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>.