Aquatic weeds and their utilization 3117.2.3 Emergent Type
These are rooted weeds that extend above the water surface. Such attached
aquatic plants usually grow well in a stable hydrological regime and are less
likely to be a problem in situations where rapid or extensive fluctuations in
water level occur. Specialized communities of emergent species may develop on
a substratum of floating aquatic plants, especially where stands of the emergent
species are particularly stable.
There is frequently a pronounced zonation of different life forms to different
depths of water (Figure 7.4). The emergent type normally grows in shallow
water and the submerged type in deeper water in which light can still penetrate
to the bottom. The floating types are independent of soil and water depth.
Like any other plants, aquatic weeds require nutrients and light. The major
factors governing their growth are:
- Ambient temperature
- Light
- Nutrients and substrate in the water
- pH of water
- Dissolved gases present in the water
- Salinity of the water
- Toxic chemicals present in the water
- Substrate and turbulence
- Water current in rivers and lakes
- River floods
- Morphology of bodies of water
While the above-mentioned factors modify the composition of the plant
communities, they are in turn modified by the latter. This results in constant
interaction between the plants and the environment. Furthermore, the
environmental factors also interact with one another, resulting in a complex
relationship between the environmental factors and the aquatic weeds.