Anomalously low crustacean zooplankton production rates along the west coast of Vancouver Island in the

spring of 2015

Akash R. Sastri1, John F. Dower2, Theresa Venello2, Aidan Neill2, Karyn D. Suchy2, Moira Galbraith3, Kelly V. Young3, R.

Ian Perry4

1 Ocean Networks Canada, University of Victoria, Victoria, BC, Canada

2 University of Victoria, Victoria, BC, Canada

3 Fisheries & Oceans Canada, Sidney, BC, Canada

4 Fisheries & Oceans Canada, Nanaimo, BC, Canada

Cold regimes

characterized by

higher northern

zooplankton

biomass

Poor salmon

survival linked to

anomalously low

biomass of northern

zooplankton

(Peterson and Schwing 2003. Geophysical Res. Letters)

PDO, Zooplankton, and Salmon

1. ‘Northern’ vs. ‘Southern’

biomass ≈ cold vs. warm

2. Temporal patterns influence

higher trophic level survival (Mackas et al. 2007)

3. Difficult to translate biomass

patterns to quantitative

estimates of food web

efficiency

(Galbraith et al in: Chandler, King, and Perry 2015, Can. Tech. Fish. Aquat. Sci.)

“So

uth

ern”

“No

rth

ern”

Bio

mas

s A

no

mal

y (l

og1

0)

In situ Zooplankton Productivity Estimates

• Calculations of transfer

efficiency demand

secondary production

rate estimates

• Weight-specific growth

rates for dominant

copepod and euphausiid

species (GOA, Oregon

coast, Stn.P)

• No historical community-

level measurements in

Canadian Pacific

Methods : Zooplankton Production Rates

Chitobiase Method:

1) Enzyme breaks down chitin in old

exoskeleton and recycles chitin for

synthesis of new exoskeleton

2) Chitobiase is liberated into water when animal moults

3) Activity varies with individual body

size, developing biomass and

increment of growth for the

community

4) The rate of production of the enzyme

in the water = biomass production

rate

(Sastri & Dower 2009 Mar. Ecol. Prog. Ser.)

Methods : Zooplankton Production Rates

loge Individual weight

(mg dry weight)

-8 -6 -4 -2 0 2

log

e C

hitobiase activity

(nm

ol M

BF L

-1

hr-1

)

-6

-4

-2

0

2

4

6

8

10

12

14

(r2= 0.95, p < 0.001)

Chitobiase Method:

1) Enzyme breaks down chitin in

old exoskeleton and recycles

chitin for synthesis of new

exoskeleton

2) Chitobiase is liberated into water when animal moults

3) Activity varies with individual

body size, developing

biomass and increment of

growth for the community

Methods : Zooplankton Production Rates

Time (hours)

0 5 10 15 20 25

Lo

ge C

BA

(U

A)

8.2

8.3

8.4

8.5

8.6

8.7

8.8

8.9

5m

15m

25m

50m

75m

100m

Chitobiase Method:

1) Enzyme breaks down chitin in old

exoskeleton and recycles chitin for

synthesis of new exoskeleton

2) Liberated into water when animal moults

3) Activity varies with individual body size,

developing biomass and increment of

growth for the community

4) The rate of production of the enzyme in the

water = biomass production rate

5) Measure enzyme decay rates assuming

balance between production & degradation

Biomass production rate

(mg C m-3 d-1)

0.0 1.5 3.0 4.5 6.0

W

(mg C m-3

)

9 12 15 18 21

Dep

th (

m)

0

20

40

60

80

100

CBA turnover rate

(Days)

0 4 8 12 16

=

= 2.41 mg C m-3 d-1

A Field Example (Gulf of Alaska: July 2009)

Production rate = DB / TCBA

(Sastri et al. 2012 J. Exp. Mar. Ecol. Biol. )

Variation of BPRBroad-scale production rate patterns

1. Sampling July’08, July’09, and October’09

2. Production rates varied in space (0.15-4 mg C m-3 d-1)

3. Production rates varied significantly with temperature and phytoplankton biomass (r2=0.67, p<0.001)

(Sastri et al. 2012 J. Exp. Mar. Ecol. Biol. )

