2012 Benthic Survey

Macroinvertebrate Identification, Count, and Categorization (sampled 26 Jul 2012) by Emma Brereton

New Hope Creek (near Gate 26, Duke Forest, Orange County NC)

Name # Found Identification
Caddisfly Larvae 14 Common
Mayfly Nymphs 11 Common
Stonefly Nymphs 6 Few
Water Penny Larvae 5 Few
Beetle Larvae 2 Few
Clams 1 Few
Crayfish 1 Few
Aquatic Worms 3 Few

Common =10-99 organisms; Few= 1-9 organisms; Abundant= 100+ organisms

NOTE: Sensitive organisms: italicized

Group Name Group Index Value
Sensitive 21.2
Somewhat Sensitive 9.6
Tolerant 1.2


Index Calculation Description

For each group (sensitive, somewhat sensitive, and tolerant), the number of each identification was multiplied by a weighting factor and then added together to produce the group index value (above).

The group index value was then added together to produce a total score: 32

The total score can be rated using this water quality key:

Excellent (>39) Good (39-26) Fair (25.9-17) Poor (<17)


From our benthic research, we can conclude that the water quality of the New Hope Creek site where we worked is considered good. This is because of the diversity of sensitive macroinvertebrate exhibited at this site.