Dr. Rasekh Ali, Dr. Mohsin Dar, Salwa Shah
Water is essential for all forms of life, but urbanization and industrialization have greatly disrupted aquatic ecosystems, leading to ecological imbalances and a decline in biodiversity. Over the past fifty years, urban expansion has resulted in harmful substances being released into freshwater bodies, adversely affecting aquatic life and terrestrial organisms, including humans. Streams and rivers, known for their rich biodiversity, are among the most endangered ecosystems globally, facing significant threats from human activities. In developing countries, around 90% of wastewater is discharged into rivers and streams with minimal or no treatment, exacerbating the pollution crisis. In India, increasing human population, agricultural intensification, and industrial activities contribute significantly to water pollution, primarily through organic and microbial contaminants resulting from untreated domestic and industrial effluents. To address these pressing issues, it is crucial to implement effective ecosystem management strategies and sustainably utilize water resources. Continuous monitoring and evaluation of water quality are essential for identifying and implementing corrective measures to mitigate pollution in lotic waters. Macrobenthic fauna are visible organisms that live on the bottom substrates of aquatic environments for part of their life cycle and can be sampled using mesh sizes of 500 μm or larger. Their visibility and response to man-made disturbances render them easy to monitor quantitatively, making them important indicators of water quality and pollution levels. These organisms play a critical role in the aquatic food chain by feeding on settled debris, which also serves as a food source for many fish species. Furthermore, they facilitate the decomposition of organic matter into inorganic forms like phosphates and nitrates, thereby linking unavailable nutrients in detritus to accessible protein materials found in fish and shellfish.
In the ecosystem, macrobenthic communities contribute significantly to energy and nutrient transfer within the trophic web, connecting the pelagic and littoral habitats. Macro invertebrates are increasingly recognized as vital components for the structural and functional integrity of streams and rivers, interacting closely with fish, periphyton, and plants, as well as with pelagic zooplankton. Their abundance and diversity are influenced by various physicochemical parameters of the environment, particularly water temperature, which is deemed the most critical factor as it directly affects biological activities and dissolved oxygen levels, thereby influencing the population dynamics of these organisms. Additionally, factors such as water velocity, transparency, and turbidity also play influential roles in shaping the composition of the macro-invertebrate community in aquatic ecosystems. Bio-monitoring is the systematic use of living organisms or their responses to determine the quality of the environment.
“Water quality affects the biology and ecology of systems. Scientists use community diversity indices and biotic indices to measure this impact. Biotic indices assess pollution by assigning a sensitivity or tolerance value to indicator species (or groups of species) found at a location. The sum of these values gives a pollution index for that station. These indices can be as simple as noting the presence or absence of certain species.”
Water pollution is essentially a biological problem. The ultimate purpose of environmental assessment and regulation is the maintenance of biological integrity. Bio-monitoring is now recognized as one of the most valuable tools available in the arsenal of environmentalists. In order to achieve and maintain the highest water quality in lakes, rivers and streams, environmental advocates are using the resident organisms living in these waters as sensitive indicators of change. The biomonitoring of aquatic bodies has been developed to measure the response of aquatic communities to anthropogenic stressors on account of energy source, water quality, habitat quality, flow regimes and biotic interaction. The environmental stressors like toxic substance, urban influences sedimentation and flow regulation have been found to affect significantly the benthic macro-invertebrates assemblages which can provide a reliable assessment tool to bio-assess the long term ecological status compared to rapidly changing physicochemical characteristics of water bodies. The macro-invertebrates are the most valuable indicators of environmental quality in aquatic ecosystem because of stable mode of life, their convenient size and distinct characters which offers an easy sorting and identification of these organisms. The qualitative and quantitative changes in the benthic communities have also been used as a tool checking pollution through the use of indices.
The health of a stream can be determined by using benthic macro invertebrates as they have differential abilities to tolerate pollution, long life cycle, and are mostly sedentary, relatively easy to collect, relatively easy to identify in view of available identification keys up to genera and universally distributed. Macro-invertebrates react speedily to any environmental perturbations thus used to study both temporal and spatial changes in various aquatic environments and pave their path for water quality assessment as they are cheaper than chemical assessment. To describe the impact of water quality on the biology and ecology of systems a range of techniques are used such as community diversity indices and biotic indices. A number of biotic indices have been introduced for water quality assessment on the basis of the sensitivity or tolerance of species or taxa to pollution. Indicator species are given a value based on their perceived susceptibility, the sum of which provides an index of pollution for the Station. These indices may be qualitative based on the presence or absence of species. Some of these indices are described below.
(The authors are freelancers. The views, opinions and conclusions expressed in this article are those of the authors and aren’t necessarily in accord with the views of “Kashmir Horizon”)
