Bioindicators are biological responses from organisms used
to assess the quality of the environment and how it changes over time. Changes
in the environment are often attributed to anthropogenic* disturbances (e.g.,
pollution, land use changes) or natural stressors (e.g., drought, late spring
freeze).
*environmental pollution and pollutants originating in
human activity
·
Aresa, a private company originally based at
the University of Copenhagen, is marketing bioindicator plants commercially. Aresa
genetically engineered a weedy plant (left) with a gene that produced a
red-coloured product when the gene's expression was induced by a receptor as a
breakdown product of TNT. On the right is a photo of a soil tray planted with the
engineered bioindicator seed in which the upper right quadrant of the soil has
been drenched with liquid TNT. The photo at the right indicates the size of
isolated plants.
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Cutthroat trout inhabit cold water streams of
the western United States. Most trout have an upper thermal tolerance of
20°–25°C; thus, their temperature sensitivity can be used as a bioindicator of
water temperature.
Biomonitoring involves the use of organisms as indicators
to detect pollutants; generally, benthic macroinvertebrates*, fish, and/or
algae are used. Certain aquatic plants have also been used. This is because biochemical,
genetic, morphological, and physiological changes in certain organisms have
been noted as being related to particular environmental stressors and can be
used as indicators to monitor and detect pollution in the water through the
changes in them, as well as acting as an early warning system for larger-scale
effects; for example, reduced photosynthesis in a plant or a coral may indicate
stress from exposure to herbicides.
A method to detect pollution developed in Israel a few
years back, "listening" to algae to detect pollution. Researchers
have discovered that by shining a laser beam on the algae they can stimulate
photosynthesis. Depending on the rate of photosynthesis and the health of algae
differing amounts of heat are shot back into the water, creating sound waves.
These waves can be picked up by an underwater microphone, allowing the
scientists to analyse the health of the algae and the condition of the
surrounding water.
Barramundi and mud skippers appear also to be sensitive
bioindicator species. Monitoring of biochemical, cellular or genetic changes in
fish tissue using sensitive new techniques can help identify if changes are due
to natural variation or human-induced effects.
However it is also good to note that the absence of a
species is not as meaningful as it might seem as there may be reasons, other
than pollution, that resulted in its absence (e.g., predation, competition, or
geographic barriers which prevented it from ever being at the site).
An example to illustrate the above point would be the
Indus River. The Indus is the primary source of freshwater for most of
Pakistan, a fast-growing nation of more than 170 million people. Waters from
the Indus are drawn for household and industrial use, and support about 90
percent of the agriculture in the arid country. The Indus is one of the great
rivers of the world, but it is now so exploited that it no longer flows into the
ocean at the Port of Karachi. Instead, in the words of New York Times writer
Steven Solomon, the Indus is "dribbling to a meager end . . . Its
once-fertile delta of rice paddies and fisheries has shrivelled up." The
lower Indus had been a lush ecosystem, supporting artisanal fishers and
providing habitat to diverse species, including the critically endangered Indus
River dolphin.
Absence of multiple species present previously at the
same site is more indicative of pollution than absence of a single species. It
is clearly necessary to know which species should be found at the site or in
the system.
* Aquatic macroinvertebrates are organisms
without backbones that are visible to the eye without the aid of a microscope.
They live on, under, and around rocks and sediment on the bottoms of lakes,
rivers, and streams. As a result of their habitat choice, macroinvertebrates
are often regarded as “benthos” which refers collectively to organisms which
live on, in or near the bottom of lakes, rivers and streams.
- ·
How many types of biomonitoring are there?
There are two types of biomonitoring. One type of
biomonitoring is surveillance before and after a project is complete or before
and after a toxic substance enters the water (detecting). The other type of
biomonitoring is to ensure compliance with regulations or guidelines or to
ensure water quality is maintained (monitoring).
Sources:
http://www.treehugger.com/natural-sciences/researchers-discover-way-to-listen-to-algae-detect-water-pollution.html
http://www.water.ncsu.edu/watershedss/info/biomon.html
http://www.aims.gov.au/docs/research/water-quality/runoff/bioindicators.html
http://www.nature.com/scitable/knowledge/library/bioindicators-using-organisms-to-measure-environmental-impacts-16821310
http://enviroscienceinc.com/benthic-macroinvertebrates/
http://www.patentlens.net/daisy/Bioindicators/g1/2223.html
http://environment.nationalgeographic.com/environment/photos/rivers-run-dry/#/freshwater-rivers-indus-1_45142_600x450.jpg
