Aquatic Botany最新文献

To predict spatial and temporal dynamics of macroalgal blooms, including the Great Atlantic Sargassum Belt, understanding the environmental tolerances and growth rates of different species under varying conditions is essential. A series of preliminary experiments were conducted exposing three common holopelagic Sargassum morphotypes to different temperature (21.6–30.6 °C) and salinity (26.2–40.0 psu) conditions. Sargassum tolerance was assessed by two methods: a Health Metric calculated daily from changes in a specimen’s blade and vesicle count and coloration patterns, and growth rates determined from pre- and post-treatment wet weights. Morphotypes exhibited different responses to treatment conditions. Health Metric values and growth rates for S. fluitans III were not significantly impacted by tested temperatures or salinities. S. natans I tolerated a wide range of temperatures but only moderate salinities. While S. natans VIII grew well and maintained strong Health Metrics across examined salinities, it was less tolerant of cold temperatures and exhibited overall lower growth rates than other morphotypes. Given inconsistent findings among recent growth rate studies, including this one, additional experiments of longer duration that continue to explore temperature and salinity effects and use specimens from across holopelagic Sargassum’s geographic range are necessary to understand growth ecology and parameterize models.

Seaweed invasions are known as one of the main threats to coastal resources and biological diversity. The brown alga Rugulopteryx okamurae is one of the non-indigenous species that became invasive more recently. The occurrence of this common species of the warm temperate western Pacific Ocean, is confirmed for the first time in the Moroccan Atlantic coast. It was previously reported only from the M’diq beach (Alboran Sea-Morocco), and this study confirm that the northwest of Morocco, including Mediterranean Sea and Atlantic Ocean, is currently experiencing a wide invasion and massive proliferation of this non-indigenous brown alga¸ with a distribution depth up to 20 m from the intertidal zone. Substantial amounts of R. okamurae have also been cast on the beach as wrack.

Vallisneria americana is a broadly distributed North American macrophyte with growth characteristics that vary across regions. While its reproductive traits may also differ with geography, most investigations have occurred in its northern extent, resulting in uncertainty regarding life history and germination strategies in sub-tropical populations. We conducted field monitoring and greenhouse and growth chamber experiments to investigate sub-tropical V. americana seed production, seed banking, and germination cues in central Florida, USA. We observed seed production nearly year-round, which produced a persistent seed bank (where present), with variable, but sometimes high densities (0–6209 seeds/m²). Unlike northern populations that germinate readily, these sub-tropical seeds were dormant, as germination was minimal across temperatures 20–30ºC in light or dark conditions. We found germination was not initiated by individual factors including temperature shifts, warm or cold stratification, high or low dissolved oxygen, or chemicals common in submerged sediments (ethylene or ethanol). However, germination did occur when organic material (sediments and/or vegetative extracts) was present combined with light or following scarification; and germination was enhanced by ethanol and cold-stratification. We also found that germination occurs in organic sediments exposed to high-oxygen conditions but is further improved in low-oxygen organic sediments, possibly mediated by the release of ethanol during oxygen reduction. This enhanced germination in light, decaying organic material, low-oxygen conditions, and ethanol suggests a germination strategy focused on exploiting openings in existing vegetation following disturbance. Without tubers that are present in northern ecotypes, sub-tropical V. americana may rely on seed germination for population maintenance.

Bryophytes can play an important role in key ecosystem processes and represent potential candidates as bioindicators for environmental monitoring programmes. Nitrate (NO₃⁻) pollution poses a growing threat to both aquatic and terrestrial ecosystems, potentially leading to imbalances in nutrient levels and altering the chemical composition of organisms, thereby impacting ecosystem function. However, the specific effects of NO₃⁻ pollution on the elemental and isotopic composition of aquatic and semi-aquatic bryophytes remain uncertain. In this study, we examined the influence of NO₃⁻ pollution from spring water on the elemental composition of aquatic and semi-aquatic (hygrophytic) bryophyte species and their respective water sources. Our investigation encompassed diverse land use, lithology, and climate conditions to identify suitable bryophyte species as bioindicators of NO₃⁻ pollution. We observed higher NO₃⁻ concentrations in spring water from intensively farmed and urban areas compared to natural and extensively farmed areas (e.g., pastures). These higher concentrations were positively correlated with the nitrogen (N) content and δ¹⁵N isotope ratio in bryophytes. However, spring water NO₃⁻ pollution did not significantly affect the overall chemical composition of the water sources, except for Cl⁻, Cr, and Zn. Our findings highlight Apopellia endiviifolia and Oxyrrhynchium speciosum as promising candidate species for bioindication of aquatic NO₃⁻ pollution, due to their δ¹⁵N sensitivity to increasing NO₃⁻, i.e., they respond to variations in the ratio of δ¹⁵N isotopes in their environment. The identification of these species will assist land managers in effectively monitoring NO₃⁻ pollution in freshwater systems, thereby addressing public health concerns and supporting wildlife conservation priorities.

