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Spring-neap variation in fecal pellet properties
within surficial sediment of the York River Estuary
Emily Wei
Middlebury College
Mentor: Carl Friedrichs
and Lindsey Kraatz
Why study sediment transport and fecal pellets?
Studying erosional processes in the York River
Estuary
•
•
Sediment transport influences:
•
Sediment infilling
•
Turbidity
•
Contaminant spread
•
•
hydrodynamics, sediment transport, biological influences
Boat navigation
seagrass communities
Erosional processes influenced by fecal pellets and flocs
•
•
•
Fecal pellets and flocs change seabed surface
~30% of seabed (Havens, 1967) in the James River
Erosion of fecal pellets differs from erosion of sand grains
(Rhoads and Young, 1969); (Whitehouse, 2000); (Dickhudt, 2008); (Cartwright, 2010)
Rodriguez, 2010
• York River:
•
•
•
Rodriguez, 2010
•
•
• Sub-estuary of the Chesapeake Bay
One main channel
• Secondary channel in the central third of the
river
Stratification due to salinity gradient
• Freshwater from Mattaponi and Pamunkey
Rivers
• Changes throughout the estuary
Estuary Turbidity Maximum and Second Turbidity
Maximum present
More physically-dominated and more biologicallydominated regimes
Clay Bank: VIMS study site
• Between physically and biologically dominated regions
• Cycle of stratification
• River discharge drives cycle of stratification
(Schaffner et al., 2001); (Dickhudt, 2008); (Friedrichs, 2009)
• Clay Bank: mud and fine sand
• Erodibility is influenced by grain size
• Grains of varying density move differently
• Smaller grains higher in suspension
• Larger grains remain closer to seabed
• Disturbance and biological activity influences
erodibility
• Burrowing
• Aggregation
• Clay and silt particles can be bound
by physical and biological processes
Aggregated sediment
Lewis & McConchie, 1994
Fecal pellets and flocculated
material
(Syvitski,1991); (Whitehouse, 2000); (Black et al., 2002)
Drake et al., 2002
Streblospio benedictii
• Pellets are compact, consolidated sediments
processed by benthic organisms
• Range in size from ~40 um to several mm
• Pellets are denser than flocs
• As turbulence increases, more/heavier
resilient pellets resuspended
• Pellets can “armor” seabed, decrease
erodibility
Heteromastus filiformis
http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=11 http://nas.er.usgs.gov/queries/factsheet.aspx?S
88
peciesID=1160
(Drake et al., 2002); (Gillett and Schaffner, 2009); (Cartwright, 2010); (Schaffner, 2011)
Mediomastus fragilis
http://www.genustraithandbook.org.uk/genus/m
ediomastus/
Erosion processes

Lower water column: Suspended sediment concentrations based on:
• tidal currents, availability of easily suspended sediment

Changes in sediment transport driven by changes in freshwater influx,
stratification, and strong spring vs. weak neap tides
River flow
• Freshwater influx
• More sediment transport/ bed
disturbance at Clay Bank
• Less consolidation and higher
erodibility
• More transport is similar to
spring tide
• Low river flow
• Less sediment transport/ bed
disturbance at Clay bank
• More consolidation and lower
erodibility
• Less transport is similar to
neap tide
(Dickhudt et. al, 2009)
Objectives
 Is
there a correlation between spring-neap tidal
cycles and fecal pellet content?

