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Table 2 Random forest classification of 25 freshwater samples with different level of fecal contamination

From: Fecal source identification using random forest

Random forest classifications

Environmental sample ID

Type of sample

Major type of contamination

Level of fecal indicator bacteria

Level of qPCR human marker‡‡

Clostridiales

Bacteroidales

FMRMN73_092

Stormwater

HC

High

High

Sewagea (98)

Sewagea (99)

FMRMN73_29

Stormwater

HC

High

High

Sewagea (84)

Sewagea (89)

FMRHC33_42

Stormwater

HC

High

Medium

Sewagec (100)

FMRMN60_100

Stormwater

HC

High

High

FMRMN29_108

Stormwater

HC

High

High

Sewagea (91)

Sewagea (95)

MKE_162

River

HC

High

Medium

Sewageb (85)

Sewagea (98)

MNE_163

River

HC

Medium

Medium

Sewageb (57)

Sewageb (86)

KK_160

River

HC

Medium

High

Sewagec (77)

Sewagea (99)

MNE_159

River

HC

Medium

Medium

Sewagec (68)

Sewageb (98)

MKE_158

River

HC

Medium

Medium

Sewageb (98)

Gap_51

Harbor

HC

Medium

High

Sewagea (82)

Sewagea (97)

Junction_54

Harbor

HC

Low

Medium

Sewageb (78)

Gap_55

Harbor

HC

Low

Medium

Sewagea (55)

Sewagec (94)

Junction_52

Harbor

HC

Low

Medium

Sewagec (64)

FMRMN53_26

Stormwater

NHC

High

Inconclusive

SHC12A_10

Stormwater

NHC

High

Inconclusive

Sewagec (90)

SMN17A_20

Stormwater

NHC

High

Inconclusive

Sewagec (100)

FMRHC43_43

Stormwater

NHC

High

Not detected

FMRHAC22_38

Stormwater

NHC

Medium

Not detected

Gap_53

Harbor

NHC

Low

Not detected

Sewageb (99)

1_mile

Lake

NC

Not detected

Not tested

2_miles

Lake

NC

Not detected

Not tested

DocIn_155

Lake

NC

Not detected

Not tested

DocMid_156

Lake

NC

Not detected

Not tested

DocOut_157

Lake

NC

Not detected

Not tested

  1. HC human contamination (fecal indicator bacteria and human marker detected), NHC non-human contamination (fecal indicator detected and human markers not detected or inconclusive reflecting potential for low levels of human contamination), NC not fecal contaminated (fecal indicator not detected)
  2. Values in parentheses represent the proportion of sequences that belong to a given classifier among the total number of sequences from all classifiers
  3. Density levels of the fecal indicator E. coli and enterococci: not detected, 0; low, > 0–250; medium, 250–1000; high, > 1000 CFU/100 mL
  4. ‡‡Quantification levels of the markers human Bacteroides, Lachno2, and Lachno3 when tested: Not detected, 0; not quantifiable, > 0–15; low, > 15–100; medium, 100–10,000; high, > 10,000 gene copies/100 mL. In case of divergence between the human Bacteroides, Lachno2, and/or Lachno3 human markers, results were considered to be inconclusive. See Additional file 1 for details
  5. aIndex representing the percentage of the vote by the trees higher than the majority (50%)
  6. bIndex representing the percentage of the vote by the trees between 45 and 50%
  7. cIndex representing the percentage of the vote by the trees between 40 and 45%