BENTHIC INDICATORS FOR THE

SUBSTANTIALLY ALTERED LANDSCAPE OF THE

MISSISSIPPI ALLUVIAL PLAINS

Ben Jessup – Tetra Tech, Inc. Valerie Alley – Mississippi DEQ

Matt Hicks – USGS

SWPBANovember 14, 2012

Lake Guntersville State Park

Sampling Locations

Analytical Steps

• Gather and Compile Data• Define the Disturbance Gradient• Classify Sites by Natural Types• Assess Metric Responses to Disturbance• Combine Metrics in an Index

Gather Data

Step 1:

Data Elements

• Collected during 2002*, 2007, 2008, and 2010 by MDEQ and the U.S.G.S.

• Macroinvertebrates, water quality, habitat ratings, general site observations, and GIS.

• 57 sites (2002 samples eliminated)• QC process for lab processes• In EDAS for metric calculation

Define the Disturbance Gradient (preliminary)

Step 2:

VariableLeast

DisturbedMost

Disturbed

% natural LU (watershed) >50, >25 <10%

% natural LU (buffer) >50% <10%

% imperviousness <3% >5%

DO NA <3mg/L

Habitat score >110 <80

LD: Score +1 for each MD: score (-1) for each

Disturbance Gradient

Disturbance Gradient Score

Re fe re n ce S co re

-9 1 .2-9 1 .0

-9 0 .8-9 0 .6

-9 0 .4-9 0 .2

-9 0 .0-8 9 .8

L o n g

3 2 .6

3 2 .8

3 3 .0

3 3 .2

3 3 .4

3 3 .6

3 3 .8

3 4 .0

3 4 .2

3 4 .4

3 4 .6

3 4 .8

3 5 .0

3 5 .2

Lat

Longitude

Latit

ude

Map0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

0

2

4

6

8

1 0

1 2

1 4

B lu ff Core

-5 -4 -3 -2 -1 0 1 2 3 4 5

BluffInter.

NMS Ordination

CoreBluff

Natural Gradient

% Alluvium -9 1 .2-9 1 .0

-9 0 .8-9 0 .6

-9 0 .4-9 0 .2

-9 0 .0-8 9 .8

L o n g

3 2 .6

3 2 .8

3 3 .0

3 3 .2

3 3 .4

3 3 .6

3 3 .8

3 4 .0

3 4 .2

3 4 .4

3 4 .6

3 4 .8

3 5 .0

3 5 .2

Lat

Flow Rate

Site Classification

• All the “best” sites (lower disturbance) have bluff and non-Delta land in their catchments

• Core Delta sites are essentially different than bluff sites (slope, substrate, flow, soils, etc.)

• This confounds the “natural” and “anthropogenic” gradients

• We should not expect bluff-like bug samples in the core of the Delta

• Two site classes: Bluff Hills and Core Delta

Step 3:

Redefine the Disturbance Gradient Interior Delta Bluff HillsVariable Least

DisturbedMost

DisturbedLeast

DisturbedMost

Disturbed% natural land cover in the whole catchment > 15 < 5 > 80 < 55

% natural land cover in the 200 m buffer > 15 < 5 n/a n/a

Habitat Index Score > 110 < 80 > 120 < 100

Road density (miles/acre) < 0.0025 > 0.005 n/a n/a

Dissolved oxygen (mg/L) n/a n/a n/a < 5

Metric Responses

Step 4:

• Screened metrics against the disturbance gradient score using correlation

• Plotted the most responsive metrics to evaluate responses within site classes

• Compared reference and stressed within site classes using DE and Z-score

-6 -4 -2 0 2 4 6

RefSig2

-2

0

2

4

6

8

1 0

1 2

1 4

EP

Ttax

Disturbance Gradient Score

Bluff Sites

Interior Sites

Metric Response among ClassesEP

T Ta

xa

LD MDOther Ref Other MD

Bluff Hills Interior Delta

-6 -4 -2 0 2 4 6

RefSig2

-1 0

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

Non

InsT

axP

ct

Disturbance Gradient Score

Bluff Sites

Interior Sites

-6 -4 -2 0 2 4 6

RefSig2

-1

0

1

2

3

4

5

6

7

8

9

Into

lTax

Disturbance Gradient Score

Bluff Sites

Interior Sites

Metric Results

• In the Interior Delta– Only five of 67 potential metrics had DE ≥69%

• In the Bluff Hills– One metric in each category had a DE = 100%

• Scoring was based on the 5th and 95th %iles

Combine Metrics in an Index Interior Delta

• Of several combinations of responsive metrics • The best index had a DE of 92%

a ”X” in the formula represents the metric valueb POET includes Plecoptera, Odonata, Ephemeroptera, & Trichoptera

Metric name DE / Z Scoring formulaa

Percent of taxa in the POET ordersb 54 / 0.9 X/8Percent of taxa as non-insect 46 / -0.5 (46-X)/32Percent EPT individuals 62 / 0.7 X/47Percent intolerant individuals 69 / 0.5 X/12Percent of taxa as swimmers 8 / 0.4 X/11Percent shredder individuals 54 / 0.5 X/42

Combine Metrics in an Index Bluff Hills

• Several combinations of responsive metrics • The best index had a DE of 100%

1”X” in the formula represents the metric value

Metric name DE / Z Scoring formulaa

EPT taxa 75 / 1.3 X/12Percent of taxa as non-insects 100 / -2.1 (37-X)/33Percent Tanytarsini of Chironomidae 100 / 8.5 X/52Intolerant taxa 75 / 1.0 X/10Percent filterer individuals 100 / 3.1 X/38Percent clinger individuals 100 / 3.3 X/57

Index Performance

• DE: 100%• Ref 25th: 75 • 90% CI: ±6.2

Bluff Hills Drainage Interior Delta

• DE: 92%• Ref 25th: 43 • 90% CI: ±14.9

L D_ b l f O th _ b l f M D_ b l f

Re f9 b l f f

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

BlfI

ndx3

1

LD Oth e r M D0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

D-B

ISQ

(Int

erio

r, #3

9)

Biological Condition Gradient

Observable Delta Sites

(?)

LD

MD

MD

LD

Bluff Hills

Interior Delta

Conclusions

• Metrics responses are related to both the stressor gradient and site classes

• In this case it is best to find metrics that respond uniquely in each site class

• Stressor gradients have different meanings in different site classes

“I’m afraid you have humans”