Post on 16-Dec-2015
Progress report: Progress report: Biological mechanisms for Hg Biological mechanisms for Hg
accumulation in largemouth bassaccumulation in largemouth bass
Ben GreenfieldBen Greenfield
San Francisco Estuary InstituteSan Francisco Estuary Institute
Fish Mercury Project Fish Mercury Project
2007 Annual Meeting2007 Annual Meeting
Revised presentation to Scientific Review Panel
Largemouth Bass Hg Largemouth Bass Hg ModelingModeling
Committee reviewed Workplan Jan. 2007Committee reviewed Workplan Jan. 2007 Workplan focus:Workplan focus:
1.1. Can biological mechanisms explain spatial Can biological mechanisms explain spatial differences in fish Hg?differences in fish Hg?
2.2. Can biological mechanisms explain variation Can biological mechanisms explain variation among individuals?among individuals?
3.3. What are the seasonal and annual dynamics What are the seasonal and annual dynamics of Hg accumulation?of Hg accumulation?
4.4. What proportion of Hg burden explained by What proportion of Hg burden explained by recent growth?recent growth?
Largemouth Bass Hg Largemouth Bass Hg ModelingModeling
Committee reviewed Workplan Jan. 2007Committee reviewed Workplan Jan. 2007 Workplan focus:Workplan focus:
1.1. Can biological mechanisms explain spatial Can biological mechanisms explain spatial differences in fish Hg?differences in fish Hg?
2.2. Can biological mechanisms explain variation Can biological mechanisms explain variation among individuals?among individuals?
3.3. What are the seasonal and annual dynamics What are the seasonal and annual dynamics of Hg accumulation?of Hg accumulation?
4.4. What proportion of Hg burden explained by What proportion of Hg burden explained by recent growth?recent growth?
Talk outlineTalk outline1.1. Conceptual modelConceptual model
2.2. Selected resultsSelected results Biological drivers of spatial variation in Hg (Questions 1 and 2)Biological drivers of spatial variation in Hg (Questions 1 and 2)
Growth rateGrowth rate Consumption rateConsumption rate
Conceptual model of Hg Conceptual model of Hg uptake into fishuptake into fish
Fish Mercury
Growth
EliminationEgestion
Spawning Loss
ConsumptionPrey Mercury(MeHg)
Multiple Drivers•Bioavailable Hg•Methylation processes•Uptake into lower trophic levels
Fish Mercury
Growth
EliminationEgestion
Spawning Loss
ConsumptionPrey Mercury(MeHg)
Multiple Drivers•Bioavailable Hg•Methylation processes•Uptake into lower trophic levels
General ApproachGeneral Approach
Query the FMP and other datasetsQuery the FMP and other datasets Focus on consumption and growthFocus on consumption and growth Statistical and mechanistic modelingStatistical and mechanistic modeling
Linear and nonlinear modelingLinear and nonlinear modeling Bioenergetics modelBioenergetics model Hg mass balance modelHg mass balance model
Results: growth rateResults: growth rate Hypothesis: Hypothesis: Higher Hg in slower growing Higher Hg in slower growing
fish explains huge variation in fish explains huge variation in largemouth bass Hglargemouth bass Hg Essington and Houser 2003; Simoneau et Essington and Houser 2003; Simoneau et
al. 2005al. 2005 ““Growth dilution”Growth dilution” Evaluate using estimates of growth rate Evaluate using estimates of growth rate
based on scale data (Gary Ichikawa, based on scale data (Gary Ichikawa, CDFG)CDFG)
Statistical and mechanistic modelingStatistical and mechanistic modeling
•Calculate nonlinear growth curve usingAge vs. length data (Von Bertalanffy)
•Use residuals of this growth curve to estimate relative growth rate of individual fish
AmericanRive
Cosumnes/Mok
Delta
FeatherRiver
SacramentoRi
SanJoaquinRi
Watershed
-200
-100
0
100
200
Gro
wth
Re
sid
ual
AmericanRive
Cosumnes/M
okDelta
FeatherRive
r
SacramentoRi
SanJoaquinRi
Watershed
0.5
1.0
