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STUDY TITLE: Shorebirds Habitats, Food Resources, Associated Infauna, Sediment 

Characteristics, and Bioremediation Potential of Resident Microbiota of Deltaic Mudflats

REPORT TITLE: Sediment Characteristics and Infauna of Deltaic Mudflats Along the 

Alaskan Beaufort Sea

CONTRACT NUMBER: M11AC0006

SPONSORING OCS REGION: Alaska

APPLICABLE PLANNING AREA: Beaufort Sea

FISCAL YEARS OF PROJECT FUNDING: FY 2011-2015

COMPLETION DATE OF REPORT: May 2016

CUMULATIVE PROJECT COST: $365,236

PROJECT MANAGER: Abby Powell

AFFILIATION: U.S. Geological Survey, Alaska Fish and Wildlife Cooperative Research 

Unit, University of Alaska, Fairbanks

ADDRESS: 216 Irving I Building, University of Alaska, Fairbanks, 99775-7020

PRINCIPAL INVESTIGATORS: Abby Powell, Ken Dunton, Roy Churchwell

KEY WORDS: Arctic National Wildlife Refuge, benthic communities, deltaic mudflats, 

shorebirds, stable isotopes, Beaufort Sea.

BACKGROUND: 

Nearshore shelf areas of the Beaufort Sea are defined by biological and physical 

gradients that have influence on the Arctic ecosystem including trophic structure, 

productivity, and the species that inhabit the area. The coast's biologically productive 

habitats support diverse biota during the summer that could be affected by oils spills or 

other physical disturbances resulting from offshore oil exploration in the Beaufort Sea. A 

greater understanding of benthic community structure and function is necessary to better 

understand the importance of these systems as food resources for migratory shorebirds. 

We describe the underlying characteristics of sediments and their influence on lower 

trophic levels to better understand the food webs that ultimately support shorebirds on 

their migration out from their arctic breeding grounds.

OBJECTIVES:

The primary objectives of this study were to (1) quantify the spatial and temporal 

distribution of bacterial assemblages, meiofauna, and macrofauna at coastal lagoons 

and river deltas along the Beaufort Sea coast, and (2) characterize the sediment pore 

water chemistry for salinity, ammonium, organic carbon, chlorophyll a, stable carbon 

isotopic signature, and sediment grain size at sample locations representative of each 

site. 
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DESCRIPTION:

Migratory shorebirds are dependent on benthic invertebrate food sources of estuarine 

Arctic river deltas. The importance of these systems as shorebird feeding grounds is 

based on their ability to support invertebrate prey species that have continuous access 

to high quality food (carbon) resources during the summer open-water period. We 

collected sediment samples from deltaic mudlflats at three Beaufort Sea deltas (Jago, 

Okpilak/Hulahula, and Canning river deltas) in August 2010 and 2011. From these 

sediment samples, we quantified sediment chlorophyll, salinity, organic carbon, 

ammonium, and sediment grain size and described their characteristics at the three 

sites. At the same time, we collected sediment core samples for quantifying spatial and 

temporal distribution of bacterial assemblages, meiofauna, and macrofauna. Polymerase 

chain reaction (PCR) analysis was used to census microbial populations (bacteria 

archaea, and eukarya) in the sediments. Organic composition of the sediments was 

related to river sources of organic matter based on stable carbon isotopic measurements 

of sediments to identify the relative importance of allochthonous and autochthonous 

carbon sources. Finally, we synthesized links between shorebirds and their macroinvertebrate prey within mudflat habitats to broader and multiple trophic food web levels 

(include meio- and macrofauna population assemblages) and the nature of the carbon 

footprints of sediments that drive their population dynamics.

STUDY RESULTS:

Bacterial communities were highly diverse in all samples, and variability was explained 

by salinity, ammonium concentrations, total organic carbon content, and organic carbon 

and nitrogen stable isotope ratios. Eukaryotic communities were also highly variable. 

