Potamogeton Species Research Articles

PALEOECOLOGY OF SUBMERGED MACROPHYTES IN THE UPPER CHESAPEAKE BAY

Fossil seed distributions of submerged aquatic vegetation (SAV) from dated sediment cores in tributaries of the upper Chesapeake Bay show prehistoric changes in species composition and abundance and reflect the response of SAV species to human disturbance since European settlement. The interval of time spanned by the cores includes several centuries prior to, and three centuries following, European settlement. Species diversity is greatest in the low-salinity northern and upper tributaries, while areas of higher salinity and extensive salt marshes are characterized by low diversity or absence of SAV. Mapped distributions of seed abundances show the migration from upstream to downstream in some tributaries of the brackish species Potamogeton perfoliatus, Zannichellia palustris, and Ruppia maritima following deforestation. The largest increase in SAV, represented by the highest abundance of fossilized seeds, occurred during the 1700s after Europeans first cleared the land for farms, and the largest and most widespread decline took place in the 1960s and 1970s after most of the watershed had been at one time or another cleared and heavily fertilized for agriculture. Distributions of SAV are highly variable both temporally and spatially, reflecting the dynamic nature of estuarine habitats. Despite high environmental variability, local and regional extinctions occurred only in the most recent decades, indicating a threshold response to land use changes and nutrient loading which had begun at least two centuries earlier and intensified in the mid- to late 19th century.

Host Range Studies with Bagous affinis (Coleoptera: Curculionidae), an Indian Weevil that Feeds on Hydrilla Tubers

The plant host feeding range of Bagous affinis Hustache was studied in a Florida quarantine facility as part of a program for the biological control of hydrilla, Hydrilla verticillata (L. fil.) Royle, an immigrant submersed aquatic weed. Larvae attack hydrilla tubers in soil exposed during droughts or drawdowns. Thirty-nine plant species in 20 families were tested with larvae, and feeding was observed on 6 species. A few adults emerged from 3 species of Potamogeton and from Vallisneria americana Michaux. Adult feeding tests were conducted with 52 plant species in 29 families. Adults fed moderately on several species in 3 families: Apiaceae, the hydrilla family Hydrocharitaceae, and Potamogetonaceae. They fed heavily in no-choice tests on stems of the immigrant submersed weed Egeria densa Planchon, a close relative of hydrilla. Newly emerged females developed small numbers of eggs on 3 species of Hydrocharitaceae. Only 1 species, V. americana , could be a potential host plant, but the low oogenesis combined with low larval development indicated that it would be difficult for B. affinis to colonize this species in the field. In its native range in India and Pakistan, B. affinis has been reported only from hydrilla. Based upon a review of these data, USDA–APHIS issued a PPQ 526 permit on 17 February 1987 for field release of this biological control agent. B. affinis was subsequently released in Florida and California, but there are no reports of permanent establishment.

An Evaluation of Trace Element Accumulation in Aquatic Macrophytes of the Novosibirsk Reservoir

ABSTRACT Concentrations of 12 trace elements (Hg, Cd, Be, Co, As, V, Pb, Cu, Ni, Zn, Ba, Mn) were determined for different organs of 6 dominant macrophytes of the Novosibirsk Reservoir (Phragmites australis (Cav.) Trin. ex Steud., Typha angustifolia L., Nymphoides peltata (S.G. Gmel) O. Kuntze, Potamogeton lucens L., Potamogeton perfoliatus L., Salvinia natans (L.) All.). This investigation showed: 1) concentrations of trace elements (excepting Mn) in roots and rootstocks were greater than in organs above the sediment surface, 2) maximum trace element concentrations were observed in Salvinia natansr, Nymphoides peltata and Potamogeton species accumulated lesser amounts than Salvinia natans; Phragmites australis and Typha angustifolia always showed the lowest concentrations of all elements in both above- and underground organs, and 3) because of their greater biomass, communities of Phragmites australis accounted for greater total amounts of trace elements than other macrophyte communities of Novosibirsk Reservoir. These communities contained 57% of Cd, 52% of As, 42% of Pb, 54% of Cu, 57% of Ni, 66% of Zn, 32% of Mn accumulated in the six studied macrophyte communities of Novosibirsk Reservoir.