The clonal diversity of Nymphoides peltata in Japan was estimated using genome-wide SNPs. In total, 27 clones were detected by considering the genetic distances between clones. The number of clones was much smaller than the estimate of 61 from a previous study that used SSR (Short Sequence Repeats) markers. This may be because population have diminished due to environmental deterioration over the past decade, fewer samples were analyzed in this study, or there were technical problems with the SSR markers used in the previous study. The populations of N. peltata were genetically differentiated between the western and eastern regions of the Japanese archipelago. Artificial movements may have occurred in a few populations.

Constructed wetlands (CW) treating runoff from agricultural catchments reduce the nutrient load of water, however, they can also be significant sources of greenhouse gases, especially methane (CH₄). We simultaneously assessed CH₄ emission potentials and phosphorus (P) removal efficiency in a 0.45 ha in-stream surface flow CW to determine the main drivers of CH₄ emissions, and to analyze the temporal dynamics of CH₄ emissions and P removal during an almost 4-year period. The TP (total phosphorus) removal efficiency had a clear seasonal dynamic, with the highest removal occurring during summer and early autumn (monthly average 60.5%), when the flow rate was lowest and water residence time longest. Due to increasing sedimentation and related anaerobic conditions, the mean hourly CH₄ emissions for each year demonstrated an increasing trend over the years: from 88 µg CH₄-C m⁻² h⁻¹ in 2018–2505 µg CH₄-C m⁻² h⁻¹ in 2021. There was a clear seasonality in CH₄ emissions: up to 90% of CH₄ fluxes occurred during the warm period (from May to October). We assume that maintenance of treatment wetlands is essential and predominantly regular removal of aboveground vegetation at the second half of the growing season would decrease CH₄ emissions. Nevertheless, due to the P saturation in sediments, regular sediment removal in the long term is also necessary.

Eleocharis carniolica is included in the EU Habitat Directive and legally protected in many European countries. It is also considered as one of the most threatened plants in Poland. It typically occurs in muddy habitats, wet meadows, lake or pond shores or temporary puddles, but in Poland this species usually occurs at disturbed anthropogenic sites such as road verges or drainage ditches. Despite being the focus of a number of ecological and conservation studies, E. carniolica still does not have a fully recognized ecology and life-strategy, particularly with regard to breaking seed dormancy and germination. To find out the population performance and species propagation potential in Poland, we have conducted experiments aimed at assessing the seed germination conditions and efficiency. The main goal was to discover the crucial factors that stimulate germination. The results of the experiments suggest that light is a pivotal factor for triggering germination of E. carniolica seeds. Moreover, E. carniolica’s seed bank consisted of about 80 % dormant seeds. The only effective method for dormancy breaking was warm stratification (placing the seeds at high temperature on a moist substrate) with application of gibberellic acid (GA₃)_, and even a few days of warm stratification resulted in effectively overcoming dormancy. Eleocharis carniolica's germination features are typical for plants adapted to frequent disturbances with a short life expectancy and large reproductive effort. Our results strongly suggest that E. carniolica has a ruderal life strategy at its northern distribution limits and probably can be considered as an alien species in Poland.

Massive blooms of pelagic Sargassum algae have caused serious problems to coastal communities and ecosystems throughout the tropical Atlantic, Caribbean Sea, and Gulf of Mexico since 2011. Efforts to monitor and predict these occurrences are challenging owing to the vast area impacted and the complexities associated with the proliferation and movement of Sargassum. Sargassum Inundation Reports (SIRs) were first produced in 2019 to estimate the potential risk to coastlines throughout the Intra-American Sea at weekly intervals at 10 km resolution. SIRs use satellite-based data products to estimate beaching risk from the amount of offshore Sargassum (quantified by a Floating Algal density index). Here we examine whether including wind metrics improves the correspondence between the offshore Floating Algal density index and observations of Sargassum along the coastline. For coastal observations, we quantified the percent coverage of Sargassum in photos obtained from the citizen science project "Sargassum Watch" that collects time-stamped, georeferenced photos at beaches throughout the region. Region-wide analyses indicate that including shoreward wind velocity with SIR risk indices greatly improves the correspondence with coastal observations of Sargassum beaching compared to SIR risk indices alone. Site-specific analyses of photos from southeast Florida, USA, and data from a continuous video monitoring study at Puerto Morelos, Mexico, suggest potential uncertainties in the suite of factors controlling Sargassum beaching. Nonetheless, the inclusion of wind velocity in the SIR algorithm appears to be a promising avenue for improving regional risk indices.

Due to the massive proliferation and stranding of holopelagic Sargassum spp. over the last decade, different strategies for the sustainable valorisation of Sargassum biomass have been explored and investigated. One limitation to the development of Sargassum biomass valorisation is related to its high arsenic (As) content. The toxicity of As depends on the chemical forms present and their oxidation or valence state, classified as inorganic and organic compounds, with the inorganic As compounds being much more toxic than the organic ones. The aim of the present study was to determine the inorganic arsenic (iAs) content in holopelagic Sargassum spp. for which almost no information on stranded biomass is available. In this study, we examined the iAs content in the three holopelagic Sargassum morphotypes collected over a seasonal cycle in 2018–2019. The iAs concentrations ranged from 12.7 to 62.9 mg kg⁻¹, representing 14.1–81.7% of total arsenic (TotAs). The iAs content was compared between species and seasons and discussed in the context of existing international regulations and guidelines.