Spatial and temporal patterns in food web accumulation of Hg Project Update RMP Technical Review...

Spatial and temporal patterns in food web accumulation of Hg

Project UpdateRMP Technical Review Committee March 18, 2008

Workplan: Specific questions to address

1. Where is mercury entering the Bay food web?

2. What habitats, conditions, or factors help to identify hotspots of food web accumulation in Bay margins?

3. Are there interannual trends in MeHg bioaccumulation resulting from wetland and margin restoration activities?

4. What are the best biomonitoring tools for characterizing hotspots of MeHg bioaccumulation?

General approach

• Spatial analysis– Stratified random design– Identify hotspots based on conceptual

model

• Seasonal trend evaluation • Interannual trend detection• Field sampling for Hg isotopes and for

DGT study

Allocation of effort

• Total of 70 sampling events per year to evaluate spatial, seasonal, and interannual patterns

Type Sites

Events per

Year

Total Events

per Year

Total EventsOver 3 Years

% Sampling Budget

Spatial 40 1 40 120 73%

Interannual 8 1 8 24 17%

Seasonal 2 9 18 54 10%

66 198

Spatial survey

• Test hypotheses of MeHg entry points and food web accumulation hotspots

A. Hg source sites

B. Wetlands and wetland type

C. Enclosed subembayments and estuarine creeks

D. Sediment parameters

Spatial survey design - hypothesis testing

Hydrology:Site Type

Open Shoreline

Sub-Embayment

Total Number

High Hg Wetland NA NA 6/yr

Low Hg Wetland NA NA 6/yr

Hg Source Area 7/yr 7/yr 14/yr

Other 7/yr 7/yr 14/yr

Total number sites 40/yr

Spatial survey sites chosen probabilistically

• Same GRTS method as Status and Trends Program

• More powerful inference than with sites of convenience

• What types of conditions Bay-wide higher Hg

• Identify spatial gradients (e.g., South/North?)

• Even if all our hypotheses are wrong, we are still characterizing conditions and identifying hotspots Bay-wide

So What Are the Areas Sampled?

• Entire shoreline of Bay• Lower South Bay to Suisun Bay• Estuarine tributaries• All subtidal wetlands• Not sampling

– Offshore locations– Salt ponds (weak connection to Bay)– Marine lakes (e.g., Aquatic Park, Anza Lagoon)– Islands within Bay (e.g., Angel Island, Red Rock)

How separating different site types?

Hydrology:Site Type

Open Shoreline

Sub-Embayment

Total Number






Preliminary map of areas to be sampled

GIS based on morphology, size, depth

-Strata 1:Open Shorelines-Strata 2:Submbayments

Identifying Hg source areas

Hydrology:Site Type

Open Shoreline

Sub-Embayment

Total Number






Source site selection • Mining sources

– Creeks draining La Joya, Bella Oaks, Borges, and New Almaden Mines

• POTW discharges– 11 shallow-water wastewater treatment plants

recommended by RB NPDES Permitting Staff• Creeks draining urban/industrial areas

– Identified for part of Bay by Prop 13 Stormwater BMP project– Based on historic industrial area and railway lines, auto

recycling facilities, and Hg hotspots• Industrial areas with high sediment THg

– BPTCP sites having sediment THg > 0.7 ppm• Total of about 50 sites

Hydrology:Site Type

Open Water Embayment Total Number






Wetland site selection

•Oversight by Josh Collins and Letitia Grenier

•Based on GRTS sampling performed for SBMP and CRAM

•Stratified based on relative wetland elevation and age

Wetland site selection

Coordination and Collaboration

• University of Michigan – RMP Hg stable isotope study (Joel Blum, Gretchen Gehrke)– Hg isotope sites characterize specific sources

• Urban runoff, mining, waste water, atmospheric deposition

• Sites will be chosen from small fish source sites after probabilistic site selection is complete

• Augment with small number additional sites (e.g., Guadalupe Reservoir to represent mine signal)

• Sediment Hg and isotope analysis

Coordination and Collaboration• Trent University – Diffusive Gradient in

Thinfilm devices (Holger Hintelmann)– Just completing analyses of the pilot study data

(2007)– Year 1 - validation

• 15 small fish sites varying in chemistry and expected bioaccumulation

• Likely overlap with mercury isotope sites– Year 2 – process studies

• Source sites of interest including fishless locations• Likely include SPL sites (e.g., Z4LA)• Report available February 2010

– Addition of water column DOC as correlate

Discussion points• Other suggested source sites?• Agree with area and types of sites covered?

– Entire shoreline of Bay– Lower South Bay to Suisun Bay– Estuarine tributaries– All subtidal wetlands– Not salt ponds, marine lakes, offshore, or small

islands – Phased plan for DGT study

END OF TALK

• REST IS ANCILLARY MATERIAL IN EVENT OF DISCUSSION

THg (ng/g)10 100 1000 10000

MeH

g (n

g/g)

0.01

0.1

1

10

Land Within 2 Km Buffer0.0 0.2 0.4 0.6 0.8 1.0

TOC (%)0.1 1 10

Latitude (Degrees N)37.4 37.6 37.8 38.0 38.2

MeH

g (n

g/g)

0.01

0.1

1

10

Sediment MeHg may be correlated with topsmelt Hg

0.5 1.0 1.5 2.0 2.53.03.5

MeHg in sediment (ng/g)

0.02

0.03

0.04

0.05

0.06

0.070.08

Hg

in f

ish

(u

g/g

)

•Topsmelt 2006 data

•RMP and Calfed sediment data within 1.5 km disk of fish

•R2 = 0.61

Trend analysis – a multiple station BACI design

0

0.05

0.1

0.15

0.2

0.25

0.3

1 2 3 4 5 6 7 8 9

Year

Mer

cury

Con

cent

ratio

ns Control 1

Impact 1

Control 2

Impact 2

Control 3

Impact 3

Control 4

Impact 4

Trend Sampling Locations

Alviso Slough

Newark Slough

Bird Island/Steinberger Slough

Eden Landing

China Camp

Benicia Park

Control

Impact (Restoration)Point Isabel

CandlestickPoint

Hamilton

Oakland Middle Harbor

Monthly sampling locations

Martin Luther King Shoreline

Additional North Bay Station Sampled by USFWS

MLK Shoreline Location

Collection of additional parameters

• Aimed at better understanding mechanisms for spatial variation in bioavailable Hg

• GIS spatial parameters

• Sediment parameters

Sediment parameters

• Sediment parameters: redox, TON, grain size, total and methyl Hg

• Samples at subset of 20 Sites

-122.6 -122.3 -122.0 -121.7Longitude

37.4

37.5

37.6

37.7

37.8

37.9

38.0

38.1

38.2La

titud

e

-3-2-1012

LOGMEHG

0.00.51.01.52.02.5

MEHG_HIGH1

Sediment MeHg: < 1 ng/g 1 – 2 ng/g > 2 ng/g

Annual monitoring of trend stations

0.5 1.0 1.5 2.0 2.53.03.5

SEDIMENT

0.02

0.03

0.04

0.05

0.06

0.070.08

FIS

H

SQ

Pt Isabel

Tiburon

Alviso

Newark

Oakland Harb

Treasure Isl

China Camp

Spatial and temporal patterns in food web accumulation of Hg Project Update RMP Technical Review...

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