LOSS
OF AQUATIC BIODIVERSITY- CAUSE AND CONSEQUENCE
Different causes of loss of aquatic biodiversity
1. Exotic Species
2. Human intervention
3. Habitat Loss and Degradation
4. Overexploitation
5. Aquaculture
6. Pollution
7. Sedimentation
8. Climate Change
9. Mining
1. Alterations to Hydrology
2. Air Pollution
3.
Dredging
Aquaculture
· Aquaculture production has increased greatly in
partial response to the evident decline in fisheries. While it can be a
beneficial process, certain types of aquaculture can also contribute to the
degradation of natural environments
ü Accidental release of non -native species
ü Habitat conversion
ü Pollution
ü Eliminate more fish than is being produced
· In addition, the food supplies of other aquatic
organisms including seabirds and seals can be depleted through the amount of
schooling fish used to make fishmeal for aquaculture production.
· In the salmon farming industry, fish feces and
uneaten fish feed can also contribute to pollution.
· In order to control fish disease during the process
of aquaculture, the use of antibiotics in fish feeds has increased.
· Antibiotics may leave residual traces in uneaten
feed and fish feces, which can become trapped in sediments in the marine
environment, potentially leading to toxic conditions for some species.
· Antibiotic use in aquaculture also leads to the
development of bacteria, which is antibiotic –resistant.
Human intervention
· Population growth – more space for shelter, more capture,
more destruction of aquatic habitat, more construction, more pollution.
· losses to aquatic biodiversity are now being linked
to public biases towards species viewed as "pests" or “threats“ or so
called “weed fish” or “trash fish” to society or towards species that are
either unobserved or whose existence and general importance to aquatic ecosystems
are unknown.
· Often "pest" or "threat" species
such as sharks, aquatic lizards and snakes have been hunted to near extinction
upsetting the natural balance of associated ecosystem.
· In addition, most people are unaware of the vast
number and importance of the small microorganisms that exist in aquatic
habitats.
· Organisms such as microbes and arthropods are a main
source of food for most aquatic organisms.
· Unfortunately, as a result of human biases
conservation and protection measures are lacking for many important aquatic
species, thus placing biodiversity at a greater risk.
Sedimentation
Some land management
practices including urbanization, farming and forestry practices, and
industrialization have all contributed to the increased flow of sediments, in
turn impacting aquatic resources over time, demands on land space and
associated resources have caused the removal of important stabilizing
vegetation and riparian buffers, altered wetlands, and increased the amounts of
impervious surfaces covering the land.
As a result of these
activities, sediment runoff into rivers, lakes, streams, and estuaries has
increased and is adversely affecting the biodiversity of these areas in a
number of ways including:
· Changing the physical structure of habitats and endangering
those species requiring specific depth, light, and water velocity conditions
through increased deposition.
· Carrying pollutants such as heavy metals, organic
pollutants, and nutrients through sediment runoff.
· Interfering with the respiration of species that
rely on gills to breathe and damaging delicate organisms such as corals in reef
communities.
· Covering important spawning habitats of fish and
other organisms.
Exotic Species
· A leading cause of biodiversity loss in many aquatic
ecosystems is the introduction of exotic species.
· An exotic species is a non -native plant or animal
deliberately or accidentally introduced into a new habitat.
· Such species include plants, fishes, algae,
mollusks, crustaceans, bacteria, and viruses.
· Such species that are able to reproduce and survive
outside of the habitats where they evolved are also referred to as alien,
introduced, invasive, non -native, or non –indigenous.
Exotic species can have
many negative impacts on the environment, the economy, and human health
· When species are introduced into an area, they may
cause increased predation and competition, disease, habitat destruction,
genetic stock habitat alterations, and even extinction.
· Approximately 68% of fish species lost in North America over the last century were caused by an invasion of
exotic species (Miller et. al, 1989).
· The invasion of exotic species has also caused the
economy to suffer through the displacement or elimination of important
commercial and sport fishing species.
Exotic plants
· Crowd out sunlight and nutrients from other plants
· Crowd out other plants, jeopardizing animals
dependent on native vegetation
· Overgrow, leading to excessive plant growth, which
in turn leads to decay and excess oxygen depletion, which results in fish losses
· Crowd out navigation channels
· Clog machinery
Exotic animals
· Consume food sources that native species would eat,
leaving insufficient food.
· Occupy safe or supportive habitat, leaving a reduced
amount of habitat for natives.
· Serve as food for native species but lack certain
essential nutrients, leading to death of native offspring.
· Consume eggs, young, and adults of native species.
