SALMON AS INTEGRATIVE SAMPLERS

Transcription

1 SALMON AS INTEGRATIVE SAMPLERS OF HIGH SEAS FOOD WEBS POSTER: INTEGRATING STABLE ISOTOPE ANALYSES OF ZOOPLANKTON & RETURNING ADULT SALMON TISSUES TO INFORM HIGH SEAS NORTH PACIFIC FOOD WEB DYNAMICS Brian P. V. Hunt, Evgeny A. Pakhomov, Sonia D. Batten, Yoshito Chikaraishi 0 Monell & Vetlesen Foundation

2 THE HNLC HIGH SEAS NORTH EAST PACIFIC Surface chlorophyll biomass March (top) September (below) Polovina et al. Progress in Oceanography 2015

3 PHYTOPLANKTON BIOMASS & NUTRIENTS Chlorophyll-a & nitrate in surface waters along Line P in winter, spring and summer of 2015 (red symbols) and (blue symbols). Pena & Nemcek, 2016 DFO State od the Oceans Report

4 SAMPLING THE NORTH EAST PACIFIC

5 STUDY CONCEPT The body stable isotope ratios of returning salmon are expected to reflect the conditions that they experienced while on the high seas. Sockeye as integrative samplers of ocean conditions. Aim: Long term measurement of Nitrogen (δ 15 N ) and Carbon (δ 13 C) isotope ratios of salmon tissues to inform food-web dynamics, and fish life history experience.

6 ISOTOPE BASED TROPHIC LEVEL ESTIMATES δ 15 N increases with each Trophic Level with a consistent enrichment factor. Sockeye salmon δ 15 N Zooplankton Phytoplankton Trophic baseline

7 ISOTOPE BASED TROPHIC LEVEL ESTIMATES δ 15 N increases with each Trophic Level with a consistent enrichment factor. Sockeye salmon δ 15 N Microzooplankton Zooplankton Phytoplankton Trophic baseline

8 THE TROPHIC BASELINE & NUTRIENT DYNAMICS Nutrient concentrations & primary productivity set phytoplankton δ 15 N. NO 3- concentration Phytoplankton biomass POM δ 15 N NO 3- δ 15 N = 4.5

9 METHODS Adult sockeye muscle tissue collected from Rivers Inlet, British Columbia ( ): Bulk C & N isotopes (n > 100/yr). Amino Acid Specific N isotopes (n = 1/yr). Continuous Plankton Recorder (CPR) zooplankton samples: Bulk N isotopes ( ) Biomass ( )

10 SAMPLING THE NORTH EAST PACIFIC

11 CPR ZOOPLANKTON BIOMASS TIME SERIES Log DW / sample

12 CPR ISOTOPES AND δ 15 N

13 CPR ISOTOPES AND δ 15 N 2010 NIGHT

14 ZOOPLANKTON N ISOTOPES REGION X YEAR

15 SOCKEYE ISOTOPES 2011 TO 2016 Increased productivity; Longer food chain; Decreased nutrient supply Increased temperature; Increased productivity * δ 13 C is lipid corrected

16 SST AT STATION P ( ) Monthly average across all years (black); Monthly average (blue). Data source:

17 SOCKEYE ISOTOPES 2011 TO 2016 Increased productivity; Longer Food chain; Decreased nutrient supply Increased temperature; Increased productivity * δ 13 C is lipid corrected

18 SOCKEYE TROPHIC LEVEL Trophic Level calculation 1. Bulk: TL = (Sockeye δ 15 N - zoo δ 15 N /3.4)+2.5 [used SGOA] 2. CSIA: TL = (Glu-Phe-2.4)/7.6+1

19 APPLYING BIOMASS SPECTRUM THEORY 1. δ 15 N = m*(log 2 wet weight) + c 2. PPMR = 2 TEF/m (e.g. TEF = 3.4) δ 15 N (trophic level) 3. TE = PPMR β+0.75 Log 2 biomass class

20 TRANSFER EFFICIENCY IN THE SALMON FOOD WEB % % % %? Zooplankton Sockeye salmon Phytoplankton Trophic baseline

21 SUMMARY Zooplankton δ 15 N in shelf regions = high productivity in off-shelf regions = low productivity Sockeye salmon isotope signatures δ 15 N & δ 13 C elevated after warm Blob conditions (2014), indicating stratification induced nutrient limitation. Productivity appeared unaffected BUT cellular stoichiometry and food quality? Sockeye Salmon Trophic dynamics Bulk & CSIA yielded similar TL estimates of ~ 3.7 Energy transfer efficiency in this system is low & potentially variable.

22 SUMMARY Next steps: Resolve the relationship between zooplankton δ 15 N and Nutrient-Phytoplankton part of the food web. Fill in the CPR δ 15 N time series Further Amino Acid specific δ 15 N measurements.