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LIPPS AND CULVER—TROPHIC ROLE OF MARINE MICROORGANISMSthe trophic structures in mass-extinctiontransitions are required, with special emphasis onthe preserved primary producers, including theacritarchs, calcareous nannoplankton, anddiatoms. The microherbivore and carnivorerecords should be examined as indicators of thenature of primary production. Whether or notdeclining primary production was intimatelyinvolved in the overall extinction dynamics, thephysical oceanographic mechanisms influencingprimary productivity may have differed in eachextinction event. Some of these mechanisms mayhave included asteroid impacts, changingoceanographic circulation, and changing degreeof oceanic heterogeneity as controlled by densitystratification. The patterns in Phanerozoicextinctions seem sufficiently consistent thatregardless of physical causes, trophic dynamicswere affected severely.IMPLICATIONS FORCONSERVATION BIOLOGYImportant for the conservation of marinebiodiversity, but commonly overlooked, is themaintenance of the trophic mechanisms andstructures without which these diverse assemblagescould not function. These structures took four billionyears to evolve, and climatic and oceanographicchanges—or a few human misjudgments—coulddamage them considerably. The fossil record andmodern marine ecology demonstrate the importanceof prokaryotes and protists in the trophic interactionsthat energize all marine ecosystems. Microfossiltrophic analyses have much to contribute to ourunderstanding of trophic dynamics and where thesesystems are most vulnerable. Modern ecologicalstudies are severely constrained by a lack ofhistorical perspective; experiments cannot bedesigned long enough to record the consequencesof events occurring on ecologic scales.Paleontologists must provide that perspective withdetailed studies of their own to complement andstrengthen ecologic work.ACKNOWLEDGMENTSJHL thanks J. Valentine, C. Blank, B.Waggoner, M. Fedonkin, A. Rozanov, A. Ivantsov,and J. Gehling for discussion of the Precambrianand Cambrian bacterial and metazoan biotas, andW. Hamner and L. Gershwin for information aboutmodern cnidarians. He also thanks the UC GumpResearch Station on Moorea and its ResearchDirector Dr. Neil Davis for the facilities to makethe study of tropical microbial mats possible; andthe Geological Natural Reserve of Haute-Provenceand M. Guiomar for permission to examine fossilsthere. SJC thanks D. Merritt, M. Buzas, F. Banner,J. Wallace, D. Stewart, and C. Smith for assistanceand support. JHL and SJC are indebted to D. Haigfor organizing an amazing week-long field tripduring Forams2002 to study microbial mats andstromatolites in Western Australia. Researchunderpinning much of this summary was supportedby grants NSF EAR 85-09301 to JHL, NSF EAR9317247 and NSF EAR 9814845 to J. Valentineand JHL. SJC thanks the USGS for funding theNorth Carolina Coastal Geology Cooperativeresearch program at ECU. Permission to undertakeresearch on the Outer Banks’ Pea Island NationalWildlife Refuge is gratefully acknowledged. Thisis UC Museum of Paleontology Contribution 1787and UC Gump Research Station Contribution 96.REFERENCESALTENBACH, A. V., U. PFLAUMANN, R. SCHIEBEL, A. THIES, S. TIMM, AND M. TRAUTH. 1999. Scaling percentages and distributionalpatterns of benthic foraminifera with flux rates of organic carbon. Journal of Foraminiferal Research, 29:173–185.ANDERS, E. 1989. Prebiotic organic matter from comets and asteroids. Nature, 342:255–257.ANDERSON, O. R. 1993. The trophic role of planktonic foraminifera and radiolaria. Marine Microbial Food Webs, 7:31–51.AWRAMIK, S. M. 1971. Precambrian columnar stromatolite diversity: reflection of metazoan appearance. Science,174:825–827.87