Sparganium Americanum Research Articles

Branching Burreed (<i>Sparganium androcladum</i> (Engelmann) Morong; Typhaceae) rediscovered in Ontario, but conservation status unclear

We report three new records of Branching Burreed (Sparganium androcladum), which has not been seen in Ontario in several decades. This species is understudied and has been confused with other taxa, primarily American Burreed (Sparganium americanum). It is not known when it was last collected in the province, and its conservation status is unclear. Specimens identified as Branching Burreed are few and do not fully clarify the situation; of the 14 putative S. androcladum specimens we examined, five are too immature to verify confidently, and at least seven are misidentified. Previous specimen-based maps are probably not accurate representations of Branching Burreed’s provincial distribution, but it is likely more widespread than records indicate. We provide a description of our new records and notes on identification to provide a basis for additional study of this plant.

Leaf Composition of American Bur-Reed (Sparganium americanum Nutt.) to Determine Pesticide Mitigation Capability.

American bur-reed (Sparganium americanum Nutt.), a common aquatic plant in the middle and eastern United States and Canada, is often located in water-retaining drainage areas. The purpose of this study was to determine the leaf composition of S. americanum, paying attention to the cuticular waxes and the epidermis, and its ability to sorb pesticides. S. americanum leaves (n = 100) were collected in both early (June) and late (August) summer. Transverse sections of S. americanum were stained and studied with brightfield and fluorescence microscopy to estimate the structural and chemical nature of the leaf tissues cross sections. Mean total lipid content in early summer leaf samples (1.47 ± 0.83mgmL-1) was significantly greater (alpha 0.05) than late summer leaves (0.15 ± 0.36mgmL-1). In vitro analysis of epidermal peel permeability exposed to atrazine and malathion determined little to no sorption by the plant. Therefore, the structure of S. americanum leaves suggest this species does not have the capacity of sorbing these pesticides from runoff water.

Mitigation of atrazine, S-metolachlor, and diazinon using common emergent aquatic vegetation

By the year 2050, the population of the United States is expected to reach over 418 million, while the global population will reach 9.6 billion. To provide safe food and fiber, agriculture must balance pesticide usage against impacts on natural resources. Challenges arise when storms cause runoff to be transported to aquatic receiving systems. Vegetated systems such as drainage ditches and constructed wetlands have been proposed as management practices to alleviate pesticide runoff. Twelve experimental mesocosms (1.3×0.71×0.61m) were filled with sediment and planted with a monoculture of one of three wetland plant species (Typha latifolia, Leersia oryzoides, and Sparganium americanum). Three mesocosms remained unvegetated to serve as controls. All mesocosms were amended with 9.2±0.8μg/L, 12±0.4μg/L, and 3.1±0.2μg/L of atrazine, metolachlor, and diazinon, respectively, over a 4hr hydraulic retention time to simulate storm runoff. Following the 4hr amendment, non-amended water was flushed through mesocosms for an additional 4hr. Outflow water samples were taken hourly from pre-amendment through 8hr, and again at 12, 24, 48, 72, and 168hr post-amendment. L. oryzoides and T. latifolia had mean atrazine, metolachlor, and diazinon retentions from 51%–55% for the first 4hr of the experiment. Aside from S. americanum and atrazine (25% retention), unvegetated controls had the lowest pesticide retention (17%–28%) of all compared mesocosms. While native aquatic vegetation shows promise for mitigation of pesticide runoff, further studies increasing the hydraulic retention time for improved efficiency should be examined.

Distribution and Conservation Status of Sparganium (Typhaceae) in the Canadian Prairie Provinces

We revised the distribution and conservation status of Sparganium L. for the Canadian Prairie Provinces ( cpp ) based on herbarium voucher specimens. In the region, we recognized eight species: Sparganium americanum , S. angustifolium , S. emersum , S. eurycarpum , S. fluctuans , S. glomeratum , S. hyperboreum , and S. natans . Among these, Sparganium americanum , S. fluctuans , S. glomeratum , and S. hyperboreum are in the rare category, with conservation rankings of Critically Endangered, Vulnerable, and Endangered. Following an exhaustive herbarium specimen examination, we discovered additional collections of S. glomeratum , revealing its circumpolar distribution in North America, hence rejecting its status as introduced. In all, we were able to update the geographic distribution and rarity status of Sparganium in the cpp , especially for S. americanum and S. glomeratum . This study demonstrates that herbarium databases are powerful in identifying regions deserving conservation priority based on high diversity and high concentrations of rare or narrowly distributed species. This information facilitates the development of management strategies for the protection of unusual species assemblages.

