To what extent is there excess sediment in the Middle Truckee River that impairs aquatic life use?

Application of benthic macroinvertebrate bioassessment to determine whether there is habitat degradation from deposited sediments

David HerbstUniversity of CaliforniaSierra Nevada Aquatic Research Laboratory

Goal: Biological Guidance for Sediment TMDLDefine deposited sediment guidelines for monitoring, protecting, and improving the biological health of the Middle Truckee RiverObjectives:1. Describe patch-scale distribution of fine + sand

(FS) deposits along the river at representative reaches below tributary stream confluences

2. Collect data to measure biotic responses and limiting effects of sediment at the patch-scale for both cover and volume of FS

3. Compare biological health to other large rivers of eastern Sierra that are less developed than MTR

What we did and how and where we did it• 10 study sites along the river

at locations below tributaries and over downstream changes in channel geomorphology

• Sampled at baseflow (in late September of 2011)

• Characterize the ambient distribution of FS sediment deposition cover using quadrat grid-frames

• Associate the invertebrates within each quadrat (n=100) to define biological effects of sediment cover over a full range of FS from none to complete cover

D-net samples from30 x 30 cm habitatpatches at which %FSis recorded at 25 points:

10 sites x 10 patches= 100 samples over full range 0-100% FS

%FSCover

What is the ambient level of sediment deposition over the Middle Truckee?Distribution of FS cover over these varied sites along the river:

Random sampling of 100 quadrats at each of the 10 reachesto establish ambient FS levels (<50 cm depth, in depositionaland erosional micro-habitat patches) = 25,000-point counts

Quadrats:

SAMPLING

Context for Results• Data analysis of quadrat FS:1. Diversity, tolerance, and food web

structure in relation to FS cover grouped in bins of -

0% 0-20% 20-40% 40-60% 60-80% 80-100% and cross-group statistical tests2. Ordination and testing for

differences between bin groups of FS cover

3. Indicator group analysis (preferences for low-high)

4. Ambient FS deposits downstream

• How does the biological integrity of Middle Truckee compare to other large rivers of the eastern Sierra that can serve as references?

0102030405060708090

100

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B

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B

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Middle Truckee Regional References

Using different types of SWAMP-standardmethods in mobile vs immobile reacheshalf of MT samples did not support standard.All regional reference large streams did.

How does the food web change over the FS cover gradient?

Changes w/ FS:• CG increase• G decrease• CF decrease

>More FPOM>Less algae>Less surface for attached CF

Grazers

Collector- Gatherers

Collector- Filterers

Shredders

Predators

Collector Filterer

17%

Collector Gatherer

29%Grazers

41%

Predators9%

Shredders4%

0 Fines+Sand Food Web Structure n=9

Collector Filterer

11%

Collector Gatherer

30%Grazers49%

Predators6%

Shredders4%

1-5 Fines+Sand Food Web Structure n=16

Collector Filterer

8%

Collector Gatherer

42%Grazers

34%

Predators8%

Shredders8%

6-10 Fines+Sand Food Web Structure n=21

Collector Filterer

4%

Collector Gatherer

52%

Grazers27%

Predators8%

Shredders9%

11-15 Fines+Sand Food Web Structure n=18

Collector Filterer

5%

Collector Gatherer

61%

Grazers17%

Predators9%

Shredders8%

16-20 Fines+Sand Food Web Structiure n=17

Collector Filterer

9%

Collector Gatherer

62%

Grazers14%

Predators7%

Shredders8%

21-25 Fines+Sand Food Web Structure n=19

How does density and body size of BMI community change over FS gradient?

• Density reduced and body sizes smaller and this limits both food quantity and food quality to fish and riparian birds

With no or low FS cover, density is ~4,000/m2

At higher FS cover, reduced to ~3,000/m2

Percent of larger EPT declines, while thesmaller midges increase with FS cover

Density /m2% EPT

% Chironomidae midges

How does community species composition change over the sediment gradient? Ordination Analysis

