Biota of Rivers and Streams - Hydro-Environmental Analysis: Freshwater Environments - page 178

TABLE 6.2
Aquatic Insect Functional Feeding Group Categorization and Food Resources

Particle Size
Range of Food (mm) Functional Groups Feeding Mechanisms Dominant Food Resources

Shredders Chew conditioned or live

vascular plant tissue, or
gouge wood

Decomposing (or living hydrophyte)
vascular plant tissue-coarse
particulate organic matter

>1.0

Filtering-Collectors Suspension feeders—ilter

particles from the water
column with nets or adapted
body parts

Decomposing ine particulate organic
matter; detrital particles, algae, and
bacteria

0.01-1.0

Gathering-Collectors Deposit feeders—ingest by

gathering sediments or brush
loose surface deposits

Decomposing ine particulate organic
matter; detrital particles, associated
detritus, and microlora and fauna

0.05-1.0

Scrapers Graze mineral and organic

surfaces

Periphyton-attached algae and
associated detritus and microlora
and fauna

0.01-1.0

Plant piercers Herbivores—pierce tissues or

cells and suck luids

Macroalgae 0.01-1.0

Predators Capture and engulf prey or

ingest body luids

Prey-living animal tissue >0.5

Source: Modiied from Merritt, R.W., Cummins, K.W., and Berg, M.B. (eds), An Introduction to the Aquatic Insects of
North America , 4th ed., Kendall/Hunt Publishing Company, Dubuque, IA, 2008.

based on methods of feeding (e.g., percentages of ilterers, grazers, and scrapers) and habitat
(e.g., percentage of clingers).
Functional feeding-type mechanisms are listed in Table 6.2. As illustrated by the RCC
(Figure 6.2), all feeding types would be expected in low-order streams and rivers, where most of
the organic matter is coarse, such as leaves and debris. In higher-order streams, where ine par-
ticulate matter dominates, the collectors and predators dominate the benthic macroinvertebrates.
Typically, a decrease in the percentage of the aquatic macroinvertebrate population represented by
each of these functional feeding groups, or the number of taxa within each group, is an indicator
of a decline in aquatic health. Conversely, an increase in the percentage population of ilterers is
evidence of a decline in aquatic health (Barbour et al. 1999).
The characteristics of functional habitat designations are also used to differentiate macroinver-
tebrates. The U.S. EPA's Biological Indicators of Watershed Health includes the following habitat
groups:

• Clinger—able to remain stationery on bottom substrates in lowing waters

• Climber—feeds on submerged aquatic vegetation (SAV) by climbing

• Sprawler—can be found on both the surface of SAV and substrates

• Burrower—feeds on ine organic matter while buried in sediments of lakes and streams

• Swimmer—can control the direction and velocity of its movements

• Diver—able to swim from the surface to the bottom of the water column

These habitat types relect macroinvertebrate adaptations for maintaining their position and
moving about in the aquatic environment (Merritt et al. 2008). Generally, a decline in any of these
feeding types in terms of the number of taxa or the percentage of the population is an indicator of a
decline in aquatic health (Barbour et al. 1999).