Workshop 1: Zooplankton and climate: response modes and linkages amongregions, regimes, and trophic levels

International Symposium, Effect of CC on the World Ocean, 2008 Gijon

Sanae Chiba, H. Sugisaki, K. Tadokoro, A. Kuwata, T. Kobari, A.Yamaguchi and D. L. Mackas

Pan-North Pacific synthesis of long-termvariation of Neocalanus spp. based on StableIsotope analysis

Neocalanus Copepods

Ontogenetic Migration

Detect regionally specific hydrograpihc & ecosystem responses tolarge scale climatic forcing, based on nitrogen stable isotopes ofhistorically collected Neocalanus specimens

Goal

δ13C

3

2

1

Trophic level

ca. 3‰

Phytoplankton

HerbivorousZooplankton

PredatoryZooplankton

δ15NProxy of trophic level higher in higher trophic levels= switch of feeding strategy == phytoplankton abundance=== nitrate availability higher at low N availabilityBut be careful in the existence of N2 fixation phytoplankton (decrease).

BackgroundWhat Zooplankton Stable Isotope Tells

δ15N

Fingerprint of the past environmental & ecosystem changesBiomass data were sometimes based on spot-observations while chemicalproperties of zooplankton indicate environmental condition of the past months

BackgroundZooplankton SI : Proxy of Environmental Changes

Time

ZooplanktonBiomass

Time

Bottom-up control?Zooplanktonδ15N

Changes inenvironment

Time

Top-down control?

Zooplanktonδ15N

No Changes inenvironment

Time

Zooplanktonδ15N

Changes inenvironment

Sample InformationWest Central (180° Line) East

Oyashio Subarctic (SA) Transition

North (TN)

Transition

South (TS)

Off -Vancouver

Island (off -Van)

St. P

Area 38°- 41° N

142° - 145°E

47°- 48°30’ N

44°- 46°N 39°30’ - 42°N 48°-51°N

124°30” -130°W

50°N

145°W

Year 1960-2002 1980-1997 1979-1997 1979-1997

Season April -July June April -July

Sampling Method NORPAC

0-150m tow

NORPAC

0-150m tow

Bongo

0-250m (max)

Preservation 5% formalin sea water

SI measurement Thermo Fisher Scientific, EA1112 -DELTA V ConFlo III System

! Common procedure used for sample preparation for SI measurement

! Correction of sampling date bias was made when monthly averages were significantly difference within a region (only for N.

flemingeri in Oyashio)

! Off Vancouver Island dada are composite northern, middle, southern Vancouver Island data.

1981-2007 1987-2007

(~20 inds CV were used for each measurement)

Interregional variations were larger thaninterspecies variations within a region

Regional Comparison of Average δ15N

N. plumchrusN. flemingeri N. cristatus

δ15N Regional comparison

ANOVA & Post Hoc (Scheffe) TestOY & Off Van > 180LIne and StP

Regional Comparison of Average δ15N

N. plumchrusN. flemingeri N. cristatus

Surface Nitrate (uM) (WOA 2001)West EastCentral

Regional Difference in average δ15N roughly corresponded to the base Nitrateconcentration => unlikely to be derived from behavioral difference amongregional Neocalanus populations.

1

20

West: Oyashio

Time series Neocalanus δ15N

N. plumchrusN. flemingeri N. cristatus

3 species average

Inter-annual variation was similar among the 3 species

Pearson R: Nc - Nf = 0.571 (P<0.01)Nc - Np = 0.557 (P<0.01)Nc - Nf = 0.693 (P<0.01)

…indicating temporal variation of regional environment

Time series Neocalanus δ15NCentral: 180° Line

SA

TN

TS

SA

TN

TS

NO

RTH

SOU

TH

Pearson R:SA: Nc - Nf = 0.826, Nc - Np = 0.788 (P<0.01), Nc - Nf = 0.561 (P<0.05)TN: Nc - Nf = 0.826, Nc - Np = 0.788 (P<0.01), Nc - Nf = 0.561 (P<0.05)TS: Nc - Np = 0.672 (<0.01)

Time series Neocalanus δ15NEast

St. P Off-Van

N. plumchrusN. flemingeri N. cristatus

Off-Van

Pearson R (St. P)Nf - Np = 0.990 (P<0.01)

