The following benthic indexes have been implemented
[!] = Exclude records from calculation for any taxon where the results have EXCLUDE_RICH_METRICS_YN = Y (To be implemented)
| Metric (by category) | Metric Description | Metric Calculation |
|---|---|---|
| Richness and diversity – this section mostly deals with counts of Taxa, not the numbers stored in results table (TAXON_COUNT). | ||
| Number of taxa | The count of unique taxa in the sample. A standard level of identification (family, genus, and species) must be defined for each taxonomic group. | Count all unique taxa [!] |
| Number of insect taxa | The count of insect taxa in the sample. | Count all unique taxa where the ancestor’s taxonomic CLASS = “INSECTA” [!] |
| % of non-insect taxa (% of taxon counts, not the number stored in TAXON_COUNT field | The percentage of taxa that are not insects | 100* (Number of taxa – Number of insect taxa) / Number of taxa |
| Number of Ephemeroptera taxa | Number of mayfly taxa | Count all unique taxa where the (ancestor’s) taxonomic order = Ephemeroptera. [!] |
| Number of Plecoptera taxa | Number of stonefly taxa | Count all unique taxa where the taxonomic order = Plecoptera. [!] |
| Number of Trichoptera taxa | Number of caddisfly taxa | Count all unique taxa where the taxonomic order = Trichoptera [!] |
| Number of Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa | Number of taxa in the insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies) | Count all unique taxa where the taxonomic order = Ephemeroptera or Plecoptera or Trichoptera [!] |
| Number of Ephemeroptera, Trichoptera, and Odonata (ETO) taxa | Number of taxa in the insect orders Ephemeroptera (mayflies), Trichoptera (caddisflies), and Odonata (dragonflies and damselflies) | N/A ? SKIP |
| Number of Odonata taxa | Number of dragonfly and damselfly taxa | Count all unique taxa where the taxonomic order = Odonata [!] |
| Number of Chironomidae taxa | Number of midge taxa | Count all unique taxa where the taxonomic family = Chironomidae [!] |
| Number of Hemiptera taxa | Number of “true” bug taxa | N/A ? SKIP |
| Number of Coleoptera taxa | Number of beetle taxa | Count all unique taxa where the taxonomic order = Plecoptera [!] |
| Number of Mollusca + Crustacea taxa | Number of mollusk (snails and clams) and crustacean (amphipods, copepods, decapods, et al.) taxa. These taxa are somewhat dependent on calcium for growth and reproduction. | N/A ? SKIP |
| Shannon diversity | An index of richness and composition calculated as: Σ –1)/Log(2); where n is the number of individuals in a taxon and N is the number of individuals in the sample, summed for all taxa in the sample. The index is commonly standardized on log of 2 (as shown here) or the natural log (log e). | Σ –2)/Log(2); where n is the number of individuals in a taxon and N is the number of individuals in the sample, summed for all taxa in the sample [!] |
| Composition and evenness - this section mostly deals with the numbers stored in results table (TAXON_COUNT). | ||
| Total Individuals | Sum of TAXON_COUNT for all results. Note that this includes result records where EXCLUDE_RICH_METRICS_YN = Y. | |
| Non-insects (%) | Non-insect individuals in the sample as a percentage of all individuals | 100*(Non-insect individuals) / (Total individuals) where “Non-insect individuals” = all records where ancestor CLASS not equal to INSECTA. |
| Oligochaetes and leeches (%) | Percentage of worm and leech individuals NEED PHYLO LEVELS | N/A – HOLD |
| EPT individuals (%) | Percentage of mayfly, stonefly, and caddisfly individuals. | 100*(EPT individuals) / (Total individuals); EPT = individuals in the taxonomic orders Ephemeroptera, Plecoptera, or Trichoptera |
| Taxa in EPT (%) | Mayfly, stonefly, and caddisfly taxa in the sample as a percentage of all taxa | THIS PERCENTAGE HAS NOTHING TO DO WITH TAXON_COUNT, JUST a count of the TAXON_ID as percent of total [!] |
| Ephemeroptera individuals (%) | Percentage of mayfly individuals | 100*(Ephemeroptera individuals) / (Total individuals); |
| Plecoptera individuals (%) | Percentage of stonefly individuals | 100*(Plecoptera individuals) / (Total individuals); |
| Trichoptera individuals (%) | Percentage of caddisfly individuals | 100*(Trichoptera individuals) / (Total individuals); |