1.52.0
Me
rcu
ry (
pp
m)
Regional patterns in growth residuals not associated with Regional patterns in growth residuals not associated with HgHg
Hg vs. growth residuals by watershed; Pearson’s r = Hg vs. growth residuals by watershed; Pearson’s r = 0.02; N = 60.02; N = 6
*
Examine growth residual (G) vs. Hg Examine growth residual (G) vs. Hg accounting for regional differencesaccounting for regional differences
General linear models to look at effect within stationsGeneral linear models to look at effect within stations Square root Hg = f (station, G, length)Square root Hg = f (station, G, length)
G positively associated with HgG positively associated with Hg Positive effect of body size at a given agePositive effect of body size at a given age Mechanism may be higher Hg in larger preyMechanism may be higher Hg in larger prey
G not significant after length accounted forG not significant after length accounted for Growth dilution hypothesis not supportedGrowth dilution hypothesis not supported
Modeling effect of growth rateModeling effect of growth rate
Mechanistic bioenergetic and Hg mass balance model Mechanistic bioenergetic and Hg mass balance model provided by Marc Trudelprovided by Marc Trudel
Ran simulation for growth and Hg uptake from age 2 to 7 Ran simulation for growth and Hg uptake from age 2 to 7 largemouth basslargemouth bass
Calibrated model to Hg data from Frank’s Tract and to Calibrated model to Hg data from Frank’s Tract and to von Bertalanffy growth curvevon Bertalanffy growth curve
Evaluated effect of refitting model to 95% upper and Evaluated effect of refitting model to 95% upper and lower confidence interval growth rates for data setlower confidence interval growth rates for data set Effect on change in Hg over simulation periodEffect on change in Hg over simulation period
Growth changed by separately changing consumption Growth changed by separately changing consumption rate or activity coefficientrate or activity coefficient
Changing growth rate has limited effect Changing growth rate has limited effect on changes to Hg concentrationon changes to Hg concentration
•Modifying growth by changing consumption -less than 5% effect
•Modifying growth by changing activity - about 20% effect
•Direction of effects are consistent with growth dilution
Increased growth
Decreased growth
Effect of growth rate much lower than Effect of growth rate much lower than effect of prey Hgeffect of prey Hg
•Prey Hg changed from silverside at Big Break to silverside at Cosumnes River
•Hypothesis not supported
Higher growth
Lower growth
Decreased growth
Hypothesis: Hypothesis: fish with higher consumption rates will fish with higher consumption rates will have higher tissue Hghave higher tissue Hg
Consumption rates back-calculated using Hg mass Consumption rates back-calculated using Hg mass balance model (Trudel et al. 2000)balance model (Trudel et al. 2000)
Parameter estimates were obtained using local data Parameter estimates were obtained using local data on size, growth, bass Hg, silverside Hg, and on size, growth, bass Hg, silverside Hg, and temperaturetemperature
Fish Mercury(C)
Growth (G)
Elimination (E)
Egestion (1-
Spawning Loss (K)
Consumption (I)Prey Mercury(Cd)
Results: consumption rateResults: consumption rate
0.001
0.01
0.1
1
Franks Cosumnes Vernalis
Station
Hg
(u
g/g
) o
r C
on
su
mp
tio
n (
1/d
)
Tissue Hg Average Consumption (Ages 3-5)
Increased consumption estimate not associated with increased tissue Hg
Consumption rate estimate proportional to Consumption rate estimate proportional to HgHgfishfish/Hg/Hgpreyprey
Model indicates potential mechanism but Model indicates potential mechanism but not an independent assessmentnot an independent assessment
Don’t have access to best prey Hg data yetDon’t have access to best prey Hg data yet
