Question

Explain any five stages of hydrosere.

Answer 1

Hint: A sere is an intermediate stage found in a plant or ecological succession. A hydrosere has the word ‘hydro’, hence it will be something related to a water body.

Complete answer:
- A succession that evolves in an aquatic environment is a hydrosere.
- The process of the succession has the following stages -
(i) Phytoplankton stage - It is the initial stage where algal spores travel and reach the location through the body of water. Microscopic and simpler forms of life such as bacteria, algae, cyanobacteria, phytoplankton, zooplankton that float and move in water are the pioneer colonizers. Organic matter and other substances are added to water due to the metabolic reactions of the organism. After their death, they settle to the floor to form a layer of mud.
(ii) Submerged stage: This is the second stage. When the organic matter and mud particles settle down to the bottom of the pond, a loose layer is formed which forms a substratum for submerged, rooted hydrophytes. This appears in regions of ponds or lakes where the depth of the water is 10 feet or more. Examples of pioneers are Utricularia, Chara, Ceratophyllum, Hydrilla, Vallisneria, etc. These plants form a tangled mass and root themselves in the mud. The dead plant remains and the soil particles, when they settle to the aquatic floor, contribute to the formation of mud. This makes the water level shallow.
(iii) Floating stage: As the water becomes more shallow, the submerged vegetation reduces, and floating vegetation gradually appears. Submerged and floating plants grow together but over time, the submerged plants are replaced entirely. Some floating species have broad leaves that cover the surface of the water, blocking light supply to submerged plants, causing them to die. Floating plant roots are embedded in the mud, but some or all their leaves float on the surface of the water. Examples of floating plants are Trapa, Pistia, Nymphaea, and Limnanthemum.
(iv) Reed-swamp stages: Here, the ponds and lakes become as shallow as three feet. The environment becomes less suited for floating plants and this makes way for new types of plants. The surface of the pond changes into water-saturated marshy land. Amphibious plants such as reeds and cattails start growing. The leaves of these plants are present much above the surface of the water and the roots are submerged in the mud. The large leaves cut off light supply to any submerged plants. Thus, further deposition of dead organic matter occurs and the water becomes more shallow. Examples of plants in these stages are Bothrioclova, Phragmites, Typha, Zizania, etc.
(v) Sedge-meadow stage: The soil now becomes marshy in nature and is unfit for the plants from the previous stages. Plants suitable for marshy climates are usually from Cyperaceae and Gramineae families. Common primary and secondary species are sedge (Carex), rushes (Juncus), Themeda, Campanula, Mentha, Caltha, Gallium, and so on. Sedge and rushes have rhizomes accumulate the soil further, making it tight-knit.

Note: - Hydrosere is also known as hydrarch succession.
- Seral communities of plants are more visible than animals.
- Succession from a water to land type community is dependent largely on the amount of siltation and takes from anywhere between a decade to two hundred years or more.