Vertical Profiles of Major Organic Geochemical Constituents and Extracellular Enzymatic Activities in Sandy Sediments of Aransas and Copano Bays, TX |
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| Authors: | Afonso C Souza Tamara K Pease and Wayne S Gardner |
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| Institution: | (1) Department of Marine Science, The University of Texas at Austin Marine Science Institute, 750 Channel View Drive Port Aransas, Austin, TX 78373, USA;(2) Present address: The University of Texas at Brownsville, Department of Chemistry and Environmental Sciences, 80 Fort Brown, Brownsville, TX 78520, USA; |
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| Abstract: | Vertical distribution patterns of organic geochemical constituents and the enzymes aminopeptidase and β-glucosidase provide
insights about the nature and reactivity of sediment organic matter in the sandy sediments of two shallow “South Texas” estuaries.
Sediment total organic carbon (TOC) δ13C values indicated that the organic matter (OM) was derived more from a mixture of seagrass and phytoplankton than from terrigenous
OM. Down-core amounts of TOC and total nitrogen (TN) were <0.2% of dry weight, respectively. Enzyme activities were highest
near surface and ranged from 25 to 1 μM/h for aminopeptidase as compared to 5 to 0.2 μM/h for glucosidase. In Aransas Bay,
aminopeptidase activity correlated with sediment TN content (r
s = 0.30) and β-glucosidase with TOC content (r
s = 0.27). In Copano Bay, aminopeptidase correlated with TOC, TN, and carbohydrate content (r
s = 0.89, 0.90, and 0.83, respectively). Variations of glucosidase activity also related positively to TOC, TN, and total carbohydrate
content (r
s = 0.68, 0.77, and 0.48, respectively). Overall, enzyme activities in these low OM, sandy sediments resembled those for other
benthic marine environments. |
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