Benthic Macroinvertebrat

es (Organisms which lack a backbone and are visible

to the unaided eye.)

Presented by:

Warren County Soil & Water Conservation District

What are Benthic Macroinvertebrates?

• Benthic means: living at the bottom of a body of water (stream, river, pond)

• Macro - large• Invertebrate - animal without a backbone or

spinal column• Macroinvertebrate - large water dwelling

invertebrate able to be seen without a microscope; organisms that have no backbone

• Eat leaves & algae in streams• Source of Energy for larger animals

Why Study

Macroinvertebrates?

• An indicator species tell scientists when there is a problem in nature - specifically the stream environment

• Source of Energy for larger animals• Help with the Food Web

Functional Feeding Groups

• Based on their feeding methods and adaptations

• They are an important part of the food web.

• They are a primary link between the base of the food chain and larger animals, such as fish.

Shredders• The first group of

macroinvertebrates to break down the detritus (leaves that have started to decompose).

• Includes craneflies, some caddisflies, stoneflies, sowbugs, and scuds.

• They break the detritus down into fine particles.

Collectors• Fine particles drifting

downstream become food for the collectors.

• Collectors use various methods of either filtering or gathering of fine particles. Filterers use fan-like filaments near the mouth to capture food particles.

• Includes some mayflies, midges, and net-spinning caddisflies

Grazers(also called Scrapers)

• Feed on the algae that grow on the surface of rocks

• Includes some caddisflies, the water penny (a beetle), and certain midges and mayflies

Predators• The shredders,

collectors, and grazers are a food source for the predators.

• Includes dobsonfly and dragonfly

• Predators have large powerful mouth parts for grasping prey.

What Do Benthic Macroinvertebrates Tell Us?

• They are divided into three groups, based upon their ability to live in polluted water:

• Taxa 1- Pollution Sensitive Group is very sensitive to pollution.

• Taxa 2- Pollution Intermediate Group can live in a somewhat polluted environment.

• Taxa 3 - Pollution Tolerant Group can usually be found in any type of water.

Macroinvertebrates that are Sensitive to Pollution

Group 1 Found in Good Quality Water

• Stonefly nymphs have two tails or cerci.

• Some species eat dead plants and algae; some stalk their prey and are carnivorous.

• They are very sensitive to low levels of oxygen.

• Some stonefly species live for 3 years as a nymph.

Stonefly

• Stonefly adults live from one week to one month. Females stoneflies live the longest.

• Most stonefly species can not eat while in the adult stage.

www.jerryhadden.com/insects/stoncycle.jpg

Stonefly Life Cycle

Larvae

Adult

• Larvae eat algae and larvae.

• Very sensitive to pollution can not live in places where rocks are covered by algae and sediment

• Gills are located at the bottom of the abdomen.

• Very little is known about the adults. Female adults lay about 400-500 eggs. The eggs hatch in the water. Mature larvae come out of the water.

Water Penny

Picture from Joyce Gross http://bugguide.net/user/view/677

• Easily recognized by shell pointing to the right (see upright position below).

• Very sensitive to low oxygen levels. Low oxygen occurs when too much sediment is deposited in the stream.

• Gilled snails lay eggs. The hatched snails look like miniature adults.

• Some of their predators include, waterfowl, leeches, crayfish and fish.

• Always make sure that the snail is alive before counting it for a stream assessment.

Gilled Snail

http://www.pennridge.org/works/gdsnail.html

http://people.virginia.edu/~sos-iwla/Stream-Study/Catalog/FGGilledSnail.HTML

• Caddisfly larvae are worm-like with legs.

• They build hollow cases that are often attached to rocks made from sand, twigs, small stones, crushed shells, rolled leaves and bark. They eat algae, small plants and animals.

• Some caddisfly species are carnivorous and spin webs to catch their prey. Some just eat algae and plants.

• Adult caddisfly only live a few weeks. These adults have partial mouth parts and can only drink water.

http://www.kidfish.bc.ca/caddis_cycle.htm

Caddisfly

Without Casing

With Casing

Adult Caddisfly

• Adults are found more often than larvae.

• Adults are unique; they are completely aquatic.

• They are very slow and cling to rocks

Riffle Beetle

http://bugguide.net/node/view/294200/bgimage

Dobsonfly• larvae can grow to up to 3 inches

• have a pair of mandibles.

