River biota is the diversity of organisms in a riverine ecosystem, mainly the riparian forest cover with suitable chemical and physical environmental conditions. The biotic health of a river indicates the health of riverine organisms, the change in the condition of the river ecosystem can cause river degradation. The survival of biota depends on the healthy chemical and physical river environment. An ideal bioindicator should have properties of ecological characteristics, species richness, high distribution, taxonomic soundness, etc. The sufficient availability of biological components in the water can help to assess the river’s health. A rapid bioassessment protocol is one of the biological methods of identifying the health of a river by identifying a sufficient quantity of biological indicators. The most common and frequently used biological indicators are macroinvertebrates, periphyton, fish, riparian species of birds, etc.
Variation in the stream flow results inthe biota health alteration. The rich diversity of plants, animals, and other biological indicators is the key indicator of a biologically healthy river.
Riparian vegetation
Riparian vegetation in particular riparian forest cover is an important integral component of river health. Healthy riparian vegetation is a most important element of a healthy aquatic ecosystem. The riparian diversity ranges from species-rich grasslands to woodland. The richness of the riparian species along the stream is considered to be one of the important indicators of river health, and also acts as a buffer zone of the area by capturing sediments and nutrients. The wetland depended on species it acts as a major source of shelter, food, and shade.
The forest ecosystem is the ecological balance of biodiversity and is the area of a high density of trees and woodlands having the largest terrestrial carbon sink. The existence of forests along the river banks has a range of benefits for the ecosystem.
Forest cover refers to the range of the canopy density greater than 10% with an area of 1 hectare and above. The change in the density of the forest reflects the forest cover.
Diatoms
Diatoms are the bio-indicators of the river which have been widely used to find the condition and change in the aquatic ecosystem water quality. The sensitive nature of the organism to the chemical and physical changes in the ecosystem makes the biotic integrity easy to find. The variation in the riverine environmental condition such as salinity, pH, minerals, organic matter, etc. will reflect the relative abundance of the species according to the tolerant level.
Macroinvertebrates
Benthic micro-invertebrates are the most common indicator for river health assessment. They are the epitome creature for the biological monitoring of aquatic habitats. The abundance of taxa is an indication of a healthy ecosystem. They are the most widespread, most common, and easily sampled species that are large enough to see with the naked eye. As the organisms are very sensitive to aquatic habitat degradation, they can serve as an excellent indicator of water quality not only for pollution but also to change in the physical condition of the water bodies. The features such as longer life cycles, worldwide distribution, low motility, and real-time sensitivity to a wide range of pollutions make the macroinvertebrates more suitable for identifying river health.
Fish
Besides the micro invertebrates, fish are the other commonly used indicator for identifying river health. By the reason of their complex habitat and their sensitive nature to the change in the water quality as well as the habitat. The sampling and identification of fish are comparatively easy and it can identify the potential impact on the water ecosystem as well as the fish population. The fish sampling technique should focus on multi habitat approach and the sampling should take from riffle, run and pool habitats if available.