2018 SCIENCELINE

Journal of Life Science and Biomedicine

J Life Sci Biomed, 8(6): 94-100, 2018

ISSN 2251-9939

Water Hyacinth (Eichhornia crassipes) Biology and its

Impacts on Ecosystem, Biodiversity, Economy and

Human Well-being

Abera Hailu Degaga^

Department of Wildlife & Ecotourism Management, Wolkite University, P.O. Box 07, Wolkite, Ethiopia

Corresponding author’s Email: aberaabos@gmail.com; abera.hailu@wku.edu.et

ABSTRACT

The aim of this review article was to show water hyacinth biology, chemical composition

and its negative impacts on aquatic ecosystem, biodiversity, economy and human wellbeing.

Water hyacinth is challenging the ecological stability of freshwater bodies. It is native to the

Original Article

PII: S225199391800015-8

Amazon Basin in Brazil and other nearby South American countries. In Africa, the first

introduction of water hyacinth was in Egypt in 1880. In Ethiopia, water hyacinth was

Rec. 28 Sep

Acc. 19 Oct

Rev. 15 Nov

Pub. 25 Nov

2018

officially reported in 1956 in Koka Lake and the Awash River. Nutrients and temperature are

considered the strongest determinants for water hyacinth growth and reproduction. Under

favorable conditions, water hyacinths can double its mass every 5 days and it also grows

from seed, which can remain viable for 20 years. Due to its extremely fast growth, the weed

has become the major floating water weed of tropical and subtropical regions. In the

absence of natural enemies, the weed quickly becomes invasive, colonizing slow moving

waters resulting in thick and extensive mats which degrade aquatic ecosystems and limit

their utilization. These mats affect fisheries and related commercial activities, functioning

of irrigation canals, navigation, hydroelectric programmes and tourism. Its 95% mass

weight is water from 5% dry matter 50% is silica and 30% is K, 15% N and 5% protein. The

spread of this invasive plant is difficult to manage and not easy to reverse. Its impact is not

only loss of biodiversity in aquatic ecosystems but also economic development and human

wellbeing. It supports as breeding ground for vectors and pests. Hand removal is most

effective for small infestations while mechanical harvesting can be an effective tool for

removing larger infestations. The best method to control water hyacinth is to prevent it

from entering a water body. This can be through education programs that have proved to be

an effective tool in preventing further spread into catchments by people for ornamental

purposes. So Ethiopian Government has to declare water hyacinth and other invasive

species as a national pest and then put legislation in place to control them.

Keywords

Aquatic Ecosystem,

Aquatic Weed,

Invasive Plant Species,

Fast Growth,

Mat Formation

INTRODUCTION

The spread of invasive species is difficult to manage and not easy to reverse, this threatens not only biodiversity

of aquatic ecosystems but also economic development and human wellbeing [1]. Water hyacinth (Eichhornia

crassipes) is an invasive aquatic plant associated with a variety of ecological and economic effects on freshwater

ecosystems [2]. It is a free-floating aquatic plant that grows in ponds or slow moving waterways. It is a

perennial monocotyledonous crop that belongs to the Pontederiaceae family. It is native to the Amazon Basin in

Brazil and other nearby South American countries [3]. And Holm, et al ., [4] reported that, E. crassipes, a native of

South America, is a major freshwater weed in most of the frost-free regions of the world and is generally

regarded as the most troublesome aquatic plant. It is considered the worst aquatic weed in the world [5]. In

Africa, the first introduction of water hyacinth was in Egypt in 1880 [6]; the main aquatic weed in East Africa is

Water hyacinth [5]. In Ethiopia, water hyacinth was officially reported in 1965 in Koka Lake and the Awash River

[7, 8] and infestation of Lake Tana was officially recognized in 2011 [9]. It has been recognized as the most

damaging aquatic weed in Ethiopia since 1965 [8]. In Lake Tana in addition to water hyacinth, other two floating

invasive weeds: Azolla and Water Lettuce, were reported [10].

