Download Sediment Depth Accumulation Analysis and Deepwater

Blue Lake
R.V. Resort
Samuel Torp, Simon Peterson,
and Suzette Frazier
Photo by Steve Johnson
Outline
 Objectives
 Methods and Materials
 Results
 Conclusion & Management Options
 Limitations
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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
Hypothesis
1)
 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.
Methods
In 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
Samples
At 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 Instruments
Instruments:
Ekman Grab
K-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 samples
 Core tubes
 Stoppers (for core tubes)
 Filter Screen (for Ekman samples)
 Label Tape
Sample: Lab Analysis
K-B core:
The cores were segmented into different layers
coinciding with visual layer as much as possible
 Wet weight was measured as raw sample
 Dry 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 sieve
 Number of macroinvertebrates counted using
microscope
 Back-track volumes with numbers found to indicate
invertebrate densities
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Results (Sediment depth)
Sediment Composition from nearshore
0
0.5
1
1.5
Weight (g)
2
2.5
3
3.5
4
0
1
2
Sample
3
Organic wt
4
Mineral wt.
5
6
7
8
9
10
Figure 1. Sediment composition near the shoreline (group X), Bonners
Ferry, ID, USA, 11/30/10.
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Sediment depth at 20 meters
Sediment Composition
(20 m from shore)
0
1
% of (Total) Wet Weight
2
3
4
5
6
0
Sediment Depth (m)
5
10
Mineral Weight
Organic Weight
15
20
25
30
Figure 2. Sediment composition at 20 meters from the shore, Blue Lake,
Bonners Ferry, ID, USA, 11/30/10.
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Sediment Compostion at 30
meters, deep lake site
Sediment Composition
(30 m from shore)
0
2
4
% of (Total) Wet Weight
6
8
10
12
14
16
0
Sediment Depth (m)
5
10
Mineral Weight
Organic Weight
15
20
25
30
35
Figure 3. Sediment composition at 30 meters (deep lake) site,
Blue Lake, Bonners Ferry, ID, USA, 11/30/10
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Results (Macroinvertebrates)
Numbers of species present in 5, 20
and 30 meters
30
25
20
Mollusks
15
Gastropoda
Ostracoda
10
Coleoptera
5
0
0
5
10
15
20
25
30
Lake depth in meters
Fig 10 . Population densities at 10, 20 and 30 meters from the shoreline, Blue Lake,
Bonners Ferry, ID, USA, 11/30/10.
• 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)
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Macroinvertebrate T-test
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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Discussion
 Incorporating 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 Diversity
There 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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