Scientific Glossary
This glossary provides definitions of key ecological, botanical, and management terms used throughout the Water Hyacinth Research Network.
A
Anoxia
A condition in which dissolved oxygen is completely absent from a water body. Anoxic zones frequently develop beneath dense water hyacinth mats due to blocked atmospheric gas exchange and microbial decomposition of organic matter. Prolonged anoxia is lethal to most aerobic aquatic organisms.
See: Ecological Impact
Aquatic Macrophyte
A macroscopic plant that grows in or near water. Aquatic macrophytes include emergent, submerged, floating-leaved, and free-floating species. Eichhornia crassipes is classified as a free-floating macrophyte due to its buoyant petioles and root system suspended in the water column.
See: Biology & Physiology
B
Biocontrol Agent
An organism deliberately introduced or managed to suppress the population of a pest species. In water hyacinth management, biocontrol agents include weevils (Neochetina spp.) and moths (Niphograpta albiguttalis) that feed on plant tissue and reduce vegetative vigor.
See: Biological Control
Biomass
The total mass of living or recently living organisms in a given area or volume. Water hyacinth is notable for its exceptionally rapid biomass accumulation, which can exceed 60 tonnes of fresh weight per hectare under optimal nutrient and temperature conditions.
See: Mechanical Control
C
Clonal Reproduction
A form of asexual reproduction in which new individuals are produced from vegetative structures of a parent organism. Water hyacinth reproduces clonally through stolons, enabling a single plant to generate thousands of genetically identical daughter plants within weeks.
D
Dissolved Oxygen (DO)
The concentration of molecular oxygen dissolved in water, typically measured in milligrams per liter. Adequate dissolved oxygen is essential for aerobic aquatic life. Dense water hyacinth infestations reduce DO by blocking atmospheric exchange, suppressing photosynthesis, and increasing biological oxygen demand.
See: Ecological Impact
E
Eutrophication
The enrichment of a water body with nutrients, particularly nitrogen and phosphorus, leading to excessive plant and algal growth. Eutrophic conditions strongly favor water hyacinth proliferation, as the species thrives in nutrient-rich environments.
See: Ecological Impact
F
Free-Floating Plant
An aquatic plant that is not rooted in sediment and floats on or near the water surface. Free-floating species such as water hyacinth derive nutrients directly from the water column through their root systems.
See: Biology & Physiology
G
Glyphosate
A broad-spectrum systemic herbicide widely used in aquatic weed management. Glyphosate-based formulations approved for aquatic use are applied to water hyacinth foliage, where the compound is absorbed and translocated to meristematic tissues, inhibiting the enzyme EPSPS and halting amino acid synthesis.
See: Chemical Management
H
Herbivory
The consumption of plant tissue by animals. In the context of water hyacinth management, herbivory by specialist insects such as Neochetina weevils reduces leaf area, petiole integrity, and overall plant fitness, contributing to population suppression.
See: Biological Control
Hypoxia
A condition of low dissolved oxygen concentration in water, typically below 2 mg/L. Hypoxic zones beneath water hyacinth mats result in fish kills and the displacement of oxygen-sensitive invertebrate communities.
See: Ecological Impact
I
Integrated Pest Management (IPM)
A management approach that combines multiple control methods — mechanical, chemical, and biological — to achieve sustainable pest population reduction. IPM is considered the most effective long-term strategy for water hyacinth control.
Invasive Species
A non-native organism whose introduction and spread cause ecological or economic harm. Water hyacinth is classified as one of the world's most harmful invasive species due to its rapid proliferation and severe impacts on freshwater ecosystems.
See: Species Overview
L
Littoral Zone
The shallow nearshore area of a lake or river where light penetrates to the bottom, supporting rooted aquatic vegetation. Dense water hyacinth infestations in the littoral zone displace native macrophyte communities and alter habitat structure for fish and invertebrates.
See: Ecological Impact
M
Macrophyte
A plant large enough to be observed with the naked eye, as distinct from microscopic algae. In aquatic ecology, the term refers broadly to visible plants growing in or near water, including emergent, submerged, and free-floating forms. Water hyacinth is one of the most prolific free-floating macrophytes in tropical and subtropical freshwater systems.
See: Biology & Physiology
N
Neochetina
A genus of weevils (Curculionidae) native to South America that are specialist herbivores of water hyacinth. Neochetina eichhorniae and N. bruchi are the most widely deployed biological control agents against E. crassipes globally.
See: Biological Control
Nutrient Loading
The total input of nutrients — primarily nitrogen and phosphorus — entering a water body from point and non-point sources such as agricultural runoff, wastewater discharge, and atmospheric deposition. Elevated nutrient loading accelerates eutrophication and creates favorable conditions for water hyacinth proliferation.
See: Ecological Impact
P
Petiole
The stalk connecting a leaf blade to the stem. In water hyacinth, the petioles contain spongy aerenchyma tissue that provides buoyancy, enabling the plant to float freely on the water surface.
See: Biology & Physiology
Phytoremediation
The use of plants to remove, degrade, or stabilize contaminants in water or soil. Water hyacinth has been studied for its capacity to absorb heavy metals and excess nutrients from wastewater, though this application requires strict containment to prevent ecological spread.
See: Species Overview
R
Riparian Zone
The interface between land and a river, stream, or other watercourse. Riparian zones support distinctive vegetation communities and serve as buffers that filter runoff, stabilize banks, and regulate water temperature. Dense water hyacinth mats can encroach on riparian areas, displacing native vegetation and altering bank stability and nutrient cycling.
S
Seed Bank
The reserve of viable seeds stored in soil or sediment. Water hyacinth seeds can remain viable in lake sediments for up to 20 years, complicating eradication efforts even when surface populations are removed.
Stolon
A horizontal stem that grows along the surface and produces new plants at its nodes. Stoloniferous growth is the primary mechanism of vegetative expansion in water hyacinth, enabling rapid mat formation across open water.
T
Tristyly
A breeding system in which a plant species produces three distinct floral morphs differing in style and stamen length. Eichhornia crassipes exhibits tristyly, though in many invasive populations only one or two morphs are present, reducing sexual reproduction and favoring clonal spread.