Aquatic Botany最新文献

Germination biology and dormancy-breaking requirements of fully aquatic (submerged and floating) plant species remain relatively understudied. This is a significant impediment to efforts to restore vegetation in freshwater systems, where the abundance of seeds, and possibility of sowing them in large numbers, suggests underutilized potential for active revegetation. We assessed the influence of seed traits (mass and shape) and two treatments to break dormancy (scarification and gibberellic acid) on the germination of seeds of four macrophyte species after cold-stratification. For all species, untreated seeds did not germinate (0% rate), despite relatively high seed viability (42–90% across species). For Potamogeton illinoensis and P. natans, scarification plus gibberellic acid increased germination the most, to 83% and 35%, respectively (corrected for viability). The other two species remained wholly (Brasenia schreberi) or overwhelmingly (Nuphar variegata) ungerminated. For the two species that did germinate, germination probability increased with seed mass (P. natans and P. illinoensis) and elongation (P. natans). While the small size of trait effects relative to seed treatment effects suggests the latter are more important for revegetation work, the trait patterns highlight evolutionary tradeoffs in seed-size investments. The two Potamogeton species we examined show promise for use in revegetation via seeding, whereas B. schreberi and N. variegata dormancy break has not been adequately developed for these species to be used in seeding-based revegetation.

In 2012, Hurricane Sandy struck Barnegat Bay, New Jersey damaging extensive beds of Zostera marina and causing major benthic ecosystem disruptions. Pre-Sandy genetic surveys of eelgrass populations in Barnegat Bay indicated low heterozygosity and connectivity with high levels of inbreeding. After such devastation, we became concerned with the long-term fate of these populations and in previous work examined the present genetic condition of eelgrass in Barnegat Bay. Counter to our expectations, the 2021 Z. marina populations were more diverse, had greater connectivity and less inbreeding than the populations from 2008. These results further motivated us to examine the trajectory of changes between 2008 and 2021 through additional investigation of archival Z. marina samples from 2013 and 2017. This present study tracks the trajectory of Barnegat Bay eelgrass population genetics before and after Hurricane Sandy. Immediately post Sandy, populations were already more diverse with heterozygosity closer to Hardy-Weinberg Equilibrium; by 2021, two populations, Oyster Creek and Ham Island, demonstrated a surplus of heterozygotes. Similarly, in 2013 there was a three to eight-fold reduction in inbreeding observed with clear outbreeding by 2017. There was no evidence of recent bottlenecks in any population, although Oyster Creek and Ham Island populations manifested historical bottlenecks. Our evidence supports that genetic recovery was already underway a year after Sandy.

Every introduction of a non-indigenous species (NIS) in coastal environments poses a threat to the native species and communities, as its effects in the ecosystem are not readily predictable. Introduction rates have kept increasing in the last decades, and our finding of the brown alga Mutimo cylindricus in the Canary Islands is another example of this general trend. This work represents the first record of the species outside its native range (Japan, Korea and the Philippines) in half a century, since its report in 1973 in Baja California, and marks the first report of M. cylindricus in the Atlantic Ocean. We analyzed the morphology of a male gametophyte observed in the Canary Islands and its phylogenetic relationship with other known populations using rbcL and cox3 genes. The morphology of M. cylindricus in the Canary Islands is consistent with previous descriptions and the phylogenetic analyses revealed the close relationship with native populations from Japan. The finding of a male gametophyte is noteworthy, as introduced and some native populations of this species are composed exclusively by female gametophytes and thought to be parthenogenic, whereas androgenesis is considered rare in the field. Maritime traffic appears as the most apparent introduction vector of the species and it seems plausible that microscopic crustose sporophytes were present near the collecting site, highlighting the need of further monitoring of the invasive potential of this species in the Atlantic Ocean.

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.