Benthic Macroinvertebrates

What these critters can tell us about water quality

Benthic Macroinvertebrates

• Aquatic organisms that lack a backbone and are large enough to be seen with naked eye

• Benthic = bottom dwelling

Why use macros for indicating aquatic ecosystem health?

• Homebodies – don’t move very far

• Easily collected• Found year round• Give longer term

picture of the past water quality – living populations take time to rebound after a pollution event

Pollution-sensitive vs. pollution-tolerant

• Index species - when found in large populations, they indicate the health of the water

• Greater diversity in macro population = health

Stress Tolerance• Ability of organisms to withstand disturbances in

their environment• Disturbances are of human or natural origin.• Environmental stress is a broader term referring

to any action that brings about undesirable changes—removal of water, dam construction, deforestation are examples of human induced stress.

• Since different organisms have different stress tolerances, we can use BMIs as ecological indicators.

Factors that limit BMI populationsOXYGEN

• Invertebrates respire, taking in oxygen and releasing carbon dioxide

• Air contains 21% oxygen, where as saturated water only contains 0.0015%

• Temperature affects oxygen concentration• Species with high oxygen requirements are

restricted to areas where water is cool, has fast current, or where splashing adds O2 to water

BREATHING

• Most depend on dissolved oxygen from water• Use gills, or through the general body surface, or both.• Some have specialized behaviors to increase oxygen

diffusion (ie wiggling)• Some breathe oxygen from the atmosphere:– Some attach a tiny quantity bubble of oxygen to body

and breathe from it while under surface of water– Some use breathing tubes or siphons and hang out near

surface of water

Factors that limit BMI populationsORGANIC SUBSTRATES

• Includes both alive (herbaceous) and dead (detrital) plant material

• Provides a place to live (habitat)• Organic substrates are excellent habitats due

to natural complexity

The Greatest Diversity of BMIs

• Found in habitats where the mineral substrate is predominantly loose cobbles and pebbles, with a few boulders.

• Size + irregular composition=infinite array of hiding places, attachment sites, current velocities, surfaces for algae to grow, edges to catch coarse detritus and woody debris, and openings where fine detritus settles

Factors that limit BMI populationsACIDITY

• pH scale-concentration of H+ ions• Range for aquatic organisms is 5-9• VT water quality standard is

6.5-8.5

Feeding Groups – what’s its job?• Collectors – feed on

decomposing organic matter– Gathering – bottom

feeders– Filtering – trap and strain

out of water• Scrapers – scrape algae

off rocks• Shredders – break large

pieces of plant material into smaller pieces

• Predators – capture and kill other organisms

• Parasites – attach to and suck fluid from other organisms

ID’ing your macros• Mouth parts – job?• Wing buds• Gills on abdomen• Antennae• Leg quantity• Special casing• Claws (tarsus)• Tails (cerci)

• Identify ORDER– Ephemeroptera *– Plecoptera *– Trichoptera *– Megaloptera– Odonata– Hemiptera– Coleoptera– Diptera– others

• Common name

Order: EphemopteraCommon: Mayfly• 6 legs• 3 long tails (cerci)• Gills along abdomen• Short antennae• Wing buds may be present

•https://www.youtube.com/watch?v=F6RKxeREHLc

MAYFLY LIFECYCLE

Order: PlecopteraCommon: Stonefly• 6 legs• 2 long tails (cerci)• moderate length antennae• “armor” on thorax• no gills on abdomen• Single tarsus (claw) at end of leg

STONEFLY LIFECYCLE

Order: TrichopteraCommon: Caddisfly larva• 6 legs on thorax•2 hooks / false legs on end of abdomen• May have gills along lower half of abdomen•May be in stick, leaf or stone case w/ head protruding•https://www.youtube.com/watch?v=_V2_aWmjpow

CADDISFLY LIFECYCLE