Aquatic Organismsby LeAnne Yenny

BenthicMacroinvertebrates

• Used as bioindicator organisms

• The presence or absence of these organisms in a stream can be used to reveal the overall ecological quality of the water.

• Generally, unpolluted waters support a greater variety of freshwater macros than polluted water.

Life Cycles• Incomplete metamorphosis (3

stages)– Eggs to Nymph to Adult

– Include mayflies, stoneflies, dragonflies, damsalflies, true bugs

• Complete metamorphosis (4 stages)– Eggs to Larva to Pupa to Adult

– Include flies, beetles, caddisflies, dobsonflies

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 the 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• Drifting downstream the

fine particles become food for the collectors.

• They 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, dragonfly.

• Predators have large powerful mouth parts for grasping prey.

1. Bacteria + Leaves = Detritus

(slimy leaves)2. Shredders break

down leaves3. Collectors filter

and gather leaf parts4. Grazers eat algae5. Predators feed on

all macros

Water Quality Indicators• Each

macroinvertebrate belongs in a Taxa - a group indicating the level of pollution tolerance

Taxa 1• Includes:

– Caddisfly (Trichoptera)

– Stonefly (Plecoptera)

– Water Penny

– Riffle Beetle

– Mayfly (Ephemeroptera)

– Gilled Snail

– Dobsonfly

STONEFLY ADULTSTONEFLY LARVA

Order: Plecoptera

ADULT MAYFLY MAYFLY LARVA

Order: Ephemeroptera

ADULT CADDISFLY CADDISFLY LARVA

Order: Tricoptera

Can you tell the difference?

Mayfly emerger

Stonefly nymph

Caddis comparison

Taxa 2• Includes:

– Crayfish– Sowbug– Scud– Alderfly Larva– Fishfly Larva– Damselfly– Watersnipe Fly– Crane Fly– Beetle Larva– Dragonfly– Clam

Taxa 3

• Includes:– Aquatic Worm

– Midge Fly Larva

– Blackfly Larva

– Leech

– Pouch Snail

– Pond Snail

– Other Snails

Questions?