A GIS approach of aquatic plant spatial heterogeneity in relation to sediment and depth gradients, Lake Geneva, Switzerland

A georeferenced database was constructed for a section of the littoral zone of Lake Geneva in order to investigate aquatic plant spatial heterogeneity at a community level, by exploring the relationships between species distribution and: (i) depth and sediment characteristics; and (ii) plant traits. This database includes information layers on vegetation, sediment and bathymetry. Vegetation was mapped from a digital photo interpretation coupled with field observation of species distribution and cover index. An abundance index was calculated for each species by multiplying the surface area of each stand by the species relative percentage and its cover index. Bathymetry was established from echosounder profiles and sediment maps were obtained from point interpolation between sediment core samples. Measured sediment characteristics include texture, nutrient and organic matter contents. Multiple regression models were developed in a related article (Lehmann et al., 1997) in order to estimate species biomass and maximum shoot length from depth and sediment characteristics. These models are applied in this article between the corresponding GIS layers to give a spatial estimation of these plant traits for three species of Potamogeton. Macrophyte stands, wherein a given species was dominant at more than 80%, were selected by a spatial selection together with the underlying depth and sediment characteristics and the estimated plant traits. When compared, P. lucens L. appeared to have the best competitive ability in relation to the observed plant traits, but it was dominated by a species more tolerant to wave disturbance in shallower depth ( P. pectinatus L.) and a species more tolerant to the stress of light attenuation and nutrient availability in deeper sites ( P. perfoliatus L.).

Establishment of Native Aquatic Plants for Fish Habitat: Test Plantings in Two North Texas Reservoirs

ABSTRACT Test plantings of native aquatic plant species were made in two Texas reservoirs. Founder populations of three native submersed or floating-leaved species were established within small (2- × 2-m) exclosures utilizing actively growing transplants. Herbivory and excessive sedimentation proved to be deterrents to plant survival and expansion. Nine small founder populations of Vallisneria americana were established within North Lake, a small reservoir with limited water level fluctuations and a developing community of native pioneer aquatic plants. Plants within all nine exclosures successfully established and began vegetative growth. In intact exclosures, the plants rapidly covered the sediment surface within the exclosures. Expansion beyond the exclosures was variable and occurred primarily during the cooler portions of the year when herbivory was assumed to be low. During the spring of the second growing season, herbivores cropped most of the previous expansion leaving only a narrow fringe of plants surrounding the exclosures. At Lewisville Lake, a large, turbid reservoir with significant seasonal water level fluctuations and no existing aquatic macrophytes, two native pioneer species (Potamogeton nodosus and Heteranthera dubia) were planted within exclosures. Good survival and growth occurred within undamaged exclosures, although no expansion ever occurred outside the fenced areas. Plantings of H. dubia in undamaged exclosures also showed excellent survival except for those planted in areas subject to very high turbidity and sedimentation rates. Again, herbivory prevented any expansion outside the protective exclosures.

Measures to develop a rich-fen wetland landscape with a full range of successional stages

Species-rich plant communities characteristic for succession from mesotrophic open water to fen are very rare in The Netherlands. These vegetation types used to occur in turf ponds in the low lying peatland area, created by peat dredging and filled with water due to seepage of mesotrophic, well-buffered groundwater. One of the goals of the National Nature Policy Plan is to create new opportunities for the initial terrestrialization communities through ecological engineering, e.g., restoration and creation of open water habitats. Restoration of the abiotic conditions in acidified floating fen communities is only possible by a combined measure of removal of the Sphagnum-layer and superficial drainage of surplus rain water. New turfponds have been excavated. This study showed that the abiotic conditions (i.e., water depth and water chemistry) are favorable for the development of aquatic communities characteristic of mesotrophic conditions. The aquatic plant species found in the new ponds also point in this direction, e.g., Chara major and Ch. delicatula are very abundant as are seven Potamogeton species. It is concluded that a constant discharge of groundwater and a good connectivity between the ponds and the existing remnants of plant communities desired in the area are essential for the conservation and development of these species-rich plant communities.

