Cabomba Research Articles

Survival of cabomba (Cabomba caroliniana) during lake drawdown within mounds of stranded vegetation

Control of submerged aquatic vegetation during drawdown is known to be hindered by mounds of stranded vegetation that protect underlying stems from desiccation. This study investigated the viability of stranded cabomba (Cabomba caroliniana) during a winter drawdown of Lake Benalla, Victoria, Australia. The viability of stems and crowns, determined by their ability to generate new shoots, was related to substrate exposure status, location in lake, mound height, and soil moisture, at 34 and 69 days after exposure (DAE). Stem viability at 34 and 69 DAE was most closely associated with exposure status, where ∼20% of stems under mounds on relatively dry substrate were viable, compared to ∼95% of stems under mounds on saturated substrate, and 92% of unexposed stems. Stem viability was similar when collected 34 and 69 DAE and was similar under naturally occurring mounds of differing thickness. In contrast, viability of exposed crowns was usually 40% or less, compared to 72% for unexposed crowns, and their viability was not influenced by substrate moisture. Instead, their viability was influenced by location in the lake and was proportional to mound thickness. Like stems, viability of crowns did not decrease over the duration of the drawdown. We concluded that for drawdown to be effective in minimizing viable stems, the substrate below them needs to dry out. Even then, viable crowns may be a source of recolonization.

Cabomba caroliniana A. Gray 1837: A new, alien and potentially invasive species in Serbia

During field studies of the vegetation in the canal network of the Hydro-System Danube-Tisa-Danube in Serbia, in 2008, 2011 and 2012, populations of Cabomba caroliniana A. Gray 1837 were recorded. Cabomba caroliniana was not previously recorded in the aquatic vegetation in Serbia. It is a popular aquarium plant native to South America (Brazil, Uruguay, Paraguay, and northeastern Argentina) and, according to some authors, to southeastern United States. It was introduced into the rest of the USA, Canada, Australia, Asia (China, Malaysia, India, Japan), and in many regions of its new range it is considered an invasive and noxious aquatic weed. In Europe, it was found in the United Kingdom (introduced to England), Belgium, the Netherlands, and Hungary. Newly recorded populations in Serbia are restricted to the canals in Backa. Populations are established only on two localities (Mali Stapar and Odzaci).

The aquarium trade: A potential risk for nonnative plant introductions in Connecticut, USA

The aquarium trade has been shown to be a source for introductions of nonnative aquatic macrophyte species. Improvements are needed in identification, labeling, and retailer awareness of banned aquatic plants. In the state of Connecticut, United States, 20 nonnative macrophytes are banned from sale by state statute. At least 13 of these species are already established in the state's lakes, while the remainder are either present in near-shore wetlands or absent but thought to be capable of naturalizing. We documented the sale of banned plants in the Connecticut aquarium trade by visiting 23 retailers in 2008 and 47 retailers in 2010. Plants that resembled Connecticut's banned species were purchased and identified using standard morphological techniques. In 2010, we also employed DNA sequencing to aid in plant identification. We found that nearly 30% of stores sold banned aquatic plants including Cabomba caroliniana, Egeria densa, Myriophyllum aquaticum, and Myriophyllum heterophyllum. Cabomba caroliniana represented more than half of the banned species being sold; it was found in 17% of the stores in 2008 and 19% of the stores in 2010. Egeria densa was mislabeled 50% of the time as Egeria najas or Anacharis najas; it was sold in 11% of the stores in 2008 and 17% of the stores in 2010. In 2010, Myriophyllum specimens from 6 stores were unidentifiable using morphological characteristics. Using these techniques, one of the specimens was identified as Myriophyllum heterophyllum. Of the 29 chain stores surveyed, 7% sold banned species compared to 56% of the 27 independent stores.

Freshwater plants synthesize sulfated polysaccharides: heterogalactans from Water Hyacinth (Eicchornia crassipes).

