Aquatic Botany最新文献

Methane (CH₄) is a potent greenhouse gas (GHG) - CH₄ of non-fossil origin has a global warming potential (GWP) of 27.0 on a 100-year time scale -and strongly contributes to climate change. Approximately half of the CH₄ emitted to the atmosphere originates from aquatic systems. While the estimate of aquatic CH₄ commissions comes with large uncertainties, this applies even more for the contribution of CH₄ emissions from vegetated aquatic areas. This is related to uncertainties in both the emission intensities as well as the areal extent of vegetated aquatic areas.

Eutrophication and cyanobacteria blooms are considered major problems for the biodiversity and water quality of urban ponds. While biomanipulation techniques such as drawdown with fish removal have great potential to restore turbid ponds to a clearwater status, it remains difficult to predict if and how macrophytes will recover naturally. Here, we used individual genotyping and population genetics based on 20 nuclear microsatellite loci to investigate the recruitment and recolonization strategies of the submerged macrophyte Stuckenia pectinata (L.) Börner. More specifically, we compared the founder genetic diversity of recovering populations just after biomanipulation to the genetic diversity of spontaneous, contiguous populations that settled over an extended period of time and were within the same catchment. Our results showed that turbid ponds may contain a persistent propagule bank that allows for an immediate re-establishment of genetically diverse populations of S. pectinata once a desired clearwater state is restored. Therefore, biomanipulation without sediment removal proved to be successful for founding populations to become immediately integrated with their established populations, thus maintaining the overall diversity of this species within local areas. Additionally, our results demonstrated an excess of heterozygotes in established populations that may be caused by substantial drift in albeit small effective population sizes of this predominantly outbreeding species.

Three experimental trials were conducted to investigate the influence of shade and cold stratification on germination success of vegetative propagules from multiple Butomus umbellatus genotypes. Shade level did not significantly impact germination of propagules in trial 1 (p=0.16); however, significant differences (p<0.0001) in germination percentages at the conclusion of the study were detected between genotypes. Rhizome segments of the triploid genotype one (G1) had the highest mean germination (95±1%); whereas bulbils of the diploid genotypes three (G3), four (G4), and five (G5) germinated to 9±2%, 1±1%, and 15±2%, respectively. Trial 2 focused on bulbils from G3, G4, and G5 diploid plants that were stratified at 4℃ for 35d. Like Trial 1, shade level was not significant (p=0.19) relative to the overall germination of cold-stratified bulbils. However, cold-stratified bulbils exhibited a much higher mean germination (≥93%) for all three genotypes. In Trial 3, the cold stratification treatments were significant and positively correlated to overall germination for G4 (p=0.005, r=0.77) and G5 (p=0.002, r=0.82), but not G3 (p=0.22, r=0.40) bulbils. Germination time significantly differed between genotypes in all cold-stratification treatments except for the 0, 120, and 180-day treatments. These studies demonstrate that a high percentage of vegetative propagules produced by B. umbellatus are capable of successfully germinating under laboratory conditions, but some require extended periods of cold exposure. Given that a single diploid bulbil can produce thousands of bulbils within a growing season; long term management of this species will need to be focused towards limiting bulbil production.

Coastal wetlands display ecohydrological zonation such that horizontal differences in plant zones are driven by soil aeration and varying groundwater levels. However, it is less clear how variable levels of drainage directly impact biotic and abiotic factors in coastal wetland ecosystems. To determine the impacts of drainage levels, simulated tides in mesocosms with varying degrees of drainage were created with Spartina alterniflora and Salicornia pacifica, the dominant coastal salt marsh plant species on the United States’ Atlantic and Pacific coasts respectively. We measured biomass production and photosynthesis as indicators of plant health, and we also measured soil and porewater characteristics to help interpret patterns of productivity. These measures included above and belowground biomass, porewater pH, salinity, ammonium concentration, sulfide concentration, soil redox potential, net ecosystem exchange, photosynthesis rate, respiration rate, and methane flux. We found the greatest plant production in soils with intermediate drainage levels, with production values that were 13.7% higher for S. alterniflora and 57.7% higher for S. pacifica. Understanding how drainage impacts plant species is important for predicting wetland resilience to sea level rise, as increasing water levels alter ecohydrological zonation.