Isozyme variation in New Zealand populations of Myriophyllum and Potamogeton species

Isozymes of six freshwater angiosperm species were examined as a measure of genetic variation within and between populations. Five species ( Myriophyllum triphyllum Orchard, Myriophyllum propinquum A. Cunn., Myriophyllum pedunculatum Hook. f., Potamogeton cheesemanii A. Benn., and Potamogeton ochreatus Raoul) are native to New Zealand, while Potamogeton crispus L., is adventive. Species were collected from a wide geographic range of lakes and rivers throughout New Zealand. Myriophyllum triphyllum, Myriophyllum propinquum and Myriophyllum pedunculatum were sampled from 23, 18 and five lakes respectively, while Potamogeton cheesemanii, Potamogeton ochreatus and Potamogeton crispus were collected from a total of 12, nine and four water bodies, respectively. The plants were grown under uniform conditions prior to analysis and analysed by starch gel electrophoresis for the following enzyme systems: PGM, PGD, MDH, GPI, AAT, EST, and IDH. All species studied showed little isozyme genetic diversity between populations and even less variability within populations. On a relative scale, Myriophyllum propinquum displayed the largest degree of genetic differentiation, Myriophyllum pedunculatum and all three Potamogeton spp. were moderately variable, and Myriophyllum triphyllum showed the lowest level of diversity. There was a close correlation between the amounts of intra- and interpopulation genetic variability in all species. No association between geographic and genetic distances between populations could be found for any of the species examined, and the patterns of distribution of isozyme phenotypes and genotypes over populations suggest that populations are often started by a single colonising propagule, or several propagules of identical genotype, and then predominantly grow through vegetative propagation. The apparent lack of genetic variability indicated by the results of this study is consistent with low levels of variability observed amongst aquatic macrophytes in other countries.

Differential effects of the microbial metabolite, acetic acid, on sprouting of aquatic plant propagules

Subterranean vegetative propagules are important life cycle stages for some species of rooted aquatic plants. Sediments contain numerous compounds resulting from anaerobic degradation of organic matter, including acetic acid. Tubers, turions, and winter buds of Hydrilla verticillata (L.f.) Royle, Potamogeton gramineus L., and Potamogeton pectinatus L. were exposed to acetic acid concentrations from 0 to 696 mmol l −1 for 1–8 days. Hydrilla verticillata propagules were more sensitive to acetic acid exposure than those of either Potamogeton species. Monoecious H. verticillata propagules did not sprout at acetic acid concentrations of 17 mmol l −1 or over, even at the shortest exposure time. Potamogeton gramineus winter buds and P. pectinatus tubers were less inhibited between 17 and 87 mmol l −1 if the exposure time was short (2 days or less). Sediment type did not influence the differential response to acetic acid, but the presence of sediments ameliorated the effects of acetic acid somewhat. More than two-thirds of P. pectinatus tubers sprouted after a 24 h exposure to 696 mmol l −1 at 4°C, at higher temperatures sprouting was greatly reduced. Hydrilla verticillata tubers did not sprout following exposure to 17 mmol l −1 at any temperature (4, 13, 19, and 25°C) examined.

Comparative kinetics of photosynthesis in floating and submerged Potamogeton leaves

We examined the morphology and photosynthetic performance of floating and submerged leaves in five Potamogeton species to evaluate the adaptations associated with air contact or full submergence. The floating leaves had stomata on the upper surface, were thicker and contained more chlorophyll per surface area than the submerged leaves. The light absorptance was higher and independent of areal chlorophyll concentration for floating leaves, but lower and strongly chlorophyll dependent for submerged leaves. The photosynthetic rate of both leaf forms was relatively high in their natural growth environment and quantum yields resembled the values attained for terrestrial leaves. Carbon utilization of floating leaves in air showed CO 2 compensation points (32–49 μl l −1, corresponding to 1.2-1.8 μM), typical of C 3 plants, and photosynthesis was not saturated at ambient atmospheric CO 2 levels. During pH-drift experiments in water, submerged leaves were able to extract the majority of the dissolved inorganic carbon pool (82–89%) and attain high pH values (9.95-10.60) and low residual CO 2 concentrations (6–80 nM), presumably as a result of HCO − 3 utilization. Photosynthesis of floating leaf forms declined only four-fold when placed in CO 2 enriched water (approximately 200 μM). Photosynthesis of submerged leaf forms declined two-fold when transferred to water-saturated air, owing to a highly increased respiration. The floating leaves of Potamogeton can support higher areal rates of photosynthesis than submerged leaves and are believed to be particularly important in habitats with turbid waters, and as floating platforms and carbon sources for the aerial flowers. The cost-efficiency of the two leaf forms will depend, however, on the environmental light and carbon conditions because floating leaves are also much thicker and expensive to produce, and their confined horizontal location at the water surface restricts the efficiency of light utilization in plant populations.