Sand & Fines

Middle Truckee Sediment

Axis 1

Axi

s 3

Sand & FineCounts

0 - 56 - 10

Sand & Fines

Middle Truckee Sediment

Axis 1

Axi

s 3

Sand & FineCounts

0 - 56 - 10

Sand & FineCounts

0 - 56 - 10

Sand & Fines

Axis 1

Axi

s 3

Middle Truckee Sediment

Sand & FineCounts

0 - 56 - 10

11 - 15

Sand & Fines

Axis 1

Axi

s 3

Middle Truckee Sediment

Sand & FineCounts

0 - 56 - 10

11 - 15

Sand & FineCounts

0 - 56 - 10

11 - 15

Sand & Fines

Axis 1

Axi

s 3

Middle Truckee Sediment

Sand & FineCounts0 - 56 - 10

11 - 1516 - 20

Sand & Fines

Axis 1

Axi

s 3

Middle Truckee Sediment

Sand & FineCounts0 - 56 - 10

11 - 1516 - 20

Sand & Fines

Axis 1

Axi

s 3

Middle Truckee Sediment

Sand & FineCounts0 - 56 - 10

11 - 1516 - 2021 - 25

Sand & Fines

Axis 1

Axi

s 3

Middle Truckee Sediment

Sand & FineCounts0 - 56 - 10

11 - 1516 - 2021 - 25

MRPP TestsShow:

Community typesgrouped bystatistical

differences

-Low FS <20%-Mid FS 20-80%-High FS >80%

Proximity ofpoints meanssimilarity, anddistance signifiesdifferences inspecies compositionfor the 100 quadratsacross all sites

abbccd

MRPPGroups:

Indicator Organisms for FS Sediment

Taxa Maxgrp Ind. value Mean S.Dev p*

P_aviceps 0 30.4 13.3 3.53 0.001

Hydropsyche 0 30.1 15.5 3.25 0.0014

C_californica 0 29.8 13 3.65 0.0018

Sperchon 0 27.3 16.4 3.16 0.0068

R_hyalinata 0 26 11.4 3.91 0.0082

Baetis 0 25.1 17.6 2.71 0.015

T_discoloripes 0 17.3 9.7 3.84 0.049

Ceratopsyche 1 31.2 16.9 3.11 0.0014

Rhithrogena 1 27.2 17 2.84 0.0046

Glossosoma 1 25.3 19 2.06 0.007

Wormaldia 1 15.2 6.8 3.74 0.0346

Ameletus 3 18.4 10.4 3.67 0.04

A_delantala 4 25 14.9 3.61 0.0176

Capniidae 4 16.6 8.2 3.7 0.0336

Lebertia 4 22.9 17.5 2.75 0.0444

Odontomesa 5 35.8 8.3 3.91 0.0006

Phaenopsectra 5 29.2 12.6 3.84 0.004

Tanytarsus 5 25.1 12.5 3.81 0.0098

Centroptilum 5 21.7 9.1 3.85 0.0114

Parametreocnemus 5 18.6 10.1 3.77 0.0332

MostlyEPT

MostlyMidges

p* significance values from indicator analysis

Promote the objective of FS cover levels below 20%Greatest density of the EPT - most common food resources to fish,and are the most diverse and sensitive forms of benthic animal life.First significant community structure shift occurs above this FS level.

20% 40% 80%60% 100%

0%

10%

20%

30%

40%

50%

60%

70%

80%

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Percent of ambient quadrats with FS >80%in depositional habitat zones

Truckee

Pro

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Distribution of FS sediment in vulnerable depositional zones along downstream river

Existing standard on MTR for turbidity states ≤25 mg/L in 90% of observations – use this approach?

Deposited sediment within any river segment including both erosional and

depositional habitats should have <80% FS cover in 90% or more of observations

0 20 40 60 80 100

Bronco CreekGray Creek

Juniper CreekHorseshoe Bend

Martis CreekTrout Creek

Regional ParkCold/DonnerSquaw Creek

Bear Creek

Percent of Quadrats with FS less than 80%

Bottom-Line• Riverwide ambient conditions on the 1000 quadrats over 10 sites

combining both erosional and depositional patches: 62.5% of habitat has <20%FS, the best conditions; in contrast 17.4% of habitat has >80%FS, poorest condition

• Minimize >80% FS, maximize <20% FS• Management to achieve reduction in worst conditions of FS

deposition in most vulnerable habitat zones (depositional patches) – e.g., flow management, erosion control

• Promote increases in the best habitat conditions where FS deposition is low across all zones of geomorphology

• Goal - beneficial effects for fish and wildlife, river function• Monitor FS patch distribution to evaluate if sediment reduction

actions work, and verify with bioassessment trends