Effects of Marine-Derived Nutrients on Productivity in Sockeye Systems

Collaborative ProjectFunded by Watersheds Initiative of the Gulf

Ecosystem Monitoring (GEM) Component of EVOS

IMS/UAFBruce Finney

Terry WhitledgeDean StockwellMelanie Rohr

ADF&G/KodiakSteve Honnold

Switgard DuesterlohSteve Thomsen

General Rationale for EVOS Initiative

• Marine-Derived Nutrients from Salmon may be Important in Aquatic and Terrestrial Ecosystem Processes

• Traced into Freshwater Plankton, Juvenile Anadromous and Resident Fish

• Traced into Riparian Vegetation and Terrestrial Animals

• MDN Fluxes are Linked to Ocean Processes Through Climate, Fishing, Oil Spills

• Ecosystem-Based Management Needs Data to Determine MDN Pathways, Ecosystem Importance and Monitoring Protocols

• Basic Research Needed!

Study Design: Sampling

Sockeye (Karluk) and Control (Spiridon) Lakes

3 Year Study

9 Samplings/year (April - October)

2 Lake and 2 River (mouth) Stations at Each Lake

Full Water Column Sampling (5 m intervals to bottom)

Karluk SpiridonElevation (ft) 368 446Watershed area (106 m2) 275 54 Lake area (106 m2) 39.4 9.2Volume (106 m3) 1920 319Mean depth (m) 48 35Residence time (yr) 4.6 8.0Anadromous YES NO

Stocked

Long-term limnological and salmon data available

Site Characteristics

Study Design: Analyses

Temperature, DO, pH, light

TP, dissolved P, NO3-, Si

Chlorophyll, POM, phytoplankton, zooplankton, juvenile and adult salmon

Primary Productivity

Stable Isotopes (15N, 13C) on: POM, periphyton, zooplankton, juvenile and adult sockeye

Exploratory Studies: 15N, 13C on terrestrial plants, bears, birds

Unique Study

• Relatively well-matched pair of lakes, except for salmon

• Previous Limnological and Paleoecological data showstrong impact of MDN in Karluk Lake

• Detailed spatial and temporal sampling

• Measuring primary productivity

• Complete/integrated stable isotope analyses

15N: enriched in salmon carcasses - tracer of MDN

Comparison of Limnological Profiles Between Lakes

4 6 8 10 12 14 16 18

0

10

20

30

40

50

Kodiak Lakes - Late Aug. 2004

KarlukSpiridon

Temperature (°C)

Depth (m)

0 0.1 0.2 0.3 0.4 0.5

0

10

20

30

40

50

Kodiak Lakes - Late Aug. 2004

KarlukSpiridon

Dissolved P (uM/L)

Depth (m)

Same for Early October

0 5 10 15

0

10

20

30

40

50

Kodiak Lakes - Early June 2004

KarlukSpiridon

Nitrate (uM)

Depth (m)

0 5 10 15

0

10

20

30

40

50

Kodiak Lakes - Early Oct. 2004

Karluk

Spiridon

Nitrate (uM)

Depth (m)

0 20 40 60 80 100

0

10

20

30

40

50

Kodiak Lakes - Late Aug. 2004

Karluk

Spiridon

Si (uM)

Depth (m)

0 1 2 3

0

10

20

30

40

50

Kodiak Lakes - Early Oct. 2004

KarlukSpiridon

Chlorlophyll a (ug)

Depth (m)

Summary Part 1 (Limnology):

• Similar physical regime

• Very different ratios of major nutrientsSpiridon: P-limitedKarluk: P, Si and N limited

• Consistent with MDN sourceMDN: high P, zero Si

• Higher algal standing stock in Karluk by ~ 4X

Comparison of seasonal cycles between lakes and rivers

0

10000

20000

30000

40000

50000

60000

70000

80000

100 150 200 250 300

Karluk Sockeye Escapement

20042005

Sockeye Escapement

Julian Day

River spawners Beach spawners

0

1

2

3

4

5

6

7

100 150 200 250 300

Kodiak Lakes 2005

KarlukSpiridonKarluk riverSpiridon river

Chl a (mg/L)

Julian Day

Surface

0

0.2

0.4

0.6

0.8

1

100 150 200 250 300

Kodiak Lakes 2005

KarlukSpiridon

Primary Productivity (gC/m

2 /day)

Julian Day

2

4

6

8

10

100 150 200 250 300

Kodiak Lakes POM 2005

KarlukSpiridonKarluk riverSpiridon river

15N

Julian Day

2

4

6

8

10

0

200000

400000

600000

800000

100 150 200 250 300

Karluk Lake 2005

15 N River POM

15 N Lake POM

Cum Esc

15N

Cumulative Escapement

Julian Day

2

4

6

8

10

12

100 150 200 250 300

Kodiak Lakes:Zooplankton 2004 and 2005

Karluk 2 2004Spiridon 1 2004Karluk 2 2005Spiridon 1 2005

15N

Julian Day

6

8

10

12

14

16

18

-28 -26 -24 -22 -20

Sockeye Smolts 2006

SpiridonKarluk

15N

13C

Summary Part 2 (Temporal perspective):

• Karluk Lake higher Chl a and primary productivity by ~ 5X

• 15N higher in Karluk Lake and river phytoplankton (POM), zooplankton and juvenile sockeye relative to Spiridon Lake

• Differing seasonality: Late summer/early fall peaks in Chl a, primary productivity, biota 15N and some nutrients in Karluk

• Temporal relationships suggests influence from the early, river spawning run of sockeye: reasonable lag between escapement at downstream weir, rivers and open lake stations

• Transfer into higher trophic levels indicated

• Data support hypothesis that MDN is main control

Thanks to:

EVOS/GEM for fundingPhil Mundy

The dedicated field and lab personnel

30201003

7

11

15

Escapement/Lake area (1000s/km2)

15N

Zooplankton

Sockeye smolts

0

4

8

12

16

100 150 200 250 300

POM 2005KarlukSpiridon

15N

Julian Day

Controversy? Two Views

Salmon-derived nutrients are essential to freshwater and terrestrial ecosystems, and are key to the restoration and sustainability of salmon

Salmon-derived nutrients are not that important, and the top-down effects of escapement on lake ecosystems is substantial

Salmon-Derived Nutrients -Productivity Feedback

FreshwaterProductivity

Nutrients

SpawnerAbundance

(escapement)

Juveniles