Biomass production and nutrient removal efficiency of Suaeda salsa in eutrophic saline water using a floating mat treatment system

To explore an economic and practical phytoremediation strategy adapted to remediate hypereutrophic water with high salt content, biomass production and nutrient removal efficiency of Suaeda salsa are determined in eutrophic saline water using a floating mat treatment system. The results suggest that S. salsa, as a pioneer species in coastal tidal flats, has a good ability to tolerate the combined stress of salt and eutrophication under hydroponic conditions, although different levels of salinity have different influence on biomass accumulation. Under optimum-growth saline conditions (274 mM NaCl), the removal efficiency of total nitrogen (TN) and total phosphorus (TP) by S. salsa for hypereutrophic water reaches 73.23% and 72.21%, respectively. The removal efficiency under different levels of eutrophication in the water shows that TN and TP contents in eutrophic saline water are conducive to plant biomass accumulation; the removal efficiency decreases with increasing element concentration. An ecological floating island system suitable for planting S. salsa has been performed and a practical application of S. salsa to remediate eutrophic water resulting from large-scale mariculture carried out. The plant grew well and aquaculture water quality was significantly improved. Therefore, S. salsa could be applied to remediate hypereutrophic water with high salt content.

Ecology of seed germination and features of ontogeny of floating mat-forming hygrogelophyte Calla palustris (Araceae) under laboratory conditions

This article examines the ecology of germination and the features of ontogenesis of the floating mat-forming hygrogelophyte Calla palustris L. in the territory of some regions in the central part of European Russia and the Republic of Belarus under laboratory conditions. It has been found that in the surveyed territory in the dense ear-like collective fruit of C. palustris, 40.7 ± 6.4 fruits, juicy berries, are formed and the number of seeds produced (actual seed productivity), averages 164.0 ± 89.3. Widely varying data on the number of berries in the collective fruit, as well as a variable number of ovules in them, shows that the seed productivity of C. palustris depends on a whole range of endogenous and exogenous factors, including the effectiveness of pollination of flowers by insects. In laboratory experiments, various storage periods (2 and 12 months) and methods of presowing seed treatment (stratification, drying, ice-freezing) were applied to simulate the ecological conditions of the growth of white alder. It is shown that freshly harvested seeds do not germinate at once, and wet cold stratification makes it possible to achieve maximum values of laboratory germination (from 84.4 to 99.0) and germination energy (from 66.6 to 88.3). Given that the features of germination are indicators of dormancy, it is demonstrated that seeds of C. palustris are in a state of shallow physiological dormancy, conditioned by the physiological mechanism of inhibition. Along with dry storage, wet cold stratification is the main way for seeds to enter a non-dormant state. Such mechanisms are consistent with the climatic features of the regions in which the species grows. It is found that C. palustris seeds, in common with many other species of hygrogelophytes, can float on the water surface for a long time (more than 30 days), spreading with water flow (hydrochoria). Seeds of C. palustris are photosensitive, germination is observed in a wide range of temperatures – from 10–14 to 30 ºС (at constant humidity), type of germination – underground (hypogeal). It is found that ontogeny of individuals of generative origin of C. palustris in the laboratory is terminated (the plants died after passing the juvenile ontogenetic state). The formation of C. palustris seedlings under laboratory conditions lasts 23–25 days and is characterized by the appearance of the main organs of the plant and the anisotropic growth of the shoot axis. At the final stage of development, the seedling is represented by a uniaxial monopodial and anisotropic growing rosette shoot with shortened internodes. The juvenile ontogenetic state in laboratory conditions lasts up to 7 months, after which the plants die off. In the framework of ontomorphogenesis, the stages of ontogenetic development under study (the seedling and the juvenile plant) correspond to the phase of the primary uniaxial rosette shoot. The plant in this period is represented by a uniaxial monopodially growing anchorage shoot. The detection of virgin plants in natural conditions indicates the possibility of their further development from the rudiments of generative origin. The main way of the species reproduction is vegetative, characteristic of most aquatic and semi-aquatic plants. In the course of ontogenesis, progressive features of development such as cotyledon greening and early death of the radicle root have been revealed.

Present state and changes that occur within plant communities growing on the floating mat that surrounds the Moszne lake (Polesie National Park)

The first recordings of flora and vegetation in the surroundings of the Moszne lake (Polesie National Park) started from 1960. In 1980s the water conditions in this area changed and affected the organisms that lived there. The aim of this research was to recognize the present state and changes that occurred within flora and vegetation in the course of 18 years (1995–2013). In 2013, at the beginning of June, 34 phytosociological relevés were made on the floating mat that surrounds the Moszne lake in the same locations as they were done in 1995. The obtained data was collated with figures from the literature by comparing the frequency of plant species and plant communities, average plant species coverage and by calculating Sørensen indexes. The results showed that almost the same plant communities were identified in both terms of research. It was found that 35% of the plant species had disappeared after 18 years and that the biggest increase in percentage coverage was noted in case of Phragmites australis and Sphagnum fallax. Those findings show that it is very difficult and sometimes even impossible to reverse the negative influence of water condition change on bogs.

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

Ponds smaller than 10 000 m2 likely account for about one-third of the global lake perimeter. The release of methane (CH4) and carbon dioxide (CO2) from these ponds is often high and significant on the landscape scale. We measured CO2 and CH4 fluxes in a temperate peatland in southern Ontario, Canada, in summer 2014 along a transect from the open water of a small pond (847 m2) towards the surrounding floating mat (5993 m2) and in a peatland reference area. We used a high-frequency closed chamber technique and distinguished between diffusive and ebullitive CH4 fluxes. CH4 fluxes and CH4 bubble frequency increased from a median of 0.14 (0.00 to 0.43) mmol m−2 h−1 and 4 events m−2 h−1 on the open water to a median of 0.80 (0.20 to 14.97) mmol m−2 h−1 and 168 events m−2 h−1 on the floating mat. The mat was a summer hot spot of CH4 emissions. Fluxes were 1 order of magnitude higher than at an adjacent peatland site. During daytime the pond was a net source of CO2 equivalents to the atmosphere amounting to 0.13 (−0.02 to 1.06) g CO2 equivalents m−2 h−1, whereas the adjacent peatland site acted as a sink of −0.78 (−1.54 to 0.29) g CO2 equivalents m−2 h−1. The photosynthetic CO2 uptake on the floating mat did not counterbalance the high CH4 emissions, which turned the floating mat into a strong net source of 0.21 (−0.11 to 2.12) g CO2 equivalents m−2 h−1. This study highlights the large small-scale variability of CH4 fluxes and CH4 bubble frequency at the peatland–pond interface and the importance of the often large ecotone areas surrounding small ponds as a source of greenhouse gases to the atmosphere.