Photosynthetic performance and photoinhibition in two species ofPotamogetonfrom lake Bohinj (Slovenia)

Summary Apparent photosynthesis, dark respiration, photochemical efficiency of photosystem II and potential respiration, estimated as terminal electron transport system (ETS) activity, were determined under experimental conditions to evaluate physiological differences in two competing species Potamogeton lucens L. and Potamogeton alpinus Balbis. The investigations showed that there are no significant differences in photosynthetic response and ETS activity. In P. lucens ETS capacity highly exceeds dark respiration measured as O2 consumption. Photochemical efficiency of PS II in P. lucens was higher and the recovery after photoinhibition was more effective.

Growth and morphology of four freshwater macrophytes under the impact of the raised salinity level of the Lower Rhine

The growth and morphology of Potamogeton lucens L., Potamogeton perfoliatus L., Potamogeton nodosus Poir. and Ranunculus circinatus Sibth. were studied in relation to salinity. Plants were grown for 8 weeks in microcosms under ambient climatic conditions at (sodium) chloride concentrations which presently occur in the main channel of the Lower Rhine and its connected lakes (7.0 mmol l−1 Cl−), which have a poorly developed vegetation, and at concentrations which presently occur in infrequently flooded lakes (1.4 mmol l−1 Cl−1) within the floodplain of the Lower Rhine, which are rich in aquatic macrophytes.The sodium chloride level of the main channel negatively affected biomass production and growth rates for all three Potamogeton species, but not for R. circinatus. The reductions in biomass and growth rates of the Potamogeton species concurred with a decline in their leaf ratios, suggesting that the growth reduction might be related to a reduced leaf cell expansion. Root:shoot ratios increased in all selected species, whereas flowering decreased in response to higher salinity. The relevance of salinity as a stress factor is discussed in relation to the occurrence of these macrophytes in the Lower Rhine and its floodplain lakes.

Thermal effects

Thermal effects

Herbivory of invertebrates on submerged macrophytes from Danish freshwaters

SUMMARY1. Invertebrate herbivory on submerged freshwater macrophytes, measured as per cent leaf area lost, was determined for sixteen species and forty‐two populations of macrophytes during peak summer biomass in Danish streams and lakes.2. All seventeen Potamogeton populations and seventeen of the remaining twenty‐five non‐Potamogeton populations were grazed. Species of Potamogeton were significantly more heavily grazed (mean 4.2%) than non‐Potamogeton species (mean 0.8%). Herbivory losses were not significantly different between stream (mean 2.4%) and lake populations (mean 1.9%). Wide ranges in herbivory loss were observed between species from the same locality and within species from different localities. The location of main damage to either old or young leaves was not species specific but varied among localities. Additional data for four macrophyte populations showed that herbivory loss had a strong seasonal variation (e.g. 1.0–26.3% for Potamogeton perfoliatus), with maximum losses during May‐June.3. Although the mean defoliation percentages were low during the period of maximum macrophyte biomass, they were not systematically lower than encountered for terrestrial plants.

Influence of temperature and moisture on vegetative propagule germination of Potamogeton species: implications for aquatic plant management

Laboratory experiments indicated that Potamogeton nodosus Poir, winter buds and Potamogeton pectinatus L. tubers germinated in response to water-saturated substrate at 15, 20, and 25°C. Outdoor experiments with intact sediment cores indicated that winter buds of Potamogeton gramineus L. also germinated in response to saturating conditions at low temperatures (10–15°C). P. gramineus winter buds and P. pectinatus tubers, collected from irrigation canals during the winters of 1985 and 1986, germinated within 10 days of being placed at 25°C, indicating that germination was inhibited by environmental conditions and not by innate dormancy. Measurements made in the springs of 1985, 1986, 1987, and 1989 in the Byrnes canal, demonstrated that terrestrial forms of P. gramineus were present at densities ranging from 50 to 746 m −2, accounting for 30–96% of the total number of winter buds present per square meter. Penetration of accumulated rainwater into the sediment appeared to influence germination of P. gramineus winter in buds and may explain why deep winter buds do not germinate prior to the canal filling with water in the spring. The ability to induce formation of terrestrial forms may lead to new management approaches.