Uranium immobilization in an iron-rich rhizosphere of a native wetland plant from the Savannah River Site under reducing conditions.

The hypothesis of this study was that iron plaques formed on the roots of wetland plants and their rhizospheres create environmental conditions favorable for iron reducing bacteria that promote the in situ immobilization of uranium. Greenhouse microcosm studies were conducted using native plants (Sparganium americanum) from a wetland located on the Savannah River Site, Aiken, SC. After iron plaques were established during a 73-day period by using an anoxic Fe(II)-rich nutrient solution, a U(VI) amended nutrient solution was added to the system for an additional two months. Compared to plant-free control microcosms, microcosms containing iron plaques successfully stimulated the growth of targeted iron reducing bacteria, Geobacter spp. Their population continuously increased after the introduction of the U(VI) nutrient solution. The reduction of some of the U(VI) to U(IV) by iron reducing bacteria was deduced based on the observations that the aqueous Fe(II) concentrations increased while the U(VI) concentrations decreased. The Fe(II) produced by the iron reducing bacteria was assumed to be reoxidized by the oxygen released from the roots. Advanced spectroscopic analyses revealed that a significant fraction of the U(VI) had been reduced to U(IV) and they were commonly deposited in association with phosphorus on the iron plaque.

Aqueous pesticide mitigation efficiency of Typha latifolia (L.), Leersia oryzoides (L.) Sw., and Sparganium americanum Nutt.

Agricultural pesticide use is necessary to help meet the increased demand for a safe and secure food supply for the United States, as well as the global community. Even with proper application and careful management, the possibility of pesticide leaching and detachment in runoff still exists following certain storm events. Several different management practices have been designed to reduce the impacts of pesticides on aquatic receiving systems. Many such practices focus on the use of vegetation to slow runoff and allow for sorption of the various contaminants. Three common drainage ditch macrophytes, Leersia oryzoides (cutgrass), Typha latifolia (cattail), and Sparganium americanum (bur-reed) were assessed for their ability to reduce effluent loads of atrazine, diazinon, and permethrin in simulated agricultural runoff water in 379L individual mesocosms. Of the three macrophytes examined, L. oryzoides was the most effective at mitigating atrazine, and permethrin. L. oryzoides and T. latifolia significantly reduced overall atrazine loads (45±7%, p=0.0073 and 35±8%, p=0.0421, respectively) when compared to unvegetated controls (13±20%). No significant differences in overall diazinon load retention were noted between plant species. Each plant species significantly decreased the initial load (after 6h) of trans-permethrin, while both L. oryzoides and T. latifolia significantly reduced the overall trans-permethrin loads (88±5%, p=0.0022 and 88±5%, p=0.0020, respectively) when compared to unvegetated controls (68±8%). Reversible adsorption of atrazine and diazinon to plants, noted during the flushing events, was greater than that observed in either cis- or trans-permethrin. These results demonstrate the ability of native ditch vegetation to mitigate pesticides associated with agricultural runoff. Likewise, they provide farmers and action agencies with supportive data for selection of vegetation in drainage ditches used as management practices.

