The seven species of
water hyacinth comprise the genus
Eichhornia. Water hyacinth is a free-floating perennial
aquatic plantAquatic plants — also called hydrophytic plants or hydrophytes — are plants that have adapted to living in or on aquatic environments. Because living on or under water surface requires numerous special adaptations, aquatic plants can only grow in water or permanently saturated soil...
native to tropical
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in height. The
leavesIn botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In...
are 10-20 cm across, and float above the water surface. They have long, spongy and bulbous stalks. The feathery, freely hanging roots are purple-black. An erect stalk supports a single spike of 8-15 conspicuously attractive
flowerA flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds...
s, mostly lavender to pink in colour with six petals. When not in bloom, water hyacinth may be mistaken for frog's-bit (
Limnobium spongia).
One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or
stolonIn biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
s, which eventually form daughter plants. It also produces large quantities of seeds, and these are viable up to thirty years. The common water hyacinth (
Eichhornia crassipes) is a vigorous grower known to double its population in two weeks.
In
AssameseAssamese is the easternmost Indo-Aryan language. It is used mainly in the state of Assam in North-East India. It is also the official language of Assam. It is also spoken in parts of Arunachal Pradesh and other northeast Indian states. Small pockets of Assamese speakers can be found in Bhutan...
it is known as
Meteka. In Sinhala it is known as
Japan Jabara (ජපන් ජබර) due to its use in World War 2 to fool Japanese pilots into thinking lakes were fields usable to land their aircraft, leading to crashes.
In
Southern Pakistan, it is the
Provincial flower of
SindhSindh , is one of the four provinces of Pakistan and historically is home to the Sindhis. Different cultural and ethnic groups also reside in Sindh including Urdu-speaking Muslim refugees who migrated to Pakistan from India upon independence as well as the people migrated from other provinces after...
.
Invasiveness as an exotic plant
Water hyacinth has been widely introduced throughout
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
,
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
and
AfricaAfrica is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people in 61 territories, it accounts for about 14.8% of the...
. It can be found in large water areas such as Louisiana, or in the
Kerala BackwatersThe Kerala backwaters are a chain of brackish lagoons and lakes lying parallel to the Arabian Sea coast of Kerala state in southern India. The network includes five large lakes linked by canals, both manmade and natural, fed by 38 rivers, and extending virtually half the length of Kerala state...
in
IndiaIndia, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal...
. In many areas it, particularly
E. crassipes, is important and pernicious
invasive species'Invasive species' is a phrase with several definitions. The first definition expresses the phrase in terms of non-indigenous species that adversely affect the habitats they invade economically, environmentally or ecologically...
. First introduced to North America in 1884, an estimated 50 kilograms per square metre of hyacinth once choked
FloridaFlorida is a state located in the southeastern region of the United States, bordering Alabama to the northwest and Georgia to the north. It was the 27th state admitted to the United States...
's waterways, although the problem there has since been mitigated.
When not controlled, water hyacinth will cover lakes and ponds entirely; this dramatically impacts water flow, blocks sunlight from reaching native aquatic plants, and starves the water of
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
, often killing fish (or turtles). The plants also create a prime habitat for
mosquitoMosquito is a common insect in the family Culicidae...
s, the classic vectors of disease, and a species of
snailThe word snail is a common name for almost all members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word snail is used in a general sense, it includes sea snails, land snails and freshwater snails. Snails lacking a shell or having only a very small one are...
known to host a parasitic
flatwormThe flatworms, known in scientific literature as Platyhelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
which causes
schistosomiasisSchistosomiasis is a parasitic disease caused by several species of fluke of the genus Schistosoma....
(snail fever). Directly blamed for starving subsistence farmers in
Papua New GuineaPapua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
, water hyacinth remains a major problem where effective control programs are not in place. Water hyacinth is often problematic in man-made ponds if uncontrolled, but can also provide a food source for gold fish, keep water clean and help to provide oxygen to man-made ponds.
Water hyacinth often invades bodies of water that have been impacted by human activities. For example, the plants can unbalance natural lifecycles in artificial reservoirs or in
eutrophiedEutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem...
lakes that receive large amounts of nutrients.
