Growth and energy status of arrowhead tubers,pondweed turions and rice seedlings under anoxic conditions

The responses of two aquatic plants, arrowhead (Sagittaria pygmaea Miq.) and pondweed (Potamogeton distinctus A. Benn), to anoxia were compared with those of rice (Oryza sativa L.). Shoot elongation of arrowhead tubers was enhanced at around 1 kPa O₂, whereas that of pondweed turions was slight in air and reached a maximum in the absence of O₂. Anaerobic enhancement of alcohol dehydrogenase (ADH) activity took place in rice coleoptiles but not in arrowhead and pondweed shoots. Shoots of both arrowhead and pondweed maintained a more stable energy status than did the rice coleoptile under anaerobic conditions. Total adenylate nucleotide contents of arrowhead and pondweed shoots were constant under anaerobic conditions. Adenylate energy charge in both shoots remained at a high and stable level of more than 0·8 for at least 8 d. Three forms of ADH from arrowhead shoots were separated by starch gel electrophoresis, showing that the activity of each ADH form was different under aerobic and anaerobic conditions. The incorporation of ³⁵S-labelled Cys and Met into soluble proteins in arrowhead shoots showed active protein biosynthesis and an involvement of a special set of polypeptides in the anaerobiosis.     

Submersed macrophytes and grazing crayfish: an experimental study of herbivory in a California freshwater marsh

Grazing by the crayfish Procambarus clarkii (Girard) on the abundance of submersed sago pondweed, Potamogeton pectinatus (L.), was quantified during 1984 through 1986 at Coyote Hills Marsh (Alameda County, California, USA). Annual marsh surveys indicated that P. pectinatus abundance declined (from 70% to 0% of the marsh surface), whereas P. clarkii abundance increased (from 1.6 to almost 3.0 crayfish trap⁻¹ week⁻¹). Crayfish in a 1425 m² trapping grid were non-aggregated when pondweed was abundant but became aggregated in the remaining pondweed beds as pondweed abundance decreased. In situ exclusion and enclosure experiments using crayfish densities of 0 to 3 individuals m⁻² were used to determine if crayfish reduced pondweed. Exclusion of crayfish from areas without pondweed, beginning in midsummer 1984, resulted in plant regrowth; addition of crayfish to these enclosed plots reduced pondweed. Exclusion of crayfish for the entire growing season in 1985 resulted in pondweed persistence in exclusion plots until August: in contrast, pondweed within adjacent, open control plots was eliminated by mid-June. Enclosure experiments showed a strong positive relationship between crayfish density and pondweed clearance. This study demonstrates that grazing crayfish can reduce and, in some cases, eliminate macrophytes from freshwater marshes.     

Effects of waterfowl, large fish and periphyton on the spring growth of Potamogeton pectinatus L. in Lake Mogan, Turkey

It has been argued that waterfowl and fish may threaten growth of submerged macrophytes, especially in spring during the early growth phase when plant biomass is low. A small reduction of biomass at that time might delay growth or decrease subsequent productivity. We investigated the impact of waterfowl and large fish on the spring growth of fennel pondweed (Potamogeton pectinatusL.) by employing an exclosure experiment in the macrophyte-dominated clear-water Lake Mogan, Turkey. Birds and large fish were excluded from eight plots and both in situvegetation and macrophytes kept in pots were compared to eight open plots. Also, to investigate the effect of periphyton on plant growth it was removed from half of the pot plants. Exclusion of waterfowl and fish may decrease predation on macroinvertebrates, which in turn may affect periphyton, and macrophyte growth, why macroinvertebrates also were sampled. Waterfowl density was high (15–70 ind. of coot, Fulica atraL. ha^–1), abundance of submerged plants was also high with a surface coverage of 70–80%, and benthivorous fish were present, mainly tench, (Tinca tincaL.) and carp, (Cyprinus carpioL.). Exclusion of waterfowl and large fish did not significantly affect the spring growth of pondweed; neither plants growing in situnor kept in pots. Removal of periphyton from the plants in the pots did not favour growth. The density of macroinvertebrates was not affected by the exclusion of waterfowl and large fish, but it was positively related to aboveground biomass of fennel pondweed. We suggest that even if waterfowl and large fish are in high densities, their effect on fennel pondweed spring growth in lakes with abundant submerged vegetation, such as Lake Mogan, is low.     