Variation of BPRBroad-scale production rate patterns

1. Sampling July’08, July’09, and October’09

2. Production rates varied in space (0.15-4 mg C m-3 d-1)

3. Production rates varied significantly with temperature and phytoplankton biomass (r2=0.67, p<0.001)

log10 Developing biomass

(mg dry weight m-3)

0.00 0.75 1.50 2.25 3.00

BP

R r

esid

ua

ls

(Tem

p. re

mo

ved

)

log10 Phytoplankton biomass

(mg Chl a m-3)

-1.50 -0.75 0.00 0.75 1.50 2.25

Temperature (oC)

-2 0 2 4 6 8 10 12

log

BP

R (

mg

C m

-3 d

-1)

-1.0

-0.5

0.0

0.5

r2 = 0.37, p < 0.001NSr2 = 0.38, p < 0.001

Production rates : La Perouse/WCVI

1. Chitobiase activity and decay

dynamics measured at several stations

2. Included on- and off- shelf stations

3. Up to 2 trips per year (June,

September)

4. 2005 – spring/summer (6 Stns/cruise)

5. 2009-2011 – summer (6 Stns/cruise)

6. 2015 – spring/summer (8 Stns/cruise)

Zooplankton Production Rates: 2005

South VI: Production rates greater on shelf and offshore in June

relative to September (very low)

North VI : No particular inter-cruise differences on or off-shelf

2005

Off Shelf

La

titu

de

BPR (mg C m-2 d-1)

Spatial patterns of production 2005-2011

1. Shelf production typically greater in the

south

2. No systematic N-S trend for offshore

stations

3. Production rates measured in cool years

(2009,2011) > warm years (2005,2010)

2005

Off Shelf

2009

Off Shelf

2010

Off Shelf

2011

Off Shelf

La

titu

de

Warm shelf waters 2014/2015

1. Sea-floor CTD on shelf at 96m

2. Captures seasonal pattern of

upwelling and downwelling

water onto shelf

3. Weak downwelling in

2013/2014 winter (blob

development)

4. Warm (~2°C>) fresher water

downwelled onto shelf

2014/2015 winter

5. Atypically warm on southern

shelf through spring/early

summer

Date

Zooplankton Production Rates: 2015

La

titu

de

2015

Off Shelf

BPR (mg C m-2 d-1)

1. Production rate low and limited to the upper 10m

2. No north-south trend

3. Rates ~0 in June, marginally higher in September

4. Production rate elevated on southern shelf but ‘0’ off shelf in Sept.

Year-specific zooplankton production rates

WARM WARM

COOL COOL

WARM

Year/Cruise

BP

R (

mg

C m

-2d

-1)

Biomass patterns: Copepods

WARM WARMCOOL COOL

WARMSouthern species anomaly:

• High in 2005 & 2015

• Positive but low 2010

• Negative in 2009 & 2011

Northern species anomaly:

• Low in 2005 & 2015

• Positive in 2010

• Positive in 2009 & 2011

Biomass patterns: Gelatinous Zooplankton

WARM

WARM

COOL

COOL

WARM

Ctenophore anomaly:

• Very high in 2015

• Positive in 2005 & 2010

• Negative in 2009 & 2011

Doliolid anomaly:

• Very high in 2015

• Positive in 2005 & 2009

• Negative in 2010 & 2011

Patterns of production rates and zooplankton

biomass

Rank correlations VS median BPR:

• Southern = -1.0, p <0.001*• Ctenophores = -0.9, p <0.05*• Northern = 0.8, p=0.10• Doliolids = -0.3, p=0.63

1. Temporal patterns of southern copepod and ctenophore biomass anomaly similar to crustacean zooplankton production rates

1. Production rate in June 2015 ~0 throughout the WCVI

2. Biomass (and composition) significantly altered

3. Warm conditions during the preceding winter probably to blame

4. Production rates slightly improved in September 2015, yet still very low

5. Poor production rates in ‘warm’ years (2005,2015) covaries with southern copepod and ctenophore biomass anomalies. Poor growth? High predation-based mortality?

Summary