Sulfated polysaccharides (SP) are found mainly in seaweeds and animals. To date, they have only been found in six plants and all inhabit saline environments. Furthermore, there are no reports of SP in freshwater or terrestrial plants. As such, this study investigated the presence of SP in freshwaters Eichhornia crassipes, Egeria densa, Egeria naja, Cabomba caroliniana, Hydrocotyle bonariensis and Nymphaea ampla. Chemical analysis identified sulfate in N. ampla, H. bonariensis and, more specifically, E. crassipes. In addition, chemical analysis, FT-IR spectroscopy, histological analysis, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDXA), as well as agarose gel electrophoresis detected SP in all parts of E. crassipes, primarily in the root (epidermis and vascular bundle). Galactose, glucose and arabinose are the main monosaccharides found in the sulfated polysaccharides from E. crassipes. In activated partial thromboplastin time (APTT) test, to evaluate the intrinsic coagulation pathway, SP from the root and rhizome prolonged the coagulation time to double the baseline value, with 0.1 mg/mL and 0.15 mg/mL, respectively. However, SP from the leaf and petiole showed no anticoagulant activity. Eichornia SP demonstrated promising anticoagulant potential and have been selected for further studies on bioguided fractionation; isolation and characterization of pure polysaccharides from this species. Additionally in vivo experiments are needed and are already underway.

Invasion and Distribution of <I>Cabomba caroliniana</I> in Wetlands of Jiangsu, China*

Invasion and Distribution of <I>Cabomba caroliniana</I> in Wetlands of Jiangsu, China*

2A2-R01 水草の光合成活性測定システム : (第1報)光合成による二酸化炭素吸収量の見積(バイオマニピュレーション)

In this paper, we report a measurement method of photosynthesis activity for water plants. In the photosynthesis process, the plants absorb carbon dioxide (CO_2) and release carbohydrates and oxygen. The pH value of the water containing plants surely fluctuates through photosynthetic process. As CO_2 is readily soluble in water and decrease pH values, the pH value could be reflect photosynthesis and respiration of the water plants. To quantify the small changes of the pH values, we applied automatic pH measurement system consisting of ion-sensitive field effect transistor (ISFET) sensor that we have previously reported. The pH value in the test tank containing a water plant, cabomba caroliniana, increased 0.840 pH after 4 hours light irradiation. The result indicates that the CO_2 absorption of the plant during photosynthesis could be referred by the pH measurement.

Effects of submerged tropical macrophytes on flow resistance and velocity profiles in open channels

In this paper, the results of flume experiments are presented, conducted to investigate the effect of different submerged flexible plant species on flow resistance and flow patterns in open channels. Three common plant types in tropical regions were selected: Cabomba caroliniana, a quite flexible fully submerged species; Echinodorus grandiflorus, a somewhat less flexible, fully submerged species; and Nymphaea rubra, a rooted species with floating leaves. For each plant type, three different densities were tested for various discharges, water depths, and depths of plant submergence. The flow resistance was expressed in terms of the commonly used Manning coefficient n. The results indicate that among the particular plant species investigated here, the floating leaf species N. rubra exhibits the lowest flow resistance (Manning's n = 0.014), viz. less than half the values for C. caroliniana and E. grandiflorus, respectively. A detailed analysis showed that this is due to the particular plant morphology, consisting of relatively large biomass (floating leaves) with only small stem density. It was observed that the flow resistance not only strongly and inversely depends on the Reynolds number, but also on the degree of plant submergence (i.e. water depth/deflected plant height ratio), and on the density of the vegetated plant beds. It appears that the biomass/drag force ratio seems of less importance. From the measured velocity profiles, the influence of the various types of vegetation species could clearly be observed. These factors are important for the design and management of vegetated open channels in tropical urban areas like Singapore.