| Chironomidae individuals (%) | Percentage of midge individuals | 100*( Chironomidae individuals) / (Total individuals); individuals in the taxonomic family Chironomidae |
| Taxa in Chironomidae (%) | Percentage of midge taxa | N/A – HOLD |
| Hemiptera individuals (%) | Percentage of “true” bug individuals | N/A – HOLD |
| Odonata individuals (%) | Percentage of dragonfly and damselfly individuals | N/A – HOLD |
| Coleoptera individuals (%) | Percentage of beetle individuals | 100*(Coleoptera individuals) / (Total individuals); individuals in the taxonomic order Coleoptera |
| Elmidae individuals (%) | Percentage of riffle beetle individuals | N/A |
| Number of individuals per taxon | The average number of individuals per unique taxon | N/A |
| Dominant taxon (%) | Individuals in the most numerous unique taxon as a percentage of all individuals | 100*(Maximum # individuals) / (Total individuals) |
| Dominant five taxa (%) | Individuals in the five most numerous unique taxa as a percentage of all individuals | N/A – HOLD |
| Pollution tolerance - In all of the pollution tolerance metrics, degrees of pollution tolerance are defined per taxon. | ||
| Number of intolerant taxa | Count of unique taxa that are sensitive to stresses (Tolerance values 0 – 3) | Count all unique taxa where the tolerance value >=0 and ⇐3.5 [!] |
| Taxa as intolerant (%) | Sensitive taxa in the sample as a percentage of all taxa | N/A – HOLD |
| Intolerant individuals (%) | Sensitive individuals in the sample as a percentage of all individuals | N/A – HOLD |
| Number of tolerant taxa | Count of unique taxa that are tolerant of stresses (Tolerance values 7 – 10) | N/A – HOLD |
| Becks Biotic Index | Weighted count of the most sensitive and moderately sensitive taxa | 2 * (Count all unique taxa where the tolerance value >=0 and ⇐1.5) + (Count all unique taxa where the tolerance value >1.5 and ⇐3.5) [!] |
| Taxa as tolerant (%) | Tolerant taxa in the sample as a percentage of all taxa | Tolerant individuals have tolerance values >=6.5 and ⇐10. Tolerant taxa/Total Taxa *100 [!] |
| Tolerant individuals (%) | Tolerant individuals in the sample as a percentage of all individuals | 100*(Tolerant individuals) / (Total individuals), where Tolerant individuals have tolerance values >=6.5 and ⇐10 |
| Hilsenhoff Biotic Index | The average individual pollution tolerance value for the sample. Modifications of the published index (Hilsenhoff 1987) may include assignment of tolerance values to previously unrated organisms or of groups of organisms at genus, family, or order taxonomic levels. | HBI = S (n)*(tolerance value)/N; where n is the number of individuals in a taxon and N is the number of individuals in the sample that have known tolerance values; summed for all taxa in the sample. |
| Functional feeding groups – has to do with adult and larval feeding types (either adult or larval type in category). | ||
| Number of collector-filterer taxa | Count of unique taxa that feed on particles filtered from the water column | N/A –HOLD |
| Collector-filterer individuals (%) | Filtering individuals in the sample as a percentage of all individuals | 100*( filterer individuals) / (Total individuals); individuals with the feeding type filterer |
| Number of collector-gatherer taxa | Count of unique taxa that feed on particles encountered among the substrates and detritus | N/A -HOLD |
| Collector-gatherer individuals (%) | Gathering individuals in the sample as a percentage of all individuals | 100*( Collector individuals) / (Total individuals); individuals with the feeding type = Collector |
| Number of predator taxa | Count of unique taxa that feed on living animal organisms | Count all unique taxa where the feeding type = predator [!] |
| Predator individuals (%) | Predatory individuals in the sample as a percentage of all individuals | 100*( Predator individuals) / (Total individuals); individuals with the feeding type = Predator |
| Number of scraper taxa | Count of unique taxa that feed on algae and bacteria that are attached to the surfaces of hard substrates | Count all unique taxa where the feeding type = scraper [!] |
| Scraper individuals (%) | Scraping individuals in the sample as a percentage of all individuals | 100*( Scraper individuals) / (Total individuals); individuals with the feeding type Scraper |
References: Hilsenhoff, W.L. 1987. An improved biotic index of organic stream pollution. Great Lakes Entomologist 20 (1):31—39