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Brazillian Waterweed, Egeria densa

Scientific Name: Egeria densa  
Common Name(s): Brazilian Waterweed

THREAT to MAINE                                        Final Edit Needed.

Research Summary
: Emily L.
Egeria densa is an invasive plant that has negative impacts on water bodies and is spread by humans. When researching Egeria densa I found many websites with the same information but there a few that conflicted with each other and that’s when it got confusing. So, some parts of researching this species were difficult and others were very easy. One thing that is very important about doing research is that you have to keep your notes very organized because you don’t want to be putting something in twice and you don’t want to be leaving important information.

One thing that I found surprising about this species was that
Egeria densa
wasn’t in Maine. Another surprising fact how much it clogs up water systems. One thing that is really important to know is that Brazilian waterweed can spread by fragments.

Identifying Characteristics
  • 4-6 leaves growing off off submerged stems.
  • Dark grey/green.
  • White petals, yellow-centered, floating at water's surface. 
  • Number of flowers vary each year.
  • 20mm across.
  • Bloom in late spring and again in the fall.
  • Up to 5m long in still water.
  • Grows on stalks from the leafs upper angle to the water surface. 


Taxonomy of Species
   Scientific Classification
 What That Classification Means
 Kingdom  Plantae  Eukaryotic, many–celled, don’t move, and members make their own food.
 Phylum  Magnoliophyta  Flowering plant.
 Class  Liliopsida  Comprising seed plants that produce an embryo with a single cotyledon.
 Order  Hydrocharitales  Aquatic or semi aquatic herbaceous flowering plant.
 Family  Hydrocharitace  Is a family of that includes a number of species of aquatic plant, broadly
 they are called tape-grasses.
 Genus  Egeria  Aquatic plant with deep green foliage useful to oxygenate an aquarium.
 Species  densa  Brazillian waterweed.

Similar species include: Hydrilla verticillata, native water weeds, water starworts, and marestail.

Location and Movement
Origin/ Native Range
  It came from Brazil, South America.  
  • It first came to the New England in 1893 to Long Island, NY.  
  • It was first sold in the U.S. in 1915 and used in aquariums as a oxygen plant.  
  • It first started spreading in Abbington, Massachusetts.  
Spread of Species
  • It spreads by the plant's fragments.     
  • The fragments root easily.   
  • It was sold for quite a while in plant nurseries as an oxygen plant. People would put Egeria densa in their tanks to provide oxygen for the other organisms living in that tank.  
  • Also. if it connects to a boat motor or a boat lunch it will spread because of its fragments.  
Where is it now invasive?  Found in many parts of the U.S including UT, TX, the northwest, southeast, and in the east from New
 England to Florida.  

Is this species in Maine?
Where has it been identified? It's not in Maine but the closest place to Maine is New Hampshire.  
How was this species introduced?

Natural Environment
  • Near the surface in shallow and still waters of lakes.  
  • In ponds, slow moving streams, and rivers with a lot of nutrients.  
  • Can grow in layers of sand, mud, or stone to depths of 6.5 meters.   
  • It will grow in almost any conditions of pH, light, and nutrients.  
Climate and Temperature Range
 Water temperatures greater than 30 degrees Fahrenheit and up to 80 degrees Fahrenheit.  

Ecological Interactions Producer. 
 By photosynthesis.  
Consumed By
 Waterfowl such as ducks.

  • It's very aggressive and it can reduce biodiversity by clogging the waterways. Other organism can't survive.  
  • It also can change predator/prey relationships in lakes by eliminating certain organisms from the ecosystem.  
  • A serious threat to lake species because these species need open water to grow and survive.
  • Forms dense stands that trap sediment which clogs the waterways.
  • When waterways are clogged with Egeria densa swimming, boating, and navigation are greatly reduced.  
  • Fish lines get caught in it.  
  • Electric hydro dams were shut down when Brazilian waterweed clogged parts of the structure.  
  • In Washington State residents spend thousand of dollars yearly to control Egeria densa.
  • In Silver Lake, Cowlitz County they have a control project that costs over one million dollars. What state is this in? Did you put the resource you got this info from in your bibliography?

  • The white amur, Chinese grass carp, and the Congo tilapia are put into areas that have Egeria densa to eat it.  
  • If you use mechanical control, such as rakes, while it's still invading it can increase the chance of spreading.
  • Location control can be done by covering the sediment with a opaque fabric which blocks light from the plant.  
  • Weed rakes and weed cutters can be successful in small areas but if you don't get all of the plant/plant fragments it will spread.   
  • It can be composted on land away from the water.  
  • People say that the best way to control Egeria densa is to prevent it in the first place.  
  • Things you can do are inspect boats, motors, and trailers. Look at this before and after you launch your boat.
  • You should talk to someone who knows a lot about weeds before you use any chemical control.
  • Diquat, cooper-containing products, acroleir, and fluridone and all herbicides that can be used to try to eliminate Brazilian Waterweed.

Interesting Facts
  • In the summer the growth may be slow.