x2 reflects many ecosystem factors x2 physical habitat changes water quality contaminant effects...

X2 reflects many ecosystem factors

X2

Physical Habitat changes

Water Quality

Contaminant effects

Larval dispersal

Adult migration and spawning

X32

X2

X22 X12

1967-871988-2000

1982-2000 (DS)All Years

Fish- X2

RelationshipsFrom Kimmerer 2002 1

2

3

4

1

2

3

4

0

1

2

3

2

3

4

5

0

1

2

3

2

3

4

5

50 60 70 80 90

0

1

2

3

50 60 70 80 90

-2

-1

0

1

Bay Shrimp

Striped BassSplittail

Longfin smeltDelta smelt

Herring Am. Shad

Flounder

Lo

g A

bu

nd

an

ce

or

Su

rviv

al

X2 (km)

X2 observations

Fish:X2 Relationships maintained across 35 years of data

Massive change in food web had little impact on relationships

Mechanisms remain unclear and probably diverse

Future Directions

• Research strategy under development (CBDA grant to Kimmerer and Bennett)– Limited ability to test mechanisms– Reduced funding likely to restrict studies

• Discussion with local biologists suggest that, for many possible mechanisms, variability is likely important (Estuarine Ecology Team July 2004)

Conclusions

• X2 seems to be working to protect aquatic resources from reductions in estuarine habitat quality

• Protecting both mean and variance of X2 seem important

• Unlikely that more effective ways to protect resources will be found soon

• Continued data collection is vital for meaningful review

• Kimmerer, W.J. 2002.  Physical, biological, and management responses to variable freshwater flow into the San Francisco estuary. Estuaries 25:1275-1290

• Jassby, A.D., W. J. Kimmerer, S.G. Monismith, C. Armor, J.E. Cloern, T.M. Powell, J.R. Schubel, and T.J. Vendlinski. 1995. Isohaline position as a habitat indicator for estuarine populations. Ecological Applications 5:272-289

Main references