Bacterial communities showed minimal interannual variability and only slight geographic 

variability suggesting a broadly distributed and persistent community that may serve as a 

sensitive indicator of shifts in detrital organic matter including oil-associated 

hydrocarbons. One genus of bacteria that includes known hydrocarbon-degrading 

species (Marinobacter) was detected in high proportions. Abundances of meiofauna 

were comparable to other estuarine habitats in the Arctic. Nematode worms dominated 

the meiofauna community. Diversity of meiofauna was relatively low, and only minor 

differences in abundance and diversity were observed across sites, sampling periods, 

and years. Microphytobenthos consisted primarily of diatoms. Pigment analysis revealed 

that chl a:total pheopigments ratios were <1, providing clear evidence for the importance 

of the microphytobenthos to primary consumers. Sediment porewaters were estuarine, 

and sediment geochemical parameters clearly revealed strong contributions of terrestrial 

organic matter based on low δ13C and δ15N signatures and high C:N ratios. The Jago 

and Okpilak/Hulahula deltas had similar sediment characteristics, but the Canning Delta 

had four times higher salinity and carbon values and tended to be cooler and drier on 

average than the other two sites resulting in differences in abundance and distributions 

of macroinvertebrates among sites. Macroinvertebrate communities were depauperate 

compared to river deltas at more boreal latitudes; only six taxa regularly occurred in 

samples (Oligochaeta, Chironomidae, Tipulidae, Amphipoda, Chaetiliidae, and 

Spionidae).
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SIGNIFICANT CONCLUSIONS:

The broadly distributed and persistent bacterial community detected in Beaufort lagoons 

may serve as a sensitive indicator of shifts in detrital organic matter including oilassociated hydrocarbons. The prevalence of Marinobacter in the Okpilak/Hulahula and 

Canning deltas implies prior or ongoing exposure to hydrocarbons associated with oil. 

This also suggests that mudflat microbial community composition may be poised to 

remediate of future oil contamination. Differences in bacterial communities among sites 

likely result from the longer residence time of freshwater in the Jago and 

Okpilak/Hulahula river deltas compared to the Canning Delta due to the presence of 

barrier islands in the Jago and Okpilak/Hulahula delta regions. Microeukaryotic 

communities showed greater interannual variability than prokaryotic communities 

suggesting that microeukaryotic community composition is less predictable and thus less 

useful as an indicator of environmental change. Meiofauna in these river deltas 

presumably contribute significantly to the annual biomass bloom and provide a vital 

carbon source that is transferred up the food web, based on their high abundance. Of 

the meiofauna, nematodes are likely competitively superior, respond quickly to increases 

in food supply, and may be more tolerant to disturbance. Sediments of sand, silt, and 

clay were fine in structure compared to sediments of other Beaufort Sea coastal 

intertidal habitats, and stable isotopic composition of organic matter in sediments 

reflected strong terrestrial contributions based on δ13

C and δ15N values. Our results also

suggest the importance of salinity and organic matter source as important determinants 

of microeukaryotic community composition. Future shifts in these environmental 

variables could have dramatic impacts on the microeukaryotic communities in these 

mudflats and have far-reaching implications for higher trophic levels that use this habitat 

as breeding and feeding grounds. The macroinvertebrate communities that provide 

important food resources to migratory shorebirds were also influenced by differences in 

salinities and sediment characteristics. The relatively depauperate macroinvertebrate 

community was composed of both marine and freshwater benthic taxa. Although the 

deltaic mudflats of the three sites had different characteristics in terms of sediments and 

associated infauna, they all provide critical food resources for shorebirds as they leave 

their arctic breeding grounds on fall migration.

STUDY PRODUCTS:

Publications:

Churchwell RT. 2015. Stopover ecology of semipalmated sandpipers (Calidris pusilla) at 

coastal deltas of the Beaufort Sea, Alaska. PhD Dissertation, University of Alaska, 

Fairbanks. 149 pp.

Churchwell RT, Kendall SJ, Blanchard AL, Dunton KH, Powell AN. 2015. Natural 

disturbance shapes benthic intertidal macroinvertebrate communities of high latitude 

river deltas. Estuaries and Coasts. DOI 10.1007/s12237-015-0028-2.

Nolan, MR, Churchwell R, Adams J, McClelland J, Tape KD, Kendall S, Powell AN, 

Dunton K, Payer D, Martin P. 2011. Predicting the Impact of Glacier Loss on Fish, 

Birds, Floodplains, and Estuaries in the Arctic National Wildlife Refuge. US 

Geological Survey Scientific Investigations Report 2011-5169, Reston, Virginia.
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Presentations:

Kellogg, CTE, Connelly TL, McClelland JW, Dunton KH, Crump BC. 2015. The influence 

of terrestrial carbon subsidies on microbial communities in the coastal Beaufort Sea. 

23rd Biennial Conference of the Coastal and Estuarine Research Federation, 

Portland.

Churchwell RT, Powell AN, Kendall S, Brown S. 2014. The delta diner: assessing 

eastern Beaufort Sea deltas as fall stopover sites for Semipalmated Sandpipers. 

American Ornithologist’s Union, Estes Park, CO.

