User:Phhutchi/sandbox

Egeria densa (syn. Anacharis densa (Planch.) Vict., Elodea densa (Planch.) Casp.; Large-flowered Waterweed[1] or Brazilian Waterweed') is a species of Egeria'' native to warm temperate South America in southeastern Brazil, Argentina, and Uruguay.[2] It is considered a problematic invasive species due to its use in home aquariums and subsequent release into non-native habitats.

Description
Egeria densa is an aquatic plant growing in water up to 4 m deep, with trailings stems to 2 m or more long, producing roots at intervals along the stem. The leaves are produced in whorls of four to eight, 1–4 cm long and 2–5 mm broad, with an acute apex. The stem of the plant will grow until it reaches the surface of the water, where it will begin to spread out, creating a thick canopy that blocks light from reaching plants below it. It is dioecious, with male and female flowers on separate plants; the flowers are 12–20 mm diameter, with three broad, rounded, white petals, 8–10 mm long on male plants, and 6–7 mm long on female plants.[3][4][5][6]

Life Cycle
Egeria densa typically displays little variation in growth patterns throughout the year when grown in tropical 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''

Location
Egeria densa is native to Argentina, Brazil, and Uruguay. However due to its popularity in aquariums the plant has now spread to North America, Europe, Asia, Australia, and Africa .

Temperature
Temperature is important to the growth of Egeria densa, however its growth is mostly stable in temperatures ranging from 16-28C, with an upper temperature limit of 32C that results in reduced shoot growth and photosynthetic output. Colder temperatures will limit growth of the plant and can be used as a method of controlling its spread in non-native habitats.

Lighting
Egaria densa is able to match photosynthetic output to available light like many macrophytes. However, it is the species ability to thrive in low light conditions and ability to form a dense canopy that make it such a successful invader compared with other macrophytes, resulting in a reduction in the diversity of plant species'''.

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.[4][5]

It grows well in the cooler aquarium and is suitable for the beginner. It is easily propagated by cuttings. According to reports (cf. Tropica link) it secretes antibiotic substances which can help prevent blue-green algae. It grows best in a nutrient-rich, high light situation.

Economics
E. densa, like other macrophytes, are effective when used in wastewater 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
E. densa has escaped from cultivation and become naturalized and invasive in many warm temperate to subtropical regions of the world, including Europe, southern Africa, Asia, Australia, New Zealand and North America.[2] In the United States it occurs from New York south to Florida and west to California and Oregon.[4] In the Sacramento-San Joaquin Delta of California, it wasintroduced in the 1960s and has since had a significant adverse impact on the local ecosystem. The plant currently infests 2,400 ha, or 12% of the total surface area of the delta. It is also a problem in several other states. It has been found in Canada. Recently, E. densa was reported as naturalized alien in Iceland where the species invaded geothermally heated water bodies.[7] Due to its occurrence in Northern Iceland E. densa is one of the first freshwater alien plant species that reached the Arctic.[7] 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.[8][9]

Role as Ecosystem Engineer
Though it is sometimes debated, E. Densa is referred to as an Ecosystem Engineer as a result of the impact it has on a habitat once it is introduced. Most notably due to its fast growth and dispersal rate due to fragmentation, ability to adapt to different light and nutrient availability, its uptake of nutrients from the water column and its affect on sedimentation of nutrients, and the large light-blocking canopy that it forms''.

E. densa is also responsible for changing the amount of phytoplankton present in the water column due to limiting light availability from the dense canopy that it forms, and from the amount of nutrients that removes from the water column. It can however function as shelter for zooplankton and smaller invertebrates.

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 or the use of herbicides to kill the plant. The best solutions include water draw downs, as the plant is very sensitive to drying out and can be lethal in as short as an hour outside of water. In addition cold weather has been found to be effective in controlling the plant, though this has practical limitations. When herbicides 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 does not reabsorb into the water column