Modeled consumption rate tracks bioaccumulation factor
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0 5 10 15 20 25
Bioaccumulation Factor
Con
sum
ptio
n (
d-1)
SummarySummary Growth rate differences not responsible for Hg Growth rate differences not responsible for Hg
variationvariation Hg positively associated with size at a given ageHg positively associated with size at a given age Mechanistic model did not explain much variationMechanistic model did not explain much variation
Preliminary consumption rate results don’t Preliminary consumption rate results don’t indicate positive association with Hgindicate positive association with Hg
Preliminary findings consistent with Preliminary findings consistent with interpretation that abiotic and lower-food web interpretation that abiotic and lower-food web processes drive bass Hgprocesses drive bass Hg Hg spatial patterns not driven by fish biologyHg spatial patterns not driven by fish biology
Next stepsNext steps More extensive mechanistic modelingMore extensive mechanistic modeling
Systematically vary growth, consumption, Systematically vary growth, consumption, temperature, and prey Hg according to temperature, and prey Hg according to observed rangesobserved ranges
Shift focus to temporal dynamics of Hg Shift focus to temporal dynamics of Hg uptake from prey (Questions 3 and 4)uptake from prey (Questions 3 and 4) Dependant on collaboration with UC Davis Dependant on collaboration with UC Davis
team to examine implications of fluctuations in team to examine implications of fluctuations in small fish Hgsmall fish Hg
AcknowledgementsAcknowledgements
Aroon Melwani, John Oram, Jennifer Hunt Aroon Melwani, John Oram, Jennifer Hunt SFEISFEI
Marc Trudel, Department of Fisheries and Marc Trudel, Department of Fisheries and Oceans, CanadaOceans, Canada
Gary Ichikawa, CDFGGary Ichikawa, CDFG
Darell Slotton and Shaun Ayres, UC DavisDarell Slotton and Shaun Ayres, UC Davis
Ancillary materialAncillary material
Potential biological drivers of Potential biological drivers of Hg variationHg variation
Growth rates (growth dilution, starvation Growth rates (growth dilution, starvation concentration)concentration)
Consumption rates Consumption rates Metabolic activityMetabolic activity Fish healthFish health Alternatively, prey Hg (e.g., trophic Alternatively, prey Hg (e.g., trophic
position)position)
Bass Hg does not closely track silverside Hg Bass Hg does not closely track silverside Hg (Grenier et al. 2005 Year 1 Sportfish Report)(Grenier et al. 2005 Year 1 Sportfish Report)
Possibility for mechanisms related to bass growth and Possibility for mechanisms related to bass growth and consumptionconsumption
Ancillary material: Ancillary material: body conditionbody condition
Length vs. mass stations significant in Ancova
2.2 2.3 2.4 2.5 2.6 2.7 2.8Log10(Length)
1
2
3
4Log10(M
ass)
1,11,00,10,0
SJRPOTATO35,SJRVERN36SJR Potato Slough
SJR Vernalis
Overall model R2 = 0.95
General approach: Develop relative body condition using General approach: Develop relative body condition using length weight residualslength weight residuals
Significant differences among sites (ANCOVA using GLM)Significant differences among sites (ANCOVA using GLM)
Results: body conditionResults: body condition Hypothesis:Hypothesis: body condition negatively body condition negatively
associated with [Hg]associated with [Hg] Greenfield et al. 2001; Swanson et al. 2007Greenfield et al. 2001; Swanson et al. 2007
Condition = Residuals of length vs. weight Condition = Residuals of length vs. weight regressionregression
Thinner, leaner fish may be consuming Thinner, leaner fish may be consuming and respiring more to maintain current and respiring more to maintain current body mass.body mass.