• eat other aquatic insects

• have gills

• larvae are often found clinging to rocks

• play an important part in the food chain - fish love them.

• Make sure you always grab them behind the head so that you don’t get pinched.

http://www.swcd.co.trumbull.oh.us/macro%20life%20history/dobsonfly/dobsonfly.htm

http://www.epa.gov/bioiweb1/html/dobsonflies.html

www.svbnc.org/images/dobsonfly.jpg

By Rich WoodIllustration by Ted Walke

• Adults only live a few days because they are week flyers.

• Dobsonflies are eaten by fish, birds and bats.

Mayfly

http://www.lifeinfreshwater.org.uk/Species%20Pages/Mayfly%20larva.jpg

• Mayfly nymphs have 3 distinct tails.

• nymphs are normally found attached to rocks

• eat small plant and animal debris

• prey to many fish and play an important role in the food chain

• nymphs have gills

http://www.swcd.co.trumbull.oh.us/macro%20life%20history/mayfly/mayfly.htm

•Adults live only a few days to lay eggs.

•Fly fisherman love to use these as bate because trout love mayflies.

•Adults will have one or two tails.

•Adults do not have mouth parts.

http://www.jerryhadden.com/insects/maycycle.jpg

Macroinvertebrates That Are Somewhat Sensitive to

Pollution Group 2

Found in Good or Fair Quality Water

Riffle Beetle Larvae

• Larvae resemble small “torpedoes” with circular stripes or rings around the body.

• less than a half-inch in length.

• eat primarily algae.

• Finding adult riffle beetles indicates that you have clean water.

http://ghsonline.net/riverproject/biologymacinvt/RiffleBeetle.htm

Damselflies

• Damsel Fly nymphs are found in stream beds, rocky areas, sand, soft sediment, ponds and in lakes.

• They have an elongated body with paddle-like tails (which are actually gills).

• Damselfly nymphs eat other aquatic bugs.

http://www.litzsinger.org/weblog/archives/damselfly.jpg

http://www.uky.edu/Ag/CritterFiles/casefile/insects/damselflies/damselflies.htm#naiad

http://richard-seaman.com/USA/States/California/CoachellaValleyPreserve/CoachellaBlueDamselfly.jpg

• Adult damselflies love to eat mosquitoes.

• They are really good flyers because damselflies can change directions when flying (like a helicopter).

• Because they are smaller, many dragonflies eat damselflies.

http://piccies.flybywire.org.uk/DamselDragonflies/20030604/RedDamselfly.jpg

Dragonflies

http://www.bugsurvey.nsw.gov.au/html/popups/lge_dr-ny-b_col.html

• Nymphs vary in shape but most have robust, elongated , or spider-like bodies.

• Sometimes algae grows on their bodies.

• They grow to about 2 inches.

• Dragonfly nymphs feed upon other aquatic macroinvertebrates, small fish and tadpoles.

• They are often found in slow moving streams and in ponds which indicate low-oxygen levels.

• Dragonflies can be nymphs for up to 4 years.

http://www.dragonfly-site.com/dragonfly-life-cycle.html

• If the nymph stage is completed in the winter, the nymph will wait till spring to come out of it’s exuvia (cast of skin or shed skin).

• The nymph climbs out of the water on a plant to leave it’s exuvia.

• The adult then looks for a mate. Females lay eggs in the water.

• Adults live only for one to two months.

Alderfly

• Alderflies are fearsome predators, often nicknamed “toe-biters”.

• They prey on other macroinvertebrates.

• Larvae take one to two years to develop.

• Adults alderflies are found in May and June.

• They typically all hatch together and then mate. Females lay their eggs on plants. The hatched larvae drop into the stream and hatch.

• Adults live only a few weeks.

Cranefly

http://www.kidfish.bc.ca/crane_fly_cycle.htm

• Larvae grow up to 3 inches.

• Larvae feed on mostly plants and plant debris.

• Adults look like giant mosquitoes.

• Adults can not eat.

• Try to leave the adults alone, because if you catch one, their legs will fall right off!

Scud

• Scuds look a lot like shrimp.

• 20% of a trout’s diet is scuds

• They will eat pretty much anything, but their diet is mostly vegetarian.

• A scud’s color can change a little.

• They spend their whole life underwater.

