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ESTUARINE PALEOPRODUCTIVITY: A COMPARISON OF THREE INDICATORS
Citation:
Chmura, G. L., A. F. Santos, V. Pospelova, Z. Spasojevic, AND J S. Latimer. ESTUARINE PALEOPRODUCTIVITY: A COMPARISON OF THREE INDICATORS. Presented at Estuarine Research Federation 16th Biennial Conference, St. Petersburg, FL, November 4-8, 2001.
Description:
Studies of paleoproductivity have documented anthropogenic impacts on lakes and estuaries - but use of multiple measures of productivity is rare. We compare three measures used as indicators of paleo-primary productivity: sedimentary concentrations of dinoflagellate cysts, biogenic silica (BSi), and fossil algal pigments as part of a paleo-ecological study of New Bedford Harbor. Our dated sediments span the history of the harbor, from the period prior to European colonization, through urbanization and high nutrient enrichment to industrialization and introduction of xenobiotics. Prior to European settlement the harbor was oligotrophic. During this period we see a correspondence of the cyst and BSi record, but little relationship to fossil pigments, which are present at very low concentrations. With increased nutrient input, pigment concentrations increase and show fluctuations that correspond to changes in the BSi and cyst record.
We assume that pigments were rapidly degraded under oligotrophic conditions in this unstratified system. With nutrient enrichment, productivity increased resulting in higher concentrations of sedimentary carbon, decreasing redox potential of sediments due to respiration of decomposers, and enhancing pigment preservation. Each indicator provides an indication of general trends in productivity, but use of fossil pigments may be limited in unstratified estuaries.