Water hyacinth reproduces both sexually and asexually. The rapid increase and spread of the plant into

new areas is due particularly to its vegetative reproduction, a single plant being able to develop very rapidly a

significant infestation [11]. Water hyacinth has a rapid propagation and morphological characteristics that

makes the weed well adapted to rapid distance dispersal and successful colonization of varying habitats in a

Degaga AH. 2018. Water Hyacinth (Eichhornia crassipes) Biology and its Impacts on Ecosystem, Biodiversity, Economy and Human Well-

being. J. Life Sci. Biomed. 8(6): 94-100; www.jlsb.science-line.com

short time [12]. Moving easily with water currents, winds or other accidental means, such as fishing nets and

boats, the plant invaded rivers, canals, ponds, lakes, dams and other freshwater bodies. In the absence of natural

enemies, the weed quickly becomes invasive, colonizing slow moving waters resulting in thick and extensive

mats [13] which degrade aquatic ecosystems and limit their utilization [14]. The negative impacts of water

hyacinth are due to its dense, impenetrable mats which restrict access to water. These mats affect fisheries and

related commercial activities, functioning of irrigation canals, navigation/transport, hydroelectric programmes

and tourism [15].

Nutrients and temperature are considered the strongest determinants for water hyacinth growth and

reproduction [17]. Salinity constraints generally limit water hyacinth establishment in coastal areas and within

estuaries [17]. Due to its extremely fast growth, the weed has become the major floating water weed of tropical

and subtropical regions. There for the aim of this review was to show water hyacinth biology, chemical

composition and its negative impacts on aquatic ecosystem biodiversity, economy and human wellbeing. And to

show water hyacinth is challenging the ecological stability of freshwater ecosystems.

Biology, chemical composition and ecology of water hyacinth

The E. crassipes growth is extremely rapid and forms large populations of inter-connected shoots which is

impenetrable mat. It forms dense, interlocking mats due to its rapid reproductive rate and complex root

structure [18]. The flowers are bluish purple, large and self-fertile. The seeds are produced in large numbers and

are contained in capsules, each capsule containing up to 300 seeds [19]. The seeds can remain viable for 5-20

years [20]. The plant can also reproduce vegetative through the production of horizontal stolons. Rakotoarisoa,

et al., [11] described that due to its high reproduction rate, the complex root structure and the formation of

dense mats with up to two million plants per hectare can be found. Under favorable conditions, water hyacinth

can double its mass every 5 days and it also grows from seed, which can remain viable for 20 years or longer [21,

22]. The biotic seeds dispersals are birds thought to be transported over long distances (e.g. waterfowl and

shore birds) and if coated in mud they may cling to both mammals and birds [23, 24]. While, wind is the abiotic

dispersal, it will readily move the plant and the upright leaves in lakes and canals. Along rivers, water flow is the

prime mover of vegetative material but strong winds may sometimes blow the plant upstream.

Water hyacinth draws all its nutrients directly from water. It absorbs heavy metals [25], organic

contaminants [26], and nutrients from the water column [27]. It comprises 95% water and 5% dry matter of

which 50% is silica, 30% Potassium, 15% Nitrogen and 5% protein [28]. While Roger and Davis [29] reported that

the uptake of nitrogen by water hyacinth is 5 to 10 times as rapidly as phosphorous. It has been known to thrive

well in nutrient-enriched fresh waters in tropical climatic zones. For this purpose it has been used in

wastewater treatment facilities [30].

The structure of a macrophyte assemblage plays a large role in determining composition of phytoplankton,

zooplankton, fish, and birds in freshwater ecosystems [31]. A shift in the primary-production base of a lake can

resonate throughout the ecosystem, affecting multiple trophic levels both directly through changes in habitat

availability and indirectly through shifts in energy pathways. Free floating plants are able to monopolize light

and absorb nutrients from the water column, preventing phytoplankton and submersed vegetation from

obtaining sufficient resources for photosynthesis [32]. Altering ecosystem services and processes, reducing

native species abundance and richness, and decreasing genetic diversity of ecosystems [33] and also water

hyacinth affects diversity, distribution and abundance of life in aquatic environments [34].

Water hyacinth impacts on biodiversity loss

Water hyacinth is challenging the ecological stability of freshwater bodies [35], out-competing all other

species growing in the vicinity, posing a threat to aquatic biodiversity [22]. Besides suppressing the growth of

native plants and negatively affecting microbes, water hyacinth prevents the growth and abundance of

phytoplankton under large mats, ultimately affecting fisheries [36]. This is because fish feed on phytoplankton.

According to the Millennium Ecosystem Assessment [37], freshwater ecosystems are among the most

significantly human-altered systems in the world. While invasive species are considered the leading threat to

global aquatic biodiversity [38].