On the phytosociology and ecology of Iso�tes asiatica (Makino) Makino in oligotrophic water bodies of South Sakhalin

In 1989, in the southeast of the Sakhalin Island and south of the village Okhotskoye, Isoetes asiatica (Makino) Makino and I. beringensis Kom. were detected in 24 oligotrophic lakes for the first time on Sakhalin. These are stands of the community of Isoetetum asiaticae ass. nov. which in the majority of the lakes form a characteristic pioneer vegetation of the shallow littoral zones. In addition to poor-species dominance stands of both of the Isoetes species, penetration stages of both of these species as well as stages rich in Comarum palustre, Eleocharis acicularis and Potamogeton species can be differentiated. Besides the structure of the species, the site conditions, particularly of the water bodies are described. The ion content is represented by absolute and relative ion field diagrams exemplified by 7 selected water bodies. The ion content is characterized by sodium and chloride which are prevailing, while calcium and magnesium as well as hydrogen carbonate and sulphate exist in low quantitative proportions only. The indicator values of individual characteristics and the complex characteristics of the Isoetes lakes are discussed. The hydrochemical characteristics of the Sakhalin, Kuriles and Kamchatka Isoetes waters are compared with the Isoetes water bodies of North America and Europe. The danger to Isoetes water bodies is discussed, necessary protective measures are defined.

Human impact on the ecological performance of Potamogeton species in northwestern Germany

The changes in habitat quality of lowland rivers in Lower Saxony (Germany) during the past 40 years are outlined. Almost all chemical, physical, and morphological parameters have changed, resulting in most cases in an enhanced potential productivity, accompanied by a complex disturbance regime. Historical reconstruction of the change in river vegetation is presented to compare the frequency of macrophyte species 40 years ago with the situation of today. For a total of 289 sampling sites, the floristic change was exactly reconstructed. Nearly all species show a decline in frequency. This trend is also recognizable in Potamogeton, with the exception of two narrow-leaved species. An attempt is made to explain both decline and maintenance in terms of life history characters (vital attributes) allowing the species to react to the changing habitat conditions. The successful species are characterized by certain life history characteristics which enable them to survive under the current disturbance regime. Most important aspects of life history are the ability to reproduce by means of turions and other fragments, a long-lived, deep-rooting rhizome system, phenotypic plasticity of above-ground parts, synchronous shoot polymorphism, and the potential to regenerate quickly from remaining buds after disturbance. The decline of formerly frequent species can be attributed mainly to the lack of certain key characters; however, physiological characters also may be important. The extirpation of some rare species could also be caused by random fluctuations in small populations. The general importance of population ecological research, particularly demography, life history theory, and the modelling of clonal populations in conservation ecology is stressed.

Effects of Cu, Pb and Zn on two Potamogeton species grown under field conditions

Two common macrophyte species, Potamogeton perfoliatus L. and Potamogeton pectinatus L. were grown for 12 weeks at shallow depths in sediments contaminated with 1250 or 2500 μg Pb or Cu and/or Zn (gDW sediment)-1. Control experiments were run at background levels of 4, 13, and 38 μg Pb, Cu and Zn (gDW sediment)-1, respectively. Effects of heavy metals on biomass production and metal uptake and distribution in plants are presented in relation to total amount and plant-available fraction of metals in the sediment.