Nine polymorphic microsatellite loci for the fennel Pondweed Potamogeton pectinatus L.

Fennel (= Sago) pondweed (Potamogeton pectinatus L.) is a submersed macrophyte of nearly cosmopolitan distribution. The plant is of worldwide ecological importance as structuring component of shallow lakes, and as food for waterfowl. We developed nine polymorphic microsatellite primers for the population genetic analysis of P. pectinatus. The loci were identified using a GA/CT‐enriched genomic library using subtractive hybridization with magnetic particles. All nine loci were highly polymorphic with 6–9 alleles and heterozygosities ranging from 0.23 to 0.80 in a subset of N = 40 genotypes from five locations.     

Mitochondrial electron transport protects floating leaves of long leaf pondweed (Potamogeton nodosus Poir) against photoinhibition: comparison with submerged leaves

Photosynthesis Research - Investigations were carried to unravel mechanism(s) for higher tolerance of floating over submerged leaves of long leaf pondweed (Potamogeton nodosus Poir) against...     

Trophic web structure in a shallow eutrophic lake during a dominance shift from phytoplankton to submerged macrophytes

In Lake Krankesjön, southern Sweden, sago pondweed (Potamogeton pectinatus L.) and a stonewort (Chara tomentosa L.) expanded spatially during the second half of the 1980's after more than a decade of phytoplankton blooms and sparse submerged vegetation. During the expansion of submerged plants the number of resting and breeding waterfowl increased. The increase was significant for herbivorous birds such as coot (Fulica atra L.) and mute swan (Cygnus olor (Gmelin)), but also for omnivorous dabbling ducks. The shift from phytoplankton to submerged macrophytes caused structural changes on higher trophic levels, and an altered trophic web developed. The density of planktonic Cladocera decreased, which is suggested to be a result of decreased phytoplankton productivity and biomass as nutrient levels dropped. The benthic macroinvertebrate assemblage changed from low diversity and biomass dominated by Chironomidae and Oligochaeta on bare sediment, to high diversity and biomass characterized by plant-associated forms like snails and isopods in areas covered by macrovegetation. The mean size of perch (Perca fluviatilis L.) increased, probably as a result of higher availability of macroinvertebrates in the vegetation. The perch reached a mean size where the species is known to shift to a fish diet, permitting an increased top down effect on the ecosystem. The results support the idea that shallow eutrophic lakes can shift between two states, each one stabilized by feed-back mechanisms including both biotic and abiotic factors. Shifts between these states are suggested to be a possible explanation for observed drastic changes in abundance of waterfowl in shallow eutrophic lakes.     

Desmutagenic substance in water extract of grass-wrack pondweed (Potamogeton oxyphylus Miquel)

It was found that the water extract of grass-wrack pondweed (Potamogeton oxyphylus Miquel) had inhibitory activity for reverse mutations induced by benzo[a]pyrene, 2-aminoanthracene and 2-nitrofluorene with Salmonella typhimurium TA100 and TA98. The active substance was heat-resistant, and the molecular weight was above 300 000. The substance acted as a desmutagen rather than an antimutagen or inhibitor of metabolic activation.     

Role of the clasping-leaved pondweed (Potamogeton perfoliatus) polysaccharides in formation of its bacterial environment

The effect of the polysaccharides of clasping-leaved pondweed (Potamogeton perfioliatus) on the formation of a bacteriocenosis of this plant was demonstrated by research on chemoreception, relative surface hydrophobicity, and the growth characteristics of the members of five bacterial genera abundant in this microbiocenosis. The plant heteropolysaccharides of anionic and cationic nature were found to participate in selective stimulation or inhibition of growth of some microbial groups in surrounding water. These findings improve our understanding of the spectrum of physiological activity of glycopolymers of diverse origin.     

