Aquatic Botany最新文献

The adverse effects of climate change, including rising sea levels and frequent floods, pose significant challenges to agricultural systems, particularly in low-lying countries like Bangladesh. To address these challenges, floating agriculture systems have emerged as a climate-resilient alternative for crop cultivation. Floating agriculture is a traditional agricultural system where aquatic free-floating macrophytes are used as the medium for the growth of plants. This cultivation system is traditionally used for seedling development in the south and south-western regions (Barishal, Pirojpur, and Gopalganj) of Bangladesh. However, very little scientific attention has been given to using macrophytes in crop production and preparing floating beds. Therefore, the present investigation has been carried out to select suitable macrophytes for preparing a floating bed by assaying the condition of the floating bed and the morphological and yield-related factors of cultivated crops during the Robi season in 2021. Five different macrophytes, namely, Salvinia molesta, Pistia stratiotes, Lemna minor, Salvinia cucullate, and Azolla pinnata, have been used as mulching material, which has been conducted in a Completely Randomized Block Design (RCBD). The plant material BARI tomato-14 has been transplanted on the floating beds to assess the effect of macrophytes on crop production. The results of the present investigation reveal that different macrophytes have distinct effects on tomato plants' growth and yield-related parameters in floating agriculture systems. Salvinia cucullata shows a better response in the stability of the floating bed, whereas Salvinia molesta exhibits better responses as mulching material on yield-related parameters of cultivated crops.

Leaf normal inclination angle distribution (LAD) determines the interception of radiation by leaves and the transmission of radiation by the vegetation canopy, which affects the distribution of incident photosynthetically active radiation on plant leaves and ultimately directly affects the net primary productivity of vegetation. However, the contact measurement method for leaf inclination angle is difficult to perform due to the complex growing environment of wetland aquatic vegetation. In this study, the method of measuring normal leaf inclination angles was improved for wetland aquatic vegetation based on horizontal digital photography combined with the application of a protractor. Phragmites australis and Typha orientalis, two typical emergent aquatic vegetation (EAV) species growing in wetlands, were used to evaluate the robustness of leaf inclination measurement methods. In addition, LAD values were measured and analyzed for their variations across seasonal and vertical gradients within the canopy. Finally, the applicability of the two simulation algorithms for leaf normal inclination was evaluated and compared. Analysis revealed that Phragmites australis LAD exhibited a variation with seasonal changes and vertical canopy height, which is beneficial for light transmission within the canopy. The LAD of Typha orientalis was always an erectophile pattern and changed only slightly with the seasons. The new findings provided additional insights and evidence on aquatic plant resistance and environmental adaptation. Comparing simulation models for EAV, the trigonometric algorithm outperforms other algorithms in accuracy and deviation. The results of this research provide a valuable reference for exploring radiation transfer within aquatic vegetation canopies and understanding vegetation growth.

The Isoëtes genus comprises a basal lineage of vascular plants with a wide distribution, including aquatic and terrestrial species, which can be attributed to environmental changes throughout its evolutionary history. The underwater quillwort, Isöetes cangae, is endemic to Lake Amendoim in the northern Amazon rainforest region of Brazil. To aid conservation strategies, we investigated the molecular and physiological changes associated with water column reduction and tolerance to terrestrial environments. Remarkably, this aquatic species has demonstrated a tolerance for periods without a water column during ex situ cultivation. Short-term experimental conditions (24 h) revealed upregulation of stress-related genes, while biochemical, morphological, and physiological parameters remained unchanged. In contrast, long-term terrestrial conditions (3–6 months) induced changes in the physiology and morphology of I. cangae, including an increase in antioxidant capacity, photoprotective mechanisms, and the preservation of reproductive structures. The Crassulacean Acid Metabolism was present in both aquatic and terrestrial conditions. Mature and immature spores were able to produce plants even after 12 months of desiccation, with desiccated spores generating more progeny than submerged spores.

