Aquatic Botany最新文献

Seagrasses are clonal plants that can form meadows in shallow coastal water. Under natural conditions, drift macroalgae can be found associated with seagrass but when facilitated by high nutrient input, opportunistic macroalgae can grow excessively and form mats that impose stressful and highly competitive conditions for seagrasses. In this study, we experimentally investigate the ecological significance of clonal integration in the ability of Cymodocea nodosa to tolerate biotic stress triggered by interactions with the drift macroalgae Chaeotomorpha linum. Our findings provide little support for the hypothesis that clonal integration can influence C. nodosa response to stress, as disconnected plants did not show significant differences in structural and morphological characteristics compared to intact plants. However, the physiological analysis suggests that C. nodosa may still benefit from shared resources with neighbouring plants to mitigate stress caused by C. linum. Moreover, the results indicate that C. nodosa adapts to the presence of the filamentous drift macroalgae C. linum by increasing leaf photosynthetic content, reducing growth rate, and modulating its morphology, regardless of its integration status.

Utilizing and discharging chemical products containing trace metals lead to widespread contamination in the aquatic environment. Although copper (Cu) and zinc (Zn) are essential plant micronutrients, excessive concentrations may induce stress and mortality. This study investigated the physiological responses of a common aquatic plant, Ceratophyllum demersum, exposed to Cu (0, 2, 5, 10, and 50 μM) or Zn (0, 50, 100, 500, and 1000 μM) for 3 days. Both Cu and Zn were accumulated in plant tissues. Cu exposure led to severe phytotoxicity effects, manifested as a rapid decrease in photosynthetic efficiency (Fv/Fm and ՓPSII), a significant reduction in pigments and an increase in oxidative stress markers. In contrast, minor effects were observed in Zn-treated plants. In addition, Cu exposure suppressed the expression of D1, rubisco large subunit, and alpha-tubulin proteins but did not affect the PSI-B core subunit of PSI. Our study suggested that Cu is a potent phytotoxin by disturbing the principal reactions of photosynthesis and inducing oxidative stress and protein degradation. The overall health status of C. demersum was assessed by adopting the biomarker response index (BRI) approach. The effects of Cu were categorized as moderate in 2 μM and severe in 5, 10, and 50 μM whereas the effects of Zn were categorized as slight in 50 μM, negligible in 100 μM and major in 500 and 1000 μM. BRI effectively substantiates data interpretation of complex plant responses to trace metals and should be further adapted into biomonitoring suites in aquatic systems.

Vallisneria is a cosmopolitan genus of aquatic plants comprising 14 species within the family Hydrocharitaceae. Previous research suggests Vallisneria is a more speciose genus than current taxonomy indicates, and there remains contention on the level of species diversity within the genus. In order to address some of these taxonomic issues, this study estimates phylogenetic relationships within the genus using a previously published molecular dataset augmented with previously unsampled species through the use of maximum likelihood analyses for all molecular data partitions (e.g., nrITS, cpDNA, and combined nuclear and cpDNA datasets). Based on our findings, we recommend the resurrection of two Vallisneria species (V. gracilis and V. neotropicalis), and formally recognize and describe a new species (V. jacobsii). Morphological data was shown to be useful for some species delimitation but overall, molecular sequence data provided the best estimates of species identification for cultivated specimens. We also show the presence of naturally occurring putative Vallisneria hybrids within Northern Territory, Australia, and give conclusive evidence that non-native hybrids are being used for a restoration project in Crystal River, Florida.

Species may respond to variation in environmental conditions by modifying their phenotype to match local levels of resource availability. This phenotypic response can be driven by plastic physiological change, or by adaptive genetic change. Here we use Lemna minor (lesser duckweed), a small aquatic macrophyte that is increasingly used as a model in ecology and evolution, to investigate the source and maintenance of phenotypic variation in natural environments. We found substantial phenotypic variation in L. minor in the field, with its frond area and root length changing predictably over natural environmental gradients of resource availability. Separating environmental and genetic variation in these traits in a common garden, we attribute the majority of phenotypic variation we observed in the field to phenotypic plasticity. Despite this, there was substantial within-site genetic variation. We found evidence of strong purifying selection in the field, that is necessarily balanced by mutation and migration. Using measures of environmental and genetic variation in phenotype and fitness, we estimate the rates of dispersal and evolution of fitness necessary to sustain the observed levels of genetic variation.