Role of the clasping-leaved pondweed (Potamogeton perfoliatus) polysaccharides in formation of its bacterial environment

The effect of the polysaccharides of clasping-leaved pondweed (Potamogeton perfoliatus) on the formation of a bacteriocenosis of this plant was demonstrated by research on chemoreception, relative surface hydrophobicity, and the growth characteristics of the members of five bacterial genera abundant in this micro biocenosis. The plant heteropolysaccharides of anionic and cationic nature were found to participate in selective stimulation or inhibition of growth of some microbial groups in surrounding water. These findings improve our understanding of the spectrum of physiological activity of glycopolymers of diverse origin.     

Potamogeton praelongus in West Greenland

An extant population of the long-stalked pondweed Potamogeton praelongus is reported from West Greenland for the first time. However, endocarps of the species have been recovered from up to 3500 years old lake sediments, so the species has a long history in this region. The species must have arrived in West Greenland by long distance dispersal, probably by geese migrating from NW Europe.     

Constraining invader dominance: Effects of repeated herbicidal management and environmental factors on curlyleaf pondweed dynamics in 50 Minnesota lakes

1. Curlyleaf pondweed (Potamogeton crispus) is one of the most widespread and widely managed aquatic invasive plants in North America. Despite decades of management, the efficacy of long-term management strategies and the effects of environmental drivers on curlyleaf pondweed populations remain uncertain.
2. To evaluate the effects of management and environmental factors on within-lake distribution and local density of curlyleaf pondweed, we collated monitoring data from point–intercept surveys collected by a variety of lake managers across Minnesota, U.S.A. Using this dataset, comprising 177 lake-years of plant data, we examined the influence of herbicide treatment, water clarity, snow depth, and ice cover duration on curlyleaf pondweed distribution and density between 2006 and 2015.
3. We evaluated the effects of herbicides on curlyleaf pondweed at three time points relative to treatment: within year, carryover effects the following year, and cumulative effects over multiple years of treatment. All three temporal measures were associated with significant reductions of curlyleaf pondweed. Additionally, herbicidal management reduced both the density and distribution of curlyleaf pondweed. Given that herbicide management led to reductions that carried over into future years, managers may be able to design multi-year treatments to reduce total management effort over time.
4. We also found strong effects of environmental conditions on curlyleaf pondweed. Elevated lake productivity and decreased winter snow cover were associated with increased springtime distributions of curlyleaf pondweed, whereas duration of winter ice cover had no influence. The influence of productivity suggests that reductions of this invasive species may be an ancillary benefit of water-quality improvements that lower lakes’ trophic status. Our results also show that decreased winter snow cover, as predicted under climate change, could exacerbate problematic growth of curlyleaf pondweed.
5. Harnessing monitoring data from multiple projects, as this study does, allows for robust inference about environmental and management constraints on macrophytes. Because of environmental and management variability, we suggest that treatment regimens follow an adaptive management cycle, with outcomes of management monitored and evaluated, and strategies updated accordingly. It is also vital to continue monitoring both managed and unmanaged lakes to enable stronger inferences about treatment effectiveness.

