Field Preparation

• Lakes
• Rivers and Streams
  - Physical Characteristics
• Estuaries
• Noxious Weeds
• Macroinvertebrates
• Hyporheic Zones
• Groundwater
• Shellfish

Macroinvertebrates

Description

Macroinvertebrates are animals without backbones which can be seen with your unaided eye. Benthic macroinvertebrates spend most of their lives on the bottom of streams, rivers or lakes.

• They consist of worms, snails, clams, crustaceans, and mostly insects.
• They may build cases, tubes or nets that they live in and attach themselves to rocks or other materials in the water.
• Others may roam freely over rocks, organic debris and other surfaces during all or part of their life cycle.
• Aquatic insects have a dual existence: they spend most of their lives in the water as immature forms - larvae, pupae or nymphs - followed by a shorter stage as winged adults.
• Bethic insects, such as mayflies, caddisflies and stoneflies develop through distinct stages:
  • egg
  • larva
  • perhaps a pupa (like caddisflies and beetles)
  • adult

Role in Streams

• Many insects have different feeding habits.
• Insects in turn are food for fish, birds, amphibians, reptiles, and other insects.

Bio-indicators

Some insects are tolerant of pollution; others are not. The presence or absence of tolerant and intolerant types can indicate the condition of the stream.

Benthic macroinvertebrates are good measures of the water quality they inhabit, because they are relatively stationary until their adult stage. The number and diversity of these creatures found at any location on a waterbody, and the degree of pollution the particular type of bug can tolerate, will predict the water quality there. Or conversely, the water quality at a particular location will predict the number, diversity and type of bug that can live there.

Aquatic insects are easy to collect, trickier to identify, but on the whole, easier and cheaper to use as indicators than fish and algae.

Collection

In riffle areas, macroinvertebrates are collected with various kinds of nets, depending on the purpose of the investigation.

They are collected in other stream habitats such as pools with different collecting gear.

Identification

Aquatic insects can be identified to their various taxonomic groupings (order, family, genus, species, etc.) by keys which use descriptions of their body parts and sequences of decisions.

It's easiest to first learn the common name and the major grouping (order) of aquatic insects, e.g.:

• caddisfly (common name)
• Trichoptera ("order" name)

After a sample is collected with a net, the organisms are usually sorted into major groups such as "order". One counts the number of each major group and then interprets the results in various ways.

Interpretation

"Bug samples" can give an indication of stream health by:

• Presence or absence of tolerant or intolerant organisms. Presence of many tolerant insects and the absence of intolerant forms suggests an unhealthy stream.
• Diversity (many different kinds) of the community. High diversity usually indicates a healthy system.
• Diversity of "feeding types:" scrapers, shredders, collectors and predators. Note: Although still commonly found in monitoring descriptions, this method of interpretation is currently being questioned by invertebrate experts and terrestrial guides.