Seagrasses are one of the most productive foundation species in the world and are important for maintaining ecosystem homeostasis. However, seagrasses have experienced a global decline in areal extent, due in part to environmental stressors. Despite ongoing decline, little is known about the lipidome of most seagrass species. Generally, lipidome profiles closely align with phenotypic changes and can be used to evaluate the condition of an individual. In this study, a nontargeted lipidomics approach, utilizing high-performance liquid chromatography tandem mass spectrometry, was used to assess the lipidome of wild seagrasses in Florida. Overall, 399 individual lipid species, comprised of 33 lipid subclasses, were identified across all specimens. The lipid classes with the highest total concentration, accounting for 75% of total identified lipids in all seagrasses were: monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG), and sulfoquinovosyl diacylglycerols (SQDG). Here, the lipidomic profiles of wild seagrasses were identified for the first time, a necessary step toward using lipodomics as a tool for prospective assessments of condition. Once regional and species-specific baselines have been mapped, lipodomic surveys could provide new insight into the effects of environmental stressors on seagrass condition and help to augment ongoing efforts to document and understand seagrass ecosystem status and trends.

Bryophytes are known bioindicators and are also emerging as effective tools for bioremediation. In vitro culture of bryophytes is an important tool for the implementation of several research and industrial applications but it is a poorly explored technology. In this study, we characterize in sterile conditions three aquatic moss species largely used all over the world for decoration but poorly studied: Leptodictyum riparium, Vesicularia montagnei and Taxiphyllum barbieri. They share interesting morphological traits that suggest their use as natural biofilters. Results include protocols for the establishment of axenic in vitro cultures, different for the different species because of their sensitivity to treatments, on which the morphological characters of the three species were described. The sporophytic generation was observed in L. riparium and V. montagnei but not in T. barbieri that may be unable to develop the diploid generation. The effect of plant growth regulators on gametophyte fragments was described applying 6-benzylaminopurine as cytokinin and α-naphthalene acetic acid as auxin. The absorption of several trace elements was measured in a mixed solution simulating environmental pollution, evidencing specie specificity toward the different elements. The possible applications for these mosses are not only in the field of bioindication but also in bioremediation and environmental restoration. Our study produced widely applicable protocols and basic information for further applications.

This research brings novel information regarding the floral traits and pollinator groups of aquatic macrophytes. Classifying functional traits and pollinator groups contributes to understanding reproductive processes, community structuring, and ecosystem functioning. Based on an extensive survey of information on 524 species of aquatic macrophyte angiosperms from the Pantanal wetland, we classified the floral traits of these species to identify their potential group of pollinators and how these traits are distributed throughout the botanical families of aquatic plants. We classified their life forms, floral traits (flower type, color, and resource), and main pollinator groups. We also investigated trends, plotting the occurrence of species throughout the phylogeny of angiosperm families, and using a network of interactions, we verified how interactions with different groups of pollinators are distributed within species traits. As a result, the species of aquatic macrophytes in the Pantanal are well distributed within the phylogeny, indicating that they may be more related to ecological than phylogenetic factors. We found a high diversity of floral traits and pollinator groups, predominating white flowers, providing nectar as a resource, and bees as their primary pollinators. Although bees were the main group of pollinators, we also found abiotic interactions linked to the species richness in Poaceae and Cyperaceae, with pollination system mainly performed by wind. Our research represents a first step towards identifying key information gaps. Future studies should focus on understanding in loco traits to fill this gap, besides information on ecological interactions with potential pollinators and species phenology.