     

Effects of plant species richness and composition on epifaunal colonization in brackish water angiosperm communities

Studies conducted in terrestrial ecosystems have shown that increasing plant diversity enhances ecosystem processes such as primary production. In marine systems, knowledge of how plant diversity influences ecosystem processes and higher trophic levels is still limited. To examine how plant richness and composition influence recruitment and colonization processes, defaunated eelgrass (Zostera marina), sago pondweed (Potamogeton pectinatus) and perfoliate pondweed (Potamogeton perfoliatus) were planted on an unvegetated, sandy bottom in all possible combinations in July and August. Both field experiments lasted 1 week. Our results showed that in these plant assemblages plant richness had a negative effect on faunal diversity (H′) and evenness (J′), while total abundance showed strong temporal variation with weak, positive relationships with plant species richness in both August and July. Plant species composition had strong effects on amphipods (Gammarus spp.), thus both the abundance and biomass were higher in treatments containing P. perfoliatus. The colonization process was significantly influenced by the numerical dominance of a few faunal species, e.g. the settlement of lagoon cockles (Cerastoderma glaucum), and by the timing of the experiments. The results indicate that faunal colonization in these communities is rapid and significantly influenced by the traits of particular plant species.     

Animal–plant–microbe interactions: direct and indirect effects of swan foraging behaviour modulate methane cycling in temperate shallow wetlands

Wetlands are among the most important ecosystems on Earth both in terms of productivity and biodiversity, but also as a source of the greenhouse gas CH₄. Microbial processes catalyzing nutrient recycling and CH₄ production are controlled by sediment physico-chemistry, which is in turn affected by plant activity and the foraging behaviour of herbivores. We performed field and laboratory experiments to evaluate the direct effect of herbivores on soil microbial activity and their indirect effects as the consequence of reduced macrophyte density, using migratory Bewick’s swans (Cygnus columbianus bewickii Yarrell) feeding on fennel pondweed (Potamogeton pectinatus L.) tubers as a model system. A controlled foraging experiment using field enclosures indicated that swan bioturbation decreases CH₄ production, through a decrease in the activity of methanogenic Archaea and an increased rate of CH₄ oxidation in the bioturbated sediment. We also found a positive correlation between tuber density (a surrogate of plant density during the previous growth season) and CH₄ production activity. A laboratory experiment showed that sediment sterilization enhances pondweed growth, probably due to elimination of the negative effects of microbial activity on plant growth. In summary, the bioturbation caused by swan grazing modulates CH₄ cycling by means of both direct and indirect (i.e. plant-mediated) effects with potential consequences for CH₄ emission from wetland systems.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Dormancy in Winter Buds of American Pondweed, Potamogeton nodosus Poir

Winter buds of American pondweed (Potamogeton nodosus Poir.)were found to be strongly dormant at maturity. Under normalconditions the dormancy lasted for several months. Cold treatmentdecreased the period required for after-ripening, and exposureof dormant buds to 32° C for three days caused most of thebuds to grow in two weeks. Removal of bud scales in light wasvery effective in promoting growth. Soaking of dormant budsin solutions of gibberellic acid, sucrose, combinations of gibberellicacid and sucrose, -naphthylacetic acid and fenac (2,3,6-trichlorophenylaceticacid) partially relieved the growth suppression. Treatmentswith indole-3-acetic acid at 1,000 ppm for 18 hours broke dormancycompletely in all buds, indicating that low levels of this substancemay be the primary cause of dormancy in this species.     

The role of membrane lipids in the resistance of clapsing-leaved pondweed (<Emphasis Type="Italic">Potamogeton perfoliatus</Emphasis> L.) to excess of cadmium in water

The effect of cadmium on clapsinng-leaved pondweed (Potamogeton perfoliatus L.) within the concentration range of 1–1000 µM was studied. It was shown that P. perfoliatus leaves accumulated cadmium during three days. This process was accompanied by changes in leaf morphology. The sensitivity of biochemical metabolites to cadmium was different. Low concentrations of cadmium (1 and 10 µM) increased the content of protein, total lipids, and photosynthetic pigments, whereas high concentrations (100 and 1000 µM) decreased the content of total lipids and pigments but increased protein content. Based on cadmium sensitivity, structural lipids were divided into three groups—resistant (neutral, phosphatidylglycerol, digalactosyldiacylglycerol, and sulfolipid), the content of which increased in the presence of cadmium; labile (monogalactosyldiacylglycerol, phosphatidylcholine, and phosphatidylinositol); and nonresistant (phosphatidylethanolamine). It is concluded that the lipid component determines the resistance of P. perfoliatus to cadmium.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 2, 2005, pp. 232–239.Original Russian Text Copyright © 2005 by Rozentsvet, Murzaeva, Gushchina.     

