''Egeria densa'', the large-flowered waterweed
or Brazilian waterweed, is a species of ''
Egeria'' native to warm temperate South America in southeastern
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
,
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
,
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
and
Uruguay
Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...
.
It is considered a problematic
invasive species due to its use in home aquariums and subsequent release into non-native ecosystems.
Description
![Egeria flower](https://upload.wikimedia.org/wikipedia/commons/e/eb/Egeria_flower.jpg)
''Egeria densa'' is an aquatic plant growing in water up to deep, with trailing stems to or more long, producing
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
s at intervals along the
stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushro ...
. The leaves are produced in whorls of four to eight, long and broad, with a pointed leaf tip. The stem system of the plant will grow until it reaches the surface of the water, where it will begin to spread out, creating a thick flower
canopy
Canopy may refer to:
Plants
* Canopy (biology), aboveground portion of plant community or crop (including forests)
* Canopy (grape), aboveground portion of grapes
Religion and ceremonies
* Baldachin or canopy of state, typically placed over an ...
that blocks light from reaching plants below it.
It is
dioecious
Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...
, with male and female flowers on separate plants; the flowers are diameter, with three broad, rounded, white petals, long on male plants, and long on female plants.
[Flora of NW Europe]
''Egeria densa''
/ref>[Flora North America]
''Egeria densa''
/ref>[Jepson Flora]
''Egeria densa''
/ref>[Washington Department of Ecology]
/ref>
Life cycle
''Egeria densa'' typically displays little variation in growth patterns throughout the year when grown in tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
environments; however, when grown in more moderate environments the plant spends most of its energy on starch production and storage in the winter and canopy growth during the summer season
Habitat and ecology
Location
''Egeria densa'' is native to Argentina, Brazil, Amerika, Chile and Uruguay.[ As a result of its popularity in ]aquarium
An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...
s the plant has now spread to North America, Europe, Asia, Australia, New Zealand, and Africa.
Temperature
Temperature is important to the growth of ''Egeria densa;'' however, its growth is mostly stable in temperatures ranging from , with an upper temperature limit of that results in reduced shoot growth and photosynthetic
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...
output. Colder temperatures will limit growth of the plant and can be used as a method of controlling its spread in non-native ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s.
Lighting
''Egeria densa'' is able to match photosynthetic output to available light like many macrophyte species. The species' ability to thrive in low light conditions and its ability to form a dense canopy makes it a very successful invader compared with other macrophytes, resulting in a reduction in the diversity
Diversity, diversify, or diverse may refer to:
Business
*Diversity (business), the inclusion of people of different identities (ethnicity, gender, age) in the workforce
*Diversity marketing, marketing communication targeting diverse customers
* ...
of plant species where it is introduced.
Cultivation and uses
''Egeria densa'' is a popular aquarium plant, but is no longer sold in some areas due to its invasive potential. Plants in cultivation are all a male clone, reproducing vegetatively.[
It grows well in the cooler aquarium and is suitable for the beginner. It is easily propagated by cuttings. According to reports it secretes ]antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...
substances which can help prevent blue-green algae
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...
. It grows best in a nutrient-rich, high light environment, but has shown an ability to outcompete other species when it is introduced.
Economics
''E. densa'', like other macrophytes, are effective when used in wastewater
Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industr ...
treatment plants due to the same factors that make it a potential invasive plant; mainly its ability to uptake nutrients, and sedimentation of particles from the water column.
Invasive species
''Egeria densa'' has escaped from cultivation and become naturalized and invasive in many warm temperate to subtropical regions of the world, including Europe, southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number of ...
, Asia, Australia, New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, New Caledonia
)
, anthem = ""
, image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg
, map_alt = Location of New Caledonia
, map_caption = Location of New Caledonia
, mapsize = 290px
, subdivision_type = Sovereign st ...
and North America.[ In the United States it occurs from ]New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
south to Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
and west to California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
and Oregon
Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
. In the Sacramento-San Joaquin Delta of California, it was introduced in the 1960s and has since had a significant adverse impact on the local ecosystem. The plant currently infests , or 12% of the total surface area of the delta, along with other states and even as far north as Canada. Recently, ''E. densa'' was reported as naturalized alien species in Iceland
Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
where it invaded the naturally heated water bodies. Due to its occurrence in northern Iceland, ''E. densa'' is one of the first freshwater alien plant species that reached the Arctic. Most of its impact occurs in the shallow waterways; the plant forms thick mats that obstruct boat passage, clog water intakes and aqueducts, trap sediments, crowd out native vegetation, and impede the migration of anadromous
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...
fish.[California Department of Boating and Waterways]
Aquatic Pest Control
Role as ecosystem engineer
Though it is sometimes debated, ''E. densa'' is referred to as an ecosystem engineer
An ecosystem engineer is any species that creates, significantly modifies, maintains or destroys a habitat. These organisms can have a large impact on species richness and landscape-level heterogeneity of an area. As a result, ecosystem enginee ...
as a result of the impact it has on a environment once it is introduced. Some of these impacts are due to its fast growth and high dispersal rate when fragmented, its ability to adapt to different light and nutrient availability, its uptake of nutrients from the water column and its effect on sedimentation of these nutrients, and the large light-blocking canopy that its flowers form at the surface of the water.
''Egeria densa'' is also responsible for changing the amount of phytoplankton
Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
present in the water column due to limiting light availability from the dense canopy
Canopy may refer to:
Plants
* Canopy (biology), aboveground portion of plant community or crop (including forests)
* Canopy (grape), aboveground portion of grapes
Religion and ceremonies
* Baldachin or canopy of state, typically placed over an ...
that it forms, and from the amount of nutrients that removes from the water column. It can, however, also function as shelter for zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
and smaller invertebrates.
Black-necked swan
The black-necked swan (''Cygnus melancoryphus'') is a species of waterfowl in tribe Cygnini of subfamily Anserinae.HBW and BirdLife International (2021) Handbook of the Birds of the World and BirdLife International digital checklist of the bir ...
s feed on the plant, and decline of ''E. densa'' has been linked to the decline of swan populations.[
]
Control
A variety of methods are needed to ensure that growth of ''E. densa'' is stopped due to its ability to regrow when fragmented through mechanical means. The best way is to remove the plant in entirety from the water column
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...
or use herbicides to kill the plant. One of the potential solutions to the problem are water drawdowns, as the plant is very sensitive to drying out and the plant can die in as short as an hour when removed from water. In addition cold weather has been found to be effective in controlling the plant, though this has practical limitations. When herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
s were applied to the plant, the levels of phosphorus and nitrogen increased but not greatly, suggesting that most of the nutrients remained in the plant biomass and did not reabsorb into the water column.
References
External links
Species Profile – Brazilian waterweed (''Egeria densa'')
National Invasive Species Information Center, United States National Agricultural Library
The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...
.
{{Taxonbar, from=Q163649
Hydrocharitaceae
Freshwater plants
Aquarium plants
Dioecious plants