Eelgrass (Zostera marina) is a marine angiosperm distributed in shallow seas that has a unique mechanism for regulating water content. Water transfer across the plasma membrane is facilitated by aquaporins, which are membrane proteins. In this study, we investigated the physiological functions of plasma membrane intrinsic proteins (PIPs) in eelgrass. ZoPIP1;1 and ZoPIP2;1 in eelgrass leaves were amplified by RT-PCR. Both ZoPIPs localized to the plasma membrane, and only ZoPIP2;1 showed water permeability. ZoPIP1;1 and ZoPIP2;1 were expressed in all tissues except male flowers. ZoPIPs were expressed during seed and fruit development, and their expression levels were low in mature seeds and elevated in germinating seeds. Moisture content decreased in the later phases of seed development and increased during seed germination. These findings imply that ZoPIPs participate in water uptake during seed germination. In leaves, ZoPIP expression was upregulated by dehydration but downregulated by rehydration. Water reabsorption of leaves was inhibited by HgCl₂, an inhibitor of aquaporins. These findings indicate that ZoPIPs are upregulated by dehydration during extremely low tides and promote water uptake when the tide turns. Therefore, eelgrass PIPs function in moisture regulation during growth, seed germination, and the flood-ebb tidal cycle in seawater.

The aquatic macrophyte Lemna minor and cyanobacterium Microcystis aeruginosa coexist and alternate in freshwater ecosystems, and nutrient changes, physical conditions, and micropollutants such as pharmaceuticals drive their succession. However, the effects of the antimalarial drug Lumefantrine on allelopathic interactions have not been previously investigated. This study investigated the effect of Lumefantrine on the allelopathic interactions between L. minor and M. aeruginosa. The drug adversely affected pigment levels at 1000 µg L^-1 on day one, while the highest levels were observed at the same concentration on days three and five in M. aeruginosa cultures. The intracellular hydrogen peroxide (H₂O₂) and lipid peroxidation (MDA) levels and peroxidase (POD) and glutathione S-transferase (GST) activity of L. minor and M. aeruginosa increased at varying degrees depending on the concentration of Lumefantrine. Increased concentrations of Lumefantrine induced higher microcystin content in M. aeruginosa. L. minor significantly decreased the growth and increased GST and POD activities of M. aeruginosa on day five of the assay. The introduction of Lumefantrine further altered these parameters when the species were co-cultured. Similarly, M. aeruginosa inhibited the growth of L. minor. The combination of M. aeruginosa and Lumefantrine increased GST activity compared with M. aeruginosa alone. Microcystin content was higher in co-cultures without Lumefantrine than in those exposed to the drug. These results show that allelopathic interactions between L. minor and M. aeruginosa are influenced by Lumefantrine and may have implications for managing freshwater ecosystems.

Elevated mercury (Hg) levels in biota is one issue facing the Everglades ecosystem in south Florida, USA. Methylmercury (MeHg) is a concern in the environment because it bioaccumulates through the food web and can harm fauna and humans if ingested through contaminated food sources (e.g., fish). Total mercury (THg) and MeHg concentrations were measured in several common macrophyte species, periphyton, and detritus in the Everglades to investigate Hg concentrations spatially and among different ecosystem components. At each site, two species from the carnivorous genus Utricularia, U. purpurea and U. foliosa, which are widespread and abundant in Everglades sloughs, had much higher average tissue MeHg concentrations (2.4–81 ng/g dry weight [dw]) than all other sampled macrophytes (<1.5–7.5 ng/g dw), periphyton (0.4–6.2 ng/g dw), and detritus (<1.5–5.7 ng/g dw). The Utricularia species were likewise enriched with THg (14.6–115 ng/g dw) compared to the other macrophytes (2.6–27 ng/g dw), although slough detritus had the highest THg at most sites (24–182 ng/g dw). The Utricularia species generally had a higher average percent of THg as MeHg (8.2–75%) compared to the other macrophytes, periphyton, and detritus (0–32%). MeHg concentrations in Utricularia species were quite variable among sites with a spatial distribution that generally reflected historical Hg concentration patterns known in mosquitofish (Gambusia holbrooki). Utricularia species merit further investigation to understand how they accumulate relatively high MeHg concentrations and how they might influence Hg accumulation up the food web.