Prospects for the Biological Control of Submerged Macrophytes in South Africa

Historically, biological control efforts against aquatic plants in South Africa have focused on floating species, and as a result, there has been a dearth of research into the invasion and control of submerged macrophytes. With numerous submerged invasive species already established in South Africa, thriving horticultural and aquarium industries, nutrient-rich water systems, and a limited knowledge of the drivers of invasions of submerged macrophytes, South Africa is highly vulnerable to a second phase of aquatic plant problems. Experience gained in the U.S.A. on biological control against submerged weeds, such as hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) and spiked/Eurasian watermilfoil, Myriophyllum spicatum L. (Haloragaceae), have provided South African researchers with the necessary foundation to initiate programmes against these weeds. Research in South Africa is currently focused on pre-release studies on the biological control of H. verticillata, using an undescribed fly, Hydrellia sp. (Diptera: Ephydridae) and a weevil, Bagous hydrillae O'Brien (Coleoptera: Curculionidae); and on M. spicatum using a North American weevil, Euhrychiopsis lecontei Dietz (Coleoptera: Curculionidae). Feasibility studies into biological control of some incipient submerged weeds are also being conducted, including Brazilian water weed, Egeria densa Planch. (Hydrocharitaceae), Canadian water weed, Elodea canadensis Mitch. (Hydrocharitaceae) and cabomba, Cabomba caroliniana A.Gray (Cabombaceae). Progress with, and potential constraints that may limit these programmes, are discussed.

Induced chemical defenses in a freshwater macrophyte suppress herbivore fitness and the growth of associated microbes

The freshwater macrophyte Cabomba caroliniana induces a chemical defense when attacked by either the crayfish Procambrus clarkii or the snail Pomacea canaliculata. Induction by either consumer lowers the palatability of the plant to both consumers. When offered food ad libitum, snails feeding on non-induced C. caroliniana grew 2.6-2.7 times more than those feeding on induced C. caroliniana. Because snails fed less on induced plants, this could be a behavioral effect (reduced feeding), a physiological effect of the induced metabolites on the consumer, or both. To assess these possibilities, we made artificial diets with lipid extracts of induced versus non-induced C. caroliniana and restricted control snails to consuming only as much as treatment snails consumed. Growth measured as shell diameter was significantly lower on the diet containing extract from induced, as opposed to non-induced, plants; change in snail mass was more variable and showed a similar, but non-significant, trend. Thus, snails may reduce feeding on induced plants to avoid suppression of fitness. The induced defenses also suppressed growth of co-occurring microbes that might attack the plant through herbivore-generated feeding scars. When two bacteria and three fungi isolated from C. caroliniana surfaces were cultured with the lipid extract from induced and non-induced C. caroliniana, both extracts inhibited the microbes, but the induced extract was more potent against three of the five potential pathogens. Thus, induced plant defenses can act against both direct consumers and microbes that might invade the plant indirectly through herbivore-generated wounds.

Submersed Aquatic Vegetation of the Jean Lafitte National Historical Park and Preserve

The Barataria Preserve unit of Jean Lafitte National Historical Park and Preserve is located in wetlands of the upper Barataria-Terrebonne estuary near New Orleans, LA and subject to perturbations that affect aquatic resources. A study of submersed aquatic vegetation (SAV) was conducted to determine community composition, distribution, and abundance. Seven native species—Cabomba caroliniana, Ceratophyllum demersum, Heteranthera dubia, Najas guadalupensis, Potamogeton pusillus, Vallisneria americana, and Zannichellia palustris—and three exotic species—Egeria densa, Hydrilla verticillata, and Myriophyllum spicatum—were present. The highly invasive, exotic, floating fern Salvinia molesta was also present. The Preserve is affected by a coastal restoration project designed to return Mississippi River flow to the upper Barataria Estuary. Preserve SAV did not conform to the general estuarine management paradigm of decline and loss with nutrient introductions. Instead, freshwater dominated the Preserve, and sufficient light was present to support robust SAV growth in ponds, canals, and Lake Cataouatche. Native and exotic species formed large surface mats that clogged waterways. Vallisneria americana may be decreasing due to the increase in nuisance SAV and floating plants.This study is the first of its kind for any wetland habitat in the states of the Northern Gulf Coast and therefore will be an important baseline to future studies both generally and specifically for the Preserve as Louisiana's coastal wetland waterways experience change brought on by the general coastal wetland loss from sea level rise and efforts to restore the wetlands.