Microphytobenthos play a key role as food resources at the base of the trophic web, particularly in sediments of highly productive seagrass meadows. Here, we investigated patterns of variation in microphytobenthic diatom communities and their driving factors in an impacted versus non-impacted meadow of Ruppia maritima in the Patos lagoon estuary (Brazil), across seasons in two consecutive years. We found higher taxa richness, diversity and equitability, together with lower dominance, at the non-impacted meadow. Seasonally, the same pattern was found in autumn and/or winter 2017 at both meadows, driven by the lower seawater temperature. Higher richness was related to lower river discharge and equitability to lower wind velocity. Diatom assemblages differed in species presence/absence and abundance between meadows, mostly due to higher phosphate at the impacted meadow, together with higher water transparency and sediment organic matter (2016) and with higher grain size (2017) for species presence/absence. Even diatom assemblages differed more in terms of species abundances than of presence/absence, Paralia sulcata and Tryblionela compressa (commonly reported as indicator of eutrophic conditions) were exclusively present at the impacted meadow, while Amphora charrua, Desikaneis howellii, D. simplex (commonly in undisturbed environments) did so at the non-impacted meadow. Often two species were responsible for more than half the dissimilarities in abundances, with Catenula adhaerens dominating at the impacted meadow and Ambo tenuissimus at the non-impacted meadow. Overall, the combination of natural and anthropogenic environmental factors acted together to determine between-meadow and seasonal patterns of variation in the presence and abundance of diatom species.

The decline in biodiversity in freshwater ecosystems occurs at an alarming rate throughout the world. In Denmark, we know from historical records that several species within the plant genus Potamogeton, that were previously widespread in Danish freshwater ecosystems, are now under severe decline. In this study, we explore root development in two common and three declining Potamogeton species applying an experimental approach. Specifically, we examined if root development characteristics can contribute to explain the contrasting success of these species in the contemporary stream vegetation in Denmark. In accordance with our hypothesis, our results showed that common species of Potamogeton produced roots faster, had longer roots and produced more roots per growth node than declining Potamogeton species. This was particularly clear for P. crispus. Overall, our results expose a mechanism that is likely to affect the ability of these species to maintain populations in highly disturbed lowland streams in Denmark and therefore contribute to explain the contrasting success of these species.

Excessive Cu is toxic to Sargassum patens. Understanding the biological control mechanism behind Cu uptake, including the effect of competitive behavior with other metals, such as Zn, is beneficial for expanding our knowledge of species-specific metal uptake behavior. In this study, we cultured a macroalgal species, S. patens, and exposed it to Cu and Zn to evaluate the metal uptake behavior and biological response of S. patens. Exposure to Cu and Zn under different culture conditions not only affected the uptake behavior of each metal but also influenced S. patens growth. At low concentrations, neither metal significantly affected algal growth, whereas high concentrations of Cu negatively affected the photosynthetic activity and growth rate of S. patens. The presence of Zn at equally high concentrations was observed to increase the tolerance of S. patens to Cu exposure. Fe plaque also played a role in modulating Cu exposure; its absence increased Cu accumulation and suppressed Zn accumulation, subsequently decreasing the ability of Zn to alleviate Cu toxicity, which in turn increased algal stress.

The microbial communities associated with seaweeds remain underexplored, despite their enormous biodiversity and the fact that they differ significantly from their free-living marinecounterpart. Studying the epiphytic bacterial microbiota, directly or indirectly, plays a vital role in normal algal morphological development, metabolism, growth and defence against fouling organisms. Furthermore, as these bacteria interact with algae in multifaceted ways, they constitute a fascinating source of new bioactive compounds with antimicrobials, antibiotic potential and produce algal-specific polysaccharidases with biotechnological applications. Microscopy, accompanied by bacterial culture and molecular biology, has made it feasible to establish and identify the phylogenetic origin of various algae-associated bacterial communities. Thus, this review first highlights the immense diversity of the epiphytic bacteria associated with algae, predominantly from the phyla Proteobacteria, Bacteroidetes, and Firmicutes. We further describe the factors affecting the composition and abundance of the epiphytic bacteria and their ecological role. We end with the bioprospecting value of this interaction, such as the production of hydrolytic enzymes and specific bioactive compounds. However, further investigation of the epiphytic bacterial communities present in different macroalgae using new technologies is still needed, mainly to evaluate the production of various metabolites with biotechnologicalapplications.

