Aquatic Botany最新文献

To meet the increasing demand for kappa carrageenan, several strategies have been employed to improve eucheumatoid seaweed productivity, such as nutrient enrichment (NE) and the application of some efficient farming methods (FM). This study aims to investigate the interaction of NE (applied as ammonium phosphate at 3.5 g L⁻¹) and farming method on the performance of the eucheumatoid seaweed Kappaphycus alvarezii. Three farming methods, that is, Sway (SW), Spring (SP), and modified fixed-off bottom (MFOB), were employed for nutrient-enriched (NE) and non-enriched control fronds for a period of 45 days. NE significantly improved the growth and carrageenan yield of the seaweed and afforded protection against the incidence of ice-ice disease; meanwhile, the effect of FM and NE-FM interaction was non-significant. NE increased the gel strength of the extracted carrageenan; meanwhile, SP farm led to the highest gel strength, followed by MFOB.

The submerged aquatic carnivorous plant Aldrovanda vesiculosa (Droseraceae) is threatened by rapid deterioration of wetlands and oligotrophic lake habitats. Its native distribution spans four continents, but many historic populations are now extinct. Previous genetic studies found distinction between populations from Australia and those from the rest of the world, but due to limited genetic markers, neither detailed phylogenetic relationships nor the migration routes of A. vesiculosa populations were revealed. We used a de novo assembly of the A. vesiculosa mitochondrial genome and a previously published plastid genome as references for mapping short DNA sequence reads from 17 globally distributed populations. Phylogenetic trees were constructed based on detected polymorphisms. Genetic diversity of both the mitochondrial and plastid genome was low (Pi 0.55 × 10⁻⁴ and 0.7 × 10⁻⁴, respectively). Greater polymorphisms were found in the mitochondrial compared with the plastid genome, owing to its larger size (1.27 Mb). Australian populations formed a monophyletic clade in both plastid and mitochondrial trees, while the mitochondrial tree also distinguished populations from southern and northern Europe. Aldrovanda vesiculosa likely migrated to Australia and Africa from a southern European refuge during the last interglacial period∼100,000 years ago. When the last glaciation started, some populations could have survived in eastern Europe and moved north, when the continental glacier retreated. Aldrovanda vesiculosa experienced repeated population bottlenecks that reduced its genetic diversity.

The genus Sargassum comprises both benthic and holopelagic species, serving as basibionts for numerous marine organisms, including frequent epibiotic occurrences of hydrozoans (Cnidaria). Several aspects of the epibiotic interaction between hydrozoans and Sargassum species remain insufficiently explored. This includes patterns such as the hydrozoan community’s composition and abundance across sections and structures of Sargassum. To address these gaps, we conducted an investigation aiming to uncover potential differences in the species composition and abundance of hydrozoan epibionts on benthic and holopelagic Sargassum species (BSS and HSS, respectively) from the Atlantic and Pacific Oceans of Mexico. Additionally, we sought to characterize hydrozoan epibionts preferences for specific sections and structures of Sargassum. Our analysis identified 18 hydrozoan epibiont species on Sargassum, belonging to Leptothecata (88.9%) and anthoathecate (11.1%), with one new register for Sargassum species. Each Sargassum species harbored a distinct hydrozoan epibiont species with a marked higher mean total coverage. The total percentage coverage of hydrozoans on BSS exhibited less variability than HSS. The basal section of BSS hosted the highest number of species. Concerning Sargassum structures, a greater species richness was found on the axis and the blades. Our study also demonstrates that differences in hydrozoan species primarily depend on the geographical distribution of Sargassum species.

Myriophyllum sibiricum and M. spicatum are sympatric in large part of their vast ranges in Eurasia and North America and have different habitat preferences only in East Europe and Siberia. Such absence of both geographic and ecological isolation should trigger extensive hybridization between these species that is indeed observed in North America. The hybrid could be reliably documented only with genetic markers, and in Eurasia this was done only in China. Using genetic markers (ITS2 region of nuclear ribosomal DNA and trnL-trnF intergenic spacer of cpDNA) we documented hybrids between M. sibiricum and M. spicatum on the North Asian Pacific islands with dynamic geological history and climate (Commander and the southern Kuril islands). The hybrid also originated in East Europe (Ivanovo Region) as a result of ecological isolation break due to rapid artificial habitat change. Using genetically verified material throughout temperate Eurasia we clarified morphological characters discriminating M. sibiricum and M. spicatum and, basing on them, refined the species distribution. For the first time we provide a full morphological characteristic of the hybrid between M. sibiricum and M. spicatum and suggest a name for it, M. × hybridum.

Fertile thalli of Sargassum oligocystum were collected from the intertidal area of Naawan, Misamis Oriental, in northern Mindanao, Philippines. The early development, fecundity, egg viability, and recruitment of S. oligocystum were studied to gain insights into the species' biology in preparation for its future ecological and commercial applications. The embryonic development of S. oligocystum followed almost the same pattern as other Sargassum species found in the literature: 1) the presence of unfertilized eight-nuclei eggs, 2) zygotes undergoing division into embryos after fertilization, and 3) the development of dense rhizoids on embryos after 4–5 days from release. The fecundity of one thallus of S. oligocystum produced 0.5 million eggs and 746 ± 1.5 eggs per receptacle, with 94.72% viability of eggs developing rhizoids for attachment. Recruitment of zygotes ranged from 0.52 ind cm⁻² to 3.37 ind cm⁻², with clay bricks found to be the most suitable substrate with a significantly higher recruitment rate than nylon rope and plastic binder. The present study implies the high potential of producing S. oligocystum biomass through the mass production of seed stocks in the hatchery.