Emerging invasive alien plants for the Mediterranean Basin

A major step in tackling invasive alien plants consists of identifying those species that represent a future threat to managed and unmanaged habitats. The European and Mediterranean Plant Protection Organization reviews and organizes data on alien plants in order to build an early warning system. A prioritization system is being developed to select species that represent emerging threats and require the most urgent pest risk analysis to implement preventive measures and to perform eradication and management measures. Attention has been drawn to the Mediterranean Basin which is particularly vulnerable because its climatic conditions potentially allow the establishment of sub‐tropical and tropical species. Surveys and rapid assessments of spread and impact have allowed identification of emerging invasive alien plants for Mediterranean countries: Alternanthera philoxeroides (Amaranthaceae), Ambrosia artemisiifolia (Asteraceae), Baccharis halimifolia (Asteraceae), Cortaderia selloana (Poaceae), Eichhornia crassipes (Pontederiaceae), Fallopia baldschuanica (Polygonaceae), Hakea sericea (Proteaceae), Humulus japonicus (Cannabaceae), Ludwigia grandiflora and L. peploides (Onagraceae), Hydrilla verticillata (Hydrocharitaceae), Microstegium vimineum (Poaceae), Myriophyllum heterophyllum (Haloragaceae), Pennisetum setaceum (Poaceae), Pistia stratiotes (Araceae), Salvinia molesta (Salviniaceae), Solanum elaeagnifolium (Solanaceae). These species represent priorities for action. Some other species are placed on the observation list, as available information does not allow them to be counted among the worst threats: Akebia quinata (Lardizabalaceae), Araujia sericifera (Apocynaceae), Delairea odorata (Asteraceae), Cabomba caroliniana (Cabombaceae), Nassella neesiana, N. tenuissima and N. trichotoma (Poaceae), Sesbania punicea (Fabaceae), and Verbesina encelioides (Asteraceae).

The aquarium and horticultural industry as a pathway for the introduction of aquatic invasive species—outreach initiatives within the Great Lakes basin

The transfer and spread of aquatic invasive species (AIS) is one of the most pressing issues facing aquatic ecosystems worldwide. The aquarium and horticultural industry is increasingly being recognized as a significant avenue for the introduction of non-indigenous aquatic species, a pathway which is increasing in risk due to steady growth in these industries. Some of the world's worst AIS have been associated with aquarium or horticultural release and at least 12 exotic species have been introduced into the Great Lakes basin via this route. Ongoing public education initiatives throughout the Great Lakes basin documented over 250 stores selling known AIS. Most commonly, the invasive Goldfish, (Carassius auratus), Koi (Cyprinus carpio), and Cabomba (Cabomba caroliniana) were observed, respectively occurring 80%, 62%, and 49% of the time. The introduction of these and other aquarium and horticultural species have or may have significant impacts on aquatic ecosystems. Details of these outreach initiatives will be presented here, outlining the availability of AIS and other non-native species and their potential to become invasive. The direct release of aquarium and horticultural organisms is not well regulated in Canada and surveys have found that individuals admit to disposing of unwanted plants and animals into the wild. With few regulations controlling the importation and sale of non-indigenous species, and in considering their widespread availability, intentional or unintentional release by the public is inevitable. Thus, public education is integral in preventing the introduction and spread of AIS yet currently falls short of educating consumers of the threats posed by their release. The relatively unrestricted movement of exotic plants and animals through international markets necessitates a more coordinated national, regional, and international approach to identifying risks posed by non-indigenous species and actions to control their introduction and spread.

