CHANGE IN LOWER TROPHIC LEVEL SEASONALITY !
AND!
COMMUNITY STRUCTURE IN THE WARMING OCEAN Sanae Chiba!
JAMSTEC!
[email protected]!
IMBIZO-II, October 2010, Crete, Greece!
Decreasing trend of Wintertime Mixing – western subarctic NP
Subsurfac DO!
Time series of DO on isopycnals from
26.6 to 27.2σθ in the Oyashio region
at 41º30ʼN, 146-147ºE. The solid line
denotes the 3-year running average!
2.4
ML Phosphate!
2.2
Time-series of phosphate concentration
in the winter (January-March) mixed
layer in the Oyashio region. Dash-dotted
line indicates 2003-2007 average, while
thin line indicates linear regression of
whole time series. Slope of the linear
regression is -0.0060 ± 002 μM y-1. After
Ono et al. (2002) with extension of time
length.!
MLP (μM)
2.0
1.8
1.6
1.4
1.2
(Oyashio, PICES NPESR-II, 2010)!
1.0
1970
1980
1990
2000
2010
Seasonal
Cycle of
Lower
Trophic
Levels
& Stratification
Zooplankton
Phenology
in WNP:
Mechanisms!
Background
Extensive? but short spring bloom!
Cold winter & Hot summer!
Moderate but longer spring bloom!
Warm winter & Cool summer!
Seasonality of upper
water stratification
determines plankton
phenology
How Would Ecosystem Response to Increasing
Stratification? !
Topics:!
Regional Response!
!Subarctic (light-lmited) vs. subtropical (nutrient-limited)!
Phenology - Trophic links – Match-mismatch!
Community composition & BCP function!
Keywords:!
Change in Seasonality!
!… not only changes in annual means!
!… not only extent of wintertime mixing !
! but also spring-summer stratification process
! !!
Spring Chl a
!
Winter Chl a
Subarctic WNP!
Light-limited!
!
Phytoplankton Responses: Subarctic vs. Subtropical!
n.s.!
Spring Chl a
Winter Chl a
Subtropical WNP!
Nutrient-limited!
Winter MLD!
!
!
Winter MLD!
Winter MLD!
Winter MLD!
(Chiba et al, 2008, Prog. Oceanogr.)!
1980s!
Late Bloom Bottom-up control!
(Low PP-ZP production)!
Winter & Spring
(Chiba et al, 2008, Prog.
Oceanogr.)!
1990s!
Early Bloom Bottom-up control in
winter!
(high PP-ZP production)
Link not clear
in spring!
(and in annual
biomass)!
Early & bloom
favorable for
zooplankton?!
Link to Higher Trohpic
Level (Stable Isotope study)!
Background
Time-series δ15N of Neocalanus & Pink salmon !
Low d15N and high biomass during the 1990s indicates that
phytoplankton availability was favorable for Neocalanus production!
BIOMASS!
d15N!
Observed Decadal Changes in the western NP!
SUMMARY!
1976-1880s! 1990s!
Wind!
Strong!
Weak!
Temp!
Cool!
Warm!
Mixing!
(Light!
(Nutrient!
Deep!
Low!
?!
Shallow!
High)!
Low)!
Winter !
PP!
Low!
Spring!
Low!
(and yr) PP!
?! High!
Lower!
ZP!
Low!
High!
Salmon!
Low!
High!
Pacific Decadal Oscillation & Zooplankton Phenology!
Eastern NP!
Western NP!
(redrawn from Mackas et al, in press)!
(redrawn from Chiba et al, 2006)!
Zooplankton biomass peak!
Zooplankton biomass peak!
水温
水温
Warm, Early!
Cold, Late!
Warm, Early!
Cold, Late!
Warm, Early!
Seesaw pattern of SST anomaly in WNP and ENP and its effect on timing of plankton production!
North Atlantic!
How Would Ecosystem Response to Increasing
Stratification? !
Topics:!
Regional Response!
!Subarctic (light-lmited) vs. subtropical (nutrient-limited)!
Phenology Trophic links – Match-mismatch!
Community composition & BCP function!
Keywords:!
Change in Seasonality!
!… not only changes in annual means!
!… not only extent of wintertime mixing !
! but also spring-summer stratification process
! !!
Phytoplankton phenology for 1998-2006
based on the satellite observation
K2
SeaWifs Chl a (1998-2006)!
45-50 N, 155-165 E!
(excluding data of 47x155, 48x155, 156, 49 x 155~157) !
Feb 1 – Aug 31 (10 days composite)!
Link? : PP composition – phenology – BCP – CO2 uptake?!
(Wakita et al. 2010, Tellus)!
Biogeochemical timeseries observation by
JAMSTEC!
decrease!
in winter!
CO2 uptake!
sea!
air!
decrease in Opal to !
CaCO3 ratio flux !
at ５０００m!
Sediment trap data
at Station K2!
K2!
S1!
delay in !
phytoplankton !
bloom!
How Would Ecosystem Response to Increasing
Stratification? !
Being Known!
Lower trophic level response to increase stratification
is regionally specific !!
Seasonality in mixed layer environment determines
phytoplankton phenology and trophic match-mismatch:
need to see spring-summer process, too.!
Less known!
Influence of changes in Plankton phenology and
community structure as a result of stratification changes
to biological carbon pump efficiency !
!!