Potential for Phosphate Mitigation from Agricultural Runoff by Three Aquatic Macrophytes

Phosphate from agricultural runoff is a major contributor to eutrophication in aquatic systems. Vegetated drainage ditches lining agricultural fields have been investigated for their potential to mitigate runoff, acting similarly to a wetland as they filter contaminants. It is hypothesized that some aquatic macrophytes will be more effective at removing phosphate than others. In a mesocosm study, three aquatic macrophyte species, cutgrass (Leersia oryzoides), cattail (Typha latifolia), and bur-reed (Sparganium americanum), were investigated for their ability to mitigate phosphate from water. Mesocosms were exposed to flowing phosphate-enriched water (10 mg L−1) for 6 h, left stagnant for 42 h, and then flushed with non-nutrient enriched water for an additional 6 h to simulate flushing effects of a second storm event. Both L. oryzoides and T. latifolia decreased the load of dissolved phosphate (DP) in outflows by greater than 50 %, significantly more than S. americanum, which only decreased DP by 15 ± 6 % (p ≤ 0.002). All treatments decreased concentrations inside mesocosms by 90 % or more after 1 week, though the decrease occurred more rapidly in T. latifolia and L. oryzoides mesocosms. By discovering which species are better at mitigating phosphate in agricultural runoff, planning the community composition of vegetation in drainage ditches and constructed wetlands can be improved for optimal remediation results.

Influence of Three Aquatic Macrophytes on Mitigation of Nitrogen Species from Agricultural Runoff

Agricultural runoff containing nitrogen fertilizer is a major contributor to eutrophication in aquatic systems. One method of decreasing amounts of nitrogen entering rivers or lakes is the transport of runoff through vegetated drainage ditches. Vegetated drainage ditches can enhance the mitigation of nutrients from runoff; however, the efficiency of nitrogen removal can vary between plant species. The efficiency of three aquatic macrophytes, cutgrass (Leersia oryzoides), cattail (Typha latifolia), and bur-reed (Sparganium americanum), to mitigate dissolved and total nitrogen from water was investigated. Replicate mesocosms of each plant species were exposed to flowing water enriched with ammonium and nitrate for 6 h, allowed to remain stagnant for 42 h, and then flushed with non-enriched water for an additional 6 h to simulate a second storm event. After termination of the final simulated runoff, all vegetated treatments lowered total nitrogen loads exiting mesocosms by greater than 50%, significantly more than unvegetated controls, which only decreased concentrations by 26.9% (p ≤ 0.0023). L. oryzoides and T. latifolia were more efficient at lowering dissolved nitrogen, decreasing ammonium by 42 ± 9% and 59 ± 4% and nitrate by 67 ± 6% and 64 ± 7%, respectively. All treatments decreased ammonium and nitrate concentrations within mesocosms by more than 86% after 1 week. However, T. latifolia and L. oryzoides absorbed nitrogen more rapidly, lowering concentrations by greater than 98% within 48 h. By determining the nitrogen mitigation efficiency of different vegetative species, plant communities in agricultural drainage ditches can be managed to significantly increase their remediation potential.

Plants as bio-monitors for Cs-137, Pu-238, Pu-239,240 and K-40 at the Savannah River Site

The Savannah River Site was constructed in South Carolina to produce plutonium (Pu) in the 1950s. Discharges associated with these now-ceased operations have contaminated large areas within the site, particularly streams associated with reactor cooling basins. Evaluating the exposure risk of contamination to an ecosystem requires methodologies that can assess the bioavailability of contaminants. Plants, as primary producers, represent an important mode of transfer of contaminants from soils and sediments into the food chain. The objective of this study was to identify local area plants for their ability to act as bio-monitors of radionuclides. The concentrations of cesium-137 ((137)Cs), potassium-40 ((40)K), (238)Pu and (239,240)Pu in plants and their associated soils were determined using γ and α spectrometry. The ratio of contamination concentration found in the plant relative to the soil was calculated to assess a concentration ratio (CR). The highest CR for (137)Cs was found in Pinus palustris needles (CR of 2.18). The correlation of soil and plant (137)Cs concentration was strong (0.76) and the R(2) (0.58) from the regression was significant (p = 0.006). This suggests the ability to predict the degree of (137)Cs contamination of a soil through analysis of the pine needles. The (238)Pu and (239,240)Pu concentrations were most elevated within the plant roots. Extremely high CR values were found in Sparganium americanum (bur-reed) roots with a value of 5.86 for (238)Pu and 5.66 for (239,240)Pu. The concentration of (40)K was measured as a known congener of (137)C. Comparing (40)K and (137)C concentrations in each plant revealed an inverse relationship for these radioisotopes. Correlating (40)K and (137)Cs was most effective in identifying plants that have a high affinity for (137)Cs uptake. The P. palustris and S. americanum proved to be particularly strong accumulators of all K congeners from the soil. Some species that were measured, warrant further investigation, are the carnivorous plant Utricularia inflata (bladderwort) and the emergent macrophyte Juncus effusus. For U. inflata, the levels of (137)Cs, (238)Pu, and (239,240)Pu (which were 3922, 8399, and 803 Bq kg(-1), respectively) in the leaves were extremely high. The highest (137)Cs concentration from the study was measured in the J. effusus root (5721 Bq kg(-1)).