Reduced tuber banks of fennel pondweed due to summer grazing by waterfowl

In this study we investigated the effect of summer bird herbivory on the belowground tuber formation of fennel pondweed (Potamogeton pectinatus L.). Cumulative grazing pressure of four waterfowl species (mute swans, mallards, gadwalls and coots) in the summer was calculated based on timing of grazing and body mass of the grazers. The resulting grazing pressures were significantly negatively correlated with mean autumn tuber biomass in three of the four years of study. Moreover, summer grazing pressures explained more of the variance in tuber densities than water depth, sediment particle size distribution or any interactions of these variables did in the same three years. We propose that herbivory early in the summer has the most substantial impact on the clonal reproduction of macrophytes. Herbivores with a large body mass and early congregation for moulting may be the key waterfowl species in diminishing propagule biomass. Hence, they may present pre-emptive, time-staggered competition to consumers of the belowground biomass in autumn, such as migratory swans and diving ducks.     

Inter-relationships between Najas marina L. and three other species of aquatic macrophytes

The ability of Najas marina L. to thrive in the presence of the submerged hydrophytes (Myriophyllum spicatum L. and Potamogeton lucens L.) and of an emerged hygrophyte (Scirpus litoralis Schard.) was investigated in Tel Aviv, Israel. Najas plants were unaffected by the presence of Potamogeton lucens and Scirpus litoralis, but were significantly suppressed by Myriophyllum. Bilateral negative relationships exist between Najas and Myriophyllum and these seem to be of an allelophatic nature, depending more on the nature of the accompanying species rather than on their mass.     

Flavonoid systematics of Potamogeton subsections Perfoliati and Praelongi (Potamogetonaceae)

The flavonoid pigments of Potamogeton praelongus Wulfen, P. perfoliatus L., and P. richardsonii (A. Benn.) Rydberg were isolated and identified. Five flavone glycosides based on three aglycone types and one C-glycosylflavone were identified. Potamogeton perfoliatus and P. richardsonii are most similar in flavonoid composition. The greatest number of compounds are found in P. praelongus with the other two species having a subset of its profile. The flavonoid data suggest that P. richardsonii arose by means other than hybridization between P. perfoliatus and P. praelongus.     

Bionomics of invertebrates within an extensive Potamogeton pectinatus bed of a California marsh

Fourteen samples of sago pondweed (Potamogeton pectinatus L.) and associated invertebrates were collected every two weeks over a single season of plant growth in a large monospecific pondweed-bed located in Coyote Hills Marsh (Alameda Co., California, USA), using pull-up samplers that collect plants, epiphytic macroinvertebrates, and microcrustaceans throughout the water column. The macro-invertebrate fauna was dominated by insects, primarily chironomids. Semi-aquatic neustonic taxa, including an aphid and a springtail, were common; this is in contrast with most aquatic plant-invertebrate studies, in which neustonic insects are seldom collected because of sampling bias. Over the entire season, P. pectinatus biomass and the densities of four insect taxa (Anopheles spp. mosquitoes, Hydrellia sp. brineflies, Ademon sp. parasitic wasps, and coenagrionid damselflies) were significantly correlated. These correlations resulted from both similar overall phenologies of the plant and each of the insect taxa, and ecological relationships in which P. pectinatus provides either a specialized habitat or food source. macroinvertebrate numbers were highest in mid-summer, when P. pectinatus forms a dense floating canopy; microcrustaceans were more common during plant senescence in early autumn. Individuals of some taxa may be distributed in proportion to plant biomass; this occurred commonly in damselflies, perhaps as a result of territoriality in these nymphs.