The role of nutrients in Puget Sound food webs: Insights from empirical and

modeling studiesCorreigh Greene & Chris Harvey

NOAA Fisheries

Do nutrients affect marine survival of Pacific salmon?• 40-year declines of Pacific salmon• Testing “bottom-up” hypotheses explaining declines• Reconstructing long-term patterns of primary

production in Puget Sound from growth in geoducks

• What happened since the 1980’s and can we improve the situation for juvenile Chinook, coho and steelhead?

• How do we improve the accuracy of adult return forecasting with early marine survival data: to better manage harvest, hatcheries and natural spawning?

• What actions can we take to improve marine survival?

Advance wild salmon recovery and sustainable fisheries

Objectives of the Salish Sea Marine Survival Project

Declines of salmon in the Salish Sea

SS CB WB HC JD SG CG JS NS CstSub-basin

Po

pu

lati

on

tre

nd

SS CB WB HC JD SG CstSub-basin

Chinook

Coho

Steelhead

Chum

Pink

Sockeye

Puget Sound

Strait of Georgia

Declines in Salish Sea Marine Survival

Washington / B.C. Coast

0.0%

2.5%

5.0%

7.5%

10.0%

12.5%

15.0%

17.5%

20.0%

1974 1979 1984 1989 1994 1999 2004 20090.0%

2.5%

5.0%

7.5%

10.0%

12.5%

15.0%

17.5%

20.0%

1974 1979 1984 1989 1994 1999 2004 2009

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

6.0%

7.0%

8.0%

1974 1978 1982 1986 1990 1994 1998 2002 2006 2010

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

1974 1978 1982 1986 1990 1994 1998 2002 2006 2010

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

1974 1978 1982 1986 1990 1994 1998 2002 2006 2010

Coho

Chinook

Steelhead0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

6.0%

7.0%

8.0%

1974 1978 1982 1986 1990 1994 1998 2002 2006 2010

Marine survival vs abundance trends

~ 350,000

~ 50,000

~ 20%

~ 3%

Ad

ult

ab

un

dan

ce

Skagit River coho

Current = 10-12%

of historical!

Ultimately, must weigh the contribution of:

• Local, human influence (water quality, predator management, hatchery management)

• Regional or global impacts (climate change, ocean acidification, natural cycles)

Hypotheses

A. Bottom-up processes that drive Chinook, coho and forage fish prey availability have changed, and salmon aren’t able to compensate.

B. Top-down processes contributing – More predators making situation worse. Eating larger juvenile steelhead, resident salmon and forage fish.

C. Multiple factors may compound the problem:• Microbes & disease• Contaminants• Habitat loss• Cumulative effects

Co

ho

sm

olt

-to

-ad

ult

su

rviv

al

Copepod community index

R² = 0.52

South Sound

0.0%

1.0%

2.0%

3.0%

4.0%

-0.2 -0.1 0 0.1 0.2 0.3-0.3

R² = 0.74

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

Central Basin

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

R² = 0.59

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

Whidbey Basin

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

R² = 0.62

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

Hood CanalZooplankton station

Evidence for “bottom-up” effects: Zooplankton and coho survival (2003-10)

J. Keister

A tangled web of possibilities

Marine survival

Marine mammals

Body size

ZooplanktonForage fish

Diatoms

Habitat loss

NutrientsGlobal warming

&ocean acidification

A tangled web of possibilities

Qualitative modeling of hypotheses

Environmental drivers

Phytoplankton

Pelagic foodweb

Impacts of people

Salmon traits

Model results

Variables Perturbation Surv Abund

Sunlight ↑

Winter Storms ↑

Precipitation ↑

Stratification ↑

Temperature ↑

River Flow ↑

Upwelling ↓

Turbidity ↓

Dissolved Oxygen ↓

Variables Perturbation Surv Abund

Nutrients ↑

Microplankton ↑

Microbial Detritivores ↑

Diatoms ↓

Variables Perturbation Surv Abund

Gelatinous Zooplankton ↑

Other Salmon ↑

Marine Mammals ↑

Zooplankton ↓

Forage Fish ↓

Ichthyoplankton ↓

Piscivorous Fish ↓

Piscivorous Birds ↓

Variables Perturbation Surv Abund

Hatcheries ↑

Harvest ↑

Habitat Loss ↑

CO2 ↑

Global Warming ↑

Contaminants ↑

Disease ↑

Probability of decline (%)

0 20 40 60 80 100

Environmental drivers

Phytoplankton production

Pelagic foodweb groups

Impacts of people

Reconstructing primary production

Uncertainties• Geoducks may not eat just phytoplankton• Geoduck growth may reflect benthic conditions, not water column• Temperature affects both geoduck growth and primary production

Evergreen College

Bryan Black

Ge

od

uck

gro

wth

ind

ex

Year

Source: Bethany Stevik (WDFW)

Reconstructing primary production• Link growth with temperature and Chlorophyll measurements

at DOE water quality monitoring stations

Chlorophyll a

Ge

od

uck

gro

wth

• After accounting for effects of temperature…

• Lots of noise, so other factors appear to affect growth

Reconstructing primary production• Link growth with temperature and Chlorophyll measurements

at DOE water quality monitoring stations

Chlorophyll a

Ge

od

uck

gro

wth

• After accounting for effects of temperature…

• Lots of noise, so other factors appear to affect growth

Reconstructing primary production

Next steps

• Whidbey Basin geoducks

• Refine models using other water column metrics

• Find appropriate time series to extend analysis backward in time

• Relate primary production to marine survival, in context of other foodweb elements