• The color of trout flesh comes from an orange pigment, called carotene. Scud get this from eating other scuds.

http://www.kidfish.bc.ca/scud_cycle.htm

Crayfish

http://magickcanoe.com/crayfish/crayfish-with-minnow-large.jpg

• Crayfish are omnivorous and use their pinchers to tear off chunks of food.

• Crayfish are prey to larger game fish.

• They grow to about 6 inches.

• Adults lay a mass of eggs under their tail.

• When they hatch, they look like a tiny adult. They often cling to their mother for protection for a little while.

• Some crayfish burrow in soil beside streams and ponds.

Clams and Mussels

• Mussels are large; fingernail clams are the smallest.

• Fingernail claims are self-fertilizing with the young developing inside the adult.

• Larvae, called glochidia, develop inside the adult female and are released into the water where they eventually attach onto a host fish. They parasitize the fish for about two weeks, or until they drop off and develop on the stream bottom.

• They are filter feeders.

• They are preyed on by fish and mammals.

http://www.fws.gov/midwest/Genoa/mussel_recovery.html

www.epa.gov/bioindicators/html/mussels.html

GROUP 2 (These organisms can exist in a wide range of

water quality conditions.)

GROUP 2 (These organisms can exist in a wide range of water quality conditions.)

Macroinvertebrates That Are Tolerant of Pollution

Group 3Found in Any Quality Water

Black Fly

Aquatic Worm• Close relative of an earthworm

• Found anywhere there is fresh water

• Aquatic worms prefer fresh water.

• They eat the mud and any small bits of plant or animal matter they find. This worm often arranges itself with the head downward by building a small tube in the mud and letting its butt (behind) stick out into the water. Many aquatic worms can be found together; their bodies stick out of their tubes and wave back and forth with the currents of the water.

• They reproduce like earthworms. They lay eggs in small cocoons that are left on rocks or the soil bottom.

• Bottom feeders are their predators.

http://www.fcps.edu/islandcreekes/ecology/aquatic_worm.htm

Midge Fly Larvae

• the smallest macroinvertebrate to collect

• can be bright red

• Midge larvae are very common.

• Trout depend on midge fly larvae because they can be found almost year round.

• Keep on the look out for these larvae if you live by a pond or stream! They often hatch in thousands and can be bothersome.

• If the water temperature is right, the complete life-cycle can take less than two weeks. Midge flies (or midges) are only larvae for 3-7 days, pupae for three days, and adults for 3-5 days.

• They do not have mouthparts.

http://www.ces.ncsu.edu/depts/ent/notes/Urban/midges.htm

Leech

http://www.kidfish.bc.ca/leech_cycle.htm

• Related to the earth worm

• Not all leeches suck blood. Some eat decaying plant and animal debris.

• They love shallow, dark water.

• If you find an abundance of leeches, it usually means very, poor water quality.

Pouch Snail

http://www.epa.gov/bioiweb1/html/pouchsnails.html

• Shell opening is on the left side.

• Does not possess gills. Instead, they have a sac-like lung to breath air.

• The pouch snail lays gelatinous egg masses that are deposited under rocks or other debris.

• Eat algae, aquatic plants and sometimes dead animals.

• Preyed upon by fish, birds, and some turtles.

• Pouch snails generally indicate nutrient enriched conditions.

Black Fly Larvae

http://bitinginsects.siteideas.net/life-cycle(blklarge).jpg

• Larvae are small and maggot-like.

• They use their bulbous end to attach themselves to rocks and other material in fast rapids.

• They can be found in large colonies.

• Adults are considered pests, but fish love them!

Overview and cross sections of a pool, riffle, and run. Varying flows and depths create a variety of habitats for macroinvertebrates.

Different habitats mean different macroinvertebrates.

Collecting Macroinvertebrates

The "kick seine" technique is used to collect organisms.It is a simple procedure used in riffle areas for collecting live stream-dwelling macroinvertebrates. Participants examine the variety of macroinvertebrates in the collected samples.

Analyzing the Samples

-The water quality rating for the sample site is calculated based on an index value that is determined by the number of different macroinvertebrate types collected.

-The index value is calculated by multiplying 3 times the number of sensitive types, 2 times number of somewhat sensitive types, and 1 times the number of tolerant (non-sensitive) types.

-The three resulting values are then summed to provide a total index value which is compared to the values for excellent, good, fair, and poor water quality ratings.

Thank you for helping our rivers!

Warren County Soil & Water Conservation District