COMIDA: Sources and Fates of Nit d C b i th B thiCOMIDA: Sources and Fates of Nit d C b i th B thiNitrogen and Carbon in the Benthic Ecosystem of the Eastern Chukchi SeaNitrogen and Carbon in the Benthic Ecosystem of the Eastern Chukchi Sea

Ken Dunton, Susan Schonberg, Nathan McTigue, and Afonso SouzaTh U i it f T t A ti

Alaska Marine Science Symposium - January 2011

The University of Texas at Austin

Acknowledgements and Co‐Authors

• Capt. John Seville & crew of the RV Alpha Helix and Mauna Wave

• BOEMRE and COR Dr. Dick Prentki (Alaska Region)

• Graduate students and scientists from CBL, FIT, UT A ti d UAFUT-Austin, and UAF

• Chief Scientist, CBL, , ,Jackie Grebmeier

• Shell Alaska CPAI andShell Alaska, CPAI, and Statoil, Pgm Mgr Michael Macrander

Objectives of this Component

• A quantitative assessment of the spatial variability in benthic faunal abundance andvariability in benthic faunal abundance and diversity throughout the entire study area (collaborative with Jackie Grebmeier)

• Conduct a detailed analysis of trophic f h b hi i dstructure of the benthic community and 

identify the ultimate sources of carbon assimilated throughout the food webassimilated throughout the food web

COMIDA CAB Study Area

Infaunal Biomass Is Dominated by Bivalves, Sipunculids, and Polychaetes 

Infaunal Abundance Is Dominated by Polychaetes, Bivalves, and Crustaceans

Plicifusus kroyeriTL=5

Benthic Invertebrate δ 15N Values

Chionoecetes opilioNeptunea heros

Hyas coarcticusBoreogadus saidaOctopusidae

Tealia sp.Tritonia diomedea

TL=4

Gorgonocephal s car iStrongylocentrotus droebachiensisPagurus rathbuniScaleworm

Buccinum sp.Hippoglossoides robustusNephtys ciliata

Leptasterias polaris

Terebellides stoemiGolfingia margaritacea

Euspira pallidaPycnogonidaNicolea zostericolaAstarte borealis

Praxillella gracilisGorgonocephalus caryiTL=3

Eucratea loricataCucumaria sp.

Synidotea bicuspidaGersemia rubiformis

Carbasea carbaseaOphiura sarsi

Psolus chitonoidesTerebellides stoemi

PoriferaEchinarachnius parma

Ennucula tenuisHydrozoa

Boltenia oviferaAlcyonidium gelatinosum

Mogula griffithsii

TL=2

δ 15N

6 8 10 12 14 16 18 20

[McTigue, Schonberg, Dunton]Samples of trawl biota: thanks to Konar, Norcross and LGL fisheries teams

Food Web Structure Sediment Chlorophyll a

Bi‐plot of δ13C vs δ15N values for 172 species  reveals wide d f tt ( 2 0 32)degree of scatter (r2 = 0.32)  suggesting multiple carbon sourcessources

[Cooper, Guarinello, and Grebmeier]]

Evidence for Consumer Assimilation of Different Ultimate Carbon Sources?

Fish (H. robustus) Crab (C. opilio)robustus)

Sea Cucumber (Ocnus)

Copepods (Calanus sp.)

BivalvesCtenophores

POM

Phytoplankton Benthic Microalgae

How are thesethese benthic microalgalpopulations linked to the timing of ice

Phytoplankton Benthic Microalgae

gretreat and loss of ice algae? Phytoplankton Benthic Microalgae

POM

algae?

POM

Nitrate - COMIDA stations

05

0 2 4 6 8 10 12 14Concentration (μM)

What are the sources f i i N? A 5

1015202530pt

h (m

)

st1015

st48

st103

of inorganic-N? Are the benthic microalgae a sink for sediment 30

35404550

Dep st103

st9

a sink for sediment derived nutrients?

Measurements of N‐Fluxes and Processes

O Fl Li ht diticontrol L

As Expected, Sediment Respiration Rates are High in the Chukchi    

Oxygen Fluxes Light conditions

200-100

0/m

2 .h)

amm Lnitrate L

-600-500-400-300-200

lux

( μm

oles

/

control D

-800-700

st 103 st 1015 st 9 st 48

StationsO2 f

l

Oxygen Fluxes Dark conditions

-1000

m2 .h)

control Damm Dnitrate D

-500-400-300-200

ux ( μ

mol

es/

-700-600

st 103 st 1015 st 9 st 48

StationsO2 f

l

Uptake of Nitrate by Benthic Microalgae at the Sediment‐Water Interface Possibly Apparent at Two Stations

Nutrient Fluxes in Controls Light Conditions

8 010.012.0

2 .h)

PhosphateNitrate

0 02.04.06.08.0

x ( μ

mol

es/m

2

-4.0-2.00.0

ST 103 ST1015 ST 9 ST 48 BR-3Stations

flux

Nutrient Fluxes in Controls Dark Conditions

8.010.012.0

m2 .h)

PhosphateNitrate

0 02.04.06.08.0

x ( μ

mol

es/m

-4.0-2.00.0

ST 103 ST1015 ST 9 ST 48 BR-3

Stations

flu

Summary 

• Observed high diversity and spatial variability for infaunal• Observed high diversity and spatial variability for infaunal community structure and biomass, with clear dominance by selected groups, likely related to sediment characteristics.

• Benthic biota occupy up to five trophic levels, with clear d d POC b t ldependence on POC, but also evidence that the food web is subsidized by contributions yfrom sediment microalgae.

• Nitrogen fluxes at the sediment water interface are a potential mechanism of importance in fueling benthic p gmicroalgal production in relatively clear shelf waters.

UT Graduate Students McTigue and Hersh