““Starvation concentration”Starvation concentration”
No regional patterns in relative body conditions No regional patterns in relative body conditions Hg vs. condition by watershed; Pearson’s r = 0.08; N = 9Hg vs. condition by watershed; Pearson’s r = 0.08; N = 9 Similar results for individual fishes (ancillary materials)Similar results for individual fishes (ancillary materials) Hypothesis not supportedHypothesis not supported
American R
iv
Central D
elt
Cos/Mok R
ive
Eastern Drai
Feather Rive
Northern D
el
Sacramento R
San Joaquin
Western Delt
WATERSHED
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
HG
American R
iv
Central D
elt
Cos/Mok R
ive
Eastern D
rai
Feather Rive
Northern D
el
Sacramento R
San Joaquin
Western D
elt
WATERSHED
-0.2
-0.1
0.0
0.1
CO
ND
ITIO
N
-1.22000E+02
-1.21567E+02
-1.21133E+02
-1.20700E+02
Longitude
37
38
39
40
Latit
ude
-0.2-0.10.00.1
CONDITION
Examine spatial patterns in relative body Examine spatial patterns in relative body conditions - no broad association with Hgconditions - no broad association with Hg
Longitude
37
38
39
40
La
titu
de
0.00.10.20.30.40.50.60.70.8
HG
Condition Hg
Delta San Joaquin
Sacram
ento
Delta San Joaquin
Sacram
ento
Body condition vs. Hg among individual Body condition vs. Hg among individual fish within a sitefish within a site
Approach:Approach: Generate body condition estimates for each Generate body condition estimates for each
individual largemouth bass (N = 498)individual largemouth bass (N = 498) Generate estimates of Hg variation within Generate estimates of Hg variation within
sitessites Residuals from ANOVA of Hg vs. site Residuals from ANOVA of Hg vs. site
No relationship between condition and Hg No relationship between condition and Hg (linear regression p > 0.5)(linear regression p > 0.5)
Body condition not associated with HgBody condition not associated with Hg
Ancillary material: Ancillary material: growth rategrowth rate
1 3 5 7 9AGE
150
240
330
420
510
600
LE
NG
TH
Feather RiveDeltaCosumnes/Mok
WATERSHED
Cosumnes/MokelumneFeather RiverDelta
Graphical analysis of growth rate differences in 3 regions
Statistical output of growth residual Statistical output of growth residual analysisanalysis
Parameters Final R2Is growth residual
significant?Station 0.41Station, G, interaction 0.55 Yes Station, length, interaction 0.75Length 0.19Length, G 0.19 No
G positively associated with HgG positively associated with Hg Results indicate a positive effect of body size at a given ageResults indicate a positive effect of body size at a given age
Length vs. Hg stronger than G vs. HgLength vs. Hg stronger than G vs. Hg Growth residual not significant after length accounted forGrowth residual not significant after length accounted for
Mechanism may be higher Hg in larger preyMechanism may be higher Hg in larger prey Hypothesis not supportedHypothesis not supported
Example plots of growth residuals vs. Hg Example plots of growth residuals vs. Hg at individual stationsat individual stations
-100 -50 0 50 100Growth Residual
0.24
0.36
0.48
0.60M
erc
ury
(u
g/g
we
t)
-50 0 50 100Growth Residual
0.30
0.45
0.60
0.75
0.90
Me
rcu
ry (
ug
/g w
et)
Sacramento River At River Mile 44
Camanche Reservoir
•At some stations (e.g., Sacramento River at River Mile 44), growth residual was positively related to Hg•This is not consistent with the growth dilution hypothesis•At many stations (e.g., Camanche Reservoir), there was not apparent relationship between growth residual and Hg
Ancillary material: Ancillary material: consumption rateconsumption rate
Hg mass balance modelHg mass balance model
Trudel, M., Tremblay, A., Schetagne, R., Rasmussen, J.B., Trudel, M., Tremblay, A., Schetagne, R., Rasmussen, J.B., 2000. Estimating food consumption rates of fish using a mercury 2000. Estimating food consumption rates of fish using a mercury mass balance model. Canadian Journal of Fisheries and mass balance model. Canadian Journal of Fisheries and Aquatic Sciences 57, 414-428.Aquatic Sciences 57, 414-428.
Fish Mercury(C)
Growth (G)
Elimination (E)
Egestion (1-
Spawning Loss (K)
Consumption (I)Prey Mercury(Cd)
Consumption Rate Estimates
0
0.01
0.02
0.03
0.04
2 3 4 5 6 7 8
Age
Con
sum
ptio
n (1
/d)
Franks
Cosumnes
Vernalis
What proportion of Hg burden can What proportion of Hg burden can be explained by recent growth?be explained by recent growth?
Hypothesis: Hypothesis: majority of Hg burden due to majority of Hg burden due to recent growthrecent growth
Preliminary estimates based on empirical Preliminary estimates based on empirical datadata Burden = body mass * Hg concentrationBurden = body mass * Hg concentration Estimated representative body mass at a Estimated representative body mass at a
given age using length at age model and given age using length at age model and length-mass regressionlength-mass regression
Calculated Hg concentration at given ageCalculated Hg concentration at given age
SJ RiverAt Vernalis
CosumnesRiver
FranksTract
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
0-2 yr3 yr4 yr5 yr
•60 to 80% Hg due to past 2 yr of growthHypothesis supported
Back up images of excel objects Back up images of excel objects
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
25%
Consumption Activity exponent