Pearson R (Off-Van)Nc - Nf = 0.823, Nc - Np = 0.740(P<0.01), Nc - Nf = 0.755 (P<0.01)

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Regional Comparison of Time-series δ15N

West (Oyashio) Central (180°Line) EastSA

TN

TS

More low δ15N years after 1990 in Oyashio, 180line SA, Off-Van

St. P (Nf & Np)

Off-Van

St. P (Nc)

…but No significant correlation in Interannual variations among the regions

Atmospheric Forcing, Hydrography & δ15N

Oyashio 180°Line Off-Van St. P

34°-50°N 140°-156°E 40°-56°N, 174°-186°E 44°-56°N, 234°-246°W 44°-56°N, 220°-246°E

Data Source Variable Details

All ICOADS Cloud Cover Jan-Mar, Mar-May, Mar-Jul, Annual

ICOADS SLP Jan-Mar, Mar-May, Mar-Jul, Annual

ICOADS SST Jan-Mar, Mar-May, Mar-Jul, Annual

ICOADS Zonal Wind Jan-Mar, Mar-May, Mar-Jul, Annual

ICOADS Meridional Wind Jan-Mar, Mar-May, Mar-Jul, Annual

Oyashio JODC SSS Feb, Apr, May

JODC MLD win

JODC DSigma-t (0-100) Feb, May

JMA & JODC Chl a win, sp

JMA & JODC PO4 Feb-Nov avg

180°Line Kobari et al, 2003, JPR Mean Temp 0-150 m June, per SA, TN, TS region

Kobari et al, 2003, JPR Chl a June, per SA, TN, TS region

Kobari et al, 2003, JPR Delta T 0-150 June, per SA, TN, TS region

Off-Van, St. P Crawford et al. 2007, PO mean T 100-500m win, sp, sm

Crawford et al. 2007, PO mean T 10-100m win, sp, sm

Crawford et al. 2007, PO mean S 100-500m win, sp, sm

Crawford et al. 2007, PO mean S 10-100m win, sp, sm

List of Climatic and Environmental Variables used for Correlation Analysis

δ15 N was HighIn the years ofCool condition withLow winter Chl a>> Neocalanus might bemore omnivorous

OyashioAtmospheric Forcing, Hydrography & δ15N

SI

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180° Line SubarcticAtmospheric Forcing, Hydrography & δ15N

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180°Line Transition North

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Atmospheric Forcing, Hydrography & δ15N

δ15 N was High inthe Years of Warmconditions withSouthern wind

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δ15 N was High in Years of Calm sprig-summer with strong Westerly

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Lower N supply(+Higher source δ15N?)

Atmospheric Forcing, Hydrography & δ15N

St. P

δ15 N was High in Years of Warm subsurface condition duringSpring-Summer (N. plumchrus & N. flemingeri only)

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Possible Factors Responsible for Temporal Variation of Neocalanus δ15N

SST Nwind δ15N

1. OY & 180 SACool winter condition, which delayed spring bloom, altered Neocalanusfeeding strategy to more omnivorous => Behavioral Change

SST S or W wind δ15N

2. 180 TN, 180TS, Off-VanAdvection of southern water altered Nitrate availability (and source δ15N?) => Hydrographic Change

subsurface T δ15N

3. St. PChange in properties of the subsurface water altered Nitrate availability(and source δ15N? )=> Hydrographic Change

Regional difference of Neocalanus δ15N reflectsdifferences in hydrographic properties among theEast, Central and Western subarctic North Pacific.

Regional difference of Time-series of Neocalanus δ15N are determined by regionally specifichydrographic and ecological responses to variousclimatic forcing

Neocalanus δ15N is a possible indicator of regionalresponses of climatic forcing

Conclusion

This study suggested….

Next Subjects

However….There are uncertainty in the proposed mechanismsof the observed changes…

Study on mechanisms of Neocalanus δ15N variationusing newly collected specimens

Oyashio (A-line Cruise, FRA)Monthly sampling, March to July, 2007 δ15N, δ13C Measurement: 3 Neocalanus spp., surface layer POMOther information: phytoplankton composition, nutrients, water column ST

Acknowledgements

Prof. Mark Ohman,Dr. Mugi Takizawa,Ms. Moira GalbraithMs. Keiko YamamotoAnd all captains, crew and researcherswho worked for collection of long-ternNeocalanus samples