Aquatic Botany最新文献

Carnivorous plants in the genus Utricularia (bladderwort) are diverse and widespread, represented in North America primarily by free-floating aquatic species. In the Nearctic ecoregion, roughly corresponding to temperate North America, there are 20 species of Utricularia, comprising a small fraction of the approximately 270 species in the genus worldwide. However, despite their low number, the Nearctic species represent seven of the 18 taxonomic sections of Utricularia, a pattern that potentially reflects multiple ancestral dispersal events into North America. Most of the Nearctic bladderwort species are represented by DNA sequence data, yet there is no single genetic locus that has been sequenced for all species, and this has precluded a thorough evaluation of their phylogenetic relationships. In this study, we obtained DNA sequence data for genetic loci and species that had not been sequenced previously, to produce a fully sampled molecular phylogeny. The resulting phylogeny includes all species that occur in the USA and data from five DNA regions: one nuclear locus (internal transcribed spacer, ITS) and four plastid loci (trnK/matK, rpl20-rps12, rps16, and trnL-trnF). We recovered a close relationship between U. inflata and U. radiata, two species that both have aerenchymatous floral support structures, and which previously had not been sequenced for any of the same genetic loci. We also sequenced numerous U. macrorhiza individuals, and our data support the phylogenetic distinctness and molecular diagnosability of this species against U. australis, U. tenuicaulis, and U. vulgaris. Curiously, we discovered plants in Ohio, USA that were identified as U. tenuicaulis and U. × neglecta (= U. tenuicaulis × U. vulgaris), and these represent the first evidence of such plants being naturalized in North America. These previously overlooked species and hybrids highlight the importance of using DNA in plant surveys and the value of having a robust reference library of DNA sequences.

Recent recurrent inundations of holopelagic Sargassum species (sargasso) in the tropical North Atlantic warrant studies to increase our understanding of this phenomenon. We carried out a multidisciplinary study to determine the drift and associated biota of sargasso rafts in nearshore waters of a reef system in the Mexican Caribbean, during the 2020–2022 influx seasons. Home-designed trackable drifting buoys revealed notorious influence of winds stronger than 4–5 m s⁻¹ on the rafts´ displacement. At lower wind velocities, the drift was almost entirely determined by currents; local topography played a role in concentrating or dispersing the algae. Video cameras attached to the drifting buoys allowed for non-invasive identification of free-swimming ichthyofauna, recording low specific richness with a dominance of species of the Carangidae family. Sargasso associated biota was sampled with a dipnet. The small motile macrofauna was abundant and diverse, with a dominance of few species. Epibionts (epifauna and epiphytic algae) showed low specific diversity, while the microbial communities were dominated by (potentially pathogenic) Vibro spp. Small motile macrofauna was the only biota group with new records for the study region. Differences among sampling events were observed in the associated community; suggesting large inherent variability of the rafts´ biota. The information on wind, coastal hydrodynamics and topography on the displacement of the sargasso rafts will allow for better predictions of strandings, and information on associated non-native biota or dominant microbial species helped identify groups that should be closely monitored; thereby aiding in targeted management actions for mitigating the impacts of the inundations.

The phenology of Laguncularia racemosa (L.) Gaertn. (Combretaceae) was investigated from a population located near the species’ northeastern range limit in Florida. Height, leaf dimensions, and the number of flower buds, flowers, and propagules were recorded, on average, every 2–3 months from May 2021 to October 2023. Irradiance, temperature, and inundation depth were measured hourly with data loggers and compared among seasons and years. Although plant heights were negatively impacted by freeze events in 2022 due to defoliation, vertical growth rates were significantly greater following the freeze. Flower bud and flower production were observed during the summer months and differed among years with greater abundances in 2021. Propagules were recorded in summer and autumn with greater abundances in 2021 and 2022 than in 2023. Light intensity was unlikely to limit growth without a canopy of L. racemosa. Maximum inundation depths > 1.2 m were recorded in autumn and winter when propagule dispersal was likely to occur. The greatest depth of 2.2 m was more than the tallest individual in the study and occurred when hurricanes coincided with extreme high tides. The L. racemosa population was resilient to freeze and flooding events suggesting that population densities may continue to increase in northeastern Florida marshes.

