Mercury Strategy for the Bay-Delta Ecosystem - CALFED Bay-Delta ...

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
examining the microbial production of methylmercury and its entry and subsequent transfer in
aquatic food webs supporting production of fish and wildlife.
6. Identification and Testing of Potential Management Approaches for Reducing
Methylmercury Contamination
The overall management goal of this core component is to identify and evaluate potential
landscape management approaches for reducing the production and abundance of methylmercury
in the ecosystem, as well as the associated exposure of resident biota. Process-oriented results
from core component 3 (Quantification of Effects of Ecosystem Restoration on Methylmercury
Exposure) and other mercury investigations studies should be used to identify potential
landscape management approaches for consideration. Specific objectives needed to achieve this
goal are as follows.
(1) To develop an empirical understanding of processes and habitat factors affecting
methylmercury production and exposure. This work should focus on wetlands and tidal flats in
the Bay and Delta and should use information from other ecosystem investigations in
conjunction with information from the Bay and Delta (from core component 3).
(2) To develop models for predicting effects of specific management scenarios on methylmercury
production and export. Initial models could be based on empirical information, but efforts
should eventually evolve toward development of process-based, numerical models. Various
model types and spatiotemporal scales should be explored, including spatially explicit landscape
models. A GIS database (with new and existing data) should be developed to map, classify, and
rank wetland types, sub-habitats, and geographic setting with respect to methylmercury supply
and biotic exposure.
(3) To determine which of the factors controlling methylmercury production and exposure can be
managed in the Bay-Delta ecosystem. This is a crucial link between management and science.
What controlling factors can be realistically manipulated without unacceptable consequences?
Potential management scenarios should be identified and evaluated as pertinent information
becomes available. Examples of potential scenarios include the siting of marsh restorations, the
control or diversion of mercury and sediment loads (especially from sources with high
bioavailability), and the alteration of vegetation or water flow and hydroperiod. The potential
utility of such manipulations should be initially considered in relation to logistical feasibility,
cost, potential decreases in methylmercury production, and effects on habitat quality.
(4) To test candidate landscape management approaches in pilot studies to assess performance
with regard to methylmercury production and biotic exposure. Potential landscape-management
approaches should be tested to assess performance. Initial experimental manipulations could be
done at the mesocosm scale. To the extent feasible, larger scale tests should be linked to
ongoing process studies and to monitoring of biosentinel organisms to evaluate performance.
25