Ability of Four Emergent Macrophytes to Remediate Permethrin in Mesocosm Experiments

Increased focus is being placed on the ability of native vegetation to mitigate potential harmful effects of agricultural runoff, especially pyrethroid insecticides. Replicate 379 L Rubbermaid tubs (1.25 m [l] x 0.6 m [w] x 0.8 m [h]) were planted with individual species of cutgrass (Leersia oryzoides), cattails (Typha latifolia), bur-reed (Sparganium americanum), and powdery alligator-flag (Thalia dealbata), all common wetland macrophytes found in the Mississippi Delta, USA, agricultural region. Permethrin-enriched water (target concentration, 5 microg L(-1)) was pumped in at a 4-h hydraulic retention time at one end of the tub and discharged at the far end. Water samples were collected from discharge at 1-h intervals for 12 h and analyzed for permethrin concentrations. Permethrin removal rates were compared for the four different plant treatments and nonvegetated sediment-water controls. Results indicated that no particular single plant species was more effective at removing permethrin in water relative to unplanted controls. Overall mass reductions (from inflow to outflow) for cis-permethrin ranged from 67% +/- 6% in T. latifolia to 71% +/- 2% in L. oryzoides. The trans-permethrin overall mass reductions ranged from 76% +/- 4% in S. americanum to 82% +/- 2% in the unplanted control. Sediment and plant samples collected at the study conclusion indicated that 77%-95% of measured permethrin mass was associated with sediment for mesocosms planted with L. oryzoides, T. latifolia, and T. dealbata. Conversely, mesocosms planted with S. americanum had 83% of measured mass associated with the plant material. Specific plant-pesticide retention studies can lead to improved planning for best management practices and remediation techniques such as constructed wetlands and vegetated agricultural drainage ditches.

Differential nitrogen and phosphorus retention by five wetland plant species

Abstract Riparian wetlands have a demonstrated ability to filter and control nitrogen (N) and phosphorus (P) movement into streams and other bodies of water; few studies, however, have examined the roles that individual plant species serve in sequestering N and P pollutants. We evaluated the potential for growth and consequent N and P accumulation by five species of wetland perennials. We planted blocks consisting of 900-cm2 plots of each species at 11 sites within a riparian wetland that receives large inputs of agricultural runoff. Plant shoots and roots were collected at the time of peak standing crop to determine net accumulation of biomass, N, and P for one growing season. A portion of the plant shoots was placed in decomposition litterbags in the field to determine biomass, N, and P losses for 60, 120, and 150 days. Of the five species, bur reed (Sparganium americanum) had the greatest aboveground accumulation of N and P but had the lowest belowground accumulation values. In contrast, woolgrass (Sci...

Nitrogen Distribution in Soils of Constructed Wetlands Treating Lagoon Wastewater

