Post on 22-Jan-2018
Meiofaunal community structure associated with sediment strata and depth in an exposed beach
Austin Edmonds
Barton College
Exposed Beaches• Exposed regularly to waves of 0.5 m high or more
• In response to sea level rise, beaches are eroding globally
• An almost universal response to beach erosion in the past decades has
been to nourish the beaches. The effects of nourishment on large
invertebrates, shorebirds, and surf fish has been well documented.
• Macroinvertebrates of Donax spp., amphipods, Emerita talpoida and
ghost crabs show lower abundance on nourished beach areas compared
to controlled beach areas, but polychaetes show no difference in
abundance (Peterson et al., 2002).
• Predatory shorebird abundance was up to seven times greater on the
control area versus the nourished area (Peterson et al., 2002)
• Surf fish activity decreases where nourishment occurs due to mass
mortality of prey, creating inhabitable prey conditions and increased
turbidity giving the fish low visibility (Manning et al., 2013)
• Less well understood are the effects of nourishment on microscopic life in
the beaches
Meiofauna• Microscopic, motile aquatic organisms which are smaller than macrofauna and larger than
microfauna that live in interstitial areas with size ranges from 44µm to 500µm (Giere, 2009)
• Food web component which primarily consume bacteria and diatoms
• Factor in the carbon flow of the ecosystem
• Can be used as indicators in any ecosystem
• Of all habitats in which meiofauna occur, none have changed as much in the past few decades as
exposed beaches
Carbon flow through the food chain of an exposed beach(McLachlan and Brown, 2006)
Major Meiofaunal Taxa
Harpacticoida
Gastrotricha
Nematoda
Turbellaria
Harpacticoida nauplius
Beach Nourishment• Beach nourishment is the process of dumping or pumping sand from another
location to further widen an eroding beach or to create a new beach (Barber, n.d.)
• Beach nourishment doesn’t stop beach erosion but temporarily fixes the problem (Barber, n.d.)
• Nourishment and dredge disposals have coarsened the sand in beaches and increased the percent composition of shell hash
• Sediment composition (sand vs. mud) has been known since the 1960’s to determine the density and species composition of meiofaunal communities in low energy habitats
Research question
• Is there evidence that nourishment-induced changes in beach sediment composition with depth affect the structure (absolute and relative abundances) of beach meiofaunalcommunities?
Study Site• Iron Steamer Pier Beach on Bogue Banks
Beach Nourishment History at this Beach
2013 Pine Knoll Shores renourishmentpost 2011 Hurricane Irene
Nourishment of Bogue Banks from 2001 to 2007
Prior studies on exposed beach meiofaunal densities relative to shell vs. sand
STUDY BEACH TIDALHT
DEPTH COMPARISON NEMATODA TURBELLARIA HARPACTICOIDA GASTROTRICHA
Fegley & Fegley(2006)
Ft. Macon, Iron Steamer Pier, Emerald Isle (2 sites)
MLW 0-10 sand vs. shell Higher in sand
Depended on the beach*
Depended on the beach*
Depended on the beach*
Smith & Fegley(2012a)
Emerald Isle MLW 0-5 sand vs. shell No difference
No difference
Higher in shell Higher in sand
Smith & Fegley(2012b)
Emerald Isle MLW 0-10 1976 vs. 2012 No difference
Muchgreater in 2012
Much greater in 2012
Much lower in 2012
Schirmer& Fegley(2013)
Iron Steamer Pier
MHW, MLHW,MTL, MHLWMLW
To thewater table
1969 vs. 2013 No difference
Muchgreater in 2013
Greater in 2013 Much lower in 2013
* - the shell assemblages were similar across all beaches, the sand assemblages depended on the beach
Nematodes show relatively no change in historical or modern data. Turbellarians and harpacticoids show a greater abundance in the modern data, but the gastrotrichs are currently much lower in abundance than previous years.