Churchwell RT, Powell AN, Kendall S, Brown S. 2014. Shorebird use of river delta 

habitat on the eastern Beaufort Sea coast, Alaska. Alaska Chapter, The Wildlife 

Society, Anchorage, AK.

Churchwell RT, Powell AN, Kendall S, Brown S. 2014. The Delta Diner: assessing 

eastern Beaufort Sea deltas as fall stopover sites for Semipalmated Sandpipers. 16th

Alaska Bird Conference, Juneau, AK.

Connelly, TL, McClelland JW, Khosh M, Crump BC, Kellogg C, Dunton KH. 2014. 

Distinct seasonality in sources and composition of particulate organic matter in Arctic 

lagoons as revealed by fatty acid profiles and bulk stable isotopes. Marine Microbes 

Gordon Research Conference, Waltham, MA.

Churchwell RT, Powell AN, Kendall S, Brown S. 2013. Shorebird use of foraging habitat 

during the post-breeding season on the coast of the Beaufort Sea, Alaska, USA. 5th

Western Hemisphere Shorebird Group Meeting, Santa Marta, Colombia.

Kamikawa AD, Baguley JG. 2013. Spatial and temporal patterns of meiofauna 

community structure within three arctic estuaries. 42nd Benthic Ecology Meeting, 

Savannah, GA. (poster)

Churchwell, RT. 2013. Food resources for post-breeding shorebirds at river deltas 

along the Beaufort Sea coast. Institute of Marine Science Seminar Series, 

Fairbanks, AK.

Crump, BC, Kellogg CTE, Doherty M, Fortunato CS, McClelland J, Connelly T, Dunton

KH. 2013. Seasonal and spatial drivers of estuarine bacterial community 

composition: a comparison of three estuaries. Invited talk at the 22nd Biennial 

Conference of the Coastal and Estuarine Research Federation, San Diego, CA

Kellogg CTE, Crump BC, Connelly TL, McClelland JW, Dunton KH. 2013. Seasonality in 

coastal Beaufort Sea microbial community. 5th International Conference on Polar & 

Alpine Microbiology, Big Sky, MT.

Churchwell, RT, Powell AN. 2012. Impacts of feeding shorebirds on the invertebrate 

community of an arctic mudflat. 15th Annual Alaska Bird Conference, Anchorage, AK.

Nolan, M, Churchwell R, Adams J, McClelland J, Tape K, Kendall S, Powell A, Dunton

K, Payer D, Martin P. 2011. Predicting the impact of glacier loss on fish, birds, 

floodplains, and estuaries on the Arctic National Wildlife Refuge. 4th Interagency 

Conference on Research in the Watersheds, Fairbanks, AK.

Outreach:

Churchwell, RT, Powell AN, Kendall S, Brown S. 2014. Forage quality for pre-migratory 

Semipalmated Sandpipers using three river deltas on the Beaufort Sea 

Alaska. Alaska Marine Science Symposium, Anchorage, AK.

Churchwell, RT, Powell AN. 2013. Food resources for post-breeding shorebirds at river 

deltas along the Beaufort Sea coast. Alaska Marine Science Symposium, 

Anchorage, AK.

Ken Dunton initiated the K-12 Summer Oceanography Program at Kaktovik several 

years ago (see: https://utmsi.utexas.edu/visit/summer-science/kaktovik-alaska). Roy 

Churchwell was one of our guest scientists in 2013.
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Archived Samples:

Sediment. — All remaining sediment samples (processed and unprocessed) are 

currently stored in a -80C freezer in Ken Dunton’s lab at University of Texas (2nd floor of 

Main Lab Building at UTMSI). The sample archive will remain on the top shelf of the 

freezer for a minimum period of one year past the formal end of the no-cost extension 

contact. Access to the samples can be made by directly contacting Ken Dunton 

(ken.dunton@utexas.edu) or Lab Manager Kim Jackson (kim.jackson@utexas.edu)

Microbes. — The remaining sample archive rests at Oregon State. Samples are stored 

in a -80C freezer in Byron Crump’s lab. As with the UT sediment samples, the samples 

archive will remain in the freezer for a minimum period of one year past the formal end of 

the no-cost extension contact. Access to the samples can be made by directly contacting 

Byron Crump at (bcrump@coas.oregonstate.edu).

Meiofauna. — All specimens and samples (processed and unprocessed) are located in 

Dr. Baguley’s sample archive at the University of Nevada, Reno. The sample archive is 

located in The Sarah Fleischman Building. For access to archived samples please 

contact Dr. Baguley at baguley@unr.edu.
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Map of Study Area