Constructed wetlands have the potential to be used for treatment of N‐rich livestock wastewater. Our objectives were to evaluate both the time effect and increasing N loading rates on soil N distribution and NH+4–N concentration in surface‐pore water of constructed wetlands. A 5‐yr study in North Carolina investigated two wetland systems that treated swine lagoon wastewater. Wetland System 1 was planted to a Schoenoplectus americanus (Pers.) Volkart ex Schinz & R. Keller, S. tabernaemontani (K.C. Gmel.) Palla, Scirpus cyperinus (L.) Kunth, and Juncus effusus L. plant community, and Wetland System 2 was planted to a Typha angustifolia L., T. latifolia L., and Sparganium americanum Nutt. plant community. Nitrogen loading rates were increased annually from 0.6 to 2.7 g m−2 d−1 Soils were analyzed for total N annually. Surface‐pore water was sampled with equilibrators and analyzed for NH+4–N. Although the total N accumulation significantly increased with time in both systems, total soil N accumulation by depth did not differ significantly between systems. Distribution profiles in the surface‐pore water column showed that NH+4–N was transported upward into surface water at N loading rates from 1.2 to 2.7 g m−2 d−1 As total N loading rates increased annually in both wetland systems, soil pore water had higher levels of NH+4–N but N removal efficiency of the wetlands sharply decreased. Accumulation of high levels of NH+4–N (>200 mg L−1) in soil pore water could negatively affect long‐term ability of wetland systems to treat wastewater with high N levels.

Denitrification in Constructed Wetlands Used for Treatment of Swine Wastewater

Constructed wetland treatment of swine wastewater probably involves substantial denitrification. Our objective was to assess denitrification and denitrification enzyme activity (DEA) in such wetlands in relation to plant communities, N loading, carbon or nitrogen limitations, and water depth. Two wetland cells each 3.6 m wide and 33.5 m long were connected in series. One set of cells was planted with rushes and bulrushes, including soft rush (Juncus effusus L.), softstem bulrush [Schoenoplectus tabernaemontani (K.C. Gmel.) Pallal, American bulrush [Schoenoplectus americanus (Pers.) Volkart ex Schinz & R. Keller], and woolgrass bulrush [Scirpus cyperinus (L.) Kunth]. Another set was planted with bur-reeds and cattails, including American bur-reed (Sparganium americanum Nutt.), broadleaf cattail (Typha latifolia L.), and narrowleaf cattail (Typha angustifolia L.). The sets will be referred to herein as bulrush and cattail wetlands, respectively. Denitrification and DEA were measured via the acetylene inhibition method in intact soil cores and disturbed soil samples that were taken during four years (1994-1997). Although DEA in the disturbed samples was greater than denitrification in the core samples, the measurements were highly correlated (r2 > or = 0.82). The DEA was greater in the bulrush wetlands than the cattail wetlands, 0.516 and 0.210 mg N kg(-1) soil h(-1), respectively; and it increased with the cumulative applied N. The DEA mean was equivalent to 9.55 kg N ha(-1) d(-1) in the bulrush wetlands. We hypothesized and confirmed that DEA was generally limited by nitrate rather than carbon. Moreover, we determined that one of the most influential factors in DEA was wetland water depth. In bulrush wetlands, the slope and r2 values of the control treatment were -0.013 mg N kg(-1) soil h(-1) mm(-1) depth and r2 = 0.89, respectively. Results of this investigation indicate that DEA can be very significant in constructed wetlands used to treat swine wastewater.

Macroinvertebrate community structure and production in a low-gradient stream in an undisturbed watershed

Macroinvertebrate community composition, abundance and production were measured in a sand-bottomed, headwater stream on the Coastal Plain physiographic province in the southeastern U.S.A. The stream's watershed had experienced almost no anthropogenic disturbance for over 100 years and thus the stream represented as close to pristine, reference conditions as occurs in this geographic region. Macroinvertebrates were sampled over one year in the three dominant habitats in the stream: sand sediment, submerged wood and macrophytes (Sparganium americanum). Total taxa richness as well as the taxa richness of Ephemeroptera, Plecoptera, Trichoptera and Chironomidae all were greater than in streams flowing through more disturbed watersheds in the area. Annual mean habitat-specific density and biomass were highest in the sediment; density was lowest on the wood and biomass lowest on Sparganium. Habitat-specific production was 39-42 g m -2 y -1 in the sediment and on wood and 16 g m -2 y -1 on Sparganium. The majority of production in all three habitats was by Chironomidae, which comprised 80-92% of total production in each habitat. Taxa in the collector-gatherer and predator functional feeding groups accounted for the majority of production in the sediment and on wood, whereas filter-feeders were predominant on Sparganium. Whole-stream production, calculated by summing habitat-specific values that had been weighted for habitat availability, was 64 g m -2 y -1 , considerably higher than production in more disturbed streams in the region. About 65 % of the total production occurred in the sediment, 26 % on wood, and 9 % on Sparganium. The tanypod chironomid Conchapelopia had the highest production of any taxon in the stream at 19 g m -2 y -1 . The production to biomass ratio for the macroinvertebrate community was 33.3; ratios for six taxa of chironomids exceeded 100. Along with the higher species richness in this stream, production of macroinvertebrates was at least twice as high as that in nearby streams with more disturbed watersheds. These differences may be attributable to the long time since the last anthropogenic disturbance of the stream's watershed, which has led to a mature forest covering nearly all of the watershed and which has resulted in a more stable stream flow and less disturbance of the sediment during high flow than in streams in more disturbed watersheds.