Most water hyacinth effects are lower phytoplankton productivity and dissolved oxygen concentrations

beneath mats [39, 40]. Reduced phytoplankton productivity can decrease zooplankton abundance by decreasing

food availability [19, 41]. It also affects diversity, distribution and abundance of life in aquatic environments and

enhances evapo-transpiration, thus affecting all aquatic organisms. The death and decay of water hyacinth

Degaga AH. 2018. Water Hyacinth (Eichhornia crassipes) Biology and its Impacts on Ecosystem, Biodiversity, Economy and Human Well-

being. J. Life Sci. Biomed. 8(6): 94-100; www.jlsb.science-line.com

vegetation in large masses create anaerobic conditions and production of lethal gases [34]. Coverage of water

hyacinth causes de-oxygenation of water, and at times anoxia below the dense mats [42]. Water quality effects

include higher sedimentation rates within the plant’s complex root structure and higher evapo-transpiration

rates from water hyacinth leaves when compared to evaporation rates from open water [43]. A shift in the

primary-production base of a lake can resonate throughout the ecosystem, affecting multiple trophic levels

both directly through changes in habitat availability and indirectly through shifts in energy pathways [44].

Dissolved oxygen less than 5 mg per litter are known to adversely affect function and survival of most fishes

and less than 2 mg per litter can lead to fish kills [45]. This low level of dissolved oxygen along the water column

will happen when large water hyacinth mats prevent light infiltration or when a relatively large area of plants

decompose at the same time.

In the 1950s, within three years of its first sighting, it had spread 1600 km along the Congo River [24]; in

Lake Tana in 2012 after a year of infestation officially recognized its estimation coverage was 20,000 hectares

[46]. This shows that if once introduced to favorable habitats, especially open waters, E. crassipes may spread

very rapidly and can form dense monotypic mats. Which is impenetrable and blocking access both for

transportation and aquatic living organisms in addition to adding to much organic matter to water bodies

leading anoxia condition. The introduction and spread of non-native species contribute to the loss of aquatic

species [47].

Economic impacts of water hyacinth

Because of its rapid growth and mat formation, E. crassipes has a range of detrimental effects on the

economy sector. The dense mats disrupt socioeconomic and subsistence activities for example ship and boat

navigation, restricted access to water for recreation, fisheries, and tourism [22, 48]. It physically interferes with

water transport, communication and access. Infestations are increasing in Ethiopia, creating a range of

problems including restricted access [49]. In Nigeria, Alimi and Akinyemiju [50] showed that costs of fuel and

repairs to boats on infested waterways was approximately three times that on un-infested waterways.

Economic losses also result from interference with recreational uses of water bodies [43, 49]. Heavy infestations

by Water Hyacinth make fishing very difficult, or impossible [5]. Fishermen are being troubled by a reduced

range of fish species, loss of nets and impeded access [51]. Water hyacinth was perceived to affect fisheries

through reduced levels of production, a reduction in species diversity, poor quality fish, rising cost of operation

resulting in lower income to fishers and higher prices to consumers [52].

In Lake Victoria mats blocked breeding, nursery, and feeding grounds for economically important fish

species, such as tilapia and Nile perch. Because water hyacinth mats can reduce natural predation and fisheries

catchability, leading to increased abundance of certain species [53]; but mats can also exclude certain species

from important breeding, nursery, and feeding grounds [54]. Expensive barriers or mechanical damage to

hydro-electric installations and other structures such as bridges; for example, to the Owen Falls Dam on Lake

Victoria [55], there are also similar concerns in South Africa [56], and Ethiopia [27].

Figure 1. Shore of Lake Tana (a) Cattle grazing and water hyacinth (b) Hippopotamus select grass but do not

graze water hyacinth [10]

Water hyacinth has limited beneficial uses. Local communities around Lake Tana, they are worried about

the invasion of their shore farm and grazing lands and cattle grazing the water hyacinth when there is no grass

[10]. It cannot be used as a livestock feed because it contains too much silica, calcium oxalate, potassium and too

little protein [30]. Therefore, this leads reducing grazing potential, have a negative impacts on animal health,

milk and meat quality (Figure 1) and economical reduction on the livestock sector of the country. Dereje, et al.,

[34] mentioned that expansion of water hyacinth around Lake Tana and its competition with the native species

Degaga AH. 2018. Water Hyacinth (Eichhornia crassipes) Biology and its Impacts on Ecosystem, Biodiversity, Economy and Human Well-

being. J. Life Sci. Biomed. 8(6): 94-100; www.jlsb.science-line.com

the submerging grasses and other native species becomes devastated. These affect a lot of cattle which are

directly and indirectly dependent on the grass. And also shore area floras which would be important for fish

breeding grounds and livestock forage source in the vicinity become damaged.