Modelling spread of the invasive macrophyte Cabomba caroliniana

Summary1. Predicting spread of non‐indigenous species requires an understanding of where propagules are being transported, and whether these propagules can survive in the novel habitat and successfully integrate into the recipient community. In this study, we model potential spread of invading Cabomba caroliniana in Ontario, Canada, using a combination of passive and active dispersal models coupled with an environmental suitability model, thereby considering the first two stages of the invasion process.2. Measures of propagule pressure incorporated both human‐mediated dispersal via trailered boats, and advective flow from invaded to non‐invaded systems, while habitat suitability was forecasted by combining native and global data sets and using boosted regression trees.3. Risk of invasion differed depending on the combination of approaches used and the time period considered. Three lakes appear to be at greatest risk owing to a combination of high boater and water movement from invaded sources, and high environmental suitability. The best predictors of lake suitability were pH, mean lake temperature and dissolved calcium concentration. Hundreds of lakes in Ontario may be suitable for establishment of Cabomba, highlighting the need for vector management.

The Biology of Invasive Alien Plants in Canada. 7. Cabomba caroliniana A. Gray

The freshwater aquatic plant Cabomba caroliniana, or fanwort, was recently reported in a lake northeast of Peterborough, Ontario, where it has successfully established and survived winter conditions since at least 1991. This is the first documented occurrence of fanwort becoming naturalized in Canada. Fanwort is a popular aquarium plant that is native to South America and possibly the southeastern United States and has been introduced in several Asian, Pacific and European countries through the discarding or deliberate planting of aquarium plants in natural waterways. It is particularly invasive in China, Japan and Australia, and in parts of the United States, where its range is spreading. Fanwort grows rapidly and forms dense stands that clog waterways, impeding flow, obstructing navigation, altering fish habitat and excluding other vegetation. It does not produce mature seed in the northern parts of its North American range, but can multiply clonally and spread quickly by stem fragmentation. It produces turion-like stems at the end of the growing season, which assist in over-wintering under adverse conditions. Fanwort is difficult to control with herbicides and is resistant to mechanical management techniques as populations can quickly re-establish from plant fragments. Populations near the Trent-Severn Waterway in Canada are extensively established and management tools are not available to attempt eradication. An integrated management plan that focuses on early detection and rapid response in surrounding water bodies may succeed in mitigating the economic and environmental impacts and limiting the spread of fanwort. Key words: Cabomba caroliniana, fanwort, cabomba de Caroline, CABCA, aquatic plant, weed biology, invasive alien

The Impacts of the Non-native Macrophyte Cabomba caroliniana on Littoral Biota of Kasshabog Lake, Ontario

An established population of Cabomba caroliniana now covers extensive littoral areas in the shallow waters of Kasshabog Lake (Ontario). This is the first known naturalized population of this non-native aquatic macrophyte, commonly called fanwort, on the Canadian side of the Great Lakes basin, despite the fact that it was first reported in the 1930s. High dispersal potentials combined with the ability to adapt and grow in a range of environmental conditions have made C. caroliniana a nuisance species in Australia, Japan, and parts of the United States. However, little is known about the broader ecological implications of its introduction and establishment. Using a survey approach, we conducted a preliminary assessment of water chemistry, macrophyte, epiphytic algae, and macroinvertebrate communities found in C. caroliniana beds and compared them with native macrophyte beds in Kasshabog Lake. Light penetration was significantly reduced in the C. caroliniana beds and was the only sampled physio-chemical parameter that differed between bed types. We also found several notable differences in the structure and composition of biological communities within macrophyte beds. While native macrophytes were present in dense C. caroliniana beds, abundance was considerably low and unevenly distributed. Significantly more epiphytic algae was present on C. caroliniana plants, however community composition was comparable with epiphytic algae found on native macrophytes. The taxonomic composition of macroinvertebrates was similar between C. caroliniana and native beds, while abundance was substantially higher in C. caroliniana beds, owing to high densities of coenagrionids and chironomids. These differences suggest that C. caroliniana is changing macrophyte community composition in this lake, having an impact on epiphytic algae, and creating a new habitat for some macroinvertebrates. Further studies are required to determine the extent of these ecological impacts.

