blue lake r.v. resort samuel torp, simon peterson, and suzette frazier photo by steve johnson
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Sediment Depth Analysis and benthic Macro-invertebrate
Blue Lake R.V. ResortSamuel Torp, Simon
Peterson, and Suzette Frazier
Photo by Steve Johnson
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Outline Objectives Methods and Materials Results Conclusion & Management OptionsLimitations
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Objectives
1) Analyze water and organic content of the sediment at different depths of the lake
2) Analyze benthic invertebrate diversity at different depths of the lake
Hypothesis1)There is higher water and organic content in
the littoral zone due to higher productivity of benthic invertebrates.
2)There is a higher species diversity in the
littoral zone due to higher organic and water content in sediment and river outlet.
MethodsIn order to accurately compare littoral zone with center of lake samples were taken in a transect from the river outlet to the center of the lake:
Transect:A) Littoral
Zone at 10m
B) Mid lake 20m
C) Lake center 30m
Source: Google Maps, http://maps.google.com. Retrieved: 12/06/10
SamplesAt each of the sample site the following measurements were taken:Triplicate samples were taken using
Ekman grab to analyze benthic invertebrates
One core sample from each site A, B, C taken using K-B core sampler
Ekman Grab (Hoskin, 2010)
K-B Core sampler (Hoskin, 2010)
Materials and InstrumentsInstruments:Ekman GrabK-B Core sampler Materials:Bucket (to hold core samples)Sample jars (contain Ekman invertebrate samples)Tape measure (measure out transect)Screen to filter Ekman grab samplesCore tubes Stoppers (for core tubes)Filter Screen (for Ekman samples)Label Tape
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Sample: Lab AnalysisK-B core:The cores were segmented into different layers coinciding with visual layer as much as possibleWet weight was measured as raw sampleDry weight (after 60 ˚c degrees for 24hrs)Ash weight (550˚c for 3hrs)
Wet weight-Dry weight= water content
Dry weight – Ash weight=organic content
Ash weight=mineral content
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Sample: Lab Analysis continue…Ekman Grab samples:Filtered through sieveNumber of macroinvertebrates counted using
microscopeBack-track volumes with numbers found to
indicate invertebrate densities
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Results (Sediment depth)
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Figure 1. Sediment composition near the shoreline (group X), Bonners Ferry, ID, USA, 11/30/10.
0 0.5 1 1.5 2 2.5 3 3.5 40
1
2
3
4
5
6
7
8
9
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Sediment Composition from nearshore
Organic wtMineral wt.
Weight (g)
Sam
ple
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Sediment depth at 20 meters
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Figure 2. Sediment composition at 20 meters from the shore, Blue Lake, Bonners Ferry, ID, USA, 11/30/10.
0 1 2 3 4 5 60
5
10
15
20
25
30
Sediment Composition (20 m from shore)
Mineral WeightOrganic Weight
% of (Total) Wet Weight
Sedim
ent
Depth
(m
)
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Sediment Compostion at 30 meters, deep lake site
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Figure 3. Sediment composition at 30 meters (deep lake) site, Blue Lake, Bonners Ferry, ID, USA, 11/30/10
0 2 4 6 8 10 12 14 160
5
10
15
20
25
30
35
Sediment Composition (30 m from shore)
Mineral WeightOrganic Weight
% of (Total) Wet Weight
Sedim
ent
Depth
(m
)
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Results (Macroinvertebrates)
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• We found fresh water clams (Mollusks), abundant snails (Gastropoda), mussel shrimp eggs (Ostracoda) and beetles (Coleoptera).
• Each species has the potential to perform an essential role in the persistence of the community & the ecosystem; some represent a particular functional group (Covich et al. 1999).
• Availability of food materials govern the distribution of benthic communities (Saether O.A 1979)
Fig 10 . Population densities at 10, 20 and 30 meters from the shoreline, Blue Lake, Bonners Ferry, ID, USA, 11/30/10.
0 5 10 15 20 25 300
5
10
15
20
25
30
MollusksGastropodaOstracodaColeoptera
Lake depth in meters
Num
bers
of
specie
s pre
sent
in 5
, 20 a
nd 3
0 m
ete
rs
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Macroinvertebrate T-test
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Species Compared samples t-stat
Gastropoda 5m and 30m 0.034
Ostracoda 5m and 30m 0.023
Molluska 5m and 30m 0.013
A t-test was run against the triplicate samples taken from the 5m and 30m sites. Three of the most abundant species were compared. All of the t-stat values were less than 0.05 indicating a significant difference. Overall the data on macroinvertebrates was insignificant due to the lack of data.
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DiscussionIncorporating phosphorus, nitrogen, and chlorophyll
data would be needed to assess ecosystem health. (Kane et al. 2009)
In freshwater sediments benthic invertebrates are often patchily distributed and relatively difficult to sample especially when they live in deep subsurface sediments.
Shannon – Weaver DiversityThere appears to be a significant difference in the total
number of macroinvertebrates at the three location. However the when comparing the data using t-test this
indicates that the values are insignificant.This may be due to the lack of data
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Conclusion Sediment accumulation could be greatest at
the middle depth (shelf). This might be due to contribution from the piece of land in the middle, in addition to those from the shore
Organic matter is the greatest contributor to the sediment accumulation
Macroinvertebrate community is dominated by Mollusks, Gastropoda, Ostrocoda, and Coleptera.
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Limitations & Options• Further investigation with replicate samples
are needed to insure the precision of the data.
• Labels that resist high temperature are recommended, this limited the reproducibility of our samples.
• The benthic community is a reflection of the biotic/abiotic factors of Blue Lake.
• More samples over a larger area would strengthen the data
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Reference List
Covich A. P.; Palmer M. A.; Crowl T. A. The Role of Benthic Invertebrate Species in Freshwater Ecosystems: Zoobenthic species influence energy flows and nutrient cycling. BioScience, Volume 49, Number 2, 1 February 1999, pp. 119-127.
Saether, Ole A. Chironomid communities as water quality indicators Ecography Volume 2 Issue 2, Pages 65 – 74. Published Online: 30 Jun 2006
Kane, Douglas D et al. The Planktonic Index of Biotic Integrity (P-IBI): An approach for assessing lake ecosystem health. Ecological Indicators; Nov 2009, Vol. 9 Issue 6, p1234-1247, 14p
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