Karen Blocksom and Joseph FlotemerschKaren Blocksom and Joseph Flotemersch

EPA/ORD/NERLEPA/ORD/NERL

NWQM Conference, San Jose, CANWQM Conference, San Jose, CA

May 11, 2006May 11, 2006

Effect of Taxonomic Resolution on Performance Characteristics of a

Method for Sampling Large Rivers

*Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Background• A new bioassessment method developed for

collecting macroinvertebrates in non-wadeable rivers (In press: River Research and Applications, vol. 22, July 2006)

• Study conducted to estimate performance characteristics using metrics: precision and sensitivity

• Evaluated at the lowest possible taxon (species) level

• Many states stop at genus or family, so relevant to evaluate performance characteristics at these levels as well

Sample Collection and Processing

• 19 sites across 5 rivers

• Deep and shallow sites across disturbance gradient

• 3 replicate samples per site in field

• Also habitat, basic water chemistry collected

• Up to three 300-organism sorts per sample in the laboratory

100 m

Flow500 m

Flow

Transect 1

2

3

4

5

6

A

A

A

A

A

A

BC

BC

BC

BC

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BC

Expectations (Family/Genus relative to Species level)

• Richness metrics will have lower values in general and hence, lower variability (higher precision) at the genus and family levels (Total and EPT taxa richness)

• Tolerance and functional feeding group metrics will have lower variability because designations will apply to broader groups and should be more consistent at this level (% Tolerant individuals and % Collector-filterers)

• Laboratory variability will be lower because less chance for error than at species level

• Sensitivity will be poorer because of broader groups at the family level – fewer correlations with abiotic variables

Precision - Methods

• Perform ANOVA with:

Site ID as factor

Multiple samples (A,B,C) as field replicates

Multiple 300-organism sorts as lab replicates

• Use RMSE from this analysis to calculate:

Detectable difference (DD) – minimum difference detectable based on sample size of 3

Relative DD (as percentage of metric range)

Precision - Field

Taxa ric

hness

EPT richness

% Tolerant

% Coll-f

ilterer

0

1

2

3

4

5

6

7

8

D

D

SpeciesGenusFamily

Precision - Field

Taxa ric

hness

EPT richness

% Tolerant

% Coll-f

ilterer

0

2

4

6

8

10

12

Re

lativ

e D

D

SpeciesGenusFamily

Precision - Laboratory

Taxa ric

hness

EPT richness

% Tolerant

% Coll-f

ilterer

0

1

2

3

4

5

6

7

D

D SpeciesGenusFamily

Precision - Laboratory

Taxa ric

hness

EPT richness

% Tolerant

% Coll-f

ilterer

0

5

10

15

R

ela

tive

DD

SpeciesGenusFamily

Results - Precision• Taxa and EPT richness

DD (variability) increased from family to species as expected

BUT relative DD similar or slight decrease from family to species

• % Tolerant individuals For lab, DD (variability) increased family to species No strong pattern for field DD

• % Collector-filterers Genus and species identical - same designations All measures similar among taxonomic levels

Sensitivity - Methods

• Spearman rank correlations

• Family, genus, and species levels

• Between mean metric values and potential gradients:

Taxa richness, EPT richness, % Tolerant individuals, % Collector-filterers

Conductivity, pH, DO, temperature, EMAP habitat and human influence variables, NWHI metrics

Sensitivity

FamilyFamily

0 1 2 3 4 5 6 7 8 90

10

20

30

40

50

60

70

80

Tax

a ric

hnes

s

GenusGenus

0 1 2 3 4 5 6 7 8 9

Human influence - Roads

SpeciesSpecies

0 1 2 3 4 5 6 7 8 9

r = -0.49 r = -0.62 r = -0.66

Sensitivity

FamilyFamily

200 400 600 8000

5

10

15

20

25

EP

T r

ichn

ess

GenusGenus

200 400 600 800

Conductivity (uS/cm)

SpeciesSpecies

200 400 600 800

r = 0.61 r = 0.59 r = 0.59

Sensitivity

FamilyFamily

0 1 2 3 4 5 6 7 8 90

102030405060708090

% T

oler

ant

indi

vidu

als

GenusGenus

0 1 2 3 4 5 6 7 8 9

Bottom Deposition score (NWHI)

SpeciesSpecies

0 1 2 3 4 5 6 7 8 9

r = -0.45 r = -0.41 r = -0.50

Sensitivity

FamilyFamily

0 1 2 3 4 5 6 7 8 90

10

20

30

40

% C

olle

ctor

-filt

erer

s

GenusGenus

0 1 2 3 4 5 6 7 8 9

Bottom Deposition score (NWHI)

SpeciesSpecies

0 1 2 3 4 5 6 7 8 9

r = 0.66 r = 0.67 r = 0.67

Results – Sensitivity

• As expected, generally more significant correlations at species level

• Strength of common correlations similar among taxonomic levels

• Variability around trend lines tends to be greater for genus and species level data

• In the context of relative DD, taxonomic level had little to no effect

• Sensitivity only slightly stronger at genus/species level than at the family level

• Overall, taxonomic resolution did not strongly affect performance characteristics of the method

Conclusions