L1 - groundwater species2 - high tide species3 - surface marine species 4 - estuarine species5 - deep marine species
1
2
5
3
4
Lindgren found a total of 34 different species
Lower Intertidal of ISP beach
Beach three dimensional structure
Core sample pits
41.5% 28.2%
13.5% 58.8% 81.4% 70.1% 80.2% 78.6% 30.3% 65.2% 0%
65.7% 60% 53.1% 50.0% 78.1% 73.7% 98.6% 97.1% 88.5%
29.0% 75.8% 81.2% 97.1% 41.5% 97.4% 74.3% 97.4% 33.3%
Towards the water
3m
2m
Percent Shell Composition from the surface to the water table
Total volume of sediment excluding top row: 37.644m3
Towards the dunes
West along the beach East along the beach
MSL
MSL
MLW
MSL + MLW2
Fine sand
Medium sand
Coarse sand
Shell hash
50 cm
50 cm
50 cm
0 m 6 m 12 m 18 m 21 m
Alongshore changes in sediment composition with depth
MSL
MLW
MSL + MLW2
50 cm
50 cm
50 cm
0 m 6 m 12 m 18 m 21 m
Alongshore changes in sediment composition with depth
Determining the relationship of meiofaunato sediment composition and depth
Alongshore variation in sediment composition and abundances of taxa
Mean grain size Sorting % Gravel
Nematoda Turbellaria Gastrotricha Harpacticoida
Sediment composition
Faunal abundances
Gastrotricha
Depth from surface
0 10 20 30 40 50
Ind
ivid
ua
ls /
10
0 c
m3
-20
0
20
40
60
80
100
120
SAND
SHELL
Copepoda
Depth from surface
0 10 20 30 40 50
Indiv
iduals
/ 1
00 c
m3
1
10
100
1000
10000
SAND
SHELL
Nematoda
Depth from surface
0 10 20 30 40 50
Ind
ivid
ua
ls /
10
0 c
m3
0
50
100
150
200
250
300
SAND
SHELL
Turbellaria
Depth from surface
0 10 20 30 40 50
Indiv
iduals
/ 1
00 c
m3
0
50
100
150
200
SAND
SHELL
Changes in abundance with depth between sediment types (sand vs. shell)
Sediment choice cage experiment
Taxa
Nematoda Turbellaria Copepoda Gastrotricha
ind
ivid
ua
ls /
ca
ge
0
10
20
30
40
50
60
SAND
SHELL
Taxon abundances within colonization cages
Summary
• The percent composition of the sediment changes along the shore, across the shore (more shell hash towards low intertidal), and with depth at any location
• Nematode and Harpacticoid abundances stay constant with depth in sand but decline in deeper shell
• Turbellarians increase in abundance with sand as it gets deeper, but decline in deeper shell
• Gastrotrichs increase in both sand and shell as depth increases
• There is some evidence that Harpacticoids and Turbellaria prefer sand over shell hash
• Shell hash at increased depth does play a role in meiofauna community structure associated with the sediment strata, generally negatively (reduces abundances)
• These changes in absolute and relative abundances may affect the functional roles of the meiofaunal community
Acknowledgements
• Peterson Lab• Dr. Fegley• Joe Morton• Allison Haddon• Steven Moran• Claude• Ellie (Duke REU)• Tony Rodriguez• Beth VanDusen• Bryan Fegley
References
Barber, Don. Beach nourishment basics. Beach Nourishment Info. N.p., n.d. Web. 23 July 2014. <http://www.brynmawr.edu/geology/geomorph/beachnourishmentinfo.html>.
Carteret Crossroads Nourishment. Carteret Crossroads. N.p., n.d. Web. 23 July 2014. <http://www.carteretcrossroads.org/1Carteret%20Crossroads%20nourishment.
Giere, Olav. Meiobenthology the microscopic motile fauna of aquatic sediments. 2nd rev. and extended ed. Berlin: Springer, 20082009. Print.
Manning L.M., Peterson C.H., Fegley S.R., 2013. Degradation of surf-fish foraging habitat driven by persistent sedimentologicalmodifications caused by beach nourishment. Bulletin of Marine Science, 89(1):83–106.
McLachlan, Anton, and Alec Brown. The Ecology of Sandy Shores. Academic Press. Version 2nd. N.p., n.d. Web. 23 July 2014. <http://upload.ukriversguidebook.co.uk/heather/Savage%20Shores/littoral%20zone/Anton_McLachlan,_A.C._Brown-The_Ecology_of_Sandy_Shores,_Second_Edition-Academic_Press%282006%29.pdf>.
Peterson C.H., Bishop M.J., Johnson G.A., D’Anna L.M., Manning L.M. 2006. Exploiting beach filling as an unaffordable experiment: benthic intertidal impacts propagating upwards to shore-birds. J Exp Mar Biol Ecol. 338:205–221.
Peterson, C.H., Bishop, M.J., 2005. Assessing the environmental impacts of beach nourishment. Bioscience 55, 887–896.
Peterson, C.H., Hickerson, D.H.M., Johnson, G.G., 2000. Short-term consequences of nourishment and bulldozing on the dominant large invertebrates of a sandy beach. J. Coast. Res. 16, 368–378.
Weisskohl, Majorie. North Carolina Completes Restoration of Coast Damaged by Hurricane Irene. BOEM Homepage. N.p., n.d.Web. 23 July 2014. <http://www.boem.gov/BOEM-Newsroom/Press-Releases/2013/press04122013.aspx>.