Macrophytes provide essential ecosystem services in lowland streams, including nutrient uptake that can reduce downstream transport to vulnerable coastal areas. Despite that, to ensure water conveyance and effective run off from agricultural fields, aquatic plant biomass is removed regularly in many European streams (i.e. weed cutting practices). However, the impacts of weed cutting on stream ecosystem processes are not yet well documented. Here, we studied the effect of weed cutting on nutrient retention and ecosystem metabolism in three lowland streams with contrasting dominant vegetation communities (submergent and emergent plants) during summer in Denmark. Our results showed a decrease in nutrient retention; uptake velocity of ammonium decreased 34–77 % and of phosphate decreased 50–77 %. Ecosystem metabolic rates also decreased after weed cutting, both in gross primary production (9 %, 60 % and 85 %) and respiration (47 %, 69 % and 76 %). The effects of weed cutting on these ecosystem processes prevailed three weeks after the cutting occurred. Understanding the effects of weed cutting on stream ecosystem functioning can improve nature-based management strategies to control eutrophication of downstream coastal areas.

Eucheumatoid seaweed farming (ESF) is an important enterprise that provides livelihood opportunities for tropical coastal communities. In this work, we surveyed the current practices of ESF in Tawi-Tawi and Sulu, southern Philippines, where major commercial ESF activities in the country are currently practiced. Seaweed farmers (N = 143) were interviewed using a structured questionnaire containing relevant information on the current farming practices. Results revealed that ESF is one of the primary livelihood sources for coastal inhabitants in the southern Philippines. Most farmers were male, 21–50 years old, and practiced farming for 6–10 years. Farmers mostly owned a farm with an area of 25–400 m², mainly filled with the rhodophyte elkhorn sea mosses, either Kappaphycus alvarezii or K. striatus. Vegetative cuttings, the major seedling source, were tied using plastic straw into a 6–10 m rope line with a distance interval of 10–20 cm. Inorganic nutrient enrichment is practiced to increase growth and lessen ice-ice disease occurrence. The modified fixed-off bottom (stakes with floaters) is the most predominant farming method. Farms were visited 2–3 times a week for maintenance. Farming is year-round, with peak seasons between August and November. Harvesting is typically done after 21–30 days. Seaweeds are usually dried using the hanging method, which takes 4–6 days. Dried Kappaphycus fronds command higher prices (90–140 PHP/kg) compared to Eucheuma denticulatum (10–50 PHP/kg). Few farmers received government support; therefore, farmers reported many problems affecting their production. This study provides an update on the current ESF practices in the southern Philippines, which have not been well-documented for almost two decades.

Identifying population genetic structure is important for the development of species-specific management plans. Investigating the population genetics of cryptic species is even more critical. Here we focus on two cryptic duckweed species easily mistaken for one another, Lemna minor L. and L. turionifera Landolt, which have overlapping ranges in our study region of Alberta, Canada, and elsewhere. We used genotyping-by-sequencing to determine the population genetic structure of both duckweed species. A total of 192 samples was sequenced. After filtering, 16,007 single nucleotide polymorphisms were used to examine patterns of genetic diversity between and within L. minor and L. turionifera. The two species showed clear differentiation. When examining L. minor singly, we discovered at least three genetically distinct populations among the 30 samples from eight sites, even though these were from a small geographic area. In contrast, when examining L. turionifera singly, we found no evidence of genetically distinct populations among 67 samples from 43 sites. We also examined the relationship between surface water quality variables and the distribution of the two Lemna species. The sites containing L. turionifera had a wider range of water chemistry variables suggesting they are more tolerant of different environmental conditions. In contrast, each of the three genetically distinct L. minor groups had different water chemistry profiles. Large differences between L. minor and L. turionifera in their regional distributions and degrees of genetic differentiation highlight the importance of documentation and careful monitoring of Lemna species within Alberta, and in other regions where they co-occur.