Aquatic Botany最新文献

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.

Crustose coralline algae are a group of calcified algae that has an important ecological role in coral reefs, such as cementation and stabilization of the reef framework, as well as providing habitat and food for different marine associates. Among the common genera, Lithophyllum and Porolithon (Corallinales) are conspicuous components of the Santa Marta reef communities in the Colombian Caribbean. From December to April, this area is influenced by seasonal trade winds, a phenomenon that is related to the upwelling of subsurface waters that causes a decrease in temperature from ∼29 °C to ∼22 °C and pH from ∼ 8.5 to ∼8.0. The aim of this study was to evaluate the effect of upwelling and non-upwelling (2017, 2018, and 2021) on the reproductive phenology of Lithophyllum sp. and Porolithon antillarum based on counts of superficial conceptacles per cm² and a determination of the reproductive stages of the algae collected in Tayrona National Natural Park and Punta Venado, Santa Marta. The algae presented the highest number of mature conceptacles during the upwelling period for P. antillarum and Lithophyllum sp. (46 and 27 conceptacles cm², respectively). Moreover, the tetrasporangial stage was the most frequent in all the thalli, thus indicating the predominance of this phase in the reproductive cycle of the algae studied. These results are important as they indicate the influence of seasonality on the reproductive stages of CCA and bring the need to do more research into the influence of the environment on the physiological mechanisms that determine the changes in the life cycle of these algae.

Hydrocotyle verticillata can tolerate varying degrees of flooding, up to complete submergence, and is at the same time extremely sensitive to drought. Understanding the structural and biochemical principles of these unusual tolerance limits is of particular importance. We analyzed the effect of soil flooding, complete submergence (rooted plants and floating stems), and dehydration on root anatomy, alcohol dehydrogenase (ADH), heat shock proteins 70 (HSP70), hydrogen peroxide, and DNA integrity using light microscopy, biochemical and histological methods. It was shown that anatomical traits of adventitious roots with a triarch stele were similar in the plants growing under different conditions; the single-layered and thin-walled epidermis formed relatively short root hairs; essential air spaces were absent in the cortex parenchyma. Results on ADH clearly showed that anaerobic energetic metabolism in root apices and individual rhizoderma cells of the mature root zone was normal for this species in optimal and suboptimal conditions, while leaves changed metabolism to anaerobic in response to submergence. Alterations in the protein spectrum were accompanied by adequate up-regulation of HSP70 under different levels of flooding and dehydration/rehydration. These results appear to indicate a flooding adaptation strategy for H. verticillata based primarily on metabolic plasticity rather than morphoanatomical adaptations. Most notably, the resistance of this species to long-term submergence has been associated with strong ADH induction in leaves, transient activation of 70 kDa isoform of HSP70 and induction of 66 kDa isoform, as well as a significant delay in the accumulation of hydrogen peroxide and DNA degradation.

Riverine macrophytes play diverse and foundational ecological roles, directly influencing ecosystem properties from local biodiversity to flows of water, energy, nutrients, and sediment, many of which in turn are central to river management. Numerical modeling is thus a crucial tool for understanding macrophyte and ecosystem responses to environmental, ecological, or management changes. However, riverine macrophytes have received relatively limited modeling attention compared to plants in many other aquatic or terrestrial systems. We conducted a systematic review of riverine macrophyte growth models, focusing on mechanisms of macrophyte growth, biomass loss, and feedback effects on river ecosystems. Processes such as light availability, thermal tolerance, nutrient limitation, and mortality were widely included in almost all models meeting the review criteria. However, models varied widely in their inclusion of processes such as shading, scour, and the roles of macrophytes in stream nutrient cycles. There has been relatively little consideration of factors such as dispersal, carbon sources, herbivory, burial, desiccation, and competition for space or nutrients, indicating directions for future modeling work. In light of this, we present a conceptual framework to help guide future macrophyte growth modelers through a thorough consideration of macrophytes’ myriad interactions with their ecosystems. We also emphasize the importance of modularity and accessibility toward improving efforts to model, and in turn manage, riverine ecosystems.

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.