The increasing spread of Undaria pinnatifida has caused concern in many parts of the world in recent decades, and this alga has been listed as invasive in the introduced countries. Its most recent spread in Europe was reported on Sylt island in the northern Wadden sea (German Bight, Eastern North Sea) between 2016 and 2017. Its direct origin remained unknown. In the present study, we obtained the mitochondrial DNA sequences including the partial coding region of cox3 and intergenic noncoding loci tatC-tLeu, atp8-trnS and trnW-trnI from one drifting population and one attached population of U. pinnatifida on Sylt and compared them with the available sequences published in previous studies. For the concatenated sequences of atp8-trnS and trnW-trnI, two haplotypes (Up01 and Up03) were detected in Sylt populations with Up01 being the dominant haplotype, which was most similar to the haplotype composition identified previously in European populations. For the concatenated sequences of cox3 and tatC-tLeu, two haplotypes (H1 and H9) were found in Sylt populations and they were the same as those identified previously in Brittany, France. These results suggest that European populations were most likely the direct origin of the newly established U. pinnatifida population on Sylt. The combined use of these sequences will be a robust tool to infer the origins of newly established populations of this seaweed in the future.

Shallow eutrophic lakes with submerged aquatic vegetation (SAV) are a large source of atmospheric methane (CH₄) emissions. However, current estimates of CH₄ emissions from lakes are uncertain owing to the lack of data on the diel and monthly variability of CH₄ emissions. In this study, we conducted monthly diel measurements in Ulansuhai Lake, China during the ice-free period (April to October, 2019) to determine the diel and monthly variability of CH₄ emissions. The diffusive CH₄ emission flux (FCH_4d) from June to September was significantly higher (∼5- to 10-fold) than that from April, May, and October, accounting for > 92% of the total emissions. Daytime measurements would overestimate emissions if extrapolated to the whole day because FCH_4d during daytime was higher than that during nighttime. Mean daily FCH_4d emission estimates are overestimated by 25%, ranging from 11% in summer to 46% in spring based solely on daytime measurement. The sampling sites were net sources of CH₄ emissions, with total FCH₄ of 9.74 ± 9.06 mmol m⁻² d⁻¹. FCH_4d increased sharply when the water temperature was above 20 °C. FCH₄ (CO₂ eq) accounted for over 90% of the total greenhouse gas emissions (CH₄ plus CO₂), with the majority occurring from June to September. Our findings indicate that diel and monthly variations should be considered for more accurate estimation of CH₄ emissions from the lakes with SAV.

Dynamic environmental factors can influence the genetic diversity and epigenetic variation of aquatic plants, thus accelerate the rate of species adaptations. Trapa bispinosa is an aquatic crop which is widely distributed in China and worldwide, yet little is known about the genetic and epigenetic variations of T. bispinosa in fishery and nature habitats. By using AFLP and MSAP, we analyzed the genetic and epigenetic variations of 27 T. bispinasa populations in a subtropical freshwater lake. A relative high level of genetic diversity (mean H_E = 0.312, I = 0.480, PPL = 54.90%) and epigenetic variation (mean eH_E = 0.351, eI = 0.531, ePPL = 67.84%) were detected. Besides, fishery habitats maintained relative higher epigenetic variations of T. bispinosa (H_E = 0.254, eI = 0.378, ePPL = 68.28%) than nature habitats (eH_E = 0.253, eI = 0.376, ePPL = 67.77%). Overall variations were basically distributed within populations (Ø_ST = 0.260, P < 0.001). Bayesian analysis revealed a pattern of genetic structure consisting of two clusters among the populations. The Mantel regression of genetic and epigenetic variation against geographic distance did not reveal any correlations, but showed a correlative relationship with environmental variables (r = −0.47, P < 0.05). Specially, genetic diversity of T. bispinosa showed a positive correlation with slope aspect. These results indicated that habitat slope may shape the pattern of genetic variation in T. bispinosa, which further illustrated that even in a fine geographical scale, genetic diversity was unevenly distributed, restoration measurements for this aquatic crop should carefully take the habitat slope into account.