Predicting the response of Cabomba caroliniana populations to biological control agent damage

Abstract Cabomba caroliniana is a submerged aquatic plant from South America that is becoming a serious weed worldwide. It spreads by seed and by fragmentation and has an extremely wide climatic range, invading lakes and ponds from tropical (Darwin, Australia: latitude 12°) to cold temperate regions (Peterborough, Canada: latitude 45°). There are currently no effective methods of managing cabomba infestations and funding has been allocated to research biological methods. Surveys have examined cabomba in its native range and have identified several potential biological control agents. The most promising are a stem boring weevil (Hydrotimetes natans) and an aquatic moth (Paracles spp.). Here we predict the change in cabomba populations after the introduction of the biological control agents. Our predictions are based on quantitative surveys of cabomba populations at three lakes in south‐east Queensland, qualitative observations of cabomba in its native range, and conceptual knowledge of how the realised niche of cabomba might be affected by herbivore damage.

Phylogeny and divergence of basal angiosperms inferred from APETALA3- and PISTILLATA-like MADS-box genes.

The B-class MADS-box genes composed of APETALA3 ( AP3) and PISTILLATA ( PI) lineages play an important role in petal and stamen identity in previously studied flowering plants. We investigated the diversification of the AP3-like and PI-like MADS-box genes of eight species in five basal angiosperm families: Amborella trichopoda (Amborellaceae); Brasenia schreberi and Cabomba caroliniana (Cabombaceae); Euryale ferox, Nuphar japonicum, and Nymphaea tetragona (Nymphaeaceae); Illicium anisatum (Illiciaceae); and Kadsura japonica (Schisandraceae). Sequence analysis showed that a four amino acid deletion in the K domain, which was found in all previously reported angiosperm PI genes, exists in a PI homologue of Schisandraceae, but not in six PI homologues of the Amborellaceae, Cabombaceae, and Nymphaeaceae, suggesting that the Amborellaceae, Cabombaceae, and Nymphaeaceae are basalmost lineages in angiosperms. The results of molecular phylogenetic analyses were not inconsistent with this hypothesis. The AP3 and PI homologues from Amborella share a sequence of five amino acids in the 5' region of exon 7. Using the linearized tree and likelihood methods, the divergence time between the AP3 and PI lineages was estimated as somewhere between immediately after to several tens of millions of years after the split between angiosperms and extant gymnosperms. Estimates of the age of the most recent common ancestor of all extant angiosperms range from approximately 140-210 Ma, depending on the trees used and assumptions made.

Food Habits and Selective Foraging by the Texas River Cooter (Pseudemys texana) in Spring Lake, Hays County, Texas

The fall-winter food habits of the Texas river cooter (Pseudemys texana) were investigated at Spring Lake, Hays County, Texas, by examination of stomach contents. Samples were collected from 33 live turtles by flushing stomach contents with water (Fields et al., 2000). Four aquatic macrophytes composed 91.6% of the diet. Aquatic macrophyte availability at Spring Lake was estimated using the Daubenmire technique (Daubenmire and Daubenmire, 1968) and compared to occurrence in the diet to assess selectivity in foraging. Cooters actively selected Carolina fanwort (Cabomba caroliniana), a plant low in fiber and high in total digestible nutrients. Hydrilla (Hydrilla verticilata), an invasive exotic aquatic plant, was an important food item due to the large amount present in the lake. The Texas river cooter, Pseudemys texana (Ward 1984), is a freshwater basking turtle of the family Emydidae. It is endemic to the Brazos, Colorado, Guadalupe, and San Antonio river basins of central and south Texas. Rivers, streams, and nearby ponds, especially those with abundant aquatic vegetation and basking sites, are preferred habitats ((??)Vermersch, 1992). It also is found in man-made impoundments, irrigation ditches, canals, and cattle tanks (Carr, 1952). Prior to Seidel and Smith (1986), some species of Pseudemys were included in the genus Chrysemys (Carr, 1952; McDowell, 1964; Zug, 1966; Weaver and Rose, 1967). In addition, P. texana was included within other species of Pseudemys, until it was recognized as a distinct species by Ward (1984). An early study of the food habits of P. texana (Strecker, 1927) found only mollusks (Sphaerium sp., Planorbis sp., and Lymnaea sp.) in the digestive tracts. Young P. texana have been observed to pursue insects, crayfish, and other invertebrates ((??)Vermersch, 1992). Other members of the genus are presumed to consume more invertebrates when young and become less carnivorous with maturation (Ernst and Barbour, 1989; Vermersch, 1992; Ernst et al., 1994). In general, P. texana is considered to be herbivorous when mature, although quantitative analysis of the diet is lacking. Analysis of stomach contents can provide informa- tion about which food items are palatable, nutritious, or abundant in the environment (Ward and Keith, 1962). Many herbivores have been shown to select plants based on their nutrient content (Gwynne and Bell, 1968). Consumption of a dietary component dispropor- tionate to its availability in the environment would suggest selectivity in foraging (Johnson, 1980). Al- though, the nutritional quality of plants is important to herbivores, important food plants also may be eaten in proportion to their availability without selection. Knowledge of food habits and foraging selectivity of P. texana is essential to the thorough understanding of how this species functions within its habitat and how it may influence the structure of the ecosystem. The objectives of this study were to describe the fall-winter food habits of P. texana at Spring Lake, Hays County, Texas; to determine if P. texana foraged selectively by comparing usage to availability in the environment; and to compare the nutritional quality of major components of the diet.

