group are not applicable for all taxa. Our study is a promising starting point for further investigations of geographical delineations for different freshwater taxa. These updated regionalisations can then be used for conserving different biotas in freshwaters, which are currently among the most threatened ecosystems in the world.

Comparative anatomy and salt management of Sonneratia caseolaris (L.) Engl. (Lythraceae) grown in saltwater and freshwater

Sonneratia caseolaris is a pioneer species in mangrove. It can naturally grow in both saltwater and freshwater. The study was aimed at investigating and comparing the anatomical character of the S. caseolaris plants growing in different conditions and how they coped with salinity. The anatomical characteristics of roots, stems, petioles and leaf blade were investigated. The plant samples were prepared into permanent slides using a paraffin method, while the wood samples were made into permanent slides using a sliding microtome technique. Tissue clearing of leaf blade and scanning electron microscopic analysis of wood were performed. In addition, sodium chloride content in various organs and tissues was examined. It was found that cable root, stem and leaf blade showed some different anatomical characteristics between the two conditions. Periderm is a prominent tissue in saltwater roots. Tanniferous cells were observed in pneumatophores, petioles, stems and leaf blades of saltwater plants, but not found in pneumatophores and lamina of freshwater plants. Mesophyll thickness was lower in the saltwater condition. The vessel density was significantly higher in the saltwater condition than in the freshwater condition, whereas the vessel diameters in the freshwater condition were significantly higher than those in the saltwater condition. From the results, it can be concluded that root periderm plays an important role in salt exclusion, and the occurrence of tanniferous cells is associated with salt elimination.