Water hyacinth impacts on human wellbeing

E. crassipes may reduce water quality in various ways and encourage mosquitoes, snails and other

organisms associated with human illnesses, including malaria, schistosomiasis, encephalitis, filariasis and

cholera [43, 56] It also increased health hazards i.e. incidence of malaria and schistosomiasis [15]. FAO [5] also

described that, this weed represents an environmental problem as well and indirectly a public health problem,

since it may create a microhabitat suitable for the breeding of many vectors of human diseases and for hosting

poisonous snakes. The infestation of water hyacinths (Eichhornia crassipes) in African lakes has increased

breeding site availability for malaria vector species, An. funestus complex were reported from a water hyacinth

mat [57]. Malaria vectors are able to breed amongst water hyacinth mats in Lake Victoria [58].

Water hyacinth control methods

Water hyacinth is extremely difficult to eradicate once established, the goal of most management efforts is

to minimize economic costs and ecological change [44] The optimum control method depends on the specific

conditions of each affected location such as the extent of water hyacinth infestation, regional climate, and

proximity to human and wildlife [36]. Hand removal is most effective for small infestations such as small dams

and drains. It is highly laborious and should only be used where the rate of removal can exceed the rate of re-

growth. It should be done before flowering and seed set in spring [1]. Mechanical shredding of water hyacinth is

cheaper than harvesting [59], but there are significant consequences of allowing the plant to die and decompose

within the system. Understanding the density threshold at which water hyacinth starts to impact ecosystems,

society, and local economies will help management establishment goals for population control that can

maximize the social benefits while minimizing the costs of the invasive species [44]. Therefore, the best method

to control water hyacinth is to prevent it from entering a water body.

Biological control is most effective on larger infestations but it can take several years for it to provide

successful control. It involves the use of natural enemies including plant pathogens [36, 60]. The aim of any

biological control is not to eradicate the weed, but to reduce its abundance to a level where it is no longer

problematic. While there exists several native enemies of water hyacinth, two South American weevil beetles

(Neochetina eichhorniae and Neochetina bruchi) and two water hyacinth moth species (Niphograpta albiguttalis

and Xubida infusella) have had effective long-term control of water hyacinth in many countries, notably at Lake

Chivero [28], Lake Victoria (Kenya), Louisiana (USA), Mexico, Papua New Guinea and Benin [35, 60, 61, 62].

Researchers have identified another tiny insect, Megamelus scutellaris, from South America which is highly host-

specific to water hyacinth and does not pose a threat to native or economically important species [63].

CONCLUSION AND RECCOMENDATION

Biological alien invasions are a major driver of biodiversity loss worldwide. Water hyacinth (Eichhornia crassipes)

is common and widely distributed all over the world, is challenging the ecological stability of freshwater

ecosystems. The spread of invasive alien species is neither easy to manage nor easy to reverse. They are

threatening not only biodiversity but also economic development and human wellbeing. Threats are

destruction of biodiversity; oxygen depletion and reduced water quality; breeding ground for pests and vectors;

blockage of waterways hampering agriculture, fisheries, recreation and hydropower; fishing, grazing and other

agricultural activities by forming impenetrable thickets and hindering movements of humans and animals, and

destroying and replacing natural biodiversity. Proliferation of water hyacinth is a symptom of broader

watershed management and pollution problems.

The best method to control water hyacinth is to prevent it from entering a water body. Development of

national and local policies for the detection, control and eradication of invasive species within and around

aquatic ecosystems, farm lands, communal lands and in all ecosystems is required to prevent impacts of

invasive species ahead not only on biodiversity loss but also, ecosystem and economy of a country. Therefore,

the recommendation based on this review is that Ethiopian Government has to declare water hyacinth and

other invasive species as a national pest and then put legislation in place to control them. Since Ethiopia being a

member of Convention on Biological Diversity (CBD) which urges the parties to “prevent the introduction of,

Degaga AH. 2018. Water Hyacinth (Eichhornia crassipes) Biology and its Impacts on Ecosystem, Biodiversity, Economy and Human Well-

being. J. Life Sci. Biomed. 8(6): 94-100; www.jlsb.science-line.com

control, or eradicate those alien species which threaten ecosystem, habitat or species”; the impact of invasive

weeds on environment, article 8(h) of the CBD signed by 161 countries at the Earth Summit [64] .

DECLARATIONS

Acknowledgements

This review paper was presented in Ethiopian Fishery and aquatics science association during this time I

took comments and suggestions. So the author will acknowledge the association members and scholars for

their valuable comments.

Competing interests

The author declare that there is no any competing interests.

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