Althenia (Potamogetonaceae) is a small genus of aquatic angiosperms from saline environments that includes the most recently evolved seagrass, Althenia marina. One or two species occur in Europe, both rare and considered Data Deficient at the regional level. We report the first records of Althenia in Portugal since 1853: two populations in the Algarve and a third in central Portugal. As in previous studies, all Portuguese populations include plants with and without visible nerves in the leaf sheaths, a character used to distinguish between A. orientalis and A. filiformis. We tentatively recognize a single Althenia species in Eurasia, pending further studies. We recommend further searches of suitable habitat, as Althenia species are small and easily overlooked, as well as monitoring and safeguarding of known populations through in situ and ex situ conservation.

Spate floods control sediment, nutrient and biodiversity patterns in river floodplains, but the diachronic effects of spate floods on these compartments are rarely assessed. The effects of a 10-year flood spate on substrate characteristics and aquatic vegetation (community composition and life-history traits) were assessed before and after the spate in eleven former river channels that had become wetlands and varied in flood frequency. The effects of spate flooding on sediment and vegetation were expected to be greater in the less frequently flooded channels. For life-history traits, we expected a greater effect of the flood on tall evergreen species with high leaf area, while species with ruderal traits were expected to be less affected. For sediments, the flood reduced fine sediment cover and organic carbon content, but did not affect nutrient content. Vegetation cover decreased particularly in the most and least frequently flooded channels. Species richness and functional indices were little affected. The disturbance had a significant effect on plant traits, reducing tall evergreen species. This effect on plant characteristics increased as the frequency of overflow increased. The results highlight the key role of erosive floods in maintaining poorly competitive aquatic plants and limiting successional processes in riverine wetlands. Given the importance of plants in maintaining spate floodplain biodiversity, these erosive spate floods are essential to maintain or restore in a context of extreme river regulation.

Non-geniculate coralline algae (NGCA), Corallinophycidae - Rhodophyta, are characterized by prominent calcified vegetative thalli. They exhibit broad phenotypic plasticity, and morphoanatomical convergences due to the simplicity of their thalli. These characteristics makes their taxonomy one of the most complex within Rhodophyta. The nomenclature and taxonomy of the NGCA have been controversial and subject to intensive debate even after the advent of molecular techniques. Until the mid-19th century, all calcareous organisms were classified as animals. Still, the algal nature of the NCG became evident with advances in microscopy and anatomical techniques, based on anatomical and reproductive attributes rather than thallus form. This review provides a comprehensive historical overview of significant milestones in the NGCA taxonomy. From 1890–1910, Mikael Foslie described about 400 species of NGCA. Since then, and after the advances in microscopy in the mid-20th century, the taxonomy of this algal group, traditionally based on morphological aspects, has been replaced by anatomical features. Paraffin and historesin-embedded microtomy and sectioning techniques allowed access to taxonomically relevant microanatomical features, while scanning and transmission electron microscopy allowed access to ultrastructural aspects. The subsequent use of molecular markers promoted a real revolution, by disclosing phylogenetic relationships between taxa. As perspectives, high-resolution confocal microscopy images can provide information on intricate three-dimensional structures and reveal unexplored aspects of NGCA morphoanatomy. Meanwhile, whole-genome sequencing and comparative genomics can uncover the genetic underpinnings of taxonomic variations, helping to elucidate the mechanisms driving the diversification of NGCA species. We envision that the recent expansion of sampling expeditions to previously unknown geographic and bathymetric regions along with the convergence of advanced morphoanatomy imaging, genomics, and bioinformatics, would clarify the complex tapestry of NGCA taxonomy and safeguard (e.g., through conservation action-plans) these ecologically important marine organisms.