Data accessibility

All codes and polymorphism raw data are openly available from the Github repository: https://github.com/yixian185/Data-for-Trapa.

Near-shore areas face multiple stressors, effects of climate change, coastal construction and contamination. Although capping the seabed in these areas with mineral masses can reduce the impact of legacy contaminants in sediment, it can also result in the loss of flora and sessile fauna, both of which are vital components of near-shore ecosystems. Eelgrass (Zostera marina) is essential to marine near-shore areas as it supports biodiversity and mitigates the effects of climate change. Therefore, it would be beneficial to modify the top layer of caps to facilitate the reestablishment of these ecosystems when capping near-shore areas. This study describes results from an in situ, six-month field experiment conducted to compare increase in leaf length over the growing season and survival of eelgrass transplanted in two commercially available substrates (Natural sand and Crushed stone) and indigenous sediment (i.e., indigenous control sediment) in a capping project in Horten Inner harbour, Norway. Similar leaf length increase was found in Natural sand and Indigenous control sediment, both significantly higher compared to Crushed stone substrate. Survival was highest in our case in the Indigenous control sediment (120 %), with no significant difference between Crushed stone (20 %) and Natural sand substrates (25 %). These findings emphasize the importance of selecting appropriate substrate for successful seagrass restoration.

In eutrophic freshwater ecosystems, submerged macrophyte communities are replaced by phytoplankton or free-floating plants. In isolated wetlands, vegetation shift occurs over short time scales and leads to water deoxygenation and chemically reduced sediments, conditions that favor the generation, accumulation and degassing of greenhouse gases (GHGs, i.e. CH₄, CO₂ and N₂O) to the atmosphere. However, the relationship between primary producer’s growth forms, hydrological connectivity and GHGs concentration is poorly studied in the literature. A set of 18 freshwater wetlands including isolated and river-connected oxbow lakes, marshes and ponds with different vegetation growth forms was therefore monitored monthly on the annual scale. Potential GHGs diffusive fluxes towards the atmosphere were calculated and compared with direct measurements reported in peer-reviewed papers within a meta-analysis. Our results demonstrate a strong link between the colonization of free-floating plants and the onset of hypoxic conditions and accumulation of dissolved methane. Methane and carbon dioxide concentration peaked in late summer, when floating-leaved and free-floating vegetation covered 100% of the water surface. Carbon dioxide accumulation was particularly evident at hydrological connected wetlands, where nitrate pollution was likely responsible for the concomitant increment of dissolved nitrous oxide. As an increasing number of studies focuses on unravelling environmental drivers of GHGs emission from small lakes and ponds, we encourage to systematically consider the vegetation growth forms and the hydrological connectivity as major drivers of GHGs accumulation and evasion rates.

The massive pelagic Sargassum horneri (Turner) C. Agardh, 1820 has increasingly occurred in the Yellow Sea and East China Sea. Significant intrusion of floating S. horneri into the southwestern Yellow Sea, the major bloom region of the green tides, has aroused speculations on the blooming mechanism and confounded concurrent prevention practices of green tides. The floating S. horneri were surveyed and sampled throughout its distributional range to study the diversity and abundance of sympatric macroalgae, including the epiphytes and non-epiphytes. The study showed that both types of macroalgae commonly coexisted with the pelagic S. horneri and showed distinct distribution patterns. The non-epiphytic green macroalgae, primarily Ulva prolifera, were free floating with S. horneri. They were initiated from the nearshore water of Jiangsu in late April followed by a rapid accumulation and expansion as the green tide developed. The non-epiphytic green algae were mostly restricted in the western coast of southern YS with biomass decreasing evidently toward offshore. Four species in Phaeophyta were commonly detected epiphytic on the pelagic S. horneri in the survey region and Proselachista taeniiformis was dominant. Unlike the co-occurring green algae, the species composition and abundance of epiphytes have no significant variation in the distributional range of the pelagic S. horneri. High frequency (80%) and abundance (0.25 ± 0.17 g_Epi/g_Sar) of epiphytes indicated significant biological interactions with their hosts and ecological functions of this pelagic system, which deserves further investigation.