Higher percentage of fecal pellets at neap tide
 Are
larger fecal pellets more abundant at spring
tide?
 Compare
methodologies: Kraatz vs. Rodriguez
 Range of sieve sizes
 Using seawater (15 ppt) vs. deionized water
•
•
2010: 1 spring sample
2011: 2 spring
2 neap
Photo: Kraatz
Sampling cruises coincide
with spring/neap
•
Photo: Cartwright
Methods: Sampling
•
•
Sliced at 1 cm intervals
• Water content, sieving
X-ray analysis
Pellet
presence/concentration
•
•
Top 0-1 cm of core
Photo: Cartwright
Gomex box corer’
•
2 Samples ~ 10.00 grams of sediment sieved
Sediment Grains + Pellets
150 um
90 um
63 um
45 um
Sample 1. Original Sediment (includes pellets)
Sediment Grains (without Pellets)
150 um
90 um
63 um
45 um
Sample 2. Individual grains separated out using calgon and sonification
(Kraatz, in prep)
1
Sediment Grains + Pellets
150 um
90 um
63 um
150 um
90 um
63 um
2
45 um
45 um
Sediment Grains (without Pellets)
Weight
11 – Weight
22 = Weight Pellets
Pellets
(Kraatz, in prep)
Sediment + Pellets (Kraatz method)
150 um
90 um
63 um
45 um
63 um
Sediment + Pellets (Rodríguez method)
(Rodríguez, 2010); (Kraatz, in prep)
>150 um
11%
Percent of fecal
pellets
captured within
each size class
spring
45-63
um
4%
45-63um
22%
>150
um
29%
90-150
um
26%
63-90
um
35%
90-150
um
32%
63-90 um
41%
Fecal pellet presence in DI water samples
Mass (g)
0.25
0.2
spring 1
0.15
spring 2
spring 3
0.1
neap *
0.05
0
45 um
63 um
90 um
150 um
neap
Seawater samples
Deionized water samples
Mass of fecal pellets as collected by sea vs. deionized water
0.3
0.2
0.1
0
45 um
63 um
90 um
0.2
0.1
0
150 um
45 um
63 um
90 um
45 um
63 um
90 um
150 um
0.3
0.3
Mass of pellets (g)
Mass of pellets (g)
Mass of pellets (g)
Mass of pellets (g)
0.3
0.2
0.1
0
45 um
63 um
90 um
150 um
0.2
0.1
0
150 um
More fecal pellets are preserved when using seawater vs. deionized water
Starting
Reworked
to be
Reworked
onreworked
top
Percent fecal pellet material of total sediment
35
30
Percent %
25
21.72%fecal
fecal
•• 28.71%
9.16%
8.48%
fecal
fecal
pellets
pellets(DI)
(DI)
30.23%fecal
fecal
•• 32.41%
15.32%
11.31%
pellets
pellets(SW)
(SW)
61.76%moisture
moisture
•• 63.92%
69.73%
65.01%
20
15
Kraatz DI
10
Kraatz SW
5
Rodríguez DI
0
neap
spring
spring
neap
Rodríguez SW
(Kraatz, in prep) water content; (Cartwright, 2011) X-rays
• There was no clear relationship between springneap tidal cycles and fecal pellet presence
• Biological activity
• There are differences between the sizes of fecal
pellets at spring tide and at neap tide
• Higher percentages of 90-150 um and >150 um
pellets in neap tide sample
• 63-90 um pellets are most abundant by mass
• Perhaps higher stresses at spring break up larger pellets
• Deionized water may break up fecal pellets
• seawater should be used when sieving to preserve
more pellets
To the CHSD lab:
Grace Cartwright
Kelsey Fall
Carissa Wilkerson
Honorary members
For information on
Fecal Pellets:
Linda Schaffner
Cielomar Rodríguez
Bob Diaz
Photo: Cartwright/ Kraatz
To my mentors:
Carl Friedrichs
Lindsey Kraatz
National Science
Foundation, REU grant
MUDBED project
For organizing the
REU program:
Rochelle Seitz
Rachael Blake
Other
acknowledgments:
Paul Nichols
Other REUs
Sources Cited
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presence of muddy flocs and pellets.
Cartwright, G. Virginia Institute of Marine Science, Gloucester Pt., VA, USA, personal communication, 2011.
Dickhudt, P.J., C.T. Friedrichs, L.C. Schaffner and L.P. Sanford, 2009. Spatial and temporal variation in cohesive sediment
erodibility in the York River estuary, eastern USA: A biologically influenced equilibrium modified by seasonal
deposition. Marine Geology, 267, 128-140.
Drake, D.E., R. Eganhouse and W. McArthur, 2002. Physical and chemical effects of grain aggregates on the Palos Verdes
margin, southern California. Continental Shelf Research 22, 967-986.
Friedrichs, C.T., 2009. York River physical oceanography and sediment transport. In: K.A. Moore and W.G. Reay (eds.), A
Site Profile of the Chesapeake Bay National Estuarine Research Reserve, Virginia. Journal of Coastal Research, SI 57,
17-22.
Gillett, D.J. and L.C. Schaffner. 2009. Benthos of the York River. Journal of Coastal Research (Special Paper 57): 80-98.
Haven, D.S., 1967. Occurrence and Transport of Faecal Pellets in Suspension in a Tidal Estuary. Sedimentary Geology 2,
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Kraatz, L.M. (in prep.). The assessment of sediment bed properties within the York River Estuary as a function of spring and
neap tidal cycles.
Kraatz, L., Virginia Institute of Marine Science, Gloucester Pt., VA, USA, personal communication, 2011.
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