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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”