Assessment of the Aquatic Plant Community in Jackson Lake, Grand Teton National Park, Wyoming: 1991 Status Report

Since the construction of the first dam at the Snake River outlet at Jackson Lake in the early 1900's, the littoral habitat has been subjected to numerous perturbations of varying intensities. Changing water levels, a consequence of reservoir drawdown schedules, alter plant community species composition and distribution over time. From the perspective of a plant, water level changes present a challenge to growth and community persistence. A plant which begins the growing season 2 m deep may be under 4 m of water after spring runoff fills the reservoir. Later in the summer, the same plant may be left at a depth of only 1 m as water is removed from the reservoir during summer drawdown. The magnitude and timing of water level fluctuations may be one of the most important factors regulating macrophyte community processes upslope on the vertical gradient in Jackson Lake (Brewer and Parker 1990). Under normal regulation, annual changes of 3-4 m are sufficient to select for a plant community with a typically weedy phenology (e.g., Elodea canadensis). In natural lakes with substantially lower annual changes in water levels, species that produce seeds annually are favored (e.g., Potamogeton species). Moreover, drawdowns greater than several meters substantially reduce the lake bed area suitable for the development of extensive shallow water plant beds. The most recent perturbations to the littoral habitat in Jackson Lake began in 1978, when the water level was lowered first from 2065 m (normal pool) to somewhere between 2060 - 2062 m. Then in 1985, the surface elevation of Jackson Lake was further lowered to 2057 m to facilitate repair and modification of the Jackson Lake dam. The entire lake bed was seriously impacted during the four years that the dam was being restored. While the lake bed in the borrow zone and the area adjacent to the dam were obviously impacted by repair activities, the entire shallow littoral zone was severely perturbed when previously inundated sediments were exposed for four years. In 1989, repair was completed and the reservoir was allowed to fill back to the normal pool elevation of 2065 m. Because of severe impacts to the littoral habitat and significant reduction of the submergent plant community caused by restoration of the dam, the status of the aquatic plant community was monitored during the summers of 1989-1991. This report summarizes the status of the aquatic plant community three years after repair of the dam was completed.

In situ experiments on interrelationships between six brackish macrophyte species

Variations in total biomass and root: shoot ratios of four macrophyte species, Potamogeton filiformis Pers., Potamogeton perfoliatus L., Potamogeton pectinatus L. and Ranunculus baudotii Godr. were investigated at natural densities, in situ, in pots with three types of sediment, sand, mud and a 50/50% mixture of these. Higher growth rates, lower percentage root and rhizome biomass at harvest, and more reproductive parts were produced on muddy substrate compared with sand in all species tested, except for R. baudotii, where the highest growth rates were found in the 50/50% mixture. Further inter- and intraspecific competitive effects of these and two more species ( Zannichellia major (Hartm.) Boenn. and Ruppia cirrhosa (Petagna) Grande) were examined using de Wit replacement series. P. pectinatus was unaffected by the presence of P. filiformis, but suppressed by P. perfoliatus. Bilateral negative relationships exist between P. pectinatus and Ranunculus baudotii, as well as Ruppia cirrhosa, and between P. filiformis and Ruppia cirrhosa. Possibly, the negative effect of Ruppia cirrhosa on the two Potamogeton species could be of an allelopathic nature. Interspecific relationships were generally weaker than intraspecific relationships in combinations of P. pectinatus with Z. major, P. filiformis with Z. major, and P. filiformis with P. perfoliatus.

Comparison of life history characters of broad-leaved species of the genus Potamogeton L. I. General characterization of morphology and reproductive strategies

A short historical outline of the development of the study of Potamogeton life history is given. Seven levels of research (population, genet, clone, patch, shoot complex, vertical shoot, modular unit) are defined and their appropriateness for studying Potamogeton ecology is discussed. The patch, the shoot complex and the vertical shoot are the central research units. A morphological analysis of the shoot complex is given in order to display the special properties of this important entity. Two basic shoot types are distinguished: the vegetative shoot (represented as either the horizontal or vertical shoot) and the sexual shoot. Based on the morphological description, a conceptual growth model is presented comprising the observed transitions between plant parts in the species studied. Five different reproductive strategies can be distinguised, which differ among the species studied. Data on the life span of different entities (genet, shoot complex, vertical shoot) of the species studied are compared. The life span of vertical shoots varies from short-liver (2 months) to biennial. The life span of shoot complexes varies from annual to very long lived. In most species, the genet is potentially immortal owing to extreme fragmentation. No direct correlations are found between reproductive strategies and environmental conditions expressed as stress and disturbance. Similar unfavourable conditions can be overcome by various strategies.