Invasions of the aquatic weed Crassula helmsii pose a serious threat to native vegetation of soft water lakes, which increases the need for understanding the factors that regulate the success or failure of C. helmsii. Creating favorable conditions for native species seems promising to control C. helmsii, as previous research indicated that C. helmsii is a poor (root) competitor. We studied the development of C. helmsii growing together with the native Littorella uniflora (biomass, cover, tissue nutrient composition) at two different calcareous poor soil types (organic/acid, mineral/buffered) and under two different water tables (not inundated, submerged) in a greenhouse experiment. We found that when growing under submerged conditions, C. helmsii coexisted with L. uniflora and other native species without becoming dominant due to carbon limitation in the water layer. In contrast, we found that C. helmsii can easily become dominant over L. uniflora when growing on desiccated buffered fen soils with moderate nutrient availability. On the acidic/organic soils, C. helmsii development was poor and die-off was observed under both water level treatments, probably induced due to aluminum toxicity under a low acidity. These results indicate that creating oligotrophic and carbon-poor conditions are required for controlling C. helmsii. Restoration measures can preferably be taken before the onset of the rainy season and/or be followed by maintenance of a temporal artificial high water table to stimulate carbon limitation. Liming more or less organic shores could alleviate aluminum toxicity under acidic conditions which can potentially stimulate the development of C. helmsii.

Sargassum species are known for their capacity to accumulate toxic elements, which may pose environmental risks and limit their use. Arsenic accumulation in Sargassum may vary in response to environmental and physiological conditions. Moreover, interactions between chemical elements may result in synergistic or antagonistic effects. This study determined the variability in the concentration of macroelements (N, P, K) and microelements (As, Cd, Pb, Cu, Zn, and Mn) through time and between growth stages in Sargassum horridum from a site adjacent to a phosphorite deposit in the Gulf of California. A generalized linear model (GLM) was performed to assess the influence of other concurrent elements, polysaccharides (alginate and fucoidan), and their main functional groups (uronic acids and sulfate) on arsenic content. Elemental concentrations showed the following decreasing order: N > K > P > Fe > Mn > Zn > Cd > As > Cu > Pb. Arsenic concentration was 4.33 ± 0.20 mg kg^-1. Significant differences in element concentrations were found by month and growth stage. The main variables associated with arsenic accumulation in S. horridum were potassium, nitrogen, zinc, fucoidan, sulfate from fucoidan, and alginate. The implications of the arsenic, cadmium, and lead concentrations in S. horridum and its potential applications in food, feed, and agricultural contexts are discussed. This research sheds light on the dynamic nature of elements accumulation in Sargassum, emphasizing the need for a comprehensive and context-specific understanding of elemental variations within Sargassum for safe and responsible applications.

Egeria najas is a submerged aquatic macrophyte native to South America, with high propagation in reservoirs and natural lakes, whose reproductive strategy is little known. Understanding the genetic diversity of macrophyte populations can provide important information about this species' dispersion and colonization strategies, and support management actions. We aimed to genetically characterize populations of E. najas that colonize reservoirs and natural aquatic habitats (in a floodplain) in the Upper Paraná River basin, using the molecular markers ITS and trnL-trnF. The results showed the absence of genetic variation for the nuclear marker ITS and 13 distinct haplotypes for trnL-trnF. One of these haplotypes occurred in all habitats and 11 are unique haplotypes, of which 5 occurred in the Itaipu Reservoir and 6 in the floodplain. The null genetic diversity for the nuclear marker and the genetic homogeneity of the studied populations indicates that the reproduction of E. najas is mostly vegetative. The source of chloroplast marker haplotype variability may be somatic mutations. The connectivity among aquatic environments associated with river flow favors the transport of aquatic macrophyte propagules to different habitats. In the case of E. najas, whose vegetative propagules regenerate easily, the frequency of migrations supports the low genetic variability observed in populations of the Upper Paraná. In addition, the ability to occupy new habitats and recolonize disturbed ones strongly indicates that E. najas populations follow the metapopulation dynamics.

Massive strandings of seaweeds on the eastern coasts of the Yucatán peninsula, Mexico have become a major socioecological problem, creating the need for establishing a baseline monitoring program in the region. A citizen science initiative, Big Seaweed Search Mexico (BSS-Mx), was developed to monitor temporal changes in the biomass stranded (abundance and species composition) in the Yucatán peninsula. The initiative was tested in two regions; Puerto Morelos, Quintana Roo, where massive strandings of Sargassum have caused severe socioecological impacts, and Sisal, Yucatán, where there is scarce information about the species composition of the strandings and their seasonal dynamics. Even the different socioeconomic and ecological context of these regions, the public participation in close collaboration with research scientists allowed detection of the temporal changes in the abundance and species composition of the strandings in both locations over a period of ten months. A total of 45 taxa were identified in Puerto Morelos, from which pelagic Sargassum and a seagrass were dominant for most time of the year; whereas 58 taxa were identified in Sisal, observing a higher diversity dominated by red seaweeds, with dominant taxa changing seasonally. The results represent baseline information that should be considered to develop management strategies and marine conservation actions according to each region. The findings highlight the role of citizen science as a potential tool to conduct large-scale and long-term monitoring and stimulate public participation to address environmental issues.

This current investigation presents the very first evidence of the vulnerable ocean turf grass, Halophila beccarii, in the intertidal region of the Andharmanik River, mid-southern coast of Bangladesh, Bay of Bengal. It was found in the muddy and shallow section of the mangroves, dominated by Sonneratia alba, Acanthus ilicifolius, and Avicennia marina. The meadow had an average density of 652 ± 71 shoots/m². The presence of H. beccarii on Bangladesh's mid-southern coast is a positive indication of the enhanced health of the ecosystem. The presence of H. beccarii in this area will enhance water quality and sediment stability. This is the first record of any seagrass species on Bangladesh's mid-southern coast.