AN ECOSYSTEM MODEL OF THE SACRAMENTO-SAN JOAQUIN DELTA AND SUISUN BAY, CALIFORNIA USA ____________ A Project Presented to the Faculty of California State University, Chico ____________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Environmental Science: Professional Science Master Option ____________ by Marissa Bauer Summer 2010 AN ECOSYSTEM MODEL OF THE SACRAMENTO-SAN JOAQUIN DELTA AND SUISUN BAY, CALIFORNIA, USA A Project by Marissa Bauer Summer 2010 APPROVED BY THE DEAN OF GRADUATE STUDIES AND VICE PROVOST FOR RESEARCH: Katie Milo, Ed.D. APPROVED BY THE GRADUATE ADVISORY COMMITTEE: John Nishio, Ph.D., Chair Larry Brown, Ph.D. Michael P. Marchetti, Ph.D. ACKNOWLEDGEMENTS First and foremost I thank Dr. Larry Brown for his unfailing patience, support and guidance through this project. Many thanks are due to Dr. Howard Townsend, my greatest Ecopath mentor whose sense of humor made the world of ecosystem modeling a tolerable beast. I also thank my committee members, Dr. John Nishio and Dr. Michael Marchetti for their advice and comments on drafts. A huge thank-you to those who graciously contributed their valuable time, data expertise and knowledge, I could not have put this model together without your help: Fred Feyrer (USBR), Wim Kimmerer (SFSU), Bill Bennett (UCD), Jan Thompson (USGS), and Erik Loboschefsky (UCD). Thanks also to the California Department of Fish and Game and the Interagency Ecological Program for the collection and maintenance of long term data sets. I am beyond fortunate to have the unflinching support and never-ending encouragement of my parents, Jim and Cheryl Bauer, without whom I would not be where I am today. Thank you so much. To Frank, who made me stay inside and type those last few pages. I love you. __________________________ This work was supported by funding from the Interagency Ecological Program to Larry Brown. The work was conducted as part of a working group convened at the National Center for Ecological Analysis and Synthesis in cooperation with the Interagency Ecological Program. iii TABLE OF CONTENTS PAGE Acknowledgements.................................................................................................... iii List of Tables ............................................................................................................. v List of Figures............................................................................................................ vi List of Symbols and Nomenclature............................................................................ vii Abstract...................................................................................................................... ix CHAPTER I. Introduction ..................................................................................................... 1 A Need for Ecosystem Modeling............................................................. 4 II. Methods........................................................................................................... 7 Introduction to the Ecopath with Ecosim Methodology.......................... 7 Ecopath ................................................................................................... 9 Ecopath Input Parameters for the Delta Model........................................ 14 Parameter Estimate Methodology............................................................ 18 Diet Composition Matrix ......................................................................... 23 Balancing the Ecopath Model.................................................................. 28 III. Results ............................................................................................................. 29 IV. Discussion ....................................................................................................... 37 Future Work............................................................................................. 41 References.................................................................................................................. 43 iv LIST OF TABLES TABLE PAGE 1. Ecopath Parameters for the Preliminary 1982 Delta Model .......................... 15 2. Ecopath Parameters for the Preliminary 1982 Delta Model .......................... 16 3. Diet Matrix for the Preliminary 1982 Delta Ecopath Model ......................... 24 4. Diet Matrix for the 1982 Delta Ecopath Model Continued ........................... 25 5. Diet Matrix for the 1982 Delta Ecopath Model Continued ........................... 26 6. Diet Composition Sources for each Functional Group.................................. 27 7. Ecological Characteristics for each Functional Group ............................................ 