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Aquatic Biodiversity : Threats and Conservation

Grishma Tewari and Akansha Bisht

Department of Fishery Biology, College of Fisheries,

G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India

Biodiversity or Biological Diversity a sum of all the different species of animals, plants, fungi, and microbial organisms living on Earth and the variety of habitats in which they live. Each species is adapted to its unique niche in the environment, from the peaks of mountains to the depths of deep-sea hydrothermal vents, and from polar ice caps to tropical rain forests. According to the definition of the Convention on Biological Diversity, biodiversity is the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.

Aquatic biodiversity can be defined as the variety of life and the ecosystems that make up the freshwater, tidal, and marine regions of the world and their interactions. Aquatic biodiversity encompasses freshwater ecosystems, including lakes, ponds, reservoirs, rivers, streams, groundwater, and wetlands. It also consists of marine ecosystems, including oceans, estuaries, salt marshes, seagrass beds, coral reefs, kelp beds, and mangrove forests. Aquatic biodiversity includes all unique species, their habitats and interaction between them. It consists of phytoplankton, zooplankton, aquatic plants, insects, fish, birds, mammals, and others.

Importance of Aquatic Biodiversity

Aquatic biodiversity has enormous economic and aesthetic value and is largely responsible for maintaining and supporting overall environmental health. Humans have long depended on aquatic resources for food, medicines, and materials as well as for recreational and commercial purposes such as fishing and tourism. Aquatic organisms also rely upon the great diversity of aquatic habitats and resources for food, materials, and breeding grounds.

Factors including overexploitation of species, the introduction of exotic species, pollution from urban, industrial, and agricultural areas, as well as habitat loss and alteration through damming and water diversion all contribute to the declining levels of aquatic biodiversity in both freshwater and marine environments. As a result, valuable aquatic resources are becoming increasingly susceptible to both natural and artificial environmental changes. Thus, conservation strategies to protect and conserve aquatic life are necessary to maintain the balance of nature and support the availability of resources for future generations.

Threats to Aquatic Biodiversity

Human activities are causing species to disappear at an alarming rate. Aquatic species are at a higher risk of extinction than mammals and birds. Losses of this magnitude impact the entire ecosystem, depriving valuable resources used to provide food, medicines, and industrial materials to human beings. Runoff from agricultural and urban areas, the invasion of exotic species, and the creation of dams and water diversion have been identified as the greatest challenges to freshwater environments (Allan and Flecker 1993; Scientific American 1997). Overexploitation of aquatic organisms for various purposes is the greatest threat to marine environments, thus the need for sustainable exploitation has been identified by the Environmental Defense Fund as the key priority in preserving marine biodiversity. Other threats to aquatic biodiversity include urban development and resource-based industries, such as mining and forestry that destroy or reduce natural habitats. In addition, air and water pollution, sedimentation and erosion, and climate change also pose threats to aquatic biodiversity.

  1. Overexploitation of species — Overexploitation of species affects the loss of genetic diversity and the loss in the relative species abundance of both individual and /or groups of interacting species. The population size gets reduced because of disturbances in age structure and sex composition. Efficient gears remove quick growing larger individuals . consequently, the proportion of slow growing ones increases and the average size of individuals in a population decreases. Over-fishing causes change in the genetic structure of fish populations due to loss of some alleles. Thus, genetic diversity gets reduced .

  2. Habitat modification — Physical modification of habitat may lead to species extinction. This is mainly caused due to damming, deforestation, diversion of water for irrigation and conversion of marshy land and small water bodies for other purposes. Construction of dams on river impedes upstream migration of fishes and displaces populations from their normal spawning grounds and separate the popultion in two smaller groups. Deforestation leads to catchment area degradation due to soil erosion which results into sedimentation and siltation. This not only affect the breeding ground of aquatic organisms but cause gill clogging of small fishes also.

  3. Pollution load — Four forms of pollutants can be distinguished-

  1. Poisonous pollutants — Agrochemicals, metals , acids and phenol cause mortality, if present in a high concentration and affect the reproductive functionality of fish (Kime, 1995).

  2. Suspended solids — it affects the respiratory processes and secration of protective mucus making the fish susceptible to infection of various pathogens.

  3. Seewage and organic pollutants — They cause deoxygenation due to eutrophication causing mortality in fishes.

  4. Thermal pollution It cause increase in ambient temperature and reduce dissolved oxygen concentration leading to death of some sensitive species.

These factors affect the aquatic biodiversity directly or indirectly. Excessive mortality of organisms due to any of these factors may lead to two type of effects – i) extinction of the species / populations ii) reduction of population size.

Conservation Approaches

Aquatic conservation strategies support sustainable development by protecting biological resources in ways that will preserve habitats and ecosystems. In order for biodiversity conservation to be effective, management measures must be broad based.

  • Aquatic areas that have been damaged or suffered habitat loss or degradation can be restored. Even species populations that have suffered a decline can be targeted for restoration (e.g., Pacific Northwest salmon populations).

  • An aquatic bio- reserve is a defined space within a water body in which fishing is banned or other restrictions are placed in an effort to protect plants, animals, and habitats, ultimately conserving biodiversity. These bio-reserves can also be used for educational purposes, recreation, and tourism as well as potentially increasing fisheries yields by enhancing the declining fish populations. These bio-reserves are also very similar to marine protected areas, fishery reserves, sanctuaries, and parks.

  • Bioregional management is a total ecosystem strategy, which regulates factors affecting aquatic biodiversity by balancing conservation, economic, and social needs within an area. This consists of both small-scale biosphere reserves and larger reserves.

  • Watershed management is an important approach towards aquatic diversity conservation. Rivers and streams, regardless of their condition, often go unprotected since they often pass through more than one political jurisdiction, making it difficult to enforce conservation and management of resources. However, in recent years, the protection of lakes and small portions of watersheds organized by local watershed groups has helped this situation.

  • Plantation of trees in the catchment area of water body prevent soil erosion and subsequently reduce the problem of slitation in water body resulting in better survival of aquatic organisms.

  • Avoid the establishment of industeries, chemical plants and thermal power plants near the water resources as their discharge affect the ecology of water body resulted in loss of biodiversity.

  • The World Resources Institute documents that the designation of a particular species as threatened or endangered has historically been the primary method of protecting the biodiversity.

  • Many specialized programs should be instituted to protect biodiversity. For example, the USDA Forest Service started a cooperative state-federal program with a goal to restore the health of riverine systems and associated species.

  • Regulatory measures must be taken on wastewater discharge in the water body to conserve biological diversity.

  • Increasing public awareness is one of the most important ways to conserve aquatic biodiversity. This can be accomplished through educational programs, incentive programs, and volunteer monitoring programs.

  • Various organizations and conferences that research biodiversity and associated conservation strategies help to identify areas of future research, analyze current trends in aquatic biodiversity.


Hendrik S. and K. Martens (2005). Aquatic Biodiversity: v. 2: The Diversity of Aquatic Ecosystems (Developments in Hydrobiology). Springer Publi.

Kumar, U. and Asija, M. J. (2009). Biodiversity: Principle and Conservation. Agrobios (India)

Ormond, Rupert F. G., John D. Gage, and Martin V. A. (Editors), 1997. Marine Biodiversity: Patterns and Processes, Cambridge University Press, New York.

Padhi, B.K. and Mandal, R. K. (2000). Applied Fish Genetics. Fishing Chimes Publi.

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