USING BIOINDICATORS TO MONITOR AND DETECT SEWAGE

•  What is it?

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

• Example of bioindicators

·         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.

·         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.

•  How is it done?
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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