35 8. Summary Statistics of the Delta Model ......................................................... 36 9. Trophic Transfer Efficiencies for each Trophic Group (%) .......................... 36 v LIST OF FIGURES FIGURE PAGE 1. Sacramento-San Joaquin Delta and Suisun Bay, California USA .................. 9 2. Visual representation of Ecopath with Ecosim model: Data needs, modeling abilities, research and application are linked.............................. 10 3. A simplified food-web model of the Delta in 1982......................................... 34 vi LIST OF SYMBOLS AND NOMENCLATURE B: EwE Biomass parameter (t · km2) BA: Biomass Accumulation (t · km2) CDWR: California Department of Water Resources cm: centimeter (metric unit of measurement) CVP: Central Valley Project DC: Diet Composition (%) DOC: Dissolved organic carbon DFG: California Department of Fish and Game Ei: net migration rate (emigration – immigration) EE: Ecotrophic efficiency EwE: Ecopath with Ecosim F: instantaneous rate of fishing mortality year-1 FMT: Fall Midwater Trawl Survey (performed by DFG) IEP: Interagency Ecological Program K: k parameter of the von Bertalanffy growth equation; K = (dL/dt)/( L∞-L) km: kilometer L∞: theoretical Length at Infinite age Lmat/L∞: Length at Maturity divided by theoretical Length at Infinite age M: instantaneous rate of natural Mortality (year-1) m: meter (metric unit of measurement) vii P: Production of biomass by a functional group (t/km2 year-1) POC: Particulate organic carbon P/B: Production per unit Biomass parameter (year-1) (equivalent to Z) P/Q: Production/Consumption (year-1) POD: Pelagic Organism Decline Q: Consumption of biomass by a functional group (t·km2 year-1) Q/B: Consumption per unit Biomass parameter (year-1) SWP: State Water Project t · km-2 metric tons per square kilometer, units used for biomass inputs USFWS: US Fish and Wildlife Services USGS: US Geological Survey VBGF: von Bertalanffy growth function Wmat/W∞: Weight at Maturity divided by theoretical Weight at Infinite age W∞: Weight at Infinite age YI Yield, catch in weight, or fishery harvest (note that Yi = FiBi where F is the fishing mortality rate) (year-1) Z: instantaneous rate of total mortality (year-1) viii ABSTRACT AN ECOSYSTEM MODEL OF THE SACRAMENTO-SAN JOAQUIN DELTA AND SUISUN BAY, CALIFORNIA USA by Marissa Bauer Master of Science in Environmental Science: Professional Science Master Option California State University, Chico Summer 2010 The San Francisco Estuary is a highly exploited system that has been drastically changed from its natural state through urban development, agriculture, and water management. Ecopath with Ecosim (EwE 6) modeling software was used to explore direct and indirect drivers of ecosystem dynamics of the Sacramento-San Joaquin Delta and Suisun Bay, with emphasis on the Pelagic Organism Decline species (delta smelt (Hypomesus transpacificus), threadfin shad (Dorosoma petenense), longfin smelt (Spirinchus thaleicthys), and striped bass (Morone saxatilis)). An Ecopath model was built to simulate the Delta and Suisun Bay ecosystem for the year 1982 based on best available data. The Ecopath modeling approach incorporates trophic interactions and community food web structure to help understand the dynamic interactions between trophic groups. The model uses parameters such as biomass, production, and mortality ix estimates of 40 functional groups, including birds, fish, benthic invertebrates, zooplankton, phytoplankton, and detritus. Model parameters were calculated from published and unpublished data taken from the literature or estimated by local experts when appropriate. The balanced Delta Ecopath model gave some surprising results about the food-web within the Delta. Of the total system biomass (270.5 t km-2) 37 % is from trophic level 3, which consists primarily of the fish species. Trophic level 1 including both detritus and phytoplankton composes 55 % of total system biomass. The final 8 % of total system biomass is composed of second and fourth trophic levels. Trophic transfer efficiencies for the Delta average 8.3%, with the highest trophic transfer efficiency at trophic level 1 (17.6%) and the lowest at trophic level 4 (3.7%).These results are consistent with the general ecological principle of a decreasing trend in transfer efficiency with increasing trophic level. The Delta Ecopath model also brings attention to the fact that the microbial and detrital loops may play an important role in the Delta food web and that further investigation into these pathways may prove useful. It was also apparent that the current Delta model was attempting to describe both the pelagic and littoral food webs of the Delta system and that while these two food webs share some similar species composition, further development