Dead delta's former productivity: Two trillion shells at the mouth of the Colorado River

Abstract

Research Article| December 01, 2000 Dead delta's former productivity: Two trillion shells at the mouth of the Colorado River Michal Kowalewski; Michal Kowalewski 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar Guillermo E. Avila Serrano; Guillermo E. Avila Serrano 2Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada, Baja California, Mexico Search for other works by this author on: GSW Google Scholar Karl W. Flessa; Karl W. Flessa 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Glenn A. Goodfriend Glenn A. Goodfriend 4Department of Earth and Environmental Sciences, George Washington University, 2029 G Street, NW, Washington, D.C. 20052, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Michal Kowalewski 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA Guillermo E. Avila Serrano 2Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada, Baja California, Mexico Karl W. Flessa 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Glenn A. Goodfriend 4Department of Earth and Environmental Sciences, George Washington University, 2029 G Street, NW, Washington, D.C. 20052, USA Publisher: Geological Society of America Received: 19 May 2000 Revision Received: 22 Aug 2000 Accepted: 31 Aug 2000 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (12): 1059–1062. https://doi.org/10.1130/0091-7613(2000)28<1059:DDFPTT>2.0.CO;2 Article history Received: 19 May 2000 Revision Received: 22 Aug 2000 Accepted: 31 Aug 2000 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michal Kowalewski, Guillermo E. Avila Serrano, Karl W. Flessa, Glenn A. Goodfriend; Dead delta's former productivity: Two trillion shells at the mouth of the Colorado River. Geology 2000;; 28 (12): 1059–1062. doi: https://doi.org/10.1130/0091-7613(2000)28<1059:DDFPTT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The diversion of the Colorado River by dams and irrigation projects, started in the 1930s, triggered the collapse of the Colorado delta ecosystem. Paleontological, ecological, geochronological, stable isotope, field, and satellite image data provide estimates of the delta's benthic productivity during the 1 k.y. directly preceding the artificial shutdown of the river. At least 2 × 1012 shells of bivalve mollusks make up the current beaches and islands of the delta. The 125 individual valves dated using 14C-calibrated amino acid racemization indicate that these shells range in age from A.D. 950 to 1950. Seasonal intrashell cycles in δ180 values indicate that average-sized bivalves lived at least 3 yr. The most conservative calculation based on these numbers indicates that during the time of natural river flow, an average standing population of ∼6 × 109 bivalve mollusks (population density ∼50/m2) thrived on the delta. In contrast, the present abundance of shelly benthic macroinvertebrates is ∼94% lower (3/m2 in 1999–2000). The dramatic decrease in abundance testifies to the severe loss of benthic productivity resulting from diversion of the river's flow and the inadequacy of its partial resumption (1981 to present). An integration of paleontological records with geomorphological, geochemical, and geochronological data can provide quantitative insights into human impact on coastal ecosystems. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.