Macrophyte vegetation of Danube canals in Kiskunság (Hungary)

South of Budapest an irrigation and drainage canal system extends from the left bank of the main river into the Kiskunsag area. The canals differ in size, discharge and salinity. Management includes mowing of aquatic vegetation and dredging. Macrophyte surveys were carried out in part of the main canal (Dunavolgyi-focsatornat), in the medium-sized Harmincas-Canal, and in the smaller Apaji-Canal. The main canal receives its water directly from the Danube River. Water flow is slow, there is no shading by riparian vegetation and the water is rich in nutrients, but usually clear. Water temperatures are relatively high in summer and are beneficial for species like Ceratophyllum demersum, C. submersum, Trapa natans, Cabomba caroliniana and Najas marina. For the first time a floristic-ecological characterization was possible for part of the canal system. The occurrence of the neophyte C. caroliniana, and the high species richness found in the canals make them interesting and valuable habitats for the aquatic vegetation, despite their anthropogenic origin.

The distribution characteristics and invasive route of Cabomba caroliniana in China

Cabomba caroliniana is a perennial aquatic plant which was originally distributed in North and South America. During investigation in wild fields, it has been found to be a naturalized species. Many actual surveys have been carried out in eastern, southern and central China, including over 300 investigation plots in more than 80 counties (cities) of 10 provinces (municipalities). The results showed that 67 spots had cabomba. At present, the distribution of cabomba in China is restricted to networks of rivers and small lakes in the Hangjiahu Plain (N. Zhejiang), the Ningshao Plain (N.Zhejiang), the drainage area of Taihu Lake (S. Jiangsu), and Diangshanhu (W. Shanghai), with the range of latitude from 29°33′7″ N to 31°35′2″ N. C. caroliniana often occurs in small rivers and lakes whereever the main water bodies are fit for its habitation. Considering that its seeds lack mature embryos and the fronds are susceptible to dehydration, cabomba was probably introduced as an aquarium ornamental plant into China and then escaped. There are 21 species of aquatic plants, belonging to 18 genera and 8 families, in water bodies inhabited by cabomba, and most of plants co existing with cabomba are Ceratophyllum demersum (percentage of co appearance, PC =51.33%), Vallisneria natans ( PC =45.05%), Hydrilla verticillata ( PC =36.56%) and Potamogeton crispus ( PC =35.64%), which implies communities with these plants are easily invaded by cabomba. Cabomba is the dominant species in some investigation spots, while other populations are just beginning to be established, indicating that cabomba is now dispersing further. Considering the similarity of environment and climate of its native place, cabomba could be capable of spreading over a large range in China. If we do not bear the fast painful lessons produced by the Eichhornia crassipes in mind, we will surely repeat the same mistake.