Ecosystems naturally labeled with carbon-13: applications to the study of consumer food-webs Item Type Thesis Authors McConnaughey, Ted Alan Download date 26/09/2021 06:28:57 Link to Item http://hdl.handle.net/11122/5032 ECOSYSTEMS NATURALLY LABELED WITH CARBON-13: APPLICATIONS TO THE STUDY OF CONSUMER FOOD-WEBS RECOMMENDED: 1 r. I j y : J r Chairman, ltdvisory Committee Program Head APPROVED: J . / & U I f . Divi^JSn Director/ 2 7 O f h ^ / / f i x ' Date f/~- f) L ~ Dean of the College of Environmental Sciences 37 Plp-Al {*i??__________________ Date ni Vice Chancellor for Research and Advanced Study y / 9 7 € Date ECOSYSTEMS NATURAL,I,Y l.AftKLKI) VJTTI! CAUliOM-1 H: APPLICATIONS TO THi- STUDY OF COiJSU’llil' FOOD-UT.BS UFO” r r I y / " I T ' / V ~ f "A -.. Chairv.ja'i, ' Ac .\i:or.y t Ik . -- pr-r.gr;:r:i I!e< ASProvf/r;: / ,• , - V /> / *■ •' "/S sy'Y T~’ - .._ Div:.</'or! Ofrector / Dnnn rr r.hc Co.l.ie;.;^ ol 15pvirom.iO»»Utl Seicni'eM or /%.-;/ (<}?? Di. V i? C V1 T ■v' -It v-r, ViC'.' AA.'MVp II oj. I'c’r aiu! A d v .'i> • <.• Si'iiA / > ' ■„ .. / w- . .. L_>_. l\:u I I ECOSYSTEMS NATURALLY LABELED WITH CARBON-13: APPLICATIONS TO THE STUDY OF CONSUMER FOOD-WEBS A THESIS Presented to the Faculty of' the University of Alaska in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE by Ted McConnaughey, B.A. Fairbanks, Alaska May 1978 ABSTRACT 1 12 Natural abundance ±JC/ C ratios provide a tracer for the origin of organic carbon in complex coastal marine food-webs and also appear to be useful for examining trophic organization and food transfer effi­ ciencies in more strictly oceanic environments. The tracer approach proved useful for analyzing the role of eel- grass (Zosteva marina) in the food-web of Izembek Lagoon, Alaska. Both eelgrass and phytoplankton contribute to the productivity of that community. That analysis was complicated by non-ideal tracer behavior, however. Animal -^C/l^C ratios appeared to depend on biochemical composition, and ways to deal with this were investigated. Furthermore, animal metabo­ lism tended to retain -^C relative to ^ C , resulting in progressive i *|0 elevation of C/ C ratios in higher trophic levels. By assuming a 13 uniform relation between C enrichment and metabolic stoichiometry, it was possible to deduce animal "trophic positions" and food transfer 1 o TO efficiencies from C/ C data taken from the Bering Sea. ACKNOWLEDGEMENTS Yxc'.x •'i relatively small scale graduate study, such as this one, require the cooperation and assistance of a surprisingly large number of people. First of all come the members of the thesis committee whose time, r.oney, effort, and insight contribute to the research program from its inception until its completion. I am especially grateful to Dr. C. Peter HcRoy both for these concrete contributions and also for his enthusiasm (and occasional nagging) which helped me along. I also wish to thank Drs. Patrick L. Parker and Prichard S. Scalen of the University of Texas Marine Science Institute for advice and analytical facilities extended to me. The Izembek National Wildlife Range provided invaluable field support and a warm place to dry out between storms, but perhaps its greatest contribution was the inspiration I developed from the range and manager Robert D. Jones. I also wish to thank John Sarvis and other range personnel for their assistance and companionship, without which that rather remote part of the globe would have been quite inhospitable. Shipboard work aboard the Alpha Helix3 Aoona, and Disaoveror con­ stituted a in.i w,r part of this and related research, and I wish to acknowledge i I . help and support of the ships’ crews and of the insti­ tutions which put these vessels to sea. This tlu■:11 -; is a contribution of the Seagrass Ecosystem Study supported by ;;t,uits from the office of the IDOE of the NSF (Grant Nos. GX-37852, OCE-7/,- 1 3 4 5 7 A02, and OCE-76-84257). TABLE OF CONTENTS ABSTRACT..................................................................iii ACKNOWLEDGEMENTS.......................................................... iv LIST OF TABLES........................................................... vii LIST OF FIGURES ........................................................viii CHAPTER 1. STATEMENT OF THE PROBLEM Introduction ..................................................... 1 Isotope Fractionation in Chemical and Biochemical Systems ...................................... 4 CHAPTER 2. FOOD-WEB STRUCTURE AND THE FRACTIONATION OF CARBON ISOTOPES IN THE BERING SEA Abstract............................................................ 10 Introduction ..................................................... 11 Oceanographic Setting ...................................... 12 Methods.............................................................. 