Effects of logging on macroinvertebrate production in a sand‐bottomed, low‐gradient stream

1. Macroinvertebrate production and macrophyte growth were studied in logged and unlogged sections of a sand‐bottomed, low‐gradient, blackwater stream on the Coastal Plain of Virginia, U.S.A. A section of the catchment had been clear‐cut 3 years prior to sampling. No logging occurred in the upstream area of the catchment, which had experienced almost no land disturbance by humans for over 100 years.2. A primary difference among the logged and unlogged sections of the stream was in the abundance of macrophytes. The combined biomass of Sparganium americanum and of Chara sp. was over 300‐times greater in the logged than the unlogged section.3. Annual macroinvertebrate production in the sediment was higher in the unlogged section (41 g dry mass m–2) than in the logged section (25 g m–2).4. Annual macroinvertebrate production on Sparganium was higher in the logged section (10 g m–2 of plant surface area) than in the unlogged section (6 g m–2). Annual production associated with Chara, which occurred only in the logged section, was 196 g m–2 of stream bottom covered by this plant.5. Whole‐stream annual macroinvertebrate production, calculated by summing habitat‐specific production that was weighted by habitat availability, was greater in the logged section (103 g m–2) than in the unlogged section (41 g m–2). Sediments supported 99% of the annual production in the unlogged section, whereas macrophytes supported 76% in the logged section.6. Much of the additional macroinvertebrate production in the logged section was by collector‐filterers living on macrophytes. Production by collector‐gatherers was also greater in the logged section, whereas production by other functional feeding groups changed little with logging.7. Although logging along high‐gradient, rocky streams also results in increased macroinvertebrate production, that increase often is stimulated by greater periphyton growth rather than the macrophyte growth observed in this low‐gradient stream.

Organic matter retention by macrophyte beds in 2 southeastern USA, low-gradient, headwater streams

AbstractWe examined particulate organic matter (POM) storage and retention in aquatic macrophyte beds (Sparganium americanum Nutt.) from 2, first-order, blackwater tributaries of Tinker Creek, South Carolina, USA. Measurements were made during the autumn (high litter input) and summer (low litter input), in 100-m study reaches, 1 with low macrophyte density (T-1) and 1 with high macrophyte density (T-2). Three experiments assessed: 1) POM retention by individual plant beds, 2) short-term retention of leaf analogs in plant beds and by other retention structures, and 3) benthic and transported POM at the reach scale. Upon completion, all above ground macrophyte biomass was removed and the experiments were repeated. At the scale of 1 bed, low plant density effectively trapped and stored POM in summer and autumn. High-density beds stored POM in the summer but during autumn POM output exceeded input. At the reach scale, both tributaries effectively retained coarse POM in summer, but only high-density beds did ...

Actinomycete-flora associated with submersed freshwater macrophytes

Aquatic vegetation from three stream sites located within the US Department of Energy's Savannah River Site, South Carolina was sampled to determine the presence, distribution and diversity of actinomycetes on submersed macrophytes. At individual sampling sites, small pieces of submersed aquatic plants ( Sparganium americanum, Ranunculus pusillus and Microanthemum umbrosum) were clipped and placed in sterile sampling containers. In the laboratory, plant fragments were subjected to a wide array of selective measures (5 pretreatments×8 media×2 antibiotic regimes×2 temperatures) in order to obtain the greatest diversity and best isolation methods. A total of 433 actinomycete colonies was isolated, which included 32 distinct strains. The streams, plants and plant tissue types (healthy, necrotic or dead) all had an effect on the presence, distribution and diversity of the actinomycetes.

