[1]The fauna specialized for life in and along running waters classically includes vertebrates such as fish, amphibians, reptiles, birds, mammals, but the mass of these spine-possessing taxa are beholden to the life history patterns and presence of stream dwelling invertebrates. Invertebrates are by far the most dominant taxon in rivers, existing in virtually every niche and microclimate. Benthic macroinvertebrates (BMIs) possess fascinating morphological and behavioral adaptions signature to the benthic denizens, but this study is particularly concerned with BMIs as water quality indicators. Because organisms in streams and rivers are limited to specific ranges of physicochemical environments by their physiological tolerances, we can make characterizations about the presence of absences of common characters in the stream community.
Water Quality
Assessing water quality is concerned with predicting, tracking, and determining symptoms and proximate causes of ecosystem degradation. Water quality data includes documentation of physicochemical parameters (such as pH, dissolved oxygen, temperature, suspended materials) and biotic sampling. Regulation agencies can look to the local flora and fauna as bioindicators, organisms shaped by present inhabitat forces. River monitoring is particularly concerned with the sampling of macroinvertebrates. As instream inhabitants, whose morphology, reproduction, and life history patterns are tethered to their biogeography, the presence or absence of these organisms can speak volumes to the processes and patterns acting upon the entire stream community.
(See Below)
The EPT Trifecta
In well oxygenated streams throughout the world, one would expectedly encounter some variety of mayfly (Ephemeroptera), stonefly (Plecoptera), and/or caddisfly (Trichoptera). The presence and proportion of EPT are looked to as bioindicators because the members of these three orders tend to have a low pollution tolerance threshold.
This assertion tells us two things:1) The breakdown and processing of organic pollution creates a severe depression in the amount of available dissolved oxygen. EPT should not be as common in polluted areas.
2) Since headwaters are well-oxygenated, we can project that EPT should be present in headwaters/low order streams/or a similarly simulated situation.
***An interesting notion when paired with predictions made in Functional Feeding Groups...
EPT's are not the only indicators of water quality, but because of their intolerance for low, dissolved oxygen levels, their population numbers can make for a quick inference. It's important to remember oxygen is just one factor affecting benthos. Toxic chemicals, nutrients and sediments impact habitat quality, and the Milwaukee River's catchment in particular has a long history of agricultural and industrial activity.
Taken directly from Friends of the Chicago River, Macroinvertebrate Fact Sheet:Stonefly Larvae
Mayfly Larvae
[2]Caddisfly Larvae • Order Plecoptera
• Long, thin antennae protrude from the front of the head
• Three pairs of segmented legs, with two claws on the end of each of the legs
• If gills are present, they are located on the bottom of the thorax
• Two long, thin tails grow out of the rear of the abdomen
• Elongated body
• Their name is such because larvae are often found among stones in streams
• Closed breathing system
• Move their bodies up and down or from side to side, to increase the amount of water moving
over the gill surface. This makes up for low dissolved oxygen or too little current
• The larval stage usually lasts for 10-11 months before they crawl out of the water and
transform into adults
• Usually live in small, cool, swift streams
• Larvae live in the water and adults live on the land
• Adults have wings but larvae do not
• Larvae often eat midges and blackflies
• Stonefly larvae break down plant parts that fall into rivers and streams, so that other
organisms can eat them later
• Other invertebrates, fish, salamanders, and birds eat stoneflies
• Pollution intolerant
• Order Ephemeroptera
• Elongated body shape
• Well-developed eyes
• Slender antennae
• Three pairs of segmented legs with one claw on the end of each
• The abdominal segments have feathery or plate-like gills
• Either two or three long, thin tails extend from the end of the abdomen
• Many species emerge from the water as adults during the month of May
• Larvae live in stones and plants found in the water
• An important part of the food web as they eat algae and dead plants
• Eaten by fish
• When there are many mayflies in an area, it is a sign that the aquatic environment is healthy
• Moderately pollution intolerant
• Order Trichoptera
• Cylinder-shaped body
• Hardened head and a softer abdomen
• Three pairs of segmented legs
• Pair of prolegs are present with a single claw on each on the end of the abdomen
• Live in rivers, streams, ponds, and lakes
• Construct portable houses for themselves out of silk, and drag their homes around with them
• Many kinds have single or branched gills on their abdomens
• Breathe by dissolved oxygen diffusing across the soft tissue parts of their bodies. A current
of water running inside their portable homes when they wiggle their bodies insures their
dissolved oxygen supply
• Many catch their food (small invertebrates, plant parts, algae) in a variety of ways, including
with nets constructed of silk
• Break down leaves and other material so they can be eaten by other organisms
• Moderately pollution intolerant
Refs--
Giller, Paul S., and Björn Malmqvist. The Biology of Streams and Rivers. Oxford: Oxford UP, 1998. Print.
"Indicator Species." EPA. Environmental Protection Agency, n.d. Web. 16 Oct. 2012. <http://www.epa.gov/bioiweb1/html/indicator.html>.
"Invertebrates as Biological Indicators." EPA. Environmental Protection Agency, n.d. Web. 16 Oct. 2012. <http://www.epa.gov/bioiweb1/html/invertebrate.html>.
Wisconsin. Department of Natural Resources. N.p., n.d. Web. 10 July 2012. <http://dnr.wi.gov/water/basin/milw/milwaukee_801.pdf>.
Wisconsin. Department of Natural Resources. N.p., n.d. Web. 10 July 2012. <http://dnr.wi.gov/water/basin/milw/milwaukee_801.pdf>.
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