In some areas, uses are being found for the abundant plants, such as for
cattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
food and in
biogasBiogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Biogas originates from biogenic material and is a type of biofuel....
production. Recently, they have also begun to be used in wastewater treatment due to their fast growth and ability to tolerate high levels of pollution. Parts of the plant are also used in the production of traditional handicrafts in Southeast Asia. In Bangladesh, farmers have started producing fertilizer using Water Hyacinth or Kochuripana as it is known there locally.
As chemical and mechanical removal is often too expensive and ineffective, researchers have turned to
biological controlBiological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
agents to deal with water hyacinth. The effort began in the 1970s when
USDAThe United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
researchers released three species of
weevilA weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than 6 mm , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
known to feed on water hyacinth into the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
,
Neochetina bruchi,
N. eichhorniae, and the water hyacinth borer
Sameodes albiguttalis. Although meeting with limited success, the weevils have since been released in more than 20 other countries. However, the most effective control method remains the control of excessive nutrients and prevention of the spread of this species.
Water hyacinth in Lake Victoria, Africa
Botanists and gardeners carry plants with them in their travels, and experts suspect that this is how the water hyacinth came to West Africa in the 1980s. Its flowers are beautiful; it was probably brought over as an ornamental for garden ponds (United Nations News, 2000). The consensus is that Water Hyacinth entered Lake Victoria from Rwanda via the river Kagera (Ambrose 1997). The exact time and place of introduction has been debated, but the plant is native to South America, and therefore reached Lake Victoria due to human activity. It has spread prolifically, due to lack of natural enemies, an abundance of space, agreeable temperature conditions, and abundant nutrients (Opande et al., 2004). It increased rapidly between 1992-1998, was greatly reduced by 2001, and has since resurged to a lesser degree. Management techniques include (hyacinth-eating) insect controls and manual beach cleanup efforts (Kateregga/Sterner 2007). A water hyacinth infestation is seldom totally eradicated. Instead, it is a situation that must be continually managed (LVEMP, 2004 ) (United Nations News, 2000)).
Water Hyacinth affects the Lake Victorian population in many negative ways. There are economic impacts when the weed blocks boat access. The effects on transportation and fishing are immediately felt. Where the weed is prolific, there is a general increase in several diseases, as the weed creates excellent breeding areas for mosquitoes and other insects. There are increased incidents of skin rash, cough, malaria, encephalitis, bilharzias, gastro intestinal disorders, and schistosomiasis. Water hyacinth also interferes with water treatment, irrigation, and water supply (Opande et al., 2004)). It can smother aquatic life by deoxygenating the water, and it reduces nutrients for young fish in sheltered bays. It has blocked supply intakes for the hydroelectric plant, interrupting electrical power for entire cities. The weed also interrupts local subsistence fishing, blocking access to the beaches (LVEMP, 2004).
Industrial utilization
Since the plant has abundant nitrogen content, it can be used a substrate for biogas production and the sludge obtained from the biogas. However, due to easy accumulation of toxins, the plant is prone to get contaminated when used as feed.
Exogenous
The plant is extremely tolerant towards, and of high capacity of uptaking heavy metals, such as
Cd, Cr, Co, Ni, Pb and Hg etc, which could be utilized for the biocleaning of industrial wastewater
, , , . Not only the heavy metals,
Eichhornia crassipes can also remove toxins, such as
cyanideA cyanide is any chemical compound that contains the cyano group , which consists of a carbon atom triple-bonded to a nitrogen atom. Inorganic cyanides are hydrogen cyanide salts in which cyanide is generally the anion CN
-. Organic compounds that have a -C≡N functional group bonded to...
, a process which is environmentally beneficial in areas that have endured gold mining operations .
Water hyacinth is also observed to enhance nitrification in waste water treatment cells of living technology. Their root zones are superb micro-sites for bacterial communities
J. Todd, B. Josephson,
The design of living technologies for waste treatment / Ecological Engineering 6 (1996) 109-136
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