Actinomycete-flora associated with submersed freshwater macrophytes

Aquatic vegetation from three stream sites located within the US Department of Energy's Savannah River Site, South Carolina was sampled to determine the presence, distribution and diversity of actinomycetes on submersed macrophytes. At individual sampling sites, small pieces of submersed aquatic plants (Sparganium americanum, Ranunculus pusillus and Microanthemum umbrosum) were clipped and placed in sterile sampling containers. In the laboratory, plant fragments were subjected to a wide array of selective measures (5 pretreatments×8 media×2 antibiotic regimes×2 temperatures) in order to obtain the greatest diversity and best isolation methods. A total of 433 actinomycete colonies was isolated, which included 32 distinct strains. The streams, plants and plant tissue types (healthy, necrotic or dead) all had an effect on the presence, distribution and diversity of the actinomycetes.

Metal concentrations in aquatic macrophytes as influenced by soil and acidification

Bioavailability of metals to aquatic plants is dependent on many factors including ambient metal concentration, pH of soil or water, concentration of ligands, competition with other metals for binding sites, and mode of exposure. Plants may be exposed to metals through water, air, or soil, depending on growth form. This paper examines the influence of soil type under two regimens of water acidification on metal uptake by four species of aquatic macrophytes: smartweed (Polygonum sagittatum), burreed (Sparganium americanum), pondweed (Potamogeton diversifolius), and bladderwort (Utricularia vulgaris) in constructed, experimentally acidified wetlands. Soil types consisted of a comparatively high-metal clay or a lower-metal sandy loam. Each pond was either acidified to pH ca. 4.8–5.3 or allowed to remain circumneutral. Metal concentrations tended to be higher in the submerged bladderwort and pondweed than in the emergent burreed and smartweed. Soils were important to plant metal concentrations in all species, but especially in the emergents. Acidification influenced plant concentrations of some metals and was especially important in the submerged pondweed. Bioaccumulation of metals occurred for Mn, B, Sr, Ba, and Zn, compared to soil concentrations.

Microtopographic Heterogeneity and Floristic Diversity in Experimental Wetland Communities

1 Coexistence is thought to be facilitated in heterogeneous environments due to interspecific differences in habitat preference. Microtopographic heterogeneity is a major factor structuring natural freshwater wetland communities and is thought to influence diversity. I tested whether interspecific differences existed in habitat preference for different microtopographic positions and whether diversity was associated with small-scale spatial microtopographic heterogeneity in experimental wetland communities. 2 I manipulated microtopographic heterogeneity to produce 'homogeneous' (flat surface) and 'heterogeneous' (hummock-hollow) treatments. Three propagule source treatments (seed bank, seeds, seed bank + seeds) were incorporated to determine if responses to heterogeneity depended on the propagule source. Habitat preferences for microhabitats within heterogeneous treatments were determined for each species by recording the number of individuals located on 'hummocks' or in 'hollows'. Responses to heterogeneity and propagule source were quantified by measuring richness, evenness, species abundances and above-ground biomass. 3 Small-scale variability in microtopography, on the order of 1-3 cm, produced highly significant differences in plant community structure. Both components of floristic diversity, species richness and evenness, were consistently greater in communities with heterogeneous microtopography. 4 Community composition, abundance of individuals and above-ground biomass responded differentially to heterogeneity and propagule source. Most species reached greater abundances in heterogeneous environments than homogeneous environments; however, species that were similarly abundant in both included Eleocharis ovata, Alisma triviale and Sparganium americanum. 5 Most species growing within the heterogeneous environments showed distinct habitat preferences for hummock or hollow microhabitats, with many rarer species, particularly woody perennials, favouring hummocks.