Changes in nutrient concentration, temperature and light intensity due to climate change can alter the species composition of aquatic ecosystems, since global climate change can intensify the process of eutrophication. Eutrophication can enhance the biological invasion and the distribution of alien aquatic plants. Here we investigated the competition ability of alien Pistia stratiotes and native Hydrocharis morsus-ranae and the effect of different light intensities, temperatures and nutrient concentrations on the functional traits of the two species. In short term (8 days) monoculture experiment, we applied low (0.5 mg L^-1 N; 0.05 mg L^-1 P) and high nutrient concentrations (2 mg L^-1 N; 0.2 mg L^-1 P), four different light intensities (25–295 μmol m⁻² s⁻¹) as well as cold and warm (21.5; 27.5 ± 0.5°C) water treatments in full factorial design. In mixed cultures we cultivated the plants for 28 days with various biomass ratio, in shaded and well illuminated conditions, at a high nutrient concentration (4 mg L^-1 N 1 mg L^-1 P). In monocultures, the relative growth rate of P. stratiotes in warm water was significantly higher than that of H. morsus-ranae, however, this difference was not significant in colder water. In the co-culture experiment, P. stratiotes had significantly higher growth rate compared to H. morsus-ranae regardless of initial plant biomass ratio. Under shaded (65 ± 5 μmol m⁻² s⁻¹) conditions, P. stratiotes outcompeted H. morsus-ranae, resulting in its decay. Experimental results imply that with elevated temperature, the spread of alien P. stratiotes can be expected. Furthermore, under shaded conditions, P. stratiotes has a higher chance of occupying the water surface over the native plant H. morsus-ranae.

The present paper aims at contributing to the knowledge of rhodolith beds by describing the associated macroalgal assemblages of two beds in the western Mediterranean Sea: Gorgona Island in the Tuscan Archipelago National Park and Capo Carbonara Marine Protected Area in the southern Sardinia. Patterns of biodiversity and spatial variability were investigated through a multifactorial sampling design. A total of 84 macroalgal species was identified, 17 Heterokontophyta, 7 Chlorophyta, 1 Prasinodermatophyta and 59 Rhodophyta. Significant differences between beds were detected and the main species characterizing the two beds were highlighted. The mean number of species per sample was quite low and beta diversity high compared to most Mediterranean macroalgal assemblages.

Blue carbon ecosystems such as mangroves, salt marshes, and seagrass beds are found globally and are fundamental to fisheries production, storm surge protection, and carbon sequestration. The contribution of seagrass ecosystems to global carbon stocks is still not well understood, including in the United States Virgin Islands (USVI). No study has been published to-date assessing the sediment carbon density (SCD) in seagrass beds in the USVI. This study focused on the carbon storage ability of the invasive species, Halophila stipulacea, which is compact in size compared to common native seagrasses and has spread rapidly to become a dominant seagrass in the USVI. This species forms dense mats across a wide depth range (<1 m to 50 m) typically uninhabitable to its native counterparts (Syringodium filiforme and Thalassia testudinum). Several biotic and abiotic factors influence the carbon storage ability of seagrass, yet little is known about carbon storage sequestration along a depth gradient for H. stipulacea. This study provides the first assessment of the biological characteristics (shoot density, leaf area, leaf height, and percent cover) and carbon storage ability of H. stipulacea across a depth gradient (shallow: 5–10 m; medium: 15–20 m; deep: 25–30 m) at two sites in St. Thomas, USVI. Mean sediment carbon density (SCD) values per core reported for H. stipulacea in this study ranged from 3.88 to 15.67mgC/cm³; these were comparable to regional and global seagrass studies. Biological characteristics were not an accurate predictor of SCD. A significant interaction between water depth and site was found to affect mean SCD of H. stipulacea beds. It is likely that site-specific factors most likely account for variations seen within the data. Although carbon values in this study compared to values reported in the literature, other factors such as land use, proximity to carbon sources, sediment microbial community, and water current patterns may be driving SCD values. These findings highlight the need for site and species-specific carbon storage assessments on local to regional scales to accurately estimate current and forecasted blue carbon stocks.