13 Results.............................................................. 19 Biochemical Composition of the Samples.......................23 Discussion.......................................................... 24 Modeling the Food-Web Distribution of Carbon Isotopes .......................................... 25 Conclusions.......................................................... 39 CHAPTER 3. EELGRASS AS A FOOD SOURCE OF MARINE COMMUNITIES: AN EVALUATION BASED ON CARBON ISOTOPIC EVIDENCE Abstract............................................................ 42 Introduction ..................................................... 43 Methods.............................................................. 47 Results and Discussion .......................................... 50 Primary Production............................................. 50 Food-Web Effects............................................... 56 Isotopic Comparisons Between Lagoon and Ocean A nimals............................................... 57 13C/12C Ratios in the Lagoon Food-Web .................... 60 Eelgrass Grazers............................................... 66 Migratory Animals .......................................... 71 Conclusions.......................................................... 73 v TABLE OF CONTENTS (Continued) CHAPTER 4. FEEDING RELATIONS OF THE FISH COMMUNITY IN IZEMBEK LAGOON Abstract........................................................... 77 Introduction.......................................................78 Study Site......................................................... 80 M e t h o d s ........................................................... 81 Results........................................................... 83 The Diets of Fishes......................................... 85 Eelgrass as a Primary Food Source and Carbon-13 Studies..........................................91 Discussion.......................... 97 Food-Web Relations............... 97 Fish Standing S t o c k s ....................................... 99 Composition of the Fish Fauna............................. 101 Conclusions......................................................103 REFERENCES............................................................ 105 APPENDIX A ............................................................ 116 APPENDIX B ............................................................ 118 APPENDIX C ............................................................ 120 APPENDIX D ............................................................ 125 LIST OF TABLES CHAPTER 2. FOOD-WEB STRUCTURE AND THE FRACTIONATION OF CARBON ISOTOPES IN THE BERING SEA Table 1. 13C/12C and C/N composition of Bering Sea organisms............................................20 CHAPTER 3. EELGRASS AS A FOOD SOURCE OF MARINE COMMUNITIES: AN EVALUATION BASED ON CARBON ISOTOPIC EVIDENCE Table 2. 13C/12C ratios (as <5') of animals col­ lected in Izembek Lagoon and in offshore w a t e r s .................................................. 58 Table 3. 13C/12C ratios (measured and corrected for lipid effects), C/N ratios," and feeding rela­ tions of animals collected in Izembek Lagoon .... 61 Table 4. Stomach contents of the crab Telmessus chieragonus collected in Izembek Lagoon...............68 Table 5. 13C/12C ratios in the tissues of migratory birds feeding in Izembek Lagoon........................72 CHAPTER 4. FEEDING RELATIONS OF THE FISH COMMUNITY IN IZEMBEK LAGOON Table 6. Volumetric stomach contents of fishes collected in Izembek Lagoon, Alaska................... 86 Table 7. Standing stocks of fishes in Izembek Lagoon, Alaska, calculated from the data of Tack (1970) ................................................. 100 r LIST OF FIGURES CHAPTER 1. STATEMENT OF THE PROBLEM Figure 1. Frequency histogram of animal 13C/12C ratios in the Bering Sea and Izembek Lagoon, Alaska...........................................9 CHAPTER 2. FOOD-WEB STRUCTURE AND THE FRACTIONATION OF CARBON ISOTOPES IN THE BERING SEA Figure 2. The Bering Sea food-web............................... 14 Figure 3. Relations used in the calculation of lipid-normalized 13C/12C content of animal samples..................................... 18 Figure 4. The partitioning of carbon and fraction­ ation of carbon isotopes by animal meta­ bolism assumed in marine food-web model ........... 30 Figure 5. Progressive enrichment of 13C in a food- chain resulting from model calculations ........... 31 Figure 6. Simultaneous dependence of animal pro­ ductivity and 13C/12C ratio on animal trophic position in a model marine food-web .... 32 Figure 7. Carbon isotope ratio distribution in a model marine food-web.................